DE2949427C2 - Measurement control device for grinding machines, in particular surface grinding machines for grinding workpieces in a continuous machining sequence - Google Patents

Description

The invention relates to a measurement control device for grinding machines, in particular surface grinding machines for grinding workpieces in a continuous machining sequence, according to the generic term of claim I.

This generic term is based on a state of the art, as it is from DE-AS 14 27 478 emerges. The known device is equipped with a workpiece that scans the ground workpieces set and provided a blocking contact having measuring device, the blocking contact is actuated when the workpiece is oversized and the oversize signals generated as a result after exceeding an adjustable workpiece oversize tracing section via a measuring signal evaluator a feed pulse for trigger the grinding tool. The disadvantage here is that the blocking contact only gives a binary signal, namely "1" when the contact is open = oversize, signal "0" when the contact is closed = good.

The undersize range when the contact is closed is not recorded, so minus values are not recorded reported. Thus, this control device cannot provide a quantitative manipulated variable for setting the forwards and backwards Deliver delivery device. Analog measured values are missing for an exact control of the workpiece size. Of the Measurement signal evaluator according to DE-AS 14 27 478 can only because of the lack of analog measured values Register and compare length ratios of workpiece oversize tracing length and tracing gap length. The comparison of the scanning distance - in the binary pattern of the signal sequence - results in random measurement errors switched off, but not systematic measurement errors that

ίο can be repeated for every workpiece. Because the lack of quantitative analog evaluation of the measuring signals can not be maximum measured values as Faults are recognized, and a minimum value selection for the purpose of eliminating interference amplitudes is therefore also not possible. Also one process-dependent, i.e. variable. Manipulated variable for the quantitative compensation of the control deviation from the nominal dimension cannot be won. With the known control device to compensate for the grinding

x tool wear, the delivery systems can only be controlled with a preselected delivery amount in one direction - delivery in the event of excess.

Reference is made to DE-OS 19 55 824 for further prior art. There is a first one for storage of the peak value of the analog signal of a capacitor store used for scanning a workpiece (Fig. 1 (6)) is used, and the potential of the first memory becomes periodically recurring Transfer times to a second memory.

jo The peak value of the analog signal is used as the measured variable used for a display device (14) and a control device (15). From Fig. 1 of the laid-open specification it becomes clear that the storage of the peak value is necessary here in order to

J5 There are three probes on the workpiece, smaller analog values for the display device and control device not to take effect. The advantages of Storage and signal processing using the peak or maximum values to cope with the Measurement gaps in interrupted grinding surfaces are known and practicable, especially with cylindrical grinding. However, according to page 11, line 27, the prerequisite is Offenlegungsschrift 119 55 824 that any relocation of The axis of rotation is small in relation to the diameter tolerances. Shifts of the axis of rotation go namely in the peak value and become larger and therefore incorrect due to the peak value storage rated. In addition, interference from abrasive grains, grinding chips, grinding burrs and vibrations are avoided.

w nen are also saved as peak values during the measurement and can therefore no longer be selected as disturbance variables. These disadvantages of peak value storage become less tensioned, especially when grinding Workpieces (centerless cylindrical grinding) and with continuous flat grinding of a sequence of Workpieces lead to greater inaccuracies because in the grinding processes with several workpieces the Peak value disturbances cannot primarily be prevented.

So the object of the invention is to provide a measurement control device to create the aforementioned genus, which makes it possible to continuously grind a Sequence of workpieces Incorrect measurements or evaluations due to interference in everyone

t> 5 workpiece to be eliminated and optimal, process-dependent to generate variable infeed or reset values for the grinding tool.

This task is related to the characteristics

of the preamble according to the invention by the features of the characterizing part of claim 1 solved

An embodiment within the scope of the invention is the subject matter of claim 2.

The inventive selection of the lowest minimum value with a still increasing subsequent value as Criterion prevents incorrect measurement of the minimum of bores or sloping workpiece edges. Due to the time delay of the initial values and selection, the minimum value is higher than any other Values are no longer afflicted with many interfering influences, e.g. B. by bumps, holes the touch surface, grinding wheel or grinding burr and machine or workpiece vibrations. The workpiece-dependent Selection also allows empty stations or any probe gaps and workpiece sequences.

The actuation of the grinding wheel infeed device corresponding to the process-dependent control deviations based on an average of several workpieces also statistically secures the knife results and prevents the controlled variable from overshooting the target dimension tolerance field of the workpieces. Also be Long-term disruptive effects such as drift or thermal shifts are compensated for in a regular manner.

In the following description of the drawings, the invention is illustrated by means of a preferred exemplary embodiment explained

It shows

F i g. 1 schematically shows an overall view of a surface grinding process with two face grinding wheels for double-sided grinding and

Fig. 2 to 7 computing circuits of the evaluation memory using the example of analog circuits.

According to FIG. 1 is a schematic overall view of a surface grinding process with two face grinding wheels 1 and 2 for double-sided continuous grinding of workpieces 3 to 10, the same in one Grinding process to be ground to the target size.

After leaving the grinding wheels, the workpieces 3 to 10 are measured in the feed device of the machine by two measuring probes 11 and J2 for their thickness, E with the measured values from £ minimum to E maximum. E is a sum of the two probe voltages T ₁ + Tj = E ^J 5.

With a known measuring control / display device 13, the measuring signals E can be used in a known manner with the aid of a limit value specification 14 to form delivery signals 15 for the machine control measure and thereby eliminate interference by selecting certain measured values E-min and Ε-start (EA) in order to obtain more precise delivery signals.

There are now 5 to 10 interfering influences and selected ^{6 (1} measured values, for example, shown on the workpieces in a schematic color position, namely:

Workpiece 5 interference:

inclined measuring surface, selected measured values EA.
Workpiece 6 interference: bS

rough surface, selected measured value Emin.
Workpiece 7 interference:

Grinding burr, selected measured value Emin.

Workpiece 8 interference:

Abrasive grain and chips, selected measured value

E min.
Workpiece 9 interference:

uneven measuring surface, selected measured value EA.
Workpiece 10 interference:

Vibration, selected measured value £ min.

Such interferences cause measurement uncertainty and measurement errors if the E max values are used here. Therefore, according to FIG. 1 in an analog or digital arithmetic circuit with evaluation memory 16, the E-min or ΕΛ values are selected for each individual workpiece Display more takes place The difference between measurement signals and limit values 14 and the § delivery signals 15 we .. Sen are more unambiguous, because only a selected measured value pre workpiece becomes effective.

If now also the computing circuit with evaluation memory 16 in connection with a Control device 17 is applied, so in addition to the grinding wheel wear, thermal changes, z. B. drift and grinding spindle expansion, with a process-dependent mean value 18 - formed from the selected individual measured values - bc-sser determined and with a process-dependent adjustment amount continuously in both directions, i.e. closing or closing Provision, to be offset.

The function of the control device 17 is as follows: A control clock signal is generated in the evaluation memory 16 when the measuring keys 11 and 12 leave the workpiece surface and lower them into the key gap. Here, the measurement signal E falls below a preselected trigger threshold TE <TE = L signal. This signal is converted into a short H signal by a gate 19, and this controls, by means of a switch 20 Ce, analog measured values EA, E-min in the operational amplifier 18 for averaging. The ali number of workpieces η , of which the mean value is to be formed, is determined with a preselection counter 21.

The Η signal from 19 also starts an actuator 33 via a connection 30 to a position controller 27. After a number of η workpieces, the mean value from 18 is sent to a memory 23 via a switch 22. A display amplifier 24 then supplies a measuring amplifier 25 with the mean values for the target / actual comparison. Deviations from the nominal dimensions are measured by the position controller 27 in digital form via an analog-digital converter 26 via a connection 28 as a control amount (1 ... X) . The plus or minus deviation determined in the measuring amplifier 25 is specified as the setting direction via a connection 29. When the fixed amount voo 28 and the actuating direction of 29 are set in the position controller 27, the control cycle of 30 starts a converter 31 and thus the actuating movement of the actuator 33. According to a position feedback 32, the control process in the position controller 27 is ended.

This measurement signal selection on each workpiece, the averaging of selected measurement signals and the process-dependent manipulated variable obtained therefrom results in a considerably improved positioning of the Grinding tools when continuously grinding a

Sequence of workpieces.

In the following, with reference to FIG. 2 to 7, the computing circuit of the evaluation memory 16 is described using an example with analog circuits in individual subsequent operations. Here, the voltage value, formed from the sum of the two probe signals T> + T \ = E , for the tracing path of a workpiece is recorded as a possible amplitude curve 34.

It means in FIG. 2:

Ti = trigger threshold at the beginning of a Measuring MeB- sung, ίι = delay time for the measurement signal F-min would take. E. \ = initial value of Measurement on the area. Oip * e ^r Wprt will type games wi> nn kpinr available.

Emin = minimum measured value with the selection criterion, that a larger measured value follows,

E max = maximum measured value.

Ti = trigger threshold at the end of the measurement.

So that the button movements z. B. do not influence the measurement on bores or on workpiece edges, a steadily decreasing amplitude curve 35 to Te is not selected as E-min.

3 shows, as an example, a circuit for generating the digital control signals from analog voltages. An operational amplifier circuit comprising a comparator 36, a Schmitt trigger 37 and a gate 38 generates the digital signals 40. The measurement signal E is compared with the reference value T - adjustable trigger threshold - at the input 39. When T is exceeded or not reached, the digital control signals H or L are generated at output 40.

In Fig. 4:

E. =
E] = Eo = EoA =

adjustable reference voltage,

for level conversion into the minus range.

Reference voltage for resetting to the original values,

equivalent signal voltage of E, but with all values in the minus range,

Ea. Eo-max = E-min, Eo-min = E-max.

The shifting of all measured values into the minus range enables in a simple manner, without measured values different polarity, the selection of £ o-max with a peak voltage memory. After that, through Reset the E-min value from Eo-max with Ej won.

For this purpose, Fig.5 shows as an example a circuit for Shifting the voltage values E with a preselectable Reference values egg

E- E ₁ = Eo.

Fun op amp with differential input supplies

ft
'—- can be selected as a gain factor, e.g. B. 1.

«Ι

6 shows at point 41 that the signal value Eo - measured from "0" potential - is greater than the initial value, Eo> EoA.

ίο At the point 42, the signal value Eo is smaller than the peak voltage Eo-max, Eo <Eo-max. With the help of a circuit according to FIG. 3, digital control signals are generated from the comparison of the analog voltages.

Eo < Eo-max s //.
''Eo> EoA = H.

These signals are used to control the network according to Fig. 7 required

Here, FIG. 7 a network with a

.ίι Instantaneous value memory 43 for storing the selected values Eo-max or EoA. A memory 44 is kept with all negative peaks between EoA. Eo-max and 7öz loaded. The current Eo values are present at input 45. With switch 46, operated by

- '"> Η-signal after ti. The initial value EoA is given via diode 47 in the memory 43. This Eo4 value remains selected if no peak value Eo-max follows in the further course of the measurement.

With switch 48, activated by the Η signal after fi

also given into memory 44 in EoA. At the output 50, the values given to the memory 44 are available for the generation of digital control signals. A switch 51 is controlled by a Η signal from Eo> EoA , so at the end of the rising characteristic

ii 41 the peak value Eo-max is given into the memory 44. A switch 52 is controlled by a Η signal from Eo> Eo-max and gives the peak value Eo-max from memory 44 via diodes 53 and 47 also into memory 43. This is the peak value

4i> Eo-max selected.

The selected values EoA or Eo-max are given to the differential amplifier input 54 with the value E1 and reset to the original level. The selected values are now at output 55

■ »'Emin or E ₄ for the further signal processing according to Fig .; ready. Switches 56 and 57 discharge the memory 44 and 43 and are actuated at the end of each measurement by a Η signal from Tk.

According to the above, all processes of measured value recording, measured value selection, t *. Measured value storage, averaging and measured value deletion are controlled automatically depending on the workpiece. The arithmetic operations carried out in the circuits 16 and 17 of FIG. 1 with operational amplifiers in analog circuits can also be implemented with a digital computer or microcomputer if the analog button signals T1 + T2 are input as a measured value E via an analog-digital wander can be digitized in the computer with evaluation memory.

For this purpose 2 sheets of drawings

Claims (2)

Patent claims: 1. Measurement control device for grinding machines, in particular surface grinding machines for grinding workpieces in a continuous machining sequence, with sum and / or difference circuits of kinematically fast measuring probes, through which thickness dimensions, unevenness and disturbance variables can be detected when scanning the grinding surfaces and whose measured values are stored in a measured value memory with predetermined Evaluation device acted upon by a setpoint can be fed, with the output signals of which a grinding wheel feed device can be acted upon, characterized in that after a trigger threshold (Ta) with a time delay (t \) the measured values (E) of individual workpieces (3 to 10) are continuously stored in an evaluation memory (16) can be entered and the minimum values can be selected depending on the workpiece, the lowest minimum value (E min) being used for a display (13) and / or for the grinding wheel infeed that either the selected thickness dimensions compare with the specified target value and the grinding wheel feed device (33) can be adjusted forwards or backwards according to the respective control deviation, or that the selected thickness dimensions are comparable with the specified target value and according to a process-dependent mean value (18) de. Control deviations the grinding wheel infeed device (33) can be adjusted forwards or backwards. 2. Apparatus according to claim ", characterized in that a digital computer is provided through which the necessary arithmetic operations for workpiece-dependent selection of the minimum values (E min) and for generating a process-dependent infeed amount (28, 29) to compensate for the control deviation can be carried out.