WO1992004663A1

WO1992004663A1 - Grinding machine controlling and monitoring device and process for operating the same

Info

Publication number: WO1992004663A1
Application number: PCT/CH1990/000204
Authority: WO
Inventors: Hanspeter Batt; Rudolf Gasser; Erwin Roth
Original assignee: Henri Hauser Ag
Priority date: 1990-08-31
Filing date: 1990-08-31
Publication date: 1992-03-19

Abstract

Sensors (11, 14, 16) arranged on the jig grinding machine (1-3, 6, 10) generate signals that are processed, partially displayed or transmitted to the CNC-control (21) by a central controlling and displaying device (18). Sensors (14) arranged on the workpiece (7) or its carrier detect contact with the tool, avoiding 'air grinding' and ensuring an optical and acoustical tool contact display. A sensor (16) arranged on the grinding motor (1) controls the balance. A sensor (11) is secured to a reference plate (10) against which the tool (2) may be guided in order to precisely determine tool dimensions. By combining said controlling and monitoring functions in a single device, the productivity and the precision of machining operations can be considerably increased.

Description

Device for monitoring and controlling a grinding machine and method for operating the same

The present invention relates to a device for monitoring and controlling a grinding machine, which is used for the precise machining of surfaces, in particular bores or contours, e.g. a coordinate grinding machine. The achievable accuracy and productivity depends on various factors, and measures are accordingly known to increase or ensure accuracy and productivity. The aim of the present invention is to provide a device which, with simple operation, permits optimum monitoring of the machine and the respective machining process and, at the same time, optimum productivity. This goal is achieved according to claim 1. Many functions can be performed here with a compact device or with little circuitry complexity.

The invention also relates to a method for operating a grinding machine with a device according to claim 1, which method is described in claim 9, and a method for tool detection according to claim 10.

The invention will now be explained with reference to an embodiment shown in the drawing, based on a coordinate grinding machine.

1 schematically shows a part of the coordinate grinding machine with a workpiece,

2 shows the front of the control and display device according to the invention, 3 schematically shows the adjustment and movement possibilities of the tool, for example the grinding wheel,

Fig. 4 shows a circuit diagram of the electrical equipment and

Fig. 5 is a diagram for explaining the movements for tool detection, i.e. to record the tool dimensions, e.g. Grinding wheel dimension.

Fig. 1 shows more or less schematically the grinding wheel drive, e.g. the grinding motor 1 with the interchangeable grinding wheel 2. The grinding motor is fastened to a schematically illustrated arm 3, which is guided radially adjustable in a grinding spindle 3a (U-axis). This grinding spindle can be adjusted along the vertical axis Z in the grinding head 3b, which in turn can be adjusted in the vertical axis W on the machine frame. These adjustment options are shown schematically in Fig. 3, i.e. the Z axis of the grinding spindle 3a is adjustable in the Z direction and the extension arm with the grinding motor 1 and the grinding wheel 2 shown in FIG. 3 is radially adjustable in the U direction with respect to the spindle axis Z. When the grinding spindle 3a rotates around the Z axis (C axis), the grinding wheel 2 carrying out a planetary movement can thus machine a circular hole 4 in a workpiece 5.

In Fig. 1, another workpiece 7 is clamped on the machine table 6 of the coordinate grinding machine, in which, for example, a rectangular opening 8 with rounded corners and holes 9 are to be machined. To machine the contour of the opening 8, the machine table 6 is adjusted in the XY plane and possibly by turning the grinding spindle (C axis) and Shift of the boom 3 (U-axis), the grinding wheel * is guided along the contour to be machined. These processes are known per se in coordinate grinding machines and do not require any further explanation.

On the machine table 6, a reference plate 10 with a vibration-sensing sensor 11, for example a piezoelectric accelerometer, is fixed in a certain position. On its side facing the grinding spindle or the clamped grinding wheel 2, the reference plate 10 is provided with an abrasion-resistant reference surface 10a, against which the rotating grinding wheel can be brought up to contact as often as desired, without being significantly worn. The sensor 11 is connected to a preamplifier 13 via a cable 12.

A workpiece 7, possibly also on a clamping device for the same or in the vicinity of the workpiece on the machine table 6, two additional sensors 14 are attached in the example shown, which are also connected to the preamplifier 13 via lines 15. The sensors 14 can be of the same type as the sensor 11. A further, preferably similar sensor 16 is attached to the grinding motor 1 and, according to FIG. 1, is connected directly to a measuring and display device 18 via a cable 17. As indicated in FIG. 4, however, the sensor 16 can optionally be used like the sensors 14 and connected to the preamplifier 13, as will be explained below. The output 19 of the preamplifier 13 is also connected to the device 18 ". The device 18 is also connected via a cable 20 to the CNC controller 21 of the coordinate grinding machine for the transmission of data in both directions. While in FIG. 1 only two sensors 14 are shown, in particular in the case of larger workpieces which are on different Any number of sensors 14 are to be machined, or in the case of several workpieces, in order to ensure optimum detection of vibrations at all times and everywhere. As indicated in Fig. 1, it may be sufficient to attach these sensors in particular in the vicinity of the surfaces of the workpiece to be machined. Accordingly, the preamplifier 13 has a certain number of inputs for connecting sensors 14. As will be explained in more detail, the sensors 14 connected to the workpiece or its carrier serve to detect the tool contact with the surface of the workpiece to be machined. The same sensors provide the signals for optical and acoustic tool contact detection. The sensor 11 is used to detect the contact of the rotating grinding wheel with the reference surface 10a of the reference plate 10. The sensor 16 is used to detect the unbalance of the grinding motor 1 with and without the grinding wheel. The sensors 11, 14 and 16 can be provided with holding magnets and can thus be easily attached to workpieces, to the housing of the grinding motor 1 or to the reference plate 10, because in most cases these parts consist of ferromagnetic material. If necessary, however, the same sensors can also be glued or screwed.

The signals from the sensors 11, 14 and 16 are pre-amplified or fed directly to the control and display device 18 and further processed therein. On the front plate of the device 18 (FIG. 2) there is a symbol 22 for the mode "tool detection" (detection of the dimension of the grinding wheel), a symbol 23 for the mode "tool contact detection hole grinding" and a symbol 24- for the mode "tool contact detection contour grinding". A control lamp is assigned to each symbol. A lamp 25 indicates malfunction, a lamp 26 lights up when tool contact occurs, and a lamp 27 lights up when using a ner button 28 a manual noise analysis is carried out in the "tool contact detection contour grinding". A headphone symbol 29 indicates that the keys 30, 31 and 32 underneath are used to adjust the volume in a headphone connected to the socket 33. A bar graph 34 is used to display the noise level or the unbalance, the keys 35, 36 and 37 being used to set the sensitivity of this display or to record the unbalance of the grinding motor. An assigned socket 38 is used to connect the unbalance sensor 16, the circuits described later for checking the unbalance being activated automatically when a connection is made in the socket 38. The preselection by means of the keys 35-37 can take place, for example, such that when all three keys are actuated, the unbalance of the motor is measured without a grinding wheel (REF), while when two keys (35, 37) are actuated, the circuit for checking the Unbalance with grinding wheel (T) is activated. A lamp 39 indicates the operational readiness of the electronics. Lamps 40-43 serve to confirm the setting of the circuit for checking the unbalance of differently dimensioned motors, in particular with different speeds, and a button 44 serves to preselect the circuit states for the unbalance control.

As indicated in FIG. 4, the signals from the various sensors 14 are summed and fed to the input of a channel 13a of the preamplifier 13. The output of the preamplifier channel 13a is connected to the inputs of two bandpass filters 46 and 47 via a changeover switch 45. The area of the bandpass filter 46 can be determined by a central logic 48 of the device. The output of the filter 46 is connected to the input of a comparator 49, at the second input of which a comparison voltage Uref, a memory 50, is indicated. which is set by logic 48. The output of the comparator 49 acts on a circuit 51, which in turn acts on the logic 48, as will be described later. The output of the bandpass filter 47 is connected via two separately controllable amplifiers 52 and 53, on the one hand to the connected headphones and on the other hand via a switch 54 to the bar graph 34. The sensor 11 is connected to the input of an amplifier channel 55 of the preamplifier 13 which is assigned to it and whose output is connected to the one contact of the changeover switch 45. It can therefore optionally be connected to the inputs of the bandpass filters 46 and 47, which is determined by the control 48 indicated by the logic 48. The sensor 16 attached to the grinding motor 1 can optionally, if no balancing control is required, also be connected to the preamplifier channel 13a, in which case it is attached like the sensors 14, for example on the workpiece 7. For balancing control, however, it is connected to the input of a charge amplifier 56, which is followed by an amplifier 57 that can be controlled by logic 48. The output signal of the amplifier 57 passes via a bandpass filter or low-pass filter 58 which can be controlled by the logic 48 and via a switch 59 which can be controlled by the logic 48 to the input of an A / D converter 60, the output of which is connected to the logic 48 . The logic 48 is connected via indicated connections 61 to the indicator lamps and key switches of the device, which are designated by the collective term P (panel). 4 also shows the CNC control 21 of the coordinate grinding machine. Commands and data can be transmitted in two directions between this controller and the logic 48 via the connection 20.

4 shows the circuit for a specific operating state, ie the changeover switch 45 is connected to the Strength channel 13a connected, the switch 54 is connected to the amplifier 53 and the switch 59 is connected to the bandpass filter part of the filter 58. The signals picked up by the sensors 14 are fed via the amplifier channel 13a, the bandpass filter 47 and the amplifiers 52 and 53 to the headphones 29 and the bar graph 34, respectively. The bandpass filter 47, which transmits frequencies in the range of 2.5 kHz, ensures that a pleasant noise is produced in the headphones for the surgeon. On the basis of this noise, it is possible to determine whether the grinding wheel is touching the workpiece at all and whether the grinding process is correct, in particular whether the grinding wheel is gripping correctly or is blunt ("tool contact display"). At the same time, the noise level can be checked on bar graph 34. The volume on the ^headphones' and the Anzeige¬ sensitivity on the bar graph 34 may ker means of Verstär¬ 52 and 53 and the keys are einge¬ 30-32 or 35-37 provides.

In the "tool detection of bore grinding" mode, the CNC 21 reports the corresponding operating mode to the device 18 with the panel P via the logic 48, so that the indicator lamp lights up at the symbol 23. Accordingly, the grinding wheel 2 is fed to the bore wall at high speed. Before the delivery, the basic noise level is automatically determined and stored in the memory 50. As soon as the grinding wheel touches the workpiece, the signal at the output of the filter 46 rises such that the comparator 49 responds and outputs a touch signal to the logic 48 via the switching stage 51. The bandpass filter 46 operates at the natural frequency of the sensors, which is preferably the same for all sensors. As soon as the contact of the grinding wheel with the workpiece is established, the logic control 48 switches the CNC control 21 to the work feed. That with this In the mode of operation, the correct sensors are switched on by means of the switch 45, the logic 48 determines, which in turn receives the required information from the part program from the CNC control. Once there has been a switch to work feed, the same bore does not switch back to overdrive unless the grinding wheel is lifted off the finished surface.

In the "tool detection contour grinding" mode, the grinding wheel is guided along the contour at high speed until the first contact with the workpiece. Otherwise, the process corresponds to that described above for grinding a hole. In this case, however, the basic noises are not determined automatically, but rather by pressing the key 28 for setting the reference level in the memory 50. This occurs while the grinding wheel is being emptied along the contour. Incidentally, the first time the grinding wheel comes into contact with the workpiece, the machine switches to the work feed. However, if the tool no longer intervenes on the workpiece, "which can occur during contour grinding, the gear is switched back to high speed after a certain delay until the grinding wheel touches the workpiece again. The" Tool contact detection "modes described above are used to: to prevent the so-called "air grinding".

The unbalance control is initiated by plugging the cable 17 of the sensor 16 into the socket 38 of the device 18 and by pressing the buttons 35-37 or 35 and 37. The button 44 is used to make the presetting for the corresponding motor size or speed, as a result of which the filter 58 is set by the logic 48 and the changeover switch 59 is possibly switched over. Furthermore, the changeover switch 54 is flipped so that a signal from the sensor 16 via the amplifiers 56 and 57 the effective filter 58, the changeover switch 59, the A / D converter 60, the logic 48, the D / A converter 60a and the changeover switch 54 reach the bar graph 34 which indicates the extent of the unbalance. As mentioned, the amplifier 57 and the bandpass filter or lowpass filter 58 are selected depending on the motor size or speed. For low-speed motors, the low-pass filter is switched on, while for faster-running motors, the bandpass filter is switched on and the logic 48 is set according to the preselection. The unbalance signal is processed in logic 48 in digital form and then analogized via D / A converter 60a and fed to the display.

In the "tool detection" mode, i.e. To determine the grinding wheel dimension, the corresponding function (22) is selected by means of the controller 21 (in the part program) via the logic 48. Here, the switch 45 is flipped to the output of the amplifier 55, so that now only the sensor 11 is effective. As with the other functions, the basic noise is initially determined automatically and the memory 50 is set. Then, when the grinding wheel is touched on the reference surface 10a of the reference plate 10, the position of the grinding wheel axis in the X or Y and U directions is detected and stored in the CNC control. From this, the CNC control calculates the necessary corrections which must be taken into account in the next processing. The cycle for the "tool detection bore grinding" can e.g. 5 as follows:

A. Use the grinding spindle (Z) to move to the upper stop position and the W axis to the programmed position.

B. Position the reference surface 10a along the X and possibly Y axis so that the distance of the same to the machine spindle center corresponds to the radius to be ground. Then move along the U-axis to the position that corresponds to the bore radius minus the grinding wheel radius entered in the tool store minus a safety distance S1 (FIG. 5).

C. Index the machine spindle in the C-axis so that the U-axis is perpendicular to the reference surface 10a of the plate 10. Drive with the grinding spindle in direction Z to the level stored in the memory, so that the grinding wheel is in front of the reference surface 10a. This situation is indicated in FIG. 5, where the grinding wheel 2 is at a safety distance S1 in front of the reference surface 10a of the plate 10. The grinding motor is now started and after a waiting period a basic noise analysis is carried out as described above.

D. The grinding wheel 2 is gradually guided against the reference surface 10a.

E. The first touch of the grinding wheel on the reference surface 10a is detected and transmitted to the CNC controller 21.

F. Retraction of the grinding wheel in the U direction and renewed delivery to a new smaller safety distance S2.

G. Start of planetary movement and recording of a new basic noise level.

H. Infeed of the grinding wheel in the U direction against the reference plate 10, one step (0.1-1 μm) being delivered per planetary revolution. I. Second touch as mentioned under E).

K. Retraction in the U direction and redelivery to a safety distance S3 of, for example, 5 μm.

L. Slow infeed as for H, with one step per four planet revolutions.

M. When the grinding wheel is touched a third time on the reference surface 10a, the CNC control calculates the difference to the theoretically entered grinding wheel radius based on the current positions X or Y and U and corrects this entry.

N. Retraction of the grinding wheel in the U direction.

O. Retraction in the Z and W axes to the starting position.

P. Drive into the rough machined hole and machine it according to the appropriate cycle.

It is possible to program two cycles, one of which contains all points A-P, the other only points G-P, with a first infeed according to A + B at the safety distance S-.

The procedure for grinding contours is basically the same, with the exception that the planetary movement is not switched on at point G and the infeed step frequencies are programmed in the cycle by means of holding times. In addition, the delivery to the reference plate 10 takes place by adjustment in the X-axis with a fixed U-axis.

The device described above is designed for a specific combination of several functions. The special However, the advantages of combining several control and monitoring functions in a single device are also achieved with other combinations of at least two functions.

Claims

1. Device for monitoring and controlling a grinding machine, for detecting and evaluating vibrations, characterized in that several functions are combined in a central, common control and display device (18), which monitor and control several parameters of the machine and the Serve processing operation.

2. Device according to claim 1, characterized in that a plurality of identical or identical sensors (11, 14, 16) are provided, to which the adjustment circuits (52, 53, 57) corresponding to the parameter, switching means (45, 54, 59) are provided. or controllable circuits (46, 58) are assigned.

3. Device according to claim 1 or 2, characterized gekenn¬ characterized in that several on one or more workpieces (7) or on a workpiece holder sensors (14) are provided for the tool contact detection and for the optical and acoustic tool contact display are.

4. Device according to claim 3, characterized in that the sensors (14, 16), preferably piezoelectric acceleration sensors, are connected in parallel to the input of a first evaluation channel (13a, 46, 49).

5. Device according to claim 4, characterized in that in the first channel (13a, 46, 49) there is a controllable band-pass filter (46) and that a sensor (11) for tool detection (detection of the tool dimensions) can optionally be connected to the channel is.

6. Device according to claim 4 or 5, characterized gekenn¬ characterized in that in the first channel is a comparison circuit with a comparator (49) and with a variable memory (50) for a comparison level.

7. Device according to one of claims 1-6, gekenn¬ characterized by a second evaluation channel (56,57,58, 60) for imbalance detection, the second channel for the different speeds of the tool spindle (1) can be switched, e.g. a switchable filter (58) is provided.

8. Device according to one of claims 1-7, characterized in that with the sensor (11, 14, 16) and with the CNC control (21) of the grinding machine connectable, i.e. Control and display device (18) compatible with an existing machine is provided, which transmits control signals to the CNC control and receives control signals from the same.

9. A method for operating a grinding machine with a device according to claims 5 and 7, characterized gekenn¬ characterized in that the imbalance of the tool spindle with the tool is first detected and corrected, whereupon the tool against a reference surface provided with a sensor for detecting the tool dimensions becomes, whereupon the machining process is controlled taking into account the recorded tool dimensions.

10. The method for tool detection by means of a device according to claim 1, characterized in that the tool is repeatedly guided against the reference surface, the tool (2) preferably being fed again with different movement sequences after each contact with the reference surface (10a) (Fig. 5).

11. The method according to claim 10, characterized in that the tool (2) is delivered with different rapid sequences of steps.