DE8708123U1 - Numerically controlled printed circuit board processing machine - Google Patents

Description

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Klingeiriberg Sons Remscheid-Berghausen

Numerically controlled printed circuit board processing machine

The invention relates to numerically controlled printed circuit board processing machines with a workpiece carrier and at least one working unit, which consists of a motor spindle with exchangeable tool and a feed device with a drive motor, a control and a position measuring system,

These machines are used to process circuit boards for printed circuits, in particular to create holes. To do this, the workpiece carrier on which the circuit boards are attached and the work unit are positioned relative to each other in two coordinate directions. During the subsequent processing process, the feed device moves the motor spindle with the tool mounted in the third coordinate to the drilling depth. As a rule, several work units are present on a machine in order to process several circuit boards or circuit board packages at the same time. In order to be able to carry out different operations and drill holes with different diameters on each circuit board, devices for automatic tool changing are provided, as can be seen, for example, from patent specification DE 33 01.

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In machines based on this state of the art, the drilling depth is determined from the amount of advance thrust of the motor spindle, which is measured with the position measuring system from a stop or upper reference point that has been set once. Due to the unavoidable tolerances in the length of the various tools, in the thickness of the circuit boards and in the guidance accuracy between the workpiece carrier and the respective work unit, the holes cannot reach the exact specified depth. This is particularly disadvantageous when multilayer boards are to be provided with blind holes, *. the depth of which - measured from the surface of the board - must be accurate to within a few micrometers.

The invention is therefore based on the object of further developing a processing machine of this type so that the specified drilling depth can be achieved with greater reproducibility and within a narrower tolerance.

This object is achieved by the means specified in claim 1.

The effect of the measure according to the invention is that the control recognizes separately for each work unit when the tip of the tool is touching the surface of the circuit board during each individual drilling process. The specified drilling depth is then reached from this position.

The invention is explained below using an embodiment.

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Fig»·· 1 is a perspective view of a numerically controlled sheet metal processing machine with four working units

Fig. 2 is a schematic view of a working unit

Fig. 3 pina section through the reference measuring point in enlarged scale

The machine shown in Fig. I consists of a table 1 on which the workpiece carrier 2 can move in one coordinate direction and a portal 3 on which a carriage 4 with four work units 5 can move in the second coordinate direction transversely to the direction of travel of the workpiece carrier. On the carriage 4 there is also a tool magazine 6 for each work unit which, together with the known auxiliary devices, enables automatic tool changing. A reference measuring point 7 is arranged on each workpiece carrier which can be approached by the associated work unit. The number of work units can vary, for example up to ten.

Each working unit (Fig. 2) has a longitudinal guide 8 on a frame 9 which is attached to the carriage 4. In the longitudinal guide, a motor spindle 10 can be moved in the direction of arrow 13 with the help of the drive motor 11 and a ball screw 12, whereby the amount of displacement

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The displacement is measured with a first displacement measuring system 14 and fed to a control system known per se. In the longitudinal guide 8 there is also a pneumatically operated workpiece hold-down device 15, the displacement of which relative to the motor spindle 10 can be measured with a second displacement measuring system 16. The motor spindle is equipped with an automatic chuck (not shown in detail) for holding and changing the tools.

Fig. 3 shows the preferred design of the reference measuring point 7. It consists of a switching element 17, the switching point of which is flush with the surface of the workpiece carrier 2. To measure, the work unit moves with its newly picked up tool 18 over the switch. The tool holder 15 is placed with its reference surface 19 on the surface of the workpiece carrier 2 and the stationary tool is lowered onto the switching element. At the switching point, the distance that the

Tip of the current tool 18 from the reference surface 19

in the starting position.

« Drilling blind holes with precise depth

is now carried out as follows:

The motor spindle 10 is set in rotation, positioned above the circuit board and lowered downwards with the feed unit. At the same time, the lower

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holder 15 and presses the circuit board onto the workpiece carrier 2. The motor spindle is now pushed further forward by the feed device in the free stroke and the distance between the motor spindle and the hold-down device read on the second position measuring system 16 is constantly compared with the stored value. If the values are the same, the tip of the current tool has reached the same position relative to the support surface of the hold-down device as at the reference measuring point, namely exactly the surface of the circuit board, regardless of how flat the circuit board is on the workpiece carrier, how thick it is at the drilling point or what distance was covered in the free stroke. The control now switches to the working stroke, which is measured by the first position measuring system up to the specified drilling depth.

All immediately following holes in a work unit with the same tool use the same distance value stored in the control system to find the correct starting position for the respective working stroke. Only after the next tool change does the new distance value of the tool tip have to be determined at the reference measuring point and stored in the control system.

The described functionality is independent for each work unit. The control system therefore stores as many distance values from the respective reference measuring points as there are work units, and it monitors the work processes so that a work step is the _first of all

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units must be completed before the next step can be initiated together.

In a further embodiment of the machine according to the invention, some functions of the second position measuring system 16 can be taken over by the first position measuring system 14. The position measuring system 16 then consists, for example, only of a microswitch, which causes the distance values to be read and stored in parallel on the position measuring system 14. The basic functionality made possible by the measures according to the invention is not changed by this. The same applies if the switching element 17 at the reference measuring point and the position measuring system 16 at the working unit are swapped.

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Claims (3)

&bull;&bgr;&bgr; · · &bgr; * * &bgr; ·» &bgr; · a a t r · a a aa a·· &bgr;a&bull; a a· «· ta «a a Protection claims 1. Numerically controlled printed circuit board processing machine with a workpiece carrier and at least one working unit, which consists of a motor spindle with interchangeable tool and a feed device with a drive motor, a control and a position measuring system, characterized, that a second position measuring system (16) is provided on each work unit (5) and a reference measuring point (7) is assigned to each work piece carrier (2), with the aid of which the distance between the tip of the current tool (18) and the reference surface (19) that rests on the work piece during the machining process can be measured, and that the specified drilling depth can be corrected using the measured distance value in the control of the feed device. 2. Processing machine according to claim 1, characterized in that that the reference measuring point (7) essentially consists of a switching element (17) which is located at a defined distance from the surface of the workpiece carrier on which the reference surface (19) rests during measurement" and which can be triggered with the tip of the tool and is electrically connected to the control system. &bull;i ·<<·<<( 44 · <« «old· 4 ti tit · · » i » t* , * ' M t '· ·· «·< I M4 I« f- * t Λ r % rm r 3. Processing machine according to claim 1, characterized in that the reference surface (19) is the support surface of a workpiece hold-down device (15). -3- I I 1 f I M I I Il * I I I * · « It* » I f II _g I Il < Ii H HIlIII