WO2001022460A1 - Snap-disk forming machine and process control algorithms - Google Patents

Abstract

A snap disk formation assembly (10) and method provides a feedback control of a snap disk form station (12) in communication with an exercise station (14) coupled to a feedback station (16). A disk blank is inserted into a pocket and loaded into a dial fixture which travels along a communication axis between the form station (12), the exercise station (14), and the feedback station (16). The pocket holds the metal disk while a snap disk reset side and a trip side are formed and exercised. A feedback station (16) determines actual snap forces for one or both sides of the disk and provides feedback control to the form station (12) via a controller configured to accept snap disk formation parameters and adjust the operation of apparatus stepper motors (20, 22) to produce a snap disk within the accepted parameters. Logic driven controls employ adaptive learning to efficiently locate the stepper motors (20, 22), in a real time as incoming material properties used to form the snap disk change, thereby eliminating trial and error fabrication methods.

Description

SNAP-DISK FORMING MACHINE AND PROCESS CONTROL ALGORITHMS

BACKGROUND OF THE INVENTION

This invention relates generally to formation machines and processes and, more particularly, to a process and machine for forming bistable snap-disks.

Bistable snap-disks are typically utilized as mechanical cycling components in fluid operated switching devices, pressure cycling devices, and other mechanisms utilizing a two-position, bistable, snap-action switch. See, for example,

U.S. Patent No. 5,198,631. Such snap-disks include a convex configuration and a concave configuration to engage or disengage electrical contacts and open and close an electrical circuit, respectively. The snap-disks snap, or "trip" between a convex and concave configuration depending on the application of sufficient external forces on one of the sides of the disk, such as, for example, a pressure, and snap or "reset" into an original configuration when those external forces fall below a predetermined value. The required forces causing a snap-disk to trip or reset between the convex and concave configurations, and vice-versa, vary from application to application, but for a given disk, the trip and reset force values are usually unequal.

Bimetallic and monometallic snap-disks are typically formed with a set of full radius punches, largely through a trial and error process complicated by an interdependency between the snap and reset forces. Trial and error experimentation typically determines which of the punches to use to form the opposite sides of the disks, and different punches are periodically determined by similar trial and error experimentation as snap-disk material properties change. Precise formation tolerances, however, are required in forming snap-disks so that the disks adequately react to external forces, such as temperature or pressure differentials, in a given switch application. The precise formation tolerances are difficult to consistently achieve using current snap-disk formation methods. Consequently, a one hundred percent sort of formed snap-disks is often required, and yields of acceptable snap-disks upon initial formation are as low as thirty percent. The low yield of acceptable disks decreases manufacturing efficiency and raises the costs of production of the snap- disks. Accordingly, it would be desirable to increase the yield of acceptable snap-disks upon initial formation and decrease production costs in snap-disc formation.

BRIEF SUMMARY OF THE INVENTION

In an exemplary embodiment of the invention, a snap-disk form assembly and method includes a form station coupled to a feedback station so that the formation of the snap-disks may be monitored in real time as the snap-disks are formed. Thus, correction of any deficiency in the formation process is detected and redressed nearly instantaneously.

More particularly, the form station includes a plurality of cams, with each cam including a respective tool. The plurality of cams and tools in the form station stretch the sides of disk blanks to plastic deformation and thereby form the reset and trip sides of the disk. The forces generated by the cams are adjustable with first and second stepper motors.

The feedback station includes a cam-driven probe that sequentially monitors the required peak force to snap the form disks into a respective alternative configuration after they are formed, and monitors the required peak reset force to snap the form disks into their original configuration. A force transducer is connected to the probe, and the probe is brought into engagement with one of the sides of the snap- disks. Therefore, the probe applies a force to the snap-disk that is measured by the force transducer and used for feedback control of the form station. Force is applied by the probe until the disk trips, and the measured peak force that caused the disk to trip is recorded by a feedback station controller. The force applied by the probe is then decreased until the disk resets into its original configuration, and the peak force before the disk resets is also recorded by feedback station controller.

A controller is coupled to the form station stepper motors and is configured to accept snap disk formation parameters and adjust the operation of the stepper motors in real time as the snap-disks are fabricated to produce snap-disks within the accepted parameters. Implemented by logic-driven controls, costly and time consuming trial and error fabrication methods are eliminated, thereby increasing manufacturing efficiency. More specifically, the input parameters include a nominal trip force for activating the bistable snap-disks, a nominal reset force for resetting the bistable snap- disks, an allowable nominal trip force error, and an allowable nominal reset force error. Using an adaptive learning setup algorithm, the controller establishes an upper bound for the desired position of each of the first stepper motor and the second stepper motor, establishes a lower bound for the desired position of each of the first stepper motor and the second stepper motor, establishes a first adjusted position of each of the first stepper motor and the second stepper motor located between the respective upper and lower bound, and establishes at least a second adjusted position of each of the first stepper motor and the second stepper motor located between the first adjusted position and one of the upper bound and lower bound. By estimating and re-estimating stepper motor positions and measuring trip and reset force values of snap-disks formed at those settings, the controller efficiently works toward the desired stepper motor positions by adjusting the respective upper and lower bounds that capture the desired positions to progressively narrow a range of potential stepper motor settings to satisfy the input parameters.

The controller is also configured to compensate for changes in snap- disk forming material as nests of snap disks are formed. The controller measures at least one of a trip force or a reset force of the nest, calculates an error between the measured force and the respective target force, and adjusts the position of at least one of the first stepper motor and the second stepper motor based upon the calculated error.

Using real time feedback and logic driven controls to compensate for interaction between trip and reset forces to set stepper motor positions and adjust those positions as needed, snap-disks are formed in compliance with the input parameters. Production is boosted due to elimination of trial and error fabrication, initial pass rate of the snap-disks is increased, and the costs of snap-disk production are lowered.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic view of a snap-disk form assembly including a form station, an exercise station, and a feedback station;

Figure 2 is a front plan view of the form station shown in Figure 1; Figure 3 is a partial cross-sectional view and side plan view of the form station shown in Figure 2;

Figure 4 is a front plan view of the exercise station shown in Figure 1 ;

Figure 5 is a front plan view of the feedback station shown in Figure 1 ;

Figure 6 is a partial cross-sectional view and side plan view of the feedback station shown in Figure 5;

Figures 7-10 are flowcharts of a form station setup algorithm for controlling the form station shown in Figures 2 and 3 to generate required forces for forming snap-disks; and

Figure 11 is a flow chart of a form station adjustment algorithm for controlling the form station shown in Figures 2 and 3 to compensate for incoming material variations.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 schematically illustrates a snap-disk formation assembly 10 including a form station 12, an exercise station 14, and a feedback station 16 aligned along a communication axis 18. Flat metallic or nonmetallic disk blanks (not shown) are positioned in pockets (not shown) in dial fixtures (not shown) and are translated from form station 12, to exercise station 14, and to feedback station 16 along communication axis 18. Form station 12 provides the disk blanks with a convex and concave configuration on each side of the disk, respectively, with probing action punches (not shown in Figure 1) that stretch the disk to plastic deformation, thereby forming the reset and trip sides of the bistable disks. Exercise station 14 repeatedly subjects the reset and trip sides of the disk to predetermined forces, respectively, to exercise the snap action of the newly formed bistable snap-disks.

Feedback station 16 includes a force transducer (not shown in Figure 1 ) and controls (not shown) that are used to determine the actual force required to trip or reset each snap-disk in a batch of formed and exercised snap-disks. The trip and/or reset forces are recorded for each snap-disk, and the results are analyzed by comparing them to target values. Based on the differential between actual trip and/or reset values for each snap-disk, statistical process feedback control is used to adjust the probing action of form station 12 with a reset stepper motor 20 (further described below) and a trip stepper motor 22 (also described below) to vary the forces used to form the reset and trip sides of the snap-disks, respectively.

Form station 12 comprises a reset portion 24 and a trip portion 26 separated by communication axis 18. Exercise station 14 includes a reset portion 28 and a trip portion 30 separated by communication axis 18, and feedback station 16 includes a reset portion 30 and a trip portion 32 separated by communication axis 18. Form station 12 and exercise station 14 are substantially inversely symmetrical about communication axis 18. In other words, the trip portions 26, 30 of form and exercise stations 12, 14 are generally mirror images of reset portions 24, 28 of form and reset stations 12, 14, respectively, about communication axis 18, but rotated 180° so that trip portions 26, 30 are reversed from side-to-side relative to reset portions 24, 28.

In operation, flat disk blanks of snap-disk material are individually loaded into pockets in the dial fixtures before reaching form station 12. A concave configuration is formed into a reset side of the snap-disk using a reciprocating reset form punch (not shown in Figure 1) that is actuated by a reset form cam 34 and a reset form cam follower 36 and stretches the reset side of the disk into plastic deformation. Once the reset side of a snap-disk is formed, a convex configuration is formed into a trip side of the disk using a reciprocating trip form punch (not shown in Figure 1 ) that is actuated by a trip form cam 38 and a trip cam follower 40 and stretches the trip side of the disk into plastic deformation. Reset form cam 34 and trip form cam 38 are rotationally out-of-phase with one another to avoid interference of the reset and trip punches during formation of the snap-disks.

Each snap-disk is then indexed, while in the pocket, along communication axis 18 to exercise station 14. The reset side and the trip side of the snap-disk are then repeatedly subjected to a predetermined reset exercise force, a predetermined trip exercise force, or beyond, through actuation of a reset exercise punch (not shown) by a reset exercise cam 42 and actuation of a trip exercise punch (not shown) by a trip exercise cam 44, respectively, to exercise the snap action of the snap-disk.

Once exercised appropriately, each snap-disk is indexed along communication axis 18 to feedback station 16 that includes a reset and/or a trip force transducer (not shown in Figure 1 ) that determines the actual required force to cause each snap-disk to snap between the convex and concave configurations. The reset force and/or trip forces are recorded, analyzed, and compared to target reset force values and trip force values. Using feedback control to stepper motors 20, 22, adjustments can be made in the applied force of the reset form punch and the reset trip punch to bring successively formed snap-discs within a desired reset force and trip force tolerance.

Snap disks are then indexed out of feedback station 16 and placed into one of three storage bins including a discard bin (not shown), a reform bin (not shown), or an acceptable pass bin (not shown). Thus, snap-disks are sorted based upon the measured values of the reset force and trip force for the disks. By providing instantaneous feedback to form station reset stepper motor 20 and trip stepper motor 22 to adjust the formation process while it is occurring, the yield of acceptable snap- disks upon initial formation of the disks can be improved dramatically.

Figure 2 is a front plan view of form station 12, including reset portion 24 and trip portion 26. Reset form cam 34 is attached to a reset form cam shaft 60 that is rotationally driven by a reset drive shaft assembly 62. Reset form drive shaft assembly 62 communicates with a trip form shaft assembly 64 via a belt (not shown) and therefore drives a trip cam shaft 66 attached to trip form cam 38. Reset cam follower 36 contacts reset form cam 34 to reciprocally move a reset form punch (not shown in Figure 2) and trip form cam follower 40 contacts trip form cam 38 to reciprocally move a trip form punch (not shown in Figure 2) inside a respective reset form tool housing 68 and trip form tool housing 70.

Reset and trip form cam followers 36, 40 each include a pivot pin 72, a form bearing 74, and a cam follower bearing 76. Each cam follower bearing 76 contacts a respective cam surface 78 of reset form cam 34 and trip form cam 38. Each cam surface 78 is configured with a raised portion 80 that engages cam follower bearing 76 and causes the respective cam follower 36, 40 to pivot about pivot pin 72.

As each cam follower 36, 40 pivots, a respective form bearing 74 moves toward and away from communication axis 18. Each form bearing 74 engages a respective reset form punch (not shown) or trip form punch (not shown) to engage or disengage the punch from a disk of snap-disk material.

Reset and trip stepper motors 20, 22, respectively, each include a driver adjust pulley 84, a driven adjust pulley 86 and a timing belt 88 connecting driver adjust pulley 84 and driven adjust pulley 86. Each driven adjust pulley 86 engages a lead screw 90 which varies the lateral position of a form stroke adjust slide 92 connected to each of reset form cam follower 36 and trip form cam follower 40. Thus, reset stepper motor 20 and trip stepper motor 22 are used to turn lead screws 90 and adjust the position of reset form cam follower 36 and trip form cam follower 40, respectively, relative to reset form cam 34 and trip form cam 38. The magnitude of the pivoting movement of reset cam follower 36 and trip cam follower 40, and hence the movement of form bearings 74, increases as the respective cam follower bearings

76 are positioned closer to reset form cam 34 and trip form cam 38. As the force applied to the snap-disks is directly related to the distance traveled by form bearings 74, stepper motors 20, 22 can be used to adjust the applied force in form station 12 to improve the acceptable pass yield of snap-disks upon initial formation. Each stepper motor 20, 22 provides two hundred stop points per revolution to reset form portion 24 and trip form portion 26, thereby allowing very fine incremental adjustments in position of cam followers 36, 40, and hence allowing very fine incremental adjustments in applied force to the snap-disks.

Figure 3 is a partial cross-sectional view and side plan view of form station 12 including a spring loaded reset form tooling plate 1 10 slidingly mounted on cylinders 112 for reciprocating movement toward and away from communication axis 18. Reset tool housing 68 is connected to reset form tooling plate 1 10, and includes a spacer 1 14 communicating with form bearing 74 of reset cam follower 36 to actuate reset form punch 116 against the bias of a return spring 118. A nose tool 120 surrounds reset form punch 116 to guide reset form punch 1 16 along an actuation axis

122.

Trip form portion 26 includes a trip form tooling plate 124 slidingly mounted on cylinders 126 for reciprocating movement toward and away from communication axis 18. Trip tool housing 70 is connected to trip form tooling plate 124, and includes a spacer 128 communicating with form bearing 74 of trip cam follower 40 to actuate trip form punch 130 against the bias of a return spring 132. A form support 134 surrounds trip form punch 130 and guides trip form punch 130 along actuation axis 122.

A dial fixture 136 is supported by form support 134 and is aligned with communication axis 18. A pocket (not shown) in dial fixture 136 supports a circumference of a disk blank of snap-disk material (not shown) that is inserted into dial fixture 136 and positioned so that the center of the disk blank is substantially aligned with actuation axis 122. Reset form punch 116 and trip form punch 130 are positioned a first distance from the disk and a second distance from the disk, respectively, to form the reset and trip sides of the snap-disk with respective forces.

Reset drive shaft assembly 62 rotates reset cam shaft 60 on reset form portion 24, and a belt 138 transfers rotational motion of reset cam shaft 60 to trip cam shaft 66. Thus, as reset cam shaft 60 is rotated, a form main cam 140 synchronously rotates with reset form cam 34 to provide a probing action of reset form punch 1 16 into a blank disk of snap-disk material, and a trip main cam 142 synchronously rotates with trip form cam 38 to provide a probing action of trip form punch 130 into the disk blank. As shown in Figure 2, cam surface raised portions 80 of reset form cam 34 and trip form cam 38 are rotationally out-of-phase with one another so that the reset probing action and trip probing action are performed sequentially and do not interfere with one another.

Once a disk of snap-disk material is properly aligned with actuation axis 122 within dial fixture 136, reset form cam 34 is rotated into engagement with reset form follower bearing 76, causing reset cam follower 36 to pivot about pivot pin

72 (shown in Figure 2). As reset form cam follower 36 pivots, reset form bearing 74 pushes spacer 1 14 and form punch 1 16 toward communication axis 18. Also, form main cam 140 engages a form tooling plate bearing 144 and moves reset form tooling plate 110 toward communication axis 18. Reset form punch 116 is therefore engaged with the reset side of the disk blank, stretching the disk material into plastic deformation and forming the reset side of a snap-disk. The distance traveled by reset form punch 1 16 is adjustable by moving reset form portion 24 form adjust slide 92 with reset stepper motor 20 (shown in Figure 2). The position of reset form adjust slide 92 determines the position of cam follower bearing 76 of reset cam follower 36 relative to reset form cam 34. Hence, the degree of pivoting of reset cam follower 36 is adjustable by adjusting the position of reset form adjust slide 92, which, in turn, varies the distance that form bearing 74 moves form punch 1 16, and consequently varies the forces developed in the disk by reset form punch 116.

As reset cam shaft 60 continues to rotate, form bearing 74 of reset cam follower 36 and main cam form tooling plate bearing 144 are disengaged from the respective cam surface raised portions of reset form cam 38 and form main cam 140, and the spring loaded reset form tooling plate 110 and form punch 1 16 are returned to a position wherein reset form punch 1 16 does not contact the snap disk and sufficient clearance is provided to allow formation of the trip side of the disk. Once form bearing 74 of reset cam follower 36 is disengaged from reset form cam 38, trip form cam 34 raised surface portion 80 (shown in Figure 2) engages cam follower bearing 76 of trip form cam follower 36 and causes trip form cam follower 36 to pivot about pivot pin 72 (shown in Figure 2). As trip form cam 34 raised surface portion 80 pivots trip cam follower 40, trip form bearing 74 pushes spacer 128 and trip form punch 130 toward communication axis 18. Also, trip form main cam 142 engages a trip form tooling plate bearing 146 and moves trip form tooling plate 124 toward communication axis 18. Trip punch 130 is therefore engaged with the trip side of the disk blank, stretching the disk material into plastic deformation and forming the trip side of a snap-disk. The distance traveled by trip form punch 130 is adjustable by moving trip form portion 26 form adjust slide 92 with trip stepper motor 22. The position of trip form adjust slide 92 determines the position of cam follower bearing 76 of trip form cam follower 40 relative to trip form cam 38. Hence, the degree of pivoting of trip form cam follower 40 is adjustable by moving trip form adjust slide 92, which, in turn, varies the distance that form bearing

74 of trip form cam follower 40 moves trip form punch 130, and consequently varies the forces developed in the disk by trip form punch 130.

As trip cam shaft 66 continues to rotate, form bearing 74 of trip form cam follower 40 and trip form tooling plate bearing 146 are disengaged from the respective cam surface raised portions of trip form cam 38 and trip main form cam

140, and the spring loaded trip tooling plate 124 and trip form punch 130 are returned to a position wherein trip form punch 130 does not contact the snap disk. The formation process in form station 12 may then be repeated or the dial fixture may be indexed to exercise station 14 (shown in Figure 1).

Figure 4 is front plan view of exercise station 14, including reset portion 28 and trip portion 30 similar in structure and operation to form station 12, but without the adjustability of stepper motors 20, 22 (shown in Figures 1 and 2) and with different cam surface configurations. Reset exercise cam 42 is attached to a reset exercise cam shaft 160 that is rotationally driven by an exercise drive shaft assembly 162. Reset exercise drive shaft assembly 162 communicates with a trip exercise shaft assembly 164 via a belt (not shown) and therefore drives a trip exercise cam shaft 166 attached to trip exercise cam 44. An exercise reset cam follower 168 contacts reset exercise cam 42 to reciprocally move a reset exercise punch (not shown in Figure 4) and an exercise trip cam follower 170 contacts trip exercise cam 44 to reciprocally move a trip exercise punch (not shown in Figure 4) inside a respective reset exercise tool housing 172 and trip exercise tool housing 174, respectively.

Exercise reset and trip form cam followers 168, 170 each include a pivot pin 176, a form bearing 178, and a cam follower bearing 180. Each cam follower bearing 180 contacts a respective cam surface 182 of reset exercise cam 42 and trip exercise cam 44. Each cam surface 182 is configured with a raised portion 184 that engages cam follower bearing 180 and causes each respective cam follower 168, 170 to pivot about pivot pin 176. More specifically, each cam surface raised portion 184 includes a rising profile 186 and a falling profile 188 that produces a pulsating reset force or pulsating trip force for exercising snap disks. As each cam follower 168, 170 pivots, a respective form bearing 178 moves toward and away from communication axis 18. Form bearings 178 engage a respective reset or trip exercise punch (not shown) to engage or disengage the respective punch from a snap-disk, as substantially described above with respect to Figure 3. Once formed snap disks have been sufficiently exercised, the snap disks are indexed to feedback station 16 (shown in Figure 1).

Figure 5 is a front plan view of feedback station 16 including a reset portion 30 and a trip portion 32. Reset portion 30 includes a feedback drive assembly 210 for driving a reset cam shaft 212 and an attached feedback cam 214. A feedback cam follower 216 is attached to a spring-loaded feedback tooling plate 218 and includes a feedback follower bearing 220 that contacts a cam surface 222 of feedback cam 214, and a force transducer unit 224. A probe 226 extends from force transducer unit 214 along a probe axis 228.

Feedback trip portion 32 includes a trip feedback shaft 230 and an attached hub 232 that are rotationally driven by feedback drive assembly 210 and a belt (not shown in Figure 5). A spring loaded trip feedback tooling plate 234 supports a feedback support 236 that facilitates force measurement with probe 226.

Figure 6 is a side plan view of feedback station 16, illustrating a feedback reset main cam 250 that is attached to reset cam shaft 212 and rotates synchronously with feedback cam 214. Feedback main cam 214 engages a feedback form bearing 252 and reciprocally moves feedback reset tooling plate 218 toward and away from communication axis 18. Feedback cam 214 contacts a cam follower bearing 220 of feedback cam follower 216 and moves probe 226 toward and away from communication axis 18. A feedback trip main cam 256 is attached to a feedback trip shaft 258 and driven by feedback drive assembly 210 and belt 260 to move feedback trip tooling plate 234 relative to communication axis 18. In one embodiment, feedback trip main cam 256 is circular so that feedback trip tooling plate 234 does not move relative to communication axis 18.

Dial fixture 136 is indexed to feedback station 16 with a formed and exercised snap-disk contained therein. Feedback reset main cam 250 and feedback cam 214 engage respective cam form bearings 220, 252 and move reset feedback tooling plate 254 and probe 226 closer to communication axis 18. Probe 226 contacts reset side of the snap-disk and exerts force against it as probe 226 is moved toward communication axis 18 until the snap-disk snaps or trips into its alternative configuration. The peak force that caused the disk to trip is electronically recorded for each disk passing through feedback station 16, and a mean or average peak trip force is calculated over a specified number of disks, such as, for example, five disks. As feedback cam 214 continues to rotate, the applied force of probe 226 decreases, and the disk eventually resets. A peak reset force is also electronically recorded for each disk passing through feedback station 16, and a mean or average peak reset force is calculated over a specified number of disks.

Using a controller (not shown), the mean trip force and mean reset force are then compared with respective target values loaded into a controller memory (not shown), and analyzed using known statistical process control methods. If corrective action is required, the controller is coupled to stepper motors 20, 22 (shown in Figures 1 and 2) for independent, real time adjustment of the applied reset and trip forces in form station 12 to correct deficiencies in the formation of the disks.

For example, if a given disk snaps too soon, i.e., at lesser force than desired, this indicates that the snap-disks are being stretched too much in form station

12 (shown in Figures 1- 3), which can be cured by sending a signal to one or both of stepper motors 20, 22 (shown in Figures 1 and 2) to move the respective form adjust slide 92 (shown in Figures 2 and 3) of reset form punch 116 and/or trip form punch 130 (shown in Figure 3) to reduce the distance traveled by reset form punch 1 16 and/or trip form punch 130 during formation of the snap-disks. Therefore, successive disks will be stretched to a lesser extent and exhibit a greater resilience. Similarly, stepper motors 20, 22 can be used to increase the distance traveled by reset form punch 1 16 and or and/or trip form punch 130 when a mean snap force is higher than desired. In this fashion, snap-disks can be formed within desired trip force and reset force tolerances.

Stepper motors 20, 22 could be controlled independently or identically. Identical control of both motors 20, 22 is sufficient in cases where the difference in reset formation force and trip formation force is relatively small, as the same adjustment of both formation forces will yield approximately the same increase or decrease in resultant actual snap forces. With larger differentials in applied reset and trip formation forces, however, independent feedback and control of both reset and trip sides of the snap-disks is necessary.

After passing through feedback station 16, the snap-disks are placed into one of three storage bins (not shown). An acceptable first pass bin collects snap- disks within specified tolerances. A discard bin collects unusable snap-disks that have been stretched too much and therefore snap too easily. A reform bin collects snap- disks that have not been stretched enough and that may be reformed in form station.

By using instantaneous feedback control, acceptable yield pass rates upon initial formation of snap-disks are dramatically improved. Pass rates of 90% or more may be realized, thereby significantly increasing manufacturing efficiency and reducing material costs by minimizing scrap. Using the fully automated process described, the labor burden may also be reduced. Thus, the costs of production of snap-disks are reduced.

Figures 7-10 are flowcharts of a form station setup algorithm 300 for controlling form station 12 (shown in Figures 1-3), and more specifically for controlling stepper motors 20, 22 (shown in Figures 1 and 2) to generate required forces for forming snap-disks within a specified force tolerance. In the embodiment described below, the snap-disks are heat treated after formation according to known techniques. It is appreciated however, that one of ordinary skill in the art could easily modify setup algorithm 300 to obtain the benefits of the invention for non-heat treated snap-disks.

As will be seen below in detail, algorithm 300 generally includes a first sub-algorithm to establish a lower bound of possible positions of stepper motors 20,

22, a second sub-algorithm to establish an upper bound of possible positions of stepper motors 20, 22, a third sub-algorithm to generate an adjusted position of each stepper motor between the respective upper and lower bounds, and a fourth sub- algorithm to further narrow the potential range of step motor settings between the adjusted position and one of the upper and lower bounds. Thus, a series of stepper motor position estimates are made and used to form snap-disks that are tested, and based upon the test results the estimates are revised and the desired positions of the stepper motors are found by an iterative process. Implemented by control logic, algorithm 300 employs adaptive learning to efficiently drive the stepper motors toward the desired positions to form snap-disks within specified parameters, thereby eliminating costly and time consuming trial and error setup methods.

Referring first to Figure 7, a plurality of operator selected inputs 302 are communicated to a controller (not shown) including a processor and a memory.

Inputs 302 include a nominal trip force value { T f_orce) 304 for snap-disks, a nominal reset force value { R_tnp ) 306 for the snap-disks, expected changes { ΔT_ht , R^ ) 308, 310 in the input trip and reset force values 304, 306, respectively, after heat treating of the snap-disks, and allowable trip force error { Tε) and allowable reset force error { Rε ) inputs 312.

Using force inputs 304, 308, the processor calculates 314 a target trip force {T_tara ) according to the following relationship:

^Tt arg = ^T force ^~ ^^Tht ( 1 )^•

Likewise, the processor calculates 316 a target reset trip force {R_{t aιg} ) according to the relationship:

^Rtaτg = ^R force ^~ ΔRfιt (²)-

To begin formation of snap-disks, the controller signals form station 12 to set 318 to a "home" position wherein stepper motors 20, 22 are in a designated state or position. Modification of the positions of stepper motors 20, 22 are monitored by the controller in relation to the home position according to known techniques.

A first sub-algorithm 320 is executed to set stepper motors 20, 22 to position cam followers 40, 36, (shown in Figure 2) respectively, for a stroke to form snap-disks having a trip force less than _arg (Eq. 1) and a reset force less than R_taTg

(Eq. 2). Sub-algorithm 320 begins by indexing 322 dial fixture 136 and determining 324 whether a formed setup snap-disk is located at test station 16 (shown in Figures 1, 5 and 6). If a formed snap-disk is not located at test station 16, dial fixture 136 is indexed 322 again.

When a formed snap-disk is located at test station 16, actual trip and reset forces T t_orce and R f_orceaιe measured 326 as described above in relation to Figures 5 and 6. A position of stepper motor 22 is then assigned 328 based upon a change trip force value AT f_orce defined by the following relationship:

force ~ * force ^~ * t arg v^

A new position T_pos for stepper motor 22 can then be determined to generate the T f_orce by advancing or retarding the motor by a number of steps from the home position.

Likewise, a position of stepper motor 20 is then assigned 330 based upon a changed reset force value AR f_orce defined by the following relationship:

R force ^~ R force ^~ °/arg (

A new position R_pos for stepper motor 20 can then be determined to generate the AR f_orce by advancing or retarding the motor by a number of steps from the home position.

Once positions of stepper motors 22, 20 have been assigned 328, 330, respectively, the controller processor determines 332 whether the sum of AT f_orce and the allowable trip force error Tε is greater than zero and also whether the sum of AR f_orce and the allowable reset force error Rε is greater than zero. In other words, it is determined whether both Δ J 'f_orce and AR f_orce are sufficiently positive so that both stepper motors 22, 20 are assigned 328, 330 respectively a number of steps so as to increase the force generated by stepper motors 22, 20 at the assigned step positions to form snap-disks having actual trip and reset forces nearer to the nominal trip and reset forces inputs 304, 306.

If either of the sum of AT f_orce and the allowable trip force error Tε or the sum of AR f_orce and the allowable trip force error Rε is less than zero, the processor checks 334 whether a maximum number of iterations of sub-algorithm 320 have been executed. If the maximum number of iterations has not been executed, i.e., if fewer than the maximum number of iterations has been executed, form station stepper motors 22, 20 are adjusted 336 so that form station punches 1 16, 132 (shown in Figure 3) are located a new distance from a snap-disk located in dial fixture 136 (shown in Figure 3) according to the new stepper motor positions T_pos and R_pos determined in steps 328 and 330 (described above). Dial fixture 136 is then indexed 322 and sub-algorithm 320 repeated.

If the maximum number of iterations has been executed, the process terminates 338, and, in one embodiment, the controller prompts an error message, indicator or flag to prompt an operator of a fault condition in which stepper motors 22, 20 were not properly calibrated to form snap-disks according to the desired inputs 304, 306, 308, 310, and 312.

If the sum of A f_orce and the allowable trip force error Tε is greater than zero and the sum of AR f_orce and the allowable reset force error Rε is greater than zero, then T _pos , T_jo- _rce, R_pos , and Rf_orce is saved 340 in the controller memory as T_x\ , T_\ , R_x\ and R_\ , respectively, for future use described below.

First sub-algorithm 320 therefore establishes, through repeated attempts, if necessary, a lower bound of stepper motor positions to form snap-disks with desired properties.

Referring now to Figure 8, after sub-algorithm 320 parameters are saved 340 (see Figure 7), a second sub-algorithm 342 is executed to set stepper motors 20, 22 to position cam followers 40, 36, (shown in Figure 2) respectively, for a stroke to form to form snap-disks having a trip force greater than T_tzxg (Eq. 1) and a reset force greater than R_{t 3Sg} (Eq. 2). Sub-algorithm 342 begins by setting stepper motors 22, 20 to their home positions plus a known machine constant (dependent upon form punch dimensions) so as to position stepper motors to generate increased force via cam followers 40, 36 (shown in Figures 1 and 2), indexing 344 dial fixture 136 and determining 346 whether a formed setup snap-disk is located at test station 16

(shown in Figures 1, 5 and 6). If a formed snap-disk is not located at test station 16, dial fixture 136 is indexed 344 again.

When a formed snap-disk is located at test station 16, actual trip and reset forces Tf_orce and Rf_orce are measured 348 as described above in relation to Figures 5 and 6. A position of stepper motor 22 is then assigned 350 based upon a change trip force value AT f_orce defined by Equation 3 above. A new position T_pos for stepper motor 22 can then be determined to generate the ATf_orce by advancing or retarding the motor by a number of steps from the home position. Likewise, a position of stepper motor 20 is assigned 352 based upon a changed reset force value AR f_orce defined by Equation 4 above. A new position R_pos for stepper motor 20 can then be determined to generate the AR f_orce by advancing or retarding the motor by a number of steps from the home position.

Once positions of stepper motors 22, 20 have been assigned 350, 352, respectively, the controller determines 354 whether the sum of ATf_orceand the allowable trip force error Tε is less than zero and also whether the sum of AR f_orce and the allowable trip force error Rε is less than zero. In other words, it is determined whether both AT ' f_orce and AR f_orce are sufficiently negative so that both stepper motors 22, 20 are assigned 350, 352 respectively a number of steps so as to decrease the force generated by stepper motors 22, 20 at the assigned step positions to form snap-disks having actual trip and reset forces nearer to the nominal trip and reset forces inputs 304, 306.

If either of the sum of AT _orce and the allowable trip force error Tε or the sum of AR_jorce and the allowable trip force error Rε is greater than zero, the processor checks 356 whether a maximum number of iterations of sub-algorithm 342 have been executed. If the maximum number of iterations has not been executed, i.e., if fewer than the maximum number of iterations has been executed, form station stepper motors 22, 20 are adjusted 358 to position cam followers 40, 36, (shown in Figure 2) respectively, for a stroke to from a snap-disk located in dial fixture 136

(shown in Figure 3) according to the new stepper motor positions T_pos and R _pos determined in steps 350 and 352 (described above) .Dial fixture 136 is then indexed

322 again and sub-algorithm 342 repeated. If the maximum number of iterations has been executed, the process terminates 360, and, in one embodiment, the controller prompts an error message, indicator or flag to inform an operator of or otherwise indicate a fault condition in which stepper motors 22, 20 were not properly calibrated to form snap-disks according to the desired inputs 304, 306, 308, 310, and 312 (shown in Figure 7).

If the sum of AT f_orce and the allowable trip force error Tε is less than zero and the sum of AR f_orceana the allowable trip force error Rε is less than zero, then T _pos is saved 362 in the controller memory as T_x2, Tf_orce is saved 362 in the controller memory as T₂ , R_pos is saved 362 into controller memory as R_x2 and

R f_orce is saved 362 in the controller memory as R₂ for future use described below. Second sub-algorithm 342 therefore establishes, through repeated attempts, if necessary, an upper bound of stepper motor positions to form snap-disks with desired properties.

While in the illustrated embodiment, the lower bound of stepper motor positions is first determined with sub-algorithm 320 (shown in Figure 7) and then the upper bound is determined with sub-algorithm 342, in an alternative embodiment the order of sub-algorithms 320, 342 could be reversed so that the upper bound is first established and the lower bound is then established without departing from the scope of the present invention.

After sub-algorithm 342 parameters are saved 362 (see Figure 8), it is determined 364 whether ATf_orceand AR_jo- _rceaxQ less than the respective allowable error Tε and Rε inputs 312 (shown in Figure 7). If both AT f_orce and AR t_orce are less than the respective allowable errors Tε and Rε inputs 312, setup algorithm 300 completes 366 and stepper motors 22, 20 are calibrated for forming snap-disks with the desired trip and reset forces within the specified tolerances.

If either of AT f_orce or ARf_orce are greater than the respective allowable error Tε and Rε inputs 312 (shown in Figure 7), adjustment is made according to a third sub-algorithm 367 as illustrated in Figure 9 to establish an intermediate stepper motor position bound for each stepper motor 22, 20 for location the desired stepper motor positions T_pos .and R _pos as described below.

Referring now to Figure 9, sub-algorithm 367 begins by determining 368 whether ATf_orce ^ιs greater than the allowable trip force error Tε . If ATf_orce is less than the allowable trip force error Tε, then T_pos is set 370 equal to T_x2. If ATf_orce ^ιs greater than the allowable trip force error Tε, then a new T_pos is calculated 372 according to the parameters determined by sub-algorithm 320 (shown in Figure 7) and sub-algorithm 342 (shown in Figure 8). Specifically, the new position T_pos for stepper motor 22 is calculated 372 according to the following relationship:

Likewise it is determined 374 whether ARf_orceis greater than the allowable reset force error Rε . If AR f_orc ce_e iis less than the allowable reset force error Rε , then R _pos is set 376 equal to R_x2. If AR f_orce is greater than the allowable trip force error Rε , then a new R_pos is calculated 378 according to the positions determined by sub-algorithm 320 (shown in Figure 7) and sub-algorithm 342 (shown in Figure 8). Specifically, the new position R_pos for stepper motor 22 is calculated 372 according to the following relationship:

Once T_pos ^an<^ R_pos ^{are set} 370, 376 and/or calculated 372, 378, respectively, stepper motors 22, 20 are set 380 to the corresponding steps, and dial fixture 136 is indexed 382. It is evident from Equations 5 and 6 that the new stepper motor positions are located in between the positions determined by first sub-algorithm

320 and second sub-algorithm 342. The processor then determines 384 whether a formed setup snap-disk is located at test station 16 (shown in Figures 1, 5 and 6). If a formed snap-disk is not located at test station 16, dial fixture 136 is indexed 384 again.

When a formed snap-disk is located at test station 16, actual trip and reset forces Tf_orce and Rf_orce are measured 388 as described above in relation to Figures 5 and 6. ATf_orce and AR f_orce are then re-calculated using Equation 3 and Equation 4, and it is again determined 390 whether Tfo_rce and Rf_orce are less than the respective allowable error Tε and Rε inputs 312 (shown in Figure 7). If both T f_or_ce ^an<^ Rfor_ce ^are '^{ess man} the respective allowable errors Tε and Rε , sub- algorithm 367 terminates 392, algorithm 300 is complete, and stepper motors 20, 22 are setup to form snap-disks within the allowable error inputs.

If Tf_orce and R fo_rCe ^are greater than the respective allowable errors

Tε and Rε , a fourth sub-algorithm 394 is executed, as illustrated in Figure 10, to further narrow the range of possible stepper motor positions toward the desired position while at the same time compensating for interaction between the trip forces and the reset forces of the snap-disks.

Referring now to Figure 10, the controller processor determines 396 whether ATf_orce is less than Tε . If AT for_ce ^1S greater than Tε, the processor determines 398 whether

is defined by the difference between the measured trip force Tf_orce when stepper motor 22 is operated at position T_x\ (determined by first sub-algorithm 320 and saved at step 340 (shown in Figure 7)) and the target trip force T_{t aτg} calculated at step 314. By determining 398 whether the product of AT^xAT 'f_orce is a positive number or a negative number, it may be determined whether the next estimate for the desired position of stepper motor 22 to produce acceptable snap-disks lies between the current position and T_x\ or between the current position and T_x2.

If Δ7_] x AT fo_rCe is less than zero, then T_x is set 400 equal to the current T_pos determined in step 380 of third sub-algorithm 367 (shown in Figures 8 and 9), and other parameters remain unchanged. If AT_] xATf_orce is greater than zero, then T_x\ is set 402 equal to the current T_pos determined in step 380 of third sub- algorithm 367 (shown in Figures 8 and 9), and other parameters remain unchanged. A range of possible solutions is then reduced from all values between T_x\ and T_x2 to a smaller range between the current position T_pos of stepper motor 22 and either T_x\ or

Using the set values from either step 400 or 402, whichever is applicable, an adjusted position T_pos for stepper motor 22 is then calculated 404 according to Equation 5 above.

Once the adjusted position T_pos is calculated 404, or if the processor determines 396 that ATf_orce is less than Tε, then the processor determines 406 whether AR f_orce is less than Rε . If AR fo_rCe ^ιs greater than Rε , the processor determines 408 whether AR_\xAR f_orc_e i l^{ess man} zero wherein AR_\ is defined by the difference between the measured trip force Rf_orce when stepper motor 22 is operated at position R_x\ (determined by first sub-algorithm 320 and saved at step 340 (shown in Figure 7)) and the target trip force R_{t arg} calculated at step 314. By determining 398 whether the product of AR^xAR f_orce is a positive number or a negative number, it may be determined whether the desired position of stepper motor 22 to produce acceptable snap-disks lies between the current position and R_x\ or between the current position and R_x2.

If AR_\xAR force ^lS less than zero, then R_x2 is set 410 equal to the current R_pos determined in step 380 of third sub-algorithm 364 (shown in Figures 8 and 9), and other parameters remain unchanged. If AR_\xAR fo_rce is determined 408 to be greater than zero, then R_x\ is set 412 equal to the current R_pos determined in step 380 of third sub-algorithm 364 (shown in Figures 8 and 9), and other parameters remain unchanged.

Using the set values from either step 410 or 412, whichever is applicable, an adjusted position R_pos for stepper motor 22 is then calculated 414 according to Equation 6 above.

Because changes in one of the trip and reset forces typically affects the other, if the processor determines 406 that AR fo_rce is less than Rε , it again checks 416 whether AT f_orce is less than Tε input of step 312 (shown in Figure 7). If AT for_ce is less than Tε, algorithm 300 is completed 418. If ATf_orce is greater than Tε the processor checks 420 whether a maximum number of iterations of sub- algorithm 394 have been executed.

If the maximum number of iterations have been executed, the process terminates 422, algorithm 300 is complete, and, in one embodiment, the controller prompts an error message, indicator or flag to inform an operator of or otherwise indicate a fault condition in which stepper motors 22, 20 were not properly calibrated to form snap-disks according to the desired inputs 304, 306, 308, 310, and 312 (shown in Figure 7)

If the maximum number of iterations has not been executed, i.e., if fewer than the maximum number of iterations has been executed, form station stepper motors 22, 20 are adjusted 424 to position cam followers 40, 36, (shown in Figure 2) respectively, for a stroke corresponding to the current stepper motor positions T_pos and R_pos determined in sub-algorithm 394 (described above)

A setup snap-disk is then formed using the new stepper motor positions, and the processor once again determines 426 whether the setup snap-disk is loaded onto dial fixture 136 at test station 16, and, if not, dial fixture 136 is indexed

428 until the formed snap-disk is loaded at test station 16. Once the formed snap- disk is loaded at test station 16, actual trip and reset forces Tf_orce and Rf_orce are measured 430 as described above in relation to Figures 5 and 6 and ATf_orce and R for_ce re calculated 432 according to Equations 3 and 4 above. The calculated values are used to repeat sub-algorithm 394 until algorithm 300 is successfully completed 418 or terminated 422. Thus, algorithm 300 estimates and re-estimates stepper motor positions to form progressively smaller ranges of potential positions that capture the desired stepper motor positions. Algorithm 300 executes in real time with feedback from newly formed setup snap-disks while compensating for interaction between the reset and trip forces until stepper motor positions are determined that will form snap-disks to specified parameters. Costly and time consuming trial and error methods and replacement of punches is therefore replaced with efficient, logic driven controls.

Figure 1 1 illustrates a form station adjustment algorithm 500 for controlling form station 12 (shown in Figures 2 and 3) to compensate for incoming material variations in snap-disk blanks after setup algorithm 300 is completed.

Algorithm 500 begins with the controller reading 502 a position of trip stepper motor 22 and reset stepper motor 20, and the controller assigning 504 appropriate positions of trip and reset motors 22, 20, respectively, for each snap-disk forming nest . Each nest /^' includes a selected number of snap-disks to provide a representative sample of formed snap-disk characteristics as the snap-disks are formed, and in various embodiments the nests include as few as one to a large number of snap-disks Assigned stepper motor positions are initially determined by algorithm 300 described above. Allowed error limits Tε and Rε are also assigned 506 in accordance with error inputs 312 (shown in Figure 7) of setup algorithm 300. Stepper motors are then set 508 to the assigned positions.

For each forming nest /, actual trip and reset forces T ^' f_orce and R force are measured 510 as described above in relation to Figures 5 and 6 at test station 16 after the snap-disks are formed, and Equations 3 and 4 above are used to calculate 512 AT p₀rc_e and ARf_orCe values, or deviations between the actual measured forces and the target values. Once ATf_orce and ARf_orce are calculated 512, a number of steps, or counts, to adjust respective stepper motors 22, 20 can be determined to generate AT ₀r_Ce and ARf_orce ■ In one embodiment, measured forces Tf_orCe ^an(^ Rfo_rce ^aτe averaged over each forming nest and used to calculate 512 ATf_orce and AR fo_rce values. In an alternative embodiment, ATf_orce and AR fo_rce values are averaged over each forming nest and used to determine an averaged number of steps or counts to adjust respective stepper motors 22, 20. Once AT_forCe and ARf_orCe ^are known, a series of comparisons are made to determine whether the snap-disks in nest / are within the allowed error tolerances Tε and Rε .

First, it is determined 514 whether AT_Force is less than -Tε . If so, T_pos (0 is ^reset 516 according to the following relationship:

^Tpos (') = ^Tpos ^{~ Ad}J Counts (7) wherein Adj Counts is the number of steps or counts derived from calculation 512 of

^" Force ^•

If AT _orce is determined 514 to be greater than - Tε , the controller then determines 518 whether ATf_orce is greater than Tε . If so, T_pos(i) is reset 516 according to the following relationship:

^Tpos (?) = ^Tpos + ^AdJ Counts (8) wherein Adj Counts is the number of steps or counts derived from calculation 512 of

A * Force ^• Once T_pos(i) is reset according to steps 516 or 520, or if ATf_orce ^x determined 518 to be less than Tε, the controller determines 522 whether ARf_orCe i less than - Rε . If so, R_pos (j) is reset 524 according to the following relationship:

^R pos iⁱ)= ^R pos ^{~ Ad}J Counts (9) wherein Adj Counts is the number of steps or counts derived from calculation 512 of ARforce -

If AR_force is determined 522 to be greater than - Rε , the controller then determines 526 whether ARf_orce is greater than Rε . If so, R_pos (i) is reset 526 according to the following relationship:

^R ^p pooss (V0l = ^{R •}"^■ ppooss + ^AdJ Counts { 10)

wherein Adj Counts is the number of steps or counts derived from calculation 512 of R Force ^■ Once R_po_s (0 is reset according to steps 524 or 528, or if AR_force is determined 518 to be less than Rε , dial fixture 136 is indexed 530, stepper motors are set 508 in the applicable positions and algorithm 500 is repeated 530.

Material variations are therefore detected as the snap-disks are tested and found to be outside the allowed error Tε and Rε , and the stepper motors are adjusted accordingly in real time as the next nest is formed to compensate for incoming material changes in real time. The smaller the nest size, the more sensitive the system is to variation of material and fluctuation in performance of snap-disks as they are tested. With appropriate selection of nest size, scrapped snap-disks due to changing properties of incoming snap-disk material can be reduced dramatically, and costly and time consuming trial and error methods to consistently produce acceptable snap-disks are eliminated.

While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.

Claims

WHAT IS CLAIMED IS:

1. A method for forming a plurality of bistable snap-disks having two alternative configurations from a plurality of double sided disk blanks, said method comprising:

stretching at least one side of each of the disks into plastic deformation with at least one of a reset form force and a trip form force, thereby forming at least one of a reset side and a trip side into the disk;

sequentially monitoring a peak force for snapping the at least one of a reset side and trip side of at least some of the disks after they are formed; and

adjusting at least one of the reset form force and the reset trip force in response to the monitored peak force to change the required peak snap force of successively formed disks and bring successive disks within desired peak snap force tolerances.

2. A method in accordance with Claim 1 wherein the step of stretching the disks comprises:

engaging a center of each disk with a probe; and

moving the probe a specified distance.

3. A method in accordance with Claim 1 wherein said method further comprises the step of exercising the at least one of a reset side and a trip side of each of the disks with at least one of a reset exercise force and trip exercise force.

4. A method in accordance with Claim 1 wherein said step of monitoring the required peak force comprises:

applying a force to the at least one of a reset side and a trip side of a batch of disks until each disc snaps into the alternative configuration;

measuring the force as it is applied; and

recording the peak snap force.

5. A method in accordance with Claim 4 wherein said step of adjusting at least one of reset form force and trip form force comprises:

calculating a mean peak snap force for a specified number of disks;

comparing the mean peak snap force to desired values; and

changing at least one of the reset form force and the trip form force to correct a deviation between desired values and calculated values.

6. A method in accordance with Claim 5 wherein said step of changing the at least one of the reset form force and the trip form force comprises incrementally increasing or decreasing the at least one of the reset form force and the trip form force.

7. A method in accordance with Claim 5 wherein the step of changing at least one of the reset form force and the trip form force comprises changing both reset form force and trip form force by an equal amount.

8. A method in accordance with Claim 1 further comprising the step of sorting the disks in response to the monitored peak force.

9. A method in accordance with Claim 1 wherein said steps of stretching, monitoring, and adjusting occur contemporaneously.

10. A method for forming a plurality of bistable snap-disks in a snap- disk form assembly, the assembly including a form station and a feedback station coupled to the form station, said method comprising the steps of:

forming reset and trip sides of snap-disks with the form station;

monitoring a peak snap force for at least one side of the disks with the feedback station; and

adjusting in real time the operation of the form station in response to the monitoring of peak snap force to bring disks formed in the form station into compliance with predetermined peak snap force values.

11. A method in accordance with Claim 10 wherein the feedback station includes a probe and a force transducer, said step of monitoring comprises:

applying a force to a snap-disk with the probe until the snap-disk snaps; and measuring a peak force causing the disk to snap with the force transducer.

12. A method in accordance with Claim 11 wherein the feedback station further includes a controller having a memory, said step of monitoring further comprising the steps of:

storing a measured peak force value of each disk after it is formed;

calculating a mean peak force value for a specified number of disks with the controller; and

analyzing the mean peak force value.

13. A method in accordance with claim 12 wherein the step of analyzing comprises comparing the calculated value to a desired value.

14. A method in accordance with Claim 10 wherein the form station includes a reset form punch engaging a reset side of a disk and stretching the reset side of the disk for a reset distance to form the reset side of the disk and a trip form punch to engage a trip side of a disk and stretching the trip side a second distance to form the trip side of a snap-disk, said step of adjusting the operation of the form station comprising adjusting at least one of the first distance and the second distance.

15. A method in accordance with Claim 10 wherein the assembly further includes an exercise station, said method further comprising the step of exercising the snap-disks with the exercise station.

16. A method in accordance with Claim 10, the assembly further including at least one dial fixture having a pocket, the method further comprising the steps of:

loading a disk into the pocket;

loading the dial fixture into the form station; and

indexing the dial fixture from the form station to the feedback station.

17. A snap-disk formation assembly comprising: a form station comprising a reset form punch and a trip form punch for forming a reset side and a trip side of a snap-disk;

an exercise station aligned with said form station and comprising a reset exercise punch and a trip exercise punch for exercising a snap-disk;

a feedback station aligned with said form station and said feedback station and coupled to said form station, said feedback station including a force transducer for measuring a peak snap force of at least one side of a snap-disk; and

said feedback station communicating with said form station to adjust the operation of said reset form punch and said trip form punch.

18. A snap-disk formation assembly in accordance with Claim 17 wherein said reset form punch and said trip form punch are cam actuated.

19. A snap-disk formation assembly in accordance with Claim 17 wherein said reset exercise punch and said trip exercise punch are cam actuated.

20. A snap-disk formation assembly in accordance with Claim 17 wherein said probe is cam actuated.

21. A snap-disk formation assembly in accordance with Claim 17 wherein said form station comprises a form portion and a trip portion, each of said form portion and trip portion comprising a stepper motor and a form adjust slide, each of said adjust slides coupled to said stepper motors for selectable positioning of each of said form adjust slide to determine a distance traveled by said reset form punch and the trip form punch.

22. A snap-disk formation assembly in accordance with Claim 21 wherein said stepper motors are responsive to said feedback station.

23. A snap-disk formation assembly in accordance with Claim 22 further comprising a communication axis, said reset portion and said trip portion are substantially inversely symmetrical about said communication axis.

24. A snap-disk formation assembly in accordance with Claim 17 wherein said form station comprises at least one cam comprising a first cam surface, said exercise station comprises at least one cam comprising a second cam surface and said feedback station comprises at least one cam comprising a third cam surface, said first, second and third surfaces being unequal.

25. A snap-disk formation assembly in accordance with Claim 17 wherein said exercise portion comprises a reset portion and a trip portion, said assembly further comprising a communication axis, said reset portion and said trip portion substantially inversely symmetrical about said communication axis.

26. A snap-disk formation assembly in accordance with Claim 17 wherein said form station comprises a reset portion and a trip portion, each of said reset and trip portions comprising:

a cam comprising a cam surface, said cam surface comprising a raised portion

a cam follower comprising a cam follower bearing surface and a pivot pin, said cam follower pivoting in response to said raised portion of said cam; and

said reset form punch and said trip punch coupled to said cam follower for reciprocal movement in response to pivoting of said cam follower.

27. A method for controlling an apparatus for forming bistable snap- disks, each snap-disk having a trip side and a reset side, the apparatus including a form station and a test station, the form station including a reciprocating trip form punch operatively coupled to a first stepper motor and a reciprocating reset form punch operatively coupled to a second stepper motor, the trip form punch and reset form punch respectively forming the trip side and reset side of the disk, the forces generated by the trip form punch and reset form punch adjustable by the respective stepper motor, the apparatus further including a controller operatively coupled to the first and second stepper motors, the test station configured for measuring trip and reset forces of the snap-disks after formation, said method comprising the step of:

accepting snap disk formation parameters including a nominal trip force for activating the bistable snap-disks, a nominal reset force for resetting the bistable snap-disks, an allowable nominal trip force error, and an allowable nominal reset force error; determining a desired position of the first and second stepper motors automatically to form snap disks in compliance with the snap disk formation parameters; and

forming snap disks according to the determined positions of the first and second stepper motors.

28. A method in accordance with Claim 27 wherein said step of determining a desired position of the first and second stepper motors comprises the step of executing an adaptive learning algorithm with real time feedback.

29. A method in accordance with Claim 27 further wherein said adaptive learning algorithm comprises the steps of:

establishing an upper bound for the desired position of each of the first stepper motor and the second stepper motor;

establishing a lower bound for the desired position of each of the first stepper motor and the second stepper motor; and

establishing an adjusted position of each of the first stepper motor and the second stepper motor, each adjusted position of the first stepper motor and the second stepper motor located between the respective upper and lower bound.

30. A method in accordance with Claim 29 wherein said step of establishing an adjusted position of the first stepper motor comprises the step of calculating an adjusted position according to the relationship

^where

T_pos is the adjusted position of the first stepper motor;

T_x\ is the position of the first stepper motor at the respective lower bound;

T_\ is the force generated by the first stepper motor at the respective lower bound; T_x is the position of the first stepper motor at the respective upper bound; and

T₂ is the position of the first stepper motor at the respective upper bound.

31. A method in accordance with Claim 29 wherein said step of establishing an adjusted position comprises the step of calculating an adjusted position according to the relationship

R ^here

R_pos is the adjusted position of the second stepper motor;

R_x\ is the position of the second stepper motor at the respective lower bound;

R_\ is the force generated by the second stepper motor at the respective lower bound;

R_x2 is the position of the second stepper motor at the respective upper bound; and

R is the position of the second stepper motor at the respective upper bound.

32. A method in accordance with Claim 29 further comprising the step of adjusting the position of each of the first stepper motor and the second stepper motor to a position between the adjusted position and one of the upper bound and lower bound.

33. A method in accordance with Claim 32 further comprising the step of readjusting the position of each of the first stepper motor and the second stepper motor to a position between the adjusted position and one of the upper bound and lower bound until the desired position is found.

34. A method in accordance with Claim 27 further comprising the step of calculating a target value for the force generated by the first stepper motor and the second stepper motor to form snap-disks within the accepted parameters.

35. A method in accordance with Claim 34 further comprising the steps of:

forming a snap-disk;

measuring the trip force to activate the disk; and

calculating a delta trip force to reach the target trip force value, the delta force determined by the relationship

ATforce = ^T force ^{~ T}t arg ^where

AT_fo_rc_e is the delta trip force;

T is the measured trip force; and

_/ ar_g is the desired target value.

36. A method in accordance with claim 35 further comprising the step of assigning an adjusted position of the first stepper motor based upon the calculated delta trip force.

37. A method in accordance with Claim 34 further comprising the steps of:

forming a snap-disk;

measuring the reset force to deactivate the disk; and

calculating a delta reset force to reach the target reset force value, the delta force determined by the relationship

F force = ^F force ^{~ F}targ ^here

AF ^'for_ce i the delta reset force; Rf is the measured reset force; and

R_{t aτg} is the desired target value.

38. A method in accordance with claim 35 further comprising the step of assigning an adjusted position of the first stepper motor based upon the calculated delta trip force.

39. A method in accordance with Claim 27 further comprising the step of adjusting the position of the first stepper motor and the second stepper motor automatically to compensate for snap-disk material variations.

40. A method in accordance with Claim 39 wherein said step of adjusting the position comprises the steps of:

forming a nest of snap-disks;

measuring trip forces of the nest of snap-disks;

calculating an error between the measured trip forces and the desired trip force for the nest; and

adjusting the position of the first stepper motor based upon the calculated error.

41. A method in accordance with Claim 40 further comprising the step of repeating the step of adjusting the position for another nest of snap-disks.

42. A method in accordance with Claim 39 wherein said step of adjusting the position comprises the steps of:

forming a nest of snap-disks;

measuring reset forces of the nest of snap-disks;

calculating an error between the measured reset forces and the desired reset force for the nest; and

adjusting the position of the second stepper motor based upon the calculated error.

43. A method in accordance with Claim 42 further comprising the step of repeating the step of adjusting the position for another nest of snap-disks.

44. A controller for an apparatus for forming bistable snap-disks, each snap-disk having a trip side and a reset side, the apparatus including a form station and a test station, the form station including a reciprocating trip form punch operatively coupled to a first stepper motor and a reciprocating reset form punch operatively coupled to a second stepper motor, the trip form punch and reset form punch respectively forming the trip side and reset side of the disk, the forces generated by the trip form punch and reset form punch adjustable by the respective stepper motor,, the test station configured for measuring trip and reset forces of the snap-disks after formation, said controller configured to:

accept snap disk formation parameters including a nominal trip force for activating the bistable snap-disks, a nominal reset force for resetting the bistable snap-disks, an allowable nominal trip force error, and an allowable nominal reset force error; and

adjust the operation of the stepper motors to produce snap-disks within the accepted parameters.

45. A controller in accordance with Claim 44, said controller configured to operate the apparatus to:

form a nest of snap-disks;

measure at least one of a trip force or a reset force of the nest;

calculate an error between the measured force and the respective target force; and

adjusting the position of at least one of the first stepper motor and the second stepper motor based upon the calculated error.

46. A controller in accordance with Claim 44, said controller configured to:

establish an upper bound for the desired position of each of the first stepper motor and the second stepper motor; establish a lower bound for the desired position of each of the first stepper motor and the second stepper motor;

establish a first adjusted position of each of the first stepper motor and the second stepper motor, each adjusted position of the first stepper motor and the second stepper motor located between the respective upper and lower bound; and

establish at least a second adjusted position of each of the first stepper motor and the second stepper motor, the at least second adjusted position of the first stepper motor and the second stepper motor located between the first adjusted position and one of the upper bound and lower bound.