GB2060176A

GB2060176A - Electrically measuring honing machine workpieces

Info

Publication number: GB2060176A
Application number: GB8032389A
Authority: GB
Original assignee: Maschinenfabrik Gehring GmbH and Co KG
Current assignee: Maschinenfabrik Gehring GmbH and Co KG
Priority date: 1979-10-09
Filing date: 1980-10-08
Publication date: 1981-04-29
Also published as: FR2467056A1; DE2940839A1; IT1133186B; JPS5656376A; IT8025162A0

Abstract

A honing machine (1) includes a device (9) which measures the honed workpiece bore (13) diameter at various axial locations and a comparable dimension of a monitoring ring (64) coaxially adjacent the workpiece (14). The measurements are made by a tool (12) on an axially movable spindle (10), and a converter (31) provides electrical signals corresponding to the measurements, which signals are fed to a measuring controller (30) connected to a statistical evaluation device (56). The measuring controller (30) is also connected to the controller of the honing machine (1) to provide correction of the honing of further workpieces in accordance with the measurements. The measuring controller (30) includes an analog computer (40) which provides data for print-out and subsequent processing. <IMAGE>

Description

SPECIFICATION Honing machine The invention relates to a honing machine having means for monitoring and evaluating measurements of the honed workpiece.

It is known from German Patent Specification 25 50 770 to measure the bore in a workpiece during or after machining and from this to obtain correction values for changing the direction of the stroke of the honing tool.

German OS 19 50 1 12 also discloses a device for the measurement-controlled finishing of machining of workpieces on honing machines, in which the feed-out of the honing tool is adjusted depending on a measurement of a diameter in a subsequent measuring station.

It is thus a pre-requirement that in mass manufacture, even with very restricted tolerances as regards shape and dimension, the machined workpieces are within the preset tolerance limits.

The production is normally monitored by a socalled statistical quality control. During this control, batches of workpieces are removed as samples from the current production, the term batch meaning a limited number of workpieces machined directly one after the other. The workpieces removed are measured very accurately outside the honing machine and from the measured values the known statistical characteristic values, for example the average value (x-value), the standard deviation (S) and the variance (V) are determined.

However, particularly due to the necessary accurate measurement of the workpieces outside the honing machine at a different measuring point, these controls are very time consuming and correspondingly expensive. Therefore, for economic reasons, the controls cannot be carried out as frequently as would be desirable.

It is therefore the object of the invention to remedy this and to develop a honing device according to the generic notion so that it automatically supplies the data necessary for the statistical quality control, without the workpieces having to be conveyed to a second measuring point and measured there.

The invention provides a honing machine with means for monitoring evaluating measurements of the honed workpiece, characterised by the fact that connected to the honing machine is a workpiece measuring device, which supplies measured values to an electronic converter, which is connected to a measuring control means for receiving the measured values when converted into electrical signals, and that this measuring control means is connected to a statistical evaluation device.Thus, according to the invention, the measuring device which preferably operates with a known pneumatic measuring mandrel and an electronic converter and evaluation device, measures the honed workpiece bore inside the honing machine, in several planes separated from each other in the axial direction, in which case a computer directly monitoring and processing the measured values is provided, which computer is connected by way of a data interface switch to a printer, which prints out the measured values and the statistical characterising values. Thus, the honing results are immediately recorded and can be directly reprocessed. This provides numerous other advantages, for example shorter setting-up times and less waste, since optimization of the honing results is immediately possible due to controlled variation of the machining parameters.

A preferred embodiment of the invention is particularly advantageous, in which the measuring device is a subsequent measuring device, i.e. a measuring device which measures the dimensions of the workpieces already machined and is connected to a control device for automatic stroke adjustment, which contains a converter for converting measured values of the workpiece geometry into correction signals and which is connected electrically to the evaluation device so that the reversal points of the operating stroke can be shifted depending on the measured defects of shape of a machined workpiece and that these defects of shape are simultaneously fed into a computer, which ascertains the characteristic values necessary for the statistical quality control and prints out the latter together with the measured values by way of a printer connected by means of a data interface switch.

The term "defects of shape" is intended to mean the deviation of the machined workpieces from a predetermined desired shape. The desired shape is generally identical to the cylinder shape (according to DIN 7 184). However it is also quite possible to provide a desired shape which varies therefrom, for example a slight conicity, partial conicity, a barrel shape or the like.

The dimension control advantageously takes place by a comparison with a monitoring ring, which has the desired dimension. Deviations from the desired ideal dimension, which occur due to wear of the monitoring ring, can be compensated electrically by a correction input. Furthermore, due to an automatic zero, any drift of the measuring installation, for example due to the effect of temperature etc., is prevented.

The measuring appliance, which preferably operates pneumatically and is provided with a measuring point, is introduced axially into the workpiece bore to be measured and moved from measuring plane to measuring plane. However, it is also possible for the measuring appliance itself to have a plurality of measuring points located apart in the axial direction.

The measuring appliance is preferably moved by a hydraulic piston-cylinder arrangement, in which the displacement control operates with an electrical actual value potentiometer and several reference value potentiometers and an electronic analog evaluation arrangement. The electronic evaluation arrangement compares the wiper voltage coming from the actual value potentiometer, which represents an analog measurement for the momentary position of the measuring appliance, with the voltages supplied by the reference value potentiometer, which represent the respective measuring planes and if the values are equal emits a signal which is used for the hydraulic displacement control of the measuring appliance.

In this case, the possibility of remote control of the measuring planes, the variability during operation and the possibility of indication of the controlled measuring planes by a digital display, are of particular advantage.

According to a further feature of the invention, it is also possible to supply the measured values and the results of calculation from the computer simultaneously to second data storage means, for example an arrangement for punching perforated tape. Use is then made of this possibility if the measured values are reprocessed by a machine outside the honing machine. One solution which is particularly advantageous for example for machining fitting parts which belong together, such as injection pump cylinder and piston, is to machine the workpieces in magazines and to store the measured values for the workpiece, the measuring temperature and the magazine number on a perforated tape. This perforated tape is introduced into the appropriate machine for machining the counterparts, which machines the counterparts accurately and correlates them on the basis of this information.

Further advantages and features of the invention will become apparent from the subclaims and description in conjunction with the drawing which shows one embodiment. In the drawing, a honing device according to the invention is shown diagrammatically and partly in block diagram.

A honing spindle 2 is mounted in a honing machine 1, which spindle can be moved up and down by a hydraulic lifting drive, namely a pistoncylinder arrangement 3. The honing spindle 2 is also set in rotation about its longitudinal axis in known manner by a rotary drive (not shown). The honing spindle 2 supports a honing tool 4, whereof the honing heads can be fed out radially by a feed-out mechanism and which machines the bore 5 of a workpiece 6 in the embodiment illustrated.

A potentiometer 7 is connected to the honing spindle 2 as the actual value transmitter for the stroke movement. The driving connection between the honing spindle 2 and the wiper of the potentiometer 7 consists of a chain drive 8 in this embodiment.

The up and down movement of the hydraulic lifting drive 3 is controlled by a solenoid valve 18, whereof the relay coil 19 is controlled by a stroke control arrangement 20. The stroke control arrangement 20 is an electronic appliance operating in an analog manner, the basic construction and operation of which are described in German Patent Specifications 24 35 498 and 25 5G 770.

The stroke control arrangement 20 consists essentially of two reference value potentiometers 21 and 22, a correction member 23 and a comparison and evaluation device 24. The desired reversal points of the honing spindle can be adjusted at the two reference value potentiometers 21 and 22 by way of a control knob with digital input, due to which a voltage similar to this adjustment is preset at the wiper of the associated potentiometer.

These voltages are supplied to the correction member 23, which comprises several inputs 25, at which values are entered, which influence the reference values for the upper and lower reversal points, for example values for the initial switching delay, oil temperature change of the hydraulic system, change in the stroke speed, change in the driving power and the like. A further input 26 of the correction member 23 is provided for the introduction of values for the control of the workpiece geometry.

The comparison and evaluation device 24 compares the voltage coming from the actual value transmitter 7 and taken from the potentiometer wiper, which represents an analog measurement for the momentary position of the honing spindle 2, with the respective corrected reference value voltage supplied by the correction member 23, which represents an analog measurement for the desired upper or lower reversing point. If the values correspond, the comparison and evaluation device 24 emits a control signal, which is used for reversing the stroke movement of the honing spindle, as is described in detail in German Patent Specification 24 35 498.

Furthermore, a measuring device 9 is provided, which comprises a measuring spindle 10 which can be moved up and down by a hydraulic lifting drive 11. The measuring spindle 10 supports a measuring tool 12, which measures the bore 13 of a workpiece 14 which has already been honed.

Monitoring the dimensions is advantageously carried out by a comparison measurement by means of a monitoring ring 64 located above the workpiece 14 in the embodiment. The arrangement is preferably such that in the upper end position of the lifting drive 11, the monitoring measuring plane G passes through the measuring tool 12. A potentiometer 15 is connected to the measuring spindle 10 as the actual value transmitter for the stroke movement. In the embodiment the connection consists of a toothed rack 16 located on the measuring spindle 10, which meshes with a pinion 17 fixed to the potentiometer shaft.

The hydraulic lifting drive 11 is controlled by a solenoid valve 27 for the up and down movement.

The relay coils 28 and 29 of the solenoid valve are controlled by a measuring control arrangement 30.

The measuring tool 12 preferably operates pneumatically in a manner known per se. The measured values coming from the measuring tool are supplied to a measuring converter 31, which sends these measured values as electrical signals to the measuring control arrangement 30.

In the embodiment, the following measurements are made in succession, the monitoring ring dimension KG in the measuring plane G, the workpiece dimension WA at the upper end of the bore in the plane A, the workpiece dimension WB in the centre of the bore in the plane B and the workpiece dimension WC at the lower end of the bore in the plane C.

The measuring control arrangement 30 is an electronic arrangement operating in an analog manner, the basic construction and operation of which are described hereafter.

As soon as a honed workpiece is located in the measuring device 9, a signal which comes from the machine control (not shown) passes to the control signal input 32 of the displacement control member 33. The measuring operation is thus initiated. It begins with the measurement of the monitoring ring dimension KG in the plane G.

Subsequently, the displacement control member 33 controls the relay coil 29 of the solenoid valve 27, which controls the lifting drive and initiates the downwards movement of the measuring spindle 10 with the measuring tool 12.

By way of its wiper, the potentiometer 15 connected as an actual value transmitter to the measuring spindle 10 supplies a voltage to the displacement control member 33, which voltage represents an analog measurement for the momentary position of the measuring tool. An input device 34 for the balancing and determination of the position of the measuring planes is also connected to the displacement control member 33. In the embodiment, the input device 34 contains a potentiometer 35 for the electrical balancing of the actual value transmitter 15 with respect to the monitoring ring measuring plane G. The input device 34 also contains potentiometers 36, 37 and 38 as reference value transmitters for adjusting the position of the workpiece measuring planes A, B and C.

The displacement control member 33 compares the voltage coming from the potentiometer wiper of the actual value transmitter 15 in succession with the voltages supplied by the reference value transmitters 36, 37 and 38, and in the case of agreement emits a control signal, which brings about a brief stoppage of the stroke control drive 11. The respective measurements in the planes A, B and C are carried out during these brief stoppage times. At the same time, the transfer of the measured values supplied by the measuring converter 31 to a store 39 is controlled by a second control signal. After the measurement at the lower end of the workpiece is completed (measuring plane C), the displacement control member 33 sends a control signal to the relay coil 28 of the solenoid valve 27, due to which the measuring tool 12 returns to its upper initial position (measuring plane G).The measuring tool is then ready for the next measurement.

The store 39 advantageously contains an automatic zero, which zeros the value KG measured in the monitoring measuring plane G and adds the difference ascertained from this zero with the correct sign to the workpiece measured values WA, WB, WC. This measure compensates for any possible drift of the measuring installation.

Thus, deviations of the measured values are corrected, which may be caused for example by the influence of temperature or other external influences on the measuring installation.

The signals from the store 39 are supplied to an analog computer 40. An input device 41 is also connected to the analog computer for the input of correction values, which input device 41 in the embodiment contains a potentiometer 42 for the correction of the monitoring ring dimension KG and potentiometers 43, 44 for the correction of the workpiece dimensions WA or WC.

The input of a correction at the potentiometer 42 is necessary or appropriate for example if the monitoring ring 64 does not have the exact nominal dimension of the workpiece, for example as a result of wear. The input causes a shift of the measuring plane G, which represents the comparison plane for the workpiece planes A, B and C. The correction value is added to the measurement signals.

The measurement signals, possibly corrected, represent the deviations of the workpiece from a predetermined ideal workpiece with an exact dimension and exact, for example cylindrical shape.

In order to be able to define a desired shape varying from the cylindrical shape, the desired deviations in the measuring plane A (upper end of the workpiece) or in the measuring plane C (lower end of the workpiece) are adjusted with respect to the measuring plane B (centre of the workpiece) at the correction potentiometers 43, 44. The value for the measuring plane A which is fed in, is associated with the measurement signal for the workpiece dimension WA, in the same manner that the value fed in for the measuring plane C is associated with the measurement signal for the workpiece dimension C, in which case these values which are fed in can be added to the measured values, but a different type of connection is possible.

Thus, from the measured values ascertained, which may be corrected, by means of a subtraction, the analog computer 40 calculates, the differences of the measured values from the measuring planes B and A, B and C as well as A and C, i.e. WB-WA, WB-WC and WA-WC.

The differential values represent the deviation from the predetermined desired shape. Together with the measured values, the calculated values are sent to an evaluation device 45. These values are also sent by a display selector switch 46 to a display device 47, in which they can be displayed in a digital and/or analog manner. A signal connecting line 48 coming from the displacement control member 33 is also connected to the display selector switch 46. This provides the particularly advantageous possibility of displaying the position of the measuring planes preset at the input device 34 on the display device 47.

An input device 49 is connected to the evaluation device 45 for feeding in limit values, which device 49 in the embodiment contains a potentiometer 50 for feeding in the limit value for the stroke correction in the case of defects of shape as well as a potentiometer 51 for feeding in the limit value for the correction of the feed-out of the tool in the case of dimensional errors, a potentiometer 52 for feeding in the limit value for recognising waste in the case of defects of shape and a potentiometer 53 for feeding in the limit value for the recognition of waste in the case of dimensional errors.

The amount of the signal differential values WB-WA and WB-WC supplied by the analog computer 40 is compared in the evaluation device 45 with the limit values set at the potentiometer 50. If the preset limit value for the deviation of shape is exceeded, then the evaluation device 45 sends a signal to the input 26 of the stroke control arrangement 20, which then brings about a corresponding stroke correction. For example, if the measured value difference WB-WA is positive, i.e. the value measured in the plane B is higher than the measured value from plane A, then a correction of the upper reversing point takes place in the upwards direction (extension of the stroke). If the measured value difference is negative, then a correction takes place in the downwards direction (shortening of the stroke).

The same is true for the measured value difference WB-WC as regards the lower reversing point.

It should be noted that when machining blind bores and the like, in which case a stroke correction is not possible on account of the generally missing or inadequate free cut at the bottom of the bore, other values can be corrected, which influence the shape of the bore. For example, in a honing machine with a stroke delay control, such as is described in German Patent Specification 21 04 459, the delay time can be corrected correspondingly. For example, if the difference WB-WC is positive, then the delay time is lengthened, but if this difference is negative, the delay time is reduced.

In the evaluation device 45, the differential measured values WB-WA, WB-WC and WA-WC are compared as regards their amount with the limit value set at the potentiometer 52. If the preset limit value for the recognition of waste is exceeded on account of excessive defects of shape, then the evaluation device 45 produces a signal at its output 54, which signal is sent to the machine control (not shown). The workpiece is thus recognised as waste and is eliminated automatically by means which are known per se.

Furthermore, the measured value WB supplied by the analog computer 40, which value determines the finished dimension of the workpiece bore, is compared in the evaluation device 45 with the limit value set at the potentiometer 51 or at the potentiometer 53. If the measured value WB exceeds the limit value for the tool adjustment preset at the potentiometer 51, then by way of its output 55 the evaluation device 45 sends a signal to the feed-out control (not shown) for the honing tool, due to which the feed-out of the honing tool is corrected accordingly.

If the measured value WB exceeds the limit value for the recognition of waste set at the potentiometer 53, on account of an excessive dimensional error, then the evaluation device 45 likewise sends a signal by way of its output 54 to the machine control (not shown). The workpiece is then once more recognised as waste and is eliminated.

According to a particularly advantageous feature of the honing device according to the invention, the measured values and calculated values supplied by the analog computer 40 to the evaluation device 45, in the embodiment the measured values WA, WB and WC as well as the differential values WB-WA, WB-WC and WA-WC are sent to a statistical evaluation device 56.

The statistical evaluation device 56 is an electronic appliance operating in a digital manner, the basic construction and function of which will be described hereafter.

The measured values supplied by the evaluation device 45 in the form of analog signals are supplied to a measured value converter 57, which converts these measured values into digital signals and supplies them to a micro computer 58.

The computer 58 is pre-programmed for the calculation of statistical characteristic values for the quality control. It contains a keyboard 59 for the manual input of values, which influence the calculation programme and calculation process, for example a value for the size of the batch (number of workpieces), on which the calculation is based.

The measured values supplied by the measured value converter 57 are read into a data store of the computer 58 and are printed out by means of a printer 61 together with a current workpiece number. It is also provided according to a further advantageous feature of the invention to print out various other data, namely a workpiece identification number, data and time of the measurement and measuring temperature, which is ascertained in manner known per se during the measurement. The printer 61 is connected to the computer 58 by a data interface switch 60. After reaching the predetermined batch size, the statistical characteristic values are calculated and printed out, in the embodiment the mean value (xvalue), the standard deviation (S) and the variance (V). According to the input to be fed in by a switch, the calculation is carried out with "n" or "n - 1", in which case "n" is the number of workpieces read in. The preset size of the batch can be displayed at any time on the display board 62 of the computer and can be changed by means of the keys of the keyboard 59.

According to a further feature of the invention, the measured values and results of the calculations may also be recorded on a further data storage system, preferably on a perforated tape by means of an arrangement 63 for punching perforated tape, which is connected to the computer 58 parallel to the printer 61 by way of the data interface switch 60.

The storage of measured values and results of calculation on perforated tapes or other data storage means has the particular advantage that mechanical reprocessing of this data outside the honing machine is possible.

A particular advantage of the honing device according to the invention consists in that for each individual workpiece manufactured on the honing machine, for example for an injection pump cylinder, a matching counterpart can be ground automatically on a second machine, for example a piston on a plain grinding machine. The mating parts intended for each other may likewise be correlated by means of the data storage systems.

For this manufacture of fitting parts, the workpieces are combined and machined in groups, for example in magazines. The magazine number or some other characteristic mark for the group, the data and time, measuring temperature as well as characteristic values of the workpieces are stored on the data storage means (perforated tape), namely the workpiece measured values and results of calculation, the current workpiece number, the workpiece identification number and possibly other data. The data storage means, for example a perforated tape, is fed into the measuring control of the machine for the machining of the counterparts, likewise in groups, so that the machine can manufacture these counterparts with an exact fit on the basis of this information.

Also, since the group or magazine number and the sequence of the workpieces within the group are stored as data, the fitting workpieces can be marked for assembly and associated with each other, so that a particularly high accuracy of fit is ensured.

Claims

1. A honing machine with means for monitoring and evaluating measurements of the honed workpiece, characterised in that connected to the honing machine is a workpiece measuring device, which supplies measured values to an electronic converter, which is connected to a measuring control means for receiving the measured values when converted into electrical signals, and that this measuring control means is connected to a statistical evaluation device.

2. A honing machine according to claim 1, characterised in that the measuring device, which comprises a measuring tool, is located inside the honing machine and is adapted to measure a bore of a workpiece at a plurality of planes spaced apart in the axial direction thereof.

3. A honing machine according to claim 1 or 2, characterised in that the measuring device comprises a measuring spindle having a measuring tool attached thereto and which is moved by a hydraulic drive, which measuring tool is provided for the subsequent measurement of the honed workpiece, and that the measuring device is provided with a control device for the automatic adjustment of the stroke of the measuring spindle.

4. A honing machine according to claim 3, characterised in that a monitoring ring is located adjacent the workpiece, so that in an end position of said measuring tool the latter is located in the plane of the monitoring ring so as to provide a measurement thereof for comparison with said measured values.

5. A honing machine according to claim 3 or 4, characterised in that connected to the measuring spindle is an actual value transmitter for indicating the position thereof.

6. A honing machine according to claim 5, characterised in that a toothed rack is located on the measuring spindle and a pinion engages said rack and is seated on a shaft of the actual value transmitter.

7. A honing machine according to any one of claims 3 to 6, characterised in that the device for controlling the stroke of the measuring spindle comprises a solenoid valve controlling said movement, relay coils of which valve are connected to the measuring control means.

8. A honing machine according to claim 7, characterised in that the measuring control means operates in an electronic analog manner and has a displacement control member, which is connected to a control of the honing machine, to the actual value transmitter, to the relay coils of the measuring device, to an input unit for the balancing of the actual value transmitter for the plane of the monitoring ring and reference value transmitters for said plurality of measuring planes and to a store with a subsequent analog computer, in which case the store is in turn connected electrically to the converter, itself connected to the measuring device.

9. A honing machine according to claim 8, characterised in that connected to the analog computer is a correction value input unit for the measured values.

10. A honing machine according to claim 9, characterised in that the analog computer is provided with a display selector switch and an evaluation device.

11. A honing machine according to claim 10, characterised in that a signal connection is provided between the display selector switch and displacement control member.

12. A honing machine according to claim 10 or 11, characterised in that an input control for the geometry of the tool is provided between the evaluation device and the stroke control I arrangement of the honing machine.

13. A honing machine according to any one of claims 8 to 12, characterised in that the store comprises an automatic zero so that the value measured in the monitoring ring measuring plane is set to zero and the difference from zero ascertained can be added to the workpiece measured values with the correct sign.

14. A honing machine according to any one of claims 3 to 13, characterised in that connected to the evaluation device is a limit value input unit for specifying the limit value for the measuring spindle stroke control on account of defects of shape, for specifying the limit value for the correction of the tool feed-out on account of dimension errors, for specifying the limit value for the recognition of waste on account of defects of shape and a limit value input for specifying limit values for the recognition of waste on account of dimension errors.

15. A honing machine according to claim 10 or any claim dependent thereon, characterised in that the evaluation device comprises signal paths leading to a correction member of the stroke control arrangement, signal paths leading to a control apparatus of the honing machine and signal paths leading to a control apparatus for the honing tool.

16. A honing machine according to claim 10 or any claim dependent thereon, characterised in that a statistical evaluation arrangement is located after the evaluation device for re-transmission of the measured values and calculated values supplied by the analog computer to the evaluation device.

17. A honing machine according to claim 10 or any claim dependent thereon, characterised in that the statistical evaluation arrangement comprises a converter in which analog measured value signals arriving from the evaluation device can be converted into digital signals and can be supplied to a subsequent micro computer.

18. A honing machine according to claim 17, characterised in that measured values supplied by the converter are read into a data storage unit of the micro computer and are printed out by a subsequent printer together with a consecutive workpiece number.

19. A honing machine according to claim 18, characterised in that characterising data such as workpiece identification numbers, data, time of measurement, measuring temperature etc. are printed out by the printer.

20. A honing machine according to one of claims 18 or 19, characterised in that the printer is connected to the computer by a data interface switch.

21. A honing machine according to any one of claims 18 to 20, characterised in that the workpiece size can be recalled on a computer display and can be changed by means of a computer keyboard.

22. A honing machine according to any one of claims 1 to 21, characterised in that the measured values and results of calculation are stored on at least one other data carrier.

23. A honing machine according to claim 22, characterised in that said other data carrier comprises a perforated tape punching means.

24. A honing machine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

25. A method for machining a workpiece on a honing machine according to any one of the preceding claims, characterised in that for the automatic co-ordination of a true-to-size counterpart to be machined on another machine tool, the workpieces to be honed are machined in magazines and the measured values and results of calculations relating to the workpiece as well as other data, such as workpiece number, workpiece identification number, data, time, measuring temperature, magazine number are stored on a data carrier, and these values are then fed into this machine for controlling the other machine tools, on which the counterparts are likewise machined in magazines, for the purpose of accurate machining of these counterparts.

26. A method of machining a workpiece on a honing machine substantially as hereinbefore described.