A real-time monitoring and control method for local pressure of double-sided grinding machine

Abstract

The present invention discloses a method for real-time monitoring and control of local pressure of a double-sided grinder, comprising the following steps: detecting and analyzing local pressure data of the contact surface of the upper grinding disc and the lower grinding disc under static conditions; measuring the local pressure between the upper grinding disc and the lower grinding disc and the workpiece respectively during loading; collecting local pressure data during processing in real time; and trimming the surface shape of the grinding pad using a suitable method. The present invention collects local pressure through a grid-type thin film pressure sensor, and presents the pressure distribution on the surface of the grinding disc in the form of a digital array, which is intuitive and clear. Before processing, the present invention can eliminate the problem of impurities on the surface of the grinding disc scratching the workpiece and the poor surface shape of the grinding disc affecting the processing quality of the workpiece, and can reduce unnecessary experimental costs. The present invention monitors the local pressure of the contact surface between the workpiece and the grinding disc in real time, and stops processing in time when an abnormality occurs, so as to avoid economic losses caused by the collapse of the workpiece or even the destruction of other workpieces by fragments.

Description

Technical Field

[0001] The invention belongs to the field of precision / ultra-precision machining and relates to a local pressure real-time monitoring and control method for a double-sided grinding machine. Background Art

[0002] The double-sided grinding process is mainly used to process crystals or other mechanical parts with two parallel surfaces, which can meet higher flatness and parallelism requirements. In the double-sided grinding process, the workpiece removes the workpiece material under the interaction with the grinding disc surface. According to the Preston equation, the material removal rate is proportional to the contact pressure and relative movement speed of the workpiece surface. Therefore, on the same workpiece surface, the surface contact pressure of each area directly affects the material removal rate of each area. The uneven material removal rate of each area will affect the process indicators such as the flatness and parallelism of the workpiece surface.

[0003] For workpieces with high process requirements and special physical properties such as wafers, lithium niobate, and sapphire, problems such as uneven local material removal leading to deterioration of flatness and parallelism, and workpiece breakage due to stress concentration often occur during double-sided grinding. These problems are closely related to the contact pressure between the workpiece and the grinding disc. Analysis shows that the reasons for uneven contact pressure are as follows: deterioration of surface quality due to disc wear during the use of the grinding disc; deformation of the workpiece caused by the release of internal stress due to workpiece material removal; fluid dynamic pressure caused by the introduction of grinding fluid into the contact area, etc.

[0004] Chinese patent CN 106926113 A discloses a high-precision double-sided grinding and polishing machine, which is provided with a pressure compensator for balancing the gravity of the upper disc seat and the upper grinding disc and for controlling the pressure applied by the upper grinding disc to the workpiece.

[0005] Chinese patent CN 216463907 U discloses a constant pressure double-sided wafer grinder, which can maintain a constant pressure on the grinding disc. A weighing sensor is installed under the cylinder responsible for lifting the upper grinding disc. During actual processing, the cylinder and the weighing sensor cooperate with each other to control the pressure of the upper grinding disc on the workpiece.

[0006] Chinese patent CN 205438164 A discloses a precision pressurizing system feedback device for a double-sided grinder and a double-sided grinder. The machine tool detects the real-time pressure of the double-sided grinder during processing through the precision pressurizing system feedback device and regulates it through a cylinder to ensure that the pressure tends to be stable.

[0007] The above patents can only control the overall pressure of the upper grinding disc on the workpiece, but cannot effectively measure the local pressure on the contact surface between the workpiece and the grinding disc, and cannot fundamentally avoid the impact of uneven local pressure. Summary of the invention

[0008] In order to solve the above problems existing in the prior art, the present invention proposes a local pressure real-time monitoring and control method for a double-sided grinder that can effectively measure the local pressure on the workpiece surface and avoid the negative impact of local pressure unevenness.

[0009] In order to achieve the above object, the technical solution of the present invention is as follows: a method for real-time monitoring and controlling the local pressure of a double-sided grinding machine, wherein the double-sided grinding machine at least comprises a machine tool body, a grid-type thin film pressure sensor and a processor,

[0010] The machine tool body at least includes a bed, an operation panel, a gantry, an upper grinding disc and a lower grinding disc; the operation panel is installed on the bed for human-machine interaction; the lower grinding disc is installed at the center of the bed through a lower disc base; the gantry is installed on the bed, spanning the lower grinding disc; the upper grinding disc is installed below the gantry through an upper disc fixing seat;

[0011] The working surfaces of the upper grinding disc and the lower grinding disc are both installed with a grid-type thin film pressure sensor, and the outer surface of the grid-type thin film pressure sensor is bonded with a grinding pad; the grid-type thin film pressure sensor is composed of a plurality of thin film pressure sensor units, and each thin film pressure sensor unit is installed on the entire working surface in a square grid unit array; there are two processors, which are respectively installed on the non-working surfaces of the upper grinding disc and the lower grinding disc; each thin film pressure sensor unit is connected to the processor of the upper grinding disc and the lower grinding disc through a data line; the method comprises the following steps:

[0012] A. When there is no workpiece on the double-sided grinder, the upper grinding disc is placed statically above the lower grinding disc. Several thin film pressure sensor units on the grid-type thin film pressure sensor collect the local pressure of the corresponding areas of the upper and lower grinding discs; transmit the local pressure data to the processor, which analyzes the local pressure data of the contact surface of the upper and lower grinding discs under static conditions; and presents the surface pressure distribution of the upper and lower grinding discs in the form of a digital array; if the size of the local pressure abnormal area is less than 1cm 2 , and the pressure increment is greater than 80% of the average pressure, check whether there are impurities on the outer surface of the grinding pads of the upper and lower grinding discs that may damage the surface of the workpiece, and deal with them. If there are no such problems, observe the overall pressure distribution between the upper and lower grinding discs and the workpiece;

[0013] B. After eliminating the local pressure anomaly caused by impurities, adjust the upper grinding disc load to the load corresponding to this processing. Measure the local pressure between the upper grinding disc and the lower grinding disc and the workpiece. If there is a large-scale anomaly in the overall pressure distribution between the upper grinding disc and the lower grinding disc and the workpiece, and the size of the abnormal area is greater than 1cm 2, and the pressure change value is less than 80% of the average pressure, then the thickness of the grinding pad is considered to be uneven. Combined with the material of the grinding pad, use appropriate methods to trim the grinding pad. If there are no above problems, place the workpiece.

[0014] C. Place the workpiece and start processing. The grid-type thin film pressure sensor collects local pressure data during the processing in real time and transmits the data to the processor in real time. The processor evaluates the release of internal stress caused by the removal of workpiece material and the fluid dynamic pressure caused by the introduction of grinding fluid into the contact area. If the local pressure exceeds 300% of the average pressure, stop processing in time; continue processing after adjusting the process parameters; if there are no above problems, continue processing.

[0015] D. For areas larger than 1cm during processing 2 If the large-scale pressure anomaly is analyzed, if the area of ​​the region continues to expand and the anomaly value increases with the progress of processing, the wear and deformation of the upper and lower grinding discs should be considered, the processing should be stopped in time, and the surface shape of the grinding pad should be trimmed by appropriate methods.

[0016] E. After a period of processing, when the pressure distribution of each workpiece is consistent and tends to be stable, process according to the following pressure distribution conditions: if the pressure in the center of the workpiece is large and the pressure around it is small, go to step E1; if the pressure in the center of the workpiece is small and the pressure around it is large, go to step E2; otherwise, go to step E3;

[0017] E1. If the corresponding surface of the workpiece is convex, then the edge area of ​​the circular ring of the grinding pad is slightly ground. After grinding, the workpiece is loaded again, and the pressure in the center of the workpiece is greater than the pressure around it, so that the material removal rate in the center area of ​​the workpiece is greater, and the overall surface shape of the workpiece tends to be flat; go to step E3;

[0018] E2. If the corresponding surface shape of the workpiece is concave, then the middle area of ​​the circular ring of the grinding pad is slightly ground. After grinding, the workpiece is loaded again. The pressure in the center of the workpiece is less than the pressure around it, so that the material removal rate around the workpiece is greater and the overall surface shape of the workpiece tends to be flat;

[0019] E3. Continue processing until the workpiece meets the processing requirements.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention collects local pressure through a grid-type thin film pressure sensor and presents the pressure distribution on the grinding disc surface in the form of a digital array, which is intuitive and clear.

[0022] 2. The present invention can eliminate the problem of impurities on the grinding disc surface scratching the workpiece and the problem of poor grinding disc surface shape affecting the workpiece processing quality before processing, thereby reducing unnecessary experimental costs and ensuring the pass rate.

[0023] 3. The present invention monitors the local pressure of the contact surface between the workpiece and the grinding disc in real time. When the local pressure exceeds the normal range threshold, the processing is stopped in time to avoid the economic loss caused by the workpiece breaking or even the fragments damaging other workpieces.

[0024] 4. The present invention monitors the local pressure of the contact surface between the workpiece and the grinding disc in real time, and timely feeds back the wear condition of the grinding disc, thereby avoiding the deterioration of the workpiece surface shape caused thereby, and reducing time cost and waste of resources.

[0025] 5. The present invention can make slight adjustments to the surface shape of the grinding pad according to the local pressure of the workpiece, thereby controlling the local pressure of the workpiece and effectively solving the problem of convex or concave in the workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is an overall diagram of the double-sided grinding machine of the present invention;

[0027] Figure 2 is a schematic diagram of a mesh-type thin film pressure sensor of the present invention;

[0028] Figure 3 It is a schematic diagram of installing the mesh-type thin film pressure sensor of the present invention;

[0029] Figure 4 It is a flow chart of the present invention.

[0030] In the figure: 1. bed, 2. operation panel, 3. gantry, 4. workpiece, 5. upper grinding disc, 6. lower grinding disc, 7. grid-type thin film pressure sensor, 8. thin film pressure sensor unit, 9. processor, 10. grinding pad. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings. Figure 1-4 As shown, a local pressure real-time monitoring and control method for a double-sided grinding machine, the double-sided grinding machine at least includes a machine tool body, a grid-type film pressure sensor 7 and a processor 9,

[0032] The machine tool body at least includes a bed 1, an operation panel 2, a gantry 3, an upper grinding disc 5 and a lower grinding disc 6; the operation panel 2 is mounted on the bed 1 for human-machine interaction; the lower grinding disc 6 is mounted at the center of the bed 1 through a lower disc base; the gantry 3 is mounted on the bed 1, spanning the lower grinding disc 6; the upper grinding disc 5 is mounted below the gantry 3 through an upper disc fixing seat;

[0033] The working surfaces of the upper grinding disc 5 and the lower grinding disc 6 are both installed with a grid-type thin film pressure sensor 7, and the outer surface of the grid-type thin film pressure sensor 7 is bonded with a grinding pad 10; the grid-type thin film pressure sensor 7 is composed of a plurality of thin film pressure sensor units 8, and each thin film pressure sensor unit 8 is installed on the entire working surface in a square grid unit array; there are two processors 9, which are respectively installed on the non-working surfaces of the upper grinding disc 5 and the lower grinding disc 6; each thin film pressure sensor unit 8 is connected to the processor 9 of the upper grinding disc 5 and the lower grinding disc 6 through a data line; the method comprises the following steps:

[0034] A. When the double-sided grinder is not equipped with a workpiece 4, the upper grinding disc 5 is placed statically above the lower grinding disc 6, and several thin film pressure sensor units 8 on the grid-type thin film pressure sensor 7 collect the local pressure of the corresponding areas of the upper grinding disc 5 and the lower grinding disc 6; the local pressure data are transmitted to the processor 9, and the processor 9 analyzes the local pressure data of the contact surface of the upper grinding disc 5 and the lower grinding disc 6 under static conditions; and presents the surface pressure distribution of the upper grinding disc 5 and the lower grinding disc 6 in the form of a digital array; if the size of the local pressure abnormal area is less than 1 cm 2 , and the pressure increment is greater than 80% of the average pressure, check whether there are impurities on the outer surface of the grinding pad 10 of the upper grinding disc 5 and the lower grinding disc 6 that may damage the surface of the workpiece 4, and deal with them. If there are no such problems, observe the overall pressure distribution between the upper grinding disc 5 and the lower grinding disc 6 and the workpiece 4;

[0035] B. After eliminating the local pressure anomaly caused by impurities, adjust the load of the upper grinding disc 5 to the load corresponding to this processing. Measure the local pressure between the upper grinding disc 5 and the lower grinding disc 6 and the workpiece 4. If there is a large-scale abnormality in the overall pressure distribution between the upper grinding disc 5 and the lower grinding disc 6 and the workpiece 4, and the size of the abnormal area is greater than 1 cm 2 , and the pressure change value is less than 80% of the average pressure, the thickness of the polishing pad 10 is considered to be uneven, and the polishing pad 10 is trimmed by a suitable method in combination with the material of the polishing pad 10. If there is no problem above, place the workpiece 4.

[0036] C. Place the workpiece 4 and start processing. The grid-type thin film pressure sensor 7 collects local pressure data during the processing in real time and transmits the data to the processor 9 in real time. The processor 9 evaluates the release of internal stress caused by the removal of material from the workpiece 4 and the fluid dynamic pressure caused by the introduction of the grinding fluid into the contact area. If the local pressure exceeds 300% of the average pressure, stop the processing in time; continue the processing after adjusting the process parameters; if there are no above problems, continue the processing.

[0037] D. For areas larger than 1cm during processing 2If the large-scale pressure anomaly is analyzed, if the area of ​​the region continues to increase and the anomaly value increases with the progress of processing, the wear and deformation of the upper grinding disc 5 and the lower grinding disc 6 should be considered, the processing should be stopped in time, and the surface shape of the grinding pad 10 should be trimmed by a suitable method.

[0038] E. After a period of processing, when the pressure distribution of each workpiece 4 is consistent and tends to be stable, the following pressure distribution is used for processing. If the pressure at the center of the workpiece 4 is large and that at the periphery is small, go to step E1; if the pressure at the center of the workpiece 4 is small and that at the periphery is large, go to step E2; otherwise, go to step E3;

[0039] E1, if the corresponding surface shape of the workpiece 4 is convex, then the edge area of ​​the annular zone of the grinding pad 10 is slightly ground. After grinding, the workpiece 4 is loaded again, and the pressure in the center of the workpiece 4 is greater than the pressure around it, so that the material removal rate in the center area of ​​the workpiece 4 is greater, and the overall surface shape of the workpiece 4 tends to be flat; go to step E3;

[0040] E2, if the corresponding surface shape of the workpiece 4 is concave, the middle area of ​​the annular belt of the grinding pad 10 is slightly ground, and the workpiece 4 is loaded again after grinding. Then, the pressure at the center of the workpiece 4 is less than the pressure around it, so that the material removal rate around the workpiece 4 is greater, and the overall surface shape of the workpiece 4 tends to be flat;

[0041] E3. Continue processing until workpiece 4 meets the processing requirements.

[0042] The above-described embodiments merely express the implementation methods of the present invention, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for real-time monitoring and control of local pressure of a double-sided grinding machine, characterized in that: The double-sided grinding machine at least comprises a machine tool body, a mesh-type thin film pressure sensor (7) and a processor (9). The machine tool body comprises at least a bed (1), an operating panel (2), a gantry (3), an upper grinding disc (5) and a lower grinding disc (6); the operating panel (2) is mounted on the bed (1) for human-machine interaction; the lower grinding disc (6) is mounted at the center of the bed (1) via a lower disc base; the gantry (3) is mounted on the bed (1) and straddles the lower grinding disc (6); the upper grinding disc (5) is mounted below the gantry (3) via an upper disc fixing seat; A grid-type thin film pressure sensor (7) is installed on the working surface of the upper grinding disc (5) and the lower grinding disc (6), and a grinding pad (10) is bonded to the outer surface of the grid-type thin film pressure sensor (7); the grid-type thin film pressure sensor (7) is composed of a plurality of thin film pressure sensor units (8), and each thin film pressure sensor unit (8) is installed on the entire working surface in a square grid unit array; there are two processors (9), which are installed on the non-working surfaces of the upper grinding disc (5) and the lower grinding disc (6), respectively; each thin film pressure sensor unit (8) is connected to the processor (9) of the upper grinding disc (5) and the lower grinding disc (6) via a data line; the method comprises the following steps: A. When the double-sided grinding machine does not have a workpiece (4) placed thereon, the upper grinding disc (5) is placed statically above the lower grinding disc (6), and a plurality of thin film pressure sensor units (8) on the grid-type thin film pressure sensor (7) collect local pressures of the corresponding areas of the upper grinding disc (5) and the lower grinding disc (6); transmit the local pressure data to the processor (9), which analyzes the local pressure data of the contact surface of the upper grinding disc (5) and the lower grinding disc (6) under static conditions; and presents the surface pressure distribution of the upper grinding disc (5) and the lower grinding disc (6) in the form of a digital array; if the size of the local pressure abnormal area is less than 1 cm 2 , and the pressure increment is greater than 80% of the average pressure, then check whether there are impurities on the outer surface of the grinding pad (10) of the upper grinding disc (5) and the lower grinding disc (6) that may damage the surface of the workpiece (4), and deal with them; if there are no such problems, observe the overall pressure distribution between the upper grinding disc (5) and the lower grinding disc (6) and the workpiece (4); B. After eliminating the local pressure anomaly caused by impurities, adjust the load of the upper grinding disc (5) to the load corresponding to the current processing; measure the local pressure between the upper grinding disc (5) and the lower grinding disc (6) and the workpiece (4) respectively. If there is a large-scale anomaly in the overall pressure distribution between the upper grinding disc (5) and the lower grinding disc (6) and the workpiece (4), and the size of the abnormal area is greater than 1 cm 2 , and the pressure change value is less than 80% of the average pressure, then the thickness of the grinding pad (10) is considered to be uneven, and the grinding pad (10) is trimmed by a suitable method in combination with the material of the grinding pad (10); if there is no such problem, place the workpiece (4); C. The workpiece (4) is placed and processing begins. The grid-type thin film pressure sensor (7) collects local pressure data during the processing in real time and transmits the data to the processor (9) in real time. The processor (9) evaluates the release of internal stress caused by the removal of material from the workpiece (4) and the fluid dynamic pressure caused by the introduction of the grinding fluid into the contact area. If the local pressure exceeds 300% of the average pressure, the processing is stopped in time. The processing is continued after the process parameters are adjusted. If there are no problems as mentioned above, the processing is continued. D. For areas larger than 1cm during processing 2 The large-scale pressure anomaly is analyzed. If the area of ​​the region is getting bigger and the anomaly value is increasing with the progress of processing, the wear and deformation of the upper grinding disc (5) and the lower grinding disc (6) are considered, and the processing is stopped in time, and the surface shape of the grinding pad (10) is trimmed by a suitable method; E. After a period of processing, when the pressure distribution of each workpiece (4) is consistent and tends to be stable, the following pressure distribution is used for processing. If the pressure at the center of the workpiece (4) is large and that at the periphery is small, go to step E1; if the pressure at the center of the workpiece (4) is small and that at the periphery is large, go to step E2; otherwise, go to step E3; E1, if the corresponding surface shape of the workpiece (4) is convex, then the edge area of ​​the annular belt of the grinding pad (10) is slightly ground; after grinding, the workpiece (4) is loaded again, so that the center pressure of the workpiece (4) is greater than the surrounding pressure, so that the material removal rate of the center area of ​​the workpiece (4) is greater, and the overall surface shape of the workpiece (4) tends to be flat; go to step E3; E2, if the corresponding surface shape of the workpiece (4) is concave, then the middle area of ​​the annular belt of the grinding pad (10) is slightly ground, and the workpiece (4) is inserted again after grinding, so that the pressure at the center of the workpiece (4) is less than the pressure around it, so that the material removal rate around the workpiece (4) is greater, and the overall surface shape of the workpiece (4) tends to be flat; E3. Continue processing until the workpiece (4) meets the processing requirements.

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