WO2019143760A1

WO2019143760A1 - Methods of manufacturing optical pieces

Info

Publication number: WO2019143760A1
Application number: PCT/US2019/013924
Authority: WO
Inventors: Phillip Donald GOLLER; Joseph Anthony COLLINS; Vincent Vic VILLANUEVA
Original assignee: Rvo 20 Inc
Current assignee: Rvo 20 Inc
Priority date: 2018-01-18
Filing date: 2019-01-17
Publication date: 2019-07-25
Anticipated expiration: 2020-07-18

Abstract

Methods of machining a surface (optionally an optical surface) into a workpiece, and devices, systems, and apparatuses for machining a surface into a workpiece.

Description

METHODS OF MANUFACTURING OPTICAU PIECES

CROSS REFERENCE TO REUATED APPUICATIONS

[0001] This application claims priority to U.S. Prov. App. 62/618,768, filed January 18, 2018, which is herein incorporated by reference in its entirety for all purposes.

INCORPORATION BY REFERENCE

[0002] All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

BACKGROUND

[0003] Some contact lenses, intraocular lenses, comeal inlays, and other plastic optics may have very tight in-process dimensional tolerances that can be +/-10 microns or less. Corneal inlays are particularly small and may have an in process edge thickness tolerance of +/- 2 microns for a hydrated comeal inlay. Given that a hydrophilic plastic is machined in the dry state at approximately half the size of the hydrated state, the dry in-process edge thickness tolerance can be approximately +/-1 micron at the lathe-machining stage. For instance, a production process with a 95% confidence interval, a +/-1 -micron tolerance would require a standard deviation of 0.5 micron or less. The current state of technology for high-volume high-yield lathe-machining of plastic parts does not provide that level of precision; therefore, production yield would be low for processes with such tight tolerances.

[0004] Additionally, in general, improved machining processes may be desired that can precisely establish the location of the collet as a workpiece is held and machined.

[0005] Additionally, in general, improved machining processes may be desired that can precisely control the amount of compression on a workpiece when a surface is being machined.

SUMMARY OF THE DISCUOSURE

[0006] The present disclosure relates to methods, devices and systems for machining one or more surfaces into a workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is an exemplary cross section of an exemplary spindle assembly.

[0008] Figure 2 shows an exemplary embodiment of a reinforcing member. [0009] Figure 3 shows testing of a material without a reinforcing member.

[0010] Figure 4 illustrates an indexed spindle nose probing test.

[0011] Figure 5 shows testing of a material with a reinforcing member.

DETAILED DESCRIPTION

[0012] The present disclosure relates to methods, devices and systems for machining one or more surfaces into a workpiece. The methods can include lathing one or more surfaces into a workpiece. The methods may be used in the lathing of one or more optical surfaces into a workpiece. The methods may be used in the lathing of one or more surfaces into a workpiece, where one or more additional steps is needed to make the surface an optical surface ready for use. The methods may be used to machine one more surfaces of an ophthalmic lens, such as a corneal inlay or onlay. The methods can be used to machine a wide variety of material, such as plastic components.

[0013] An exemplary advantage of the disclosure herein is that the methods, device, and systems can provide a very stable and repeatable collet as an integrated system of spatial workpiece placement for easily compressed materials.

[0014] Figure 1 illustrates a side cross-sectional view of an exemplary spindle that can be used for the lathe- machining of exemplary workpiece 6, which can be used to machine, for example, a corneal inlay or onlay, or other relatively soft critical components and optics. Workpiece 6 can include a blank (which may also be referred to as a button), which may or may not be blocked (i.e., coupled to an arbor). Workpiece 6 can be cylindrically- shaped and can be placed into a collet 5 that has a receiving area such as a counter-bored inside diameter that is dimensionally very similar to an outer diameter of workpiece 6. Workpiece 6 is commonly held in a collet 5 or chuck for machining. The workpiece can be a "blank" or "button" that is directly machined into a finished part, or the workpiece may include an arbor that holds the "blanks" or "buttons" in a "blocking" process. Collet 5 may be pulled back by a drawbar 8 into a tapered collet adapter 4, which creates a compressive force onto the workpiece 6. The compressive force allows workpiece 6 to be held securely and overcome the torque applied by the lathe-machining processes. Unfortunately, the elasticity of some workpieces under compressive and cutting forces will also cause the collet 5 to vary in stiffness and location, resulting in unwanted variable geometries such as radii and thicknesses changes in the finished parts by several microns or more.

[0015] Figure 1 illustrates an exemplary embodiment for compensating for this. This exemplary embodiment includes a new high-precision reinforcing member 7, which can be a set pin, that precisely establishes the location of the collet 5 as one or more workpiece 6 are held and machined. A fixed-location collet is also known as a dead-length or true-length collet. The reinforcing member is positioned into a collet internal channel that is behind the workpiece receiving area, as shown in figure 1. The internal channel can be a counterbore that is machined into the collet behind the front counterbore. Once positioned in the internal channel, the reinforcing member can limit the amount of compression on the workpiece 6 to an acceptable and repeatable amount through the selection of a proper reinforcing member 7 diameter. A collet adapter 4, collet 5, and reinforcing member 7 are preferable made of an extremely high compressive strength material, such as a steel so that as the workpiece 6 allows compression to take up the clearances between the high strength parts (e.g., between the collet and reinforcing member), the collet 5 location is firmly established in space for production of multiple subsequent workpieces 6. The repeatability of the collet 5 location may be l-micron or less when the reinforcing member approach is used. The reinforcing member system provides extremely high stiffness which significantly improves the ability to produce very tight tolerance parts to dimensional specifications, and improves the form accuracy and surface finish of the machined parts. Tighter tolerances with improved process capability provides for higher quality optics, higher yield, and thus lower production costs. The reinforcing member also allows the use of a draw-back collet (if used) without having to premeasure the workpiece 6 or probe the part before lathe-machining. The reinforcing member 7 diameter is dependent and selected based upon the workpiece 6 diameter. For most high-volume production processes, the workpiece 6 diameter is a nominal constant, therefore the selected reinforcing member 7 diameter should not require frequent changes. The reinforcing member approach can also be used with collets 5 that are stationary that may or may not require drawbars 8, whereas the collet closing mechanism/adapter 4 may provide the longitudinal or axial movement required to actuate the collet 5.

[0016] In some embodiments, the reinforcing member can be selected based upon the channel (e.g., bore) size for the reinforcing member, and the nominal bore size for the workpiece diameter. For example, if the collet has a reinforcing member (e.g., set pin) bore diameter of 0.2500", then a reinforcing member could be selected from an assortment that includes reinforcing member that are larger and smaller than 0.2500" in 0.0001" increments (e.g., 0.2495, 0.2496, 0.2497, 0.2498, 0.2499, 0.2500, 0.2501, etc.).

[0017] This example provides a merely exemplary illustration of dimensions that can be chosen for a system. For a reinforcing member channel diameter of 0.2500", a workpiece receiving area of 0.5000", a workpiece diameter of 0.5001", a desired workpiece compression of 0.0002", a resulting reinforcing member diameter can be calculated as 0.2500 + (0.5001-0.5000) - 0.0002 = 0.2499." [0018] Reinforcing member diameter verification and selection can also be performed by feel. With the reinforcing member installed and the collet closed, the workpiece should be adequately gripped to overcome the cutting forces yet is compressed such that the reinforcing member is engaged and prevents further compression of the workpiece.

[0019] The reinforcing member may be made from a variety of materials. For example without limitation class X gage pins in 0.0001" increments are readily available from manufacturers such as Deltronic Corporation. They can be modified for length as necessary in order be used as a reinforcing member. In Figure 2 reinforcing member 7 that is created is shown to the right of an exemplary gage pin that is the starting material.

[0020] Examples and studies. The purpose of the study was to develop, test, and document a more precise and efficient method of controlling comeal inlay radii and edge thickness. Various tests were conducted to establish a baseline performance of a lathe without a reinforcing member, and with the collet set pin to determine the collet's dimensional stability relative to the spindle.

[0021] Figure 3 illustrates an exemplary test of material without a reinforcing member in the collet. To determine the baseline repeatability of the collet while holding the material (e.g., a hydrophilic acrylic machined in the dry state that can be used for corneal inlays). The workpiece 6 had a cylindrical shape and was placed into the collet, and the collet was closed. The machine was cycled quantity 30 times. After each cycle the collet was manually rotated and indexed to a marked location, and subsequently probed. The Z-axis values representing the probe trip points are recorded as dataset 11. The resolution of the probe/Z-axis values is 0.00001 mm. The resulting range of measurements was 0.00404 mm, which is poor performance for a

manufacturing process with a dry in-process tolerance of approximately +/-0.001 mm. As the plastic material would continue to compress over time, the collet 5 would draw back further into the collet adapter 4. This test proved that the collet was not stable reinforcing member while holding a plastic workpiece.

[0022] Figure 4 illustrates another test (dataset 5), an indexed spindle nose probing to determine the baseline repeatability of the Z-axis/spindle nose (collet adapter, 4) over the course of quantity 30 machine cycles. After each cycle, the nose of the spindle was manually rotated and indexed to a marked location, and subsequently probed. The Zaxis values representing the probe trip points are recorded as dataset 5. The resulting range of measurements was 0.00017 mm, representing a very good best-case repeatability of the spindle position itself. This test proved that the Z- axis/spindle was a stable and repeatable platform for the new reinforcing member system.

[0023] Figure 5 illustrates another test (dataset 7), indexed collet probing with the material from figure 3 and with a reinforcing member. A test was conducted to determine the stability and repeatability of the collet 5 with the reinforcing member 7 while holding a hydrophilic plastic part (7822 Material) over time. After each cycle, the collet was manually rotated and indexed to a marked location, and subsequently probed. The Z-axis values representing the probe trip points are recorded as dataset 7. The resulting range of measurements was 0.00015 mm, representing a stable collet position relative to the spindle itself. This test proved that the new collet reinforcing member system provides an extremely stable collet for machining and achieving sub-micron precision and accuracy as required for extremely critical plastic optics and other components.

[0024] Materials other than plastics can also be applied with the collet reinforcing system, such as rubber and wood. If the collet closing mechanism can compress the workpiece material and allow the collet channel or bore to contact the reinforcing member, then the repeatability of the collet position will be excellent. Preferably, the workpiece material is softer and more compressible than the collet reinforcing member.

[0025] U.S. Publication 2015/0375355, published December 31, 2015 is incorporated by reference herein for all purposes. For example, the disclosure in U.S. Publication 2015/0375355 can help provide a description of terms (e.g., arbor, blank, button, blocking, etc.), and unless used in a contrary manner herein, can be incorporated into any aspect of the disclosure herein. Any of the description on lathing in general in U.S. Publication 2015/0375355 is incorporated by reference herein, including into the claims.

Claims

1. A method of machining at least one surface into a workpiece, comprising: positioning a reinforcing member within an internal channel in a collet, the internal channel having an internal channel diameter, the internal channel positioned behind a workpiece receiving area;

positioning a workpiece in the workpiece receiving area of the collet;

compressing the workpiece with the workpiece receiving area;

causing the collet internal channel to come into contact with the reinforcing member and thereby limit the amount of compression on the workpiece from the workpiece receiving area; and

machining a surface into the workpiece.

2. The method of claim 1, wherein the positioning steps include positioning a reinforcing member that is less compressible than the workpiece.

3. The method of claim 1, wherein the positioning steps include positioning a reinforcing member that has a higher compressive strength than the workpiece.

4. The method of claim 1, wherein compressing the workpiece with the workpiece receiving area causes one or more surfaces of the internal channel to be moved radially closer to an outer surface of the reinforcing member.

5. The method of claim 1, wherein positioning a reinforcing member comprises positioning a cylindrically shaped reinforcing member within the internal channel.

6. The method of claim 1, wherein positioning a reinforcing member comprises positioning a solid reinforcing member in the internal channel.

7. The method of claim 1, wherein positioning a reinforcing member comprises positioning a set pin in the internal channel.

8. The method of claim 1, wherein positioning a workpiece in the workpiece receiving area comprises positioning a blank in the workpiece receiving area without an arbor, and wherein compressing the workpiece comprises compressing the blank.

9. The method of claim 1, wherein positioning a workpiece in the workpiece receiving area comprises positioning an arbor in the workpiece receiving area, and wherein compressing the workpiece comprises compressing the arbor.

10. The method of claim 1, wherein machining a surface into the workpiece comprises machining an optical surface into the workpiece.

11. The method of claim 1, wherein causing the collet internal channel to come into contact with the reinforcing member and thereby limit the amount of compression on the workpiece from the workpiece receiving area comprises preventing the workpiece receiving area from collapsing radially beyond a certain amount.

12. The method of claim 1, further comprising retracting the collet, wherein retracting the collet causes compression of the workpiece with the workpiece receiving area.

13. The method of claim 1, wherein positioning the reinforcing member within an internal channel in a collet comprises positioning a reinforcing member with an outer dimension less than the diameter of the internal channel in a first state.

14. The method of claim 1, wherein compressing the workpiece with the workpiece receiving area comprises tightening the collet.

15. A method of machining at least one surface into a workpiece, comprising: positioning a workpiece in the workpiece receiving area of a collet;

compressing the workpiece with the workpiece receiving area;

preventing the workpiece receiving area from compressing the workpiece beyond a certain amount.

17. The method claim 15, further comprising any of the method steps in claim 1-14.

18. A collet for machining a workpiece, the collet comprising: a workpiece receiving area of the collet; and

a reinforcing member receiving area disposed behind the workpiece receiving area, the reinforcing member receiving area having a smaller diameter than the workpiece receiving area of the collet.

19. The collect of claim 18, wherein the reinforcing member receiving area is a counterbore in the collet.

20. The collet of claim 18, wherein the workpiece receiving area and the reinforcing member receiving area are disposed about a common collet axis.

21. A reinforcing member sized and configured for being placed in a reinforcing member receiving area of a collet, including in any of the reinforcing member receiving areas described or claimed herein.

22. The reinforcing member of claim 21, wherein the reinforcing member has a cylindrical configuration.

23. The reinforcing member of claim 21, wherein the reinforcing member is a solid material.

24. The reinforcing member of claim 21, wherein the reinforcing member is a set pin.

25. A system, comprising any of the collets from claims 18-20, and any of the reinforcing members from claims 21-24.

26. The system of claim 25, wherein the reinforcing member receiving area is adapted to be opened to have a size greater than an outer diameter of the reinforcing member.

27. The system of claims 25, wherein one or more dimensions of the system can be any of the dimensions included herein.