Device and method for controlling setup of a grinding machine

Abstract: A method of controlling setup of a grinding machine (1) wherein a grinding wheel is positionable with respect to a workpiece (6) for grinding. The wheel and workpiece (6) are closed (100, 110) inside a safety enclosure, and the wheel is moved (130) towards the workpiece to achieve contact between the parts. Contact is determined (140) by monitoring the vibration produced by interaction between the wheel and workpiece, and the position (X 0 , Z 0 ) of the wheel and of the workpiece, at which the parts come into contact, is then determined and memorized.

Description: The present invention relates to a device and method for controlling setup of a grinding machine, as set forth in the preambles of claims 1 and 6, respectively. Grinding machines are known on which a supporting structure comprises a supporting device for supporting the opposite ends of a substantially axially symmetrical workpiece, for rotating the workpiece about its longitudinal axis, and for moving the workpiece back and forth in a first straight direction. Grinding machines also comprise at least one grinding wheel rotated by an electric motor and movable radially to and from the workpiece in a second direction crosswise - in particular, perpendicular - to the first direction. WO 95/03913 for instance describes a grinding machine. Known grinding machines are normally controlled by an electronic control unit, which controls the movements of the grinding wheel and supporting device to move the wheel to and from the workpiece in various directions and perform various grinding operations on the workpiece. The electronic control unit comprises interface means - normally a keyboard and video - for programming the unit, i.e. entering commands by which to create coded instructions for controlling the movement of the wheel and performing various elementary grinding cycles, each of which is characterized by a given position of the wheel and by the way in which the wheel is moved towards and contacts the workpiece. Such programming is preceded, however, by a so-called machine setup stage, in which the wheel is moved manually towards the workpiece until the rotating wheel makes physical contact (touches) the workpiece; at which point, a command is issued to determine and memorize the wheel and workpiece coordinates relative to the contact position. The above coordinates are then used for performing successive programming stages. Contact between the wheel and workpiece is normally monitored by an operator, who issues a command to move the wheel towards the workpiece and, at the same time, visually determines the position of the wheel with respect to the workpiece. Upon contact of the parts, as determined by direct visual observation, a command is issued manually to determine and memorize the contact positions of the wheel and workpiece. For the wheel position to be determined visually, the grinding machine must have an opening allowing a clear view of the moving parts, i.e. the wheel and workpiece, inside. The above manual procedure obviously fails to conform with numerous (e.g. European) safety directives, which require that all the moving parts of a grinding machine, when in operation, be housed inside a safety enclosure affording absolutely no access from the outside. Any setup procedure based on visual observation of the moving parts therefore cannot possibly be performed in accordance with safety regulations, since enclosing the moving parts of the machine inside a safety enclosure - even one with transparent portions - prevents a clear view of the point of contact between the wheel and workpiece. It is an object of the present invention to provide a device and method for controlling setup of a grinding machine in conditions of the utmost safety at all times, i.e. with the internal moving parts of the machine housed inside a safety enclosure affording no access from the outside. According to the present invention, there is provided a device for controlling setup of a grinding machine, as described in Claim 1. The present invention also relates to a method of controlling setup of a grinding machine, as described in Claim 6. The invention will now be described with particular reference to the accompanying drawings, in which: Figure 1 shows an outside view in perspective of a grinding machine operating in accordance with the present invention; Figure 2 shows a schematic top plan view of the Figure 1 grinding machine; Figure 3 shows a block diagram of the method for controlling setup of a grinding machine according to the present invention; Figure 4 shows a larger-scale view of a detail of the Figure 1 grinding machine. Number 1 in Figures 1 and 2 indicates as a whole a known grinding machine, wherein a supporting structure 2 (Figure 2) comprises a straight guide 3, along which a carriage 4, powered by actuating devices (not shown), runs reversibly in a direction Z defined by straight guide 3. Carriage 4 carries a known supporting device 5 for supporting a substantially axially symmetrical workpiece 6 aligned with direction Z. More specifically, supporting device 5 comprises two vertical structures 5a, 5b located on opposite sides of carriage 4 and for supporting opposite ends 6a, 6b of workpiece 6 with its longitudinal axis H parallel to direction Z. Workpiece 6 is a generic metal part (e.g. a shaft) for grinding. Supporting device 5 also provides for rotating workpiece 6 about longitudinal axis H. Grinding machine 1 also comprises a straight guide 7, along which a carriage 8, powered by actuating devices (not shown), runs reversibly in a direction X perpendicular to direction Z. Carriage 8 carries a supporting structure 9 having a grinding wheel 10 rotated by an electric motor 11 about a rotation axis R crosswise to direction X. Carriage 8 may, of course, support a number of grinding wheels - in particular, two - as opposed to the one shown. Supporting structure 9 may also be oriented angularly (by actuators not shown) about a vertical axis with respect to carriage 8, so as to modify the angle formed between the Z and X directions. In the embodiment shown, said angle is a fixed 90° angle. Grinding machine 1 is controlled by an electronic control unit 12, which controls: the movement of carriage 4 along guide 3 to adjust the Z-direction position of workpiece 6; and the movement of carriage 8 along guide 7 to adjust the X-direction position of grinding wheel 10 and move grinding wheel 10 towards/away from workpiece 6. Grinding machine 1 also comprises sensors (not shown) for continuously determining, with respect to the origin of a reference system (not shown), the X-direction position Xp of grinding wheel 10, and the Z-direction position Zp of carriage 4, and therefore of workpiece 6. Grinding machine 1 also comprises an outer metal safety enclosure 13 (Figure 1), which is substantially parallelepiped-shaped and houses all the mechanical/electromechanical components of machine 1. More specifically, safety enclosure 13 comprises a front opening 14 enabling access to internal machine parts, such as structure 9 supporting grinding wheel 10, and the carriage supporting workpiece 6. Front opening 14 has a sliding door 15, which is movable between a rest position wherein the above internal machine components are accessible from outside enclosure 13 through opening 14, and a closed position wherein opening 14 is fully closed and allows no access from the outside to any machine parts inside enclosure 13. More specifically, door 15 comprises a contoured metal frame 16 supporting a contoured transparent wall 17 made of shockproof synthetic material. According to the present invention, electronic unit 12 cooperates with a vibration sensing device 18 (Figure 4) connected to grinding wheel 10. Alternatively, vibration sensing device 18 may be connected to workpiece supporting device 5. Vibration sensing device 18 comprises an ultrasonic transducer positioned coaxially with grinding wheel 10 and for detecting the vibration produced when grinding wheel 10 contacts workpiece 6. More specifically (Figure 4), grinding wheel 10 is fitted to a first tubular sleeve 20a extending axially from wheel 10 and fitted on its free end with a second tubular sleeve 20b housing a first component element 19a of sensor 18. First component element 19a rotates with wheel 10, is connected rigidly to wheel 10 by sleeves 20a, 20b, and has a free end facing a second component element 19b of sensor 18. Second component element 19b transmits to first component element 19a energy in the form of waves (electromagnetic waves or infrared rays) and which contributes towards supplying an electronic circuit (not shown) of first element 19a. The electronic circuit (not shown) is connected to a sensor (not shown) for detecting the vibration produced in wheel 10 on contacting a touch element (workpiece or diamond tool) and transmitted from wheel 10 to first component element 19a via sleeves 20a, 20b. The electronic circuit is capable of discriminating between the above vibration and any other vibration and/or interference picked up by the sensor, so as to supply a transmitting circuit (not shown) with information relative to the detected vibration and which is supplied to second element 19b in the form of electromagnetic radiation. Transducer 18 as a whole generates a bistable signal (generated by component element 19b), which assumes a first logic value - e.g. a logic "zero" - upon detection of a vibration caused by grinding wheel 10 contacting a touch element, and a second logic value - in particular, a logic "one" - when no vibration is detected, i.e. indicating no contact between wheel 10 and the touch element. Operation of grinding machine 1 according to the method of the present invention will be described with reference to the Figure 3 block diagram. To begin with, a first block 100 closes front opening 14 by moving door 15 from the rest to the closed position. This may be done manually using a handle 22 on door 15 (Figure 1), or automatically by means of a servocontrol (not shown) controlled by electronic unit 12. Block 100 is followed by a block 110, which determines whether opening 14 is closed. If it is, block 110 is followed by a block 120, which initiates a safety, i.e. closed-door, machine 1 setup procedure with opening 14 closed by door 15 and all the internal parts of machine 1 inaccessible from outside enclosure 13. Closure of door 15 may be determined, for example, by means of position sensors (not shown) for detecting the correct closed position of door 15; and provision may also be made for programmed mechanical locking of door 15 to prevent door 15 from being opened again until grinding wheel 10 is perfectly stationary. Block 120 is followed by a block 130 permitting manual positioning of grinding wheel 10 with respect to workpiece 6. In particular, the operations in block 130 comprise: moving wheel 10 in direction X towards supporting device 5 and, hence, towards workpiece 6 - this may be controlled using a first handwheel 23 connected to a transducer (not shown) for supplying signals to electronic unit 12, which, in response, produces signals for controlling the actuators (not shown) of carriage 8 and so moving grinding wheel 10 in direction X; and moving workpiece 6 in direction Z to vary the position of workpiece 6 laterally with respect to grinding wheel 10 - this may be controlled by means of a second handwheel 24 connected to a transducer (not shown) for supplying signals to electronic unit 12, which, in response, produces signals for controlling the actuators (not shown) of carriage 4 and so moving workpiece 6 in direction Z. Block 130 is followed by a block 140, which constantly controls the signal generated by vibration sensing device 18. More specifically, when the signal generated by vibration sensing device 18 assumes a logic "1" value, i.e. when no vibration is detected, thus indicating no contact between wheel 10 and workpiece 6, block 140 goes back to block 130. Conversely, when the signal generated by vibration sensing device 18 assumes a logic "0" value, i.e. when vibration is detected, thus indicating contact between wheel 10 and workpiece 6, block 140 goes on to a block 150. According to the present invention, supporting device 5 - in particular, vertical structure 5b - may also be fitted with a known diamond tool D comprising a shank extending from vertical structure 5b towards wheel 10 and fitted on the free end with an industrial diamond. As an alternative to the above wheel 10-workpiece 6 contact procedure, diamond tool D provides for dressing wheel 10. That is, the industrial diamond is brought into contact with the rotating grinding wheel 10 to remove a surface layer of, and so dress, wheel 10 by removing the surface layer of the grinding wheel blunted in the course of previous grinding cycles. Block 130 also permits mutual manual positioning of grinding wheel 10 and diamond tool D; and the operations in block 130 again comprise moving wheel 10 in direction X towards diamond tool D by means of first handwheel 23, and moving diamond tool D in direction Z by means of second handwheel 24. In the above embodiment, block 140 obviously provides for detecting vibration indicating contact between wheel 10 and diamond tool D. Block 150 arrests the grinding wheel 10-workpiece 6 manual positioning procedure to prevent any further movement of grinding wheel 10 in direction X and/or of workpiece 6 in direction Z. If diamond tool D is used, block 150 arrests the grinding wheel 10-diamond tool D manual positioning procedure to prevent any further movement of grinding wheel 10 in direction X and/or of diamond tool D in direction Z. When grinding wheel 10 contacts (or "touches") workpiece 6 or diamond tool D, a visual and/or sound signal is generated to inform the machine 1 operator 25 (Figure 2). The visual signal may, for example, be in the form of a message - "WHEEL-WORKPIECE CONTACT" or "WHEEL-DIAMOND TOOL CONTACT" - shown on an alphanumeric display device 26. Block 150 then goes on to a block 160, in which the operator (using control keys 27, for example) can select between two procedural options: a first option whereby the coordinates of grinding wheel 10 and workpiece 6 or of grinding wheel 10 and diamond tool D, measured upon contact between the parts being detected, are immediately memorized automatically; and a second option whereby wheel 10 is positioned further with respect to workpiece 6 or diamond tool D. If the first option is selected, block 160 is followed by a block 170, which determines the X-direction position (X 0 coordinate) of grinding wheel 10, at which contact between wheel 10 and workpiece 6 or between wheel 10 and diamond D was detected (logic "zero" signal generated by the vibration sensing device); and the Z-direction position (Z 0 coordinate) of carriage 4, at which contact between wheel 10 and workpiece 6 or between wheel 10 and diamond D was detected (logic "zero" signal generated by the vibration sensing device). The X 0 and Z 0 coordinates are then memorized by a manual command entered by operator 25. Block 170 also terminates the procedure. If the second option is selected, block 160 is followed by a block 180, which permits low-speed micrometric feed of grinding wheel 10 towards workpiece 6 and/or of workpiece 6 towards wheel 10, to remove a surface layer of material from, and so pregrind, workpiece 6. If a diamond tool D is used, block 180 commands low-speed micrometric feed of grinding wheel 10 towards diamond tool D, which is movable in direction Z, to remove a surface layer of material from, and so dress, wheel 10. Block 180 is followed by a block 190, which awaits a manual command to terminate the above pregrinding or dressing operation. In the event the pregrinding or dressing operation is not terminated, block 190 goes back to block 180. Conversely (pregrinding or dressing operation terminated), block 190 is followed by block 170, which, after arresting the relative movement of wheel 10 and workpiece 6 or wheel 10 and diamond tool D, determines the X-direction position (coordinate X 01 ) of grinding wheel 10, at which the pregrinding or dressing operation was terminated; and the Z-direction position (coordinate Z 01 ) of carriage 4 (and hence of workpiece 6 or diamond tool D carried by carriage 4), at which the pregrinding or dressing operation was terminated. The X 01 and Z 01 coordinates are then memorized by a manual command. The advantages of the present invention will be clear from the foregoing description. That is, it provides for setting up the machine in conditions of the utmost safety at all times, i.e. completely closed throughout the setup procedure. The moving parts, i.e. at least wheel 10, workpiece 6, diamond tool D, carriage 4 and carriage 8, are enclosed, throughout the setup procedure, inside machine 1, which is closed and therefore in a condition of the utmost safety. The coordinates indicating the wheel-workpiece or wheel-diamond tool contact position, in fact, are determined by determining vibration, with no operator assistance required to determine contact between the parts. The contact position coordinates are memorized manually by simply pressing a key to enter the data, and possibly a second key to confirm the data. Clearly, changes may be made to the device and method of controlling setup of a grinding machine, as described and illustrated herein, without, however, departing from the scope of the claims.

Claims: A device for controlling setup of a grinding machine (1), wherein at least one grinding wheel (10) rotated by drive means (11) is positionable (23, 24), by actuating means, with respect to a touch body (6, D) carried by supporting and positioning means (4, 5b) and interacting physically with the rotating wheel (10); said grinding machine comprising: a safety enclosure (13) for enclosing moving parts (10, 6, 4, 8) of the machine; said moving parts comprising at least said grinding wheel (10) and said touch body (6, D), and being accessible from outside said enclosure (13) through at least one opening (14) in the enclosure; closing means (15) movable between a rest position and a work position closing said opening (14); and vibration sensing means (18) for determining contact (140) between said grinding wheel (10) and said touch body (6, D); said device being characterized by comprising setup means comprising: closure sensing means (100, 110) for determining the position of said closing means in said work position to determine closure of said enclosure and enable a setup procedure; actuating means (23, 24) for generating control signals, in the course of said setup procedure, to adjust the mutual position (130, 140) of said grinding wheel (10) and said touch body (6, D); said vibration sensing means (18) determining a first state wherein contact is detected and vibration generated between said grinding wheel and said touch body (6, D), and a second state wherein said contact is excluded; and means (170) for determining the position (X, Z) of said grinding wheel (10) and of said supporting and positioning means (4, 5b) to determine and memorize the coordinates (X 0 , Z 0 ) of said grinding wheel (10) and said touch body (6, D) upon detection of said contact. A device as claimed in Claim 1, characterized in that , upon detection of the first state, said vibration sensing means activate selecting means (160) for selecting: first control means for controlling a first operating step (170) wherein the coordinates of the grinding wheel (10) and said touch body (6, D), measured in the position in which said first state was determined, can be memorized (27); and second control means for controlling a second operating step (170) wherein the grinding wheel (10) is positioned further with respect to said touch body (6, D) to bring about an interaction between the contacting parts and removal of a surface layer from one of the two contacting parts. A device as claimed in Claim 2, characterized in that said second control means activate said means for determining the position (X, Z) of said grinding wheel (10) and of said touch body (6, D), to respectively memorize the coordinates (X 01 , Z 01 ) of said grinding wheel (10) and said touch body (6, D) following said interaction between the parts. A device as claimed in any one of the foregoing Claims, characterized in that said touch body (6, D) comprises a workpiece (6) for grinding by said grinding wheel (10). A device as claimed in any one of Claims 1 to 3, characterized in that said touch body (6, D) comprises a diamond tool (D) by which to dress said grinding wheel (10). A method of controlling setup of a grinding machine (1), wherein a grinding wheel (10) rotated by drive means (11) is positionable (23, 24), by actuating means, with respect to a touch body (6, D) interacting physically with the wheel; said touch body (6, D) being carried by supporting means (4, 5b); comprising the step of: closing (100, 110) the moving parts (10, 6, D) of said machine inside a safety enclosure (13); said moving parts (10, 6) comprising at least said grinding wheel (10) and said touch body (6, D); characterized by the further steps of: generating (23, 24) a control signal and, in response to said control signal, adjusting the mutual position (130, 140) of said grinding wheel (10) and said touch body (6, D); determining contact (140) between the parts comprising said grinding wheel (10) and said touch body (6, D); said step of determining contact (140) between the parts comprising the steps of: detecting (18) a signal correlated to the vibration produced by mechanical interaction between the contacting parts; and determining the position (X, Z) of said grinding wheel (10) and of said touch body (6, D) upon generation of said signal, and memorizing the coordinates of said positions. A method as claimed in Claim 6, characterized in that , following detection of said contact between the parts, a selection step (160) is performed to select between two operating steps comprising: a first operating step (170) wherein the coordinates of the grinding wheel (10) and the touch body (6, D), determined in the position in which said contact between the parts was determined, can be memorized immediately; and a second operating step (170) wherein the grinding wheel (10) is positioned further with respect to the touch body (6, D) to bring about said contact between the parts and removal of a surface layer from one of the two contacting parts. A method as claimed in Claim 7, characterized in that said second operating step (170) is followed by a step (170) wherein the coordinates (X 01 , Z 01 ) of the grinding wheel (10) and said touch body (6, D), determined upon said contact between the parts and removal of a surface layer from one of the two parts, are memorized.

Inventors: TACCHELLA CLAUDIO, TACCHELLA, CLAUDIO
Applicants: TACCHELLA MACCHINE SPA, TACCHELLA MACCHINE S.P.A.
Application year: 2000
Main classification: B24B47
IPC codes: B24B47, B24B55, B24B5, B24B51