A mold repair method for preparing a mold for a plastic product with a round shaft feature

Abstract

The invention discloses a mold repair method for preparing a plastic product with a circular axis feature. The method takes the center of the circular axis actually measured as the coordinate origin, takes the coordinate origin as the center, and takes the average diameter of a reference circle marked in a product drawing as the diameter to obtain a corrected cylindrical surface, and obtains a corrected deviation value of each actual measured point relative to the corrected cylindrical surface. Finally, according to the corrected deviation value, the part corresponding to the actual measured point on the mold after the trial mold is corrected. The requirement can be met through one mold repair, which not only solves the mold repair problem that has troubled technical personnel in this field for many years, but also greatly improves the efficiency of mold repair and reduces the cost of mold repair.

Description

Technical Field

[0001] The invention relates to a mold repair method for a precision mold, in particular to a mold repair method for preparing a plastic product with a round shaft feature. Background Art

[0002] In the existing field of precision mold design and processing, the development cycle of products with high dimensional requirements is controllable during the entire mold making process, from mold design to the first mold trial. However, the size of the plastic product produced at this time cannot be 100% qualified, and there will be margins in the key dimensions. Usually, the product size is adjusted to 100% qualified through continuous adjustment through later mold repair. However, the mold repair and adjustment process is a long process, and this process is uncontrollable. Many molds will have more than 10 rounds of mold repair, and even more than 20 rounds of mold repair cannot adjust the product size to 100% qualified. The results of repeated mold repair have the following adverse consequences:

[0003] (1) The cost of mold repair remains high. The cost of mold repair for some precision molds is even higher than the manufacturing cost from design to the first mold trial, which brings great cost pressure to enterprises;

[0004] (2) From the first mold trial to the final product size of the mold being 100% qualified, the mold development is successful. There are more than 10 or even 20 rounds of mold repairs. If one round of mold repair takes 10-20 days, the development cycle of some precision molds can even take up to 2 years to complete. The uncontrollable development cycle is not conducive to the company's product market share.

[0005] In the field of precision mold repair, for plastic products with round shaft features, which are usually defined by multiple dimensions, the mold repair process is a long and painful process. According to the existing mold repair method, each data deviation is corrected one by one; but in this process, the technicians found that when correcting one data and then correcting the second data, the first corrected data will change. This situation makes mold repair difficult, and the cause of this phenomenon cannot be found. Instead, it can only be repeatedly corrected. As a result, the mold repair time is greatly extended, and even the mold may be scrapped. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a mold repair method for preparing a plastic product with a round shaft feature, which can complete the correction of three data at one time.

[0007] The technical solution adopted by the present invention to solve the above technical problem is: a mold repair method for preparing a mold for a plastic product with a round shaft feature, comprising the following steps:

[0008] Step 1: For the outer surface of the circular axis of the reference circle marked in the corresponding product drawing of the product after the mold trial, a group of actual measurement points distributed along the circumferential direction are selected around the circular axis at positions with a first preset distance and a second preset distance from the top surface, respectively, and the center of the circular axis actually measured is used as the coordinate origin to measure and obtain the plane coordinate values ​​of each actual measurement point;

[0009] Step 2: According to the tolerance requirements of the theoretical profile diameter of the outer surface in the product drawing, the coordinate origin of step 1 is taken as the center of the circle and the average diameter of the reference circle marked in the product drawing is taken as the diameter to obtain the corrected cylindrical surface, and the corrected deviation value of each actual measurement point relative to the corrected cylindrical surface is obtained;

[0010] Step 3: According to the correction deviation value of each actual measurement point relative to the correction cylindrical surface obtained in step 2, the part corresponding to the actual measurement point on the mold after the trial mold is corrected to complete the mold repair.

[0011] Compared with the prior art, the advantage of the present invention is that a corrected cylindrical surface is obtained with the center of the actually measured circular axis of the reference circle indicated in the product drawing as the coordinate origin, and the coordinate origin as the center and the average diameter of the reference circle indicated in the product drawing as the diameter, and the corrected deviation value of each actual measured point relative to the corrected cylindrical surface is obtained, and finally, the part corresponding to the actual measured point on the mold after the trial mold is corrected according to the corrected deviation value, and the requirement can be met through one mold repair, which not only solves the mold repair problem that has troubled technical personnel in this field for many years, but also greatly improves the efficiency of mold repair and reduces the cost of mold repair.

[0012] Preferably, the specific method of step 2 is as follows:

[0013] Step 2-1: According to the plane coordinate values ​​of each actual measurement point, a first cylindrical surface is fitted based on the least square method, and the minimum distance between each actual measurement point and the first cylindrical surface is obtained, and the minimum distance is used as the first deviation value;

[0014] Step 2-2: According to the fitted first cylindrical surface, obtain the coordinate values ​​of the upper center and the lower center of the first cylindrical surface;

[0015] Step 2-3: Compare the distance values ​​between the upper center and the lower center and the origin of the coordinate system respectively, take the center of the circle with the larger distance value as the center of the first cylindrical surface, move the first cylindrical surface so that the center of the first cylindrical surface coincides with the origin of the coordinate system to obtain the second cylindrical surface, and then obtain the minimum distance between each actual measurement point and the second cylindrical surface, and take this minimum distance as the second deviation value;

[0016] Step 2-4: According to the tolerance requirements of the theoretical contour diameter of the outer surface in the product drawing, the diameter of the second cylindrical surface is changed to the average diameter of the theoretical cylindrical surface to obtain the corrected cylindrical surface, and then the minimum distance of each actual measurement point relative to the corrected cylindrical surface is obtained, and this minimum distance is used as the correction deviation value.

[0017] The above method avoids a complicated measurement process, and can obtain the second deviation value according to the distance of the second cylindrical surface relative to the first cylindrical surface, and directly obtain the corrected deviation value on the computer according to the diameter change of the second cylindrical surface relative to the corrected cylindrical surface.

[0018] Preferably, the number of actual measurement points at the first preset distance and the second preset distance around the circular axis is 4 to 8.

[0019] Preferably, in step 3, after the portion of the mold corresponding to the actual measurement point after the mold trial is corrected, the corrected portion is smoothed. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A top view of the product structure of a brush holder in a car window motor system in an example of an embodiment of the present invention;

[0021] Figure 2 for Figure 1 The cross-sectional view along CC direction;

[0022] Figure 3 for Figure 1 A partial enlarged view of point B;

[0023] Figure 4 It is a right view of the product structure of the brush holder in the automobile window motor system in the embodiment of the present invention;

[0024] Figure 5 It is a left view of the product structure of the brush holder in the automobile window motor system in the embodiment of the present invention;

[0025] Figure 6 for Figure 4 The enlarged view of point D in the figure;

[0026] Figure 7 for Figure 5 The enlarged view of point E in the figure;

[0027] Figure 8 is a schematic diagram of 12 actual measurement points relative to the first cylindrical surface G1 in an embodiment of the present invention;

[0028] Fig. 9 is a schematic diagram of 12 actual measurement points relative to the second cylindrical surface G2 in an embodiment of the present invention;

[0029] Fig.10It is a schematic diagram of 12 actual measurement points relative to the corrected cylindrical surface G3 according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below with reference to the accompanying drawings.

[0031] Embodiment: A mold repair method for preparing a mold for a plastic product having a round shaft feature, comprising the following steps:

[0032] Step 1: For the outer surface of the circular axis 1 of the reference circle marked in the corresponding product drawing after the mold trial, 4 to 8 actual measurement points are selected along the circumferential direction around the circular axis 1 at positions which are respectively the first preset distance and the second preset distance from the top surface, and the center of the circular axis 1 actually measured is taken as the coordinate origin to measure and obtain the plane coordinate value of each actual measurement point;

[0033] Step 2: According to the tolerance requirements of the theoretical profile diameter of the outer surface in the product drawing, the coordinate origin of step 1 is taken as the center of the circle, and the average diameter of the reference circle marked in the product drawing is taken as the diameter to obtain the corrected cylindrical surface, and the corrected deviation value of each actual measurement point relative to the corrected cylindrical surface is obtained. The specific method is as follows:

[0034] Step 2-1: According to the plane coordinate values ​​of each actual measurement point, a first cylindrical surface is fitted based on the least square method, and the minimum distance between each actual measurement point and the first cylindrical surface is obtained, and this minimum distance is used as the first deviation value;

[0035] Step 2-2: According to the fitted first cylindrical surface, obtain the coordinate values ​​of the upper center and the lower center of the first cylindrical surface;

[0036] Step 2-3: Compare the distances between the upper and lower centers and the origin of the coordinate system respectively, take the center of the circle with the larger distance value as the center of the first cylindrical surface, move the first cylindrical surface so that the center of the first cylindrical surface coincides with the origin of the coordinate system to obtain the second cylindrical surface, and then obtain the minimum distance between each actual measurement point and the second cylindrical surface, and take this minimum distance as the second deviation value;

[0037] Step 2-4: According to the tolerance requirements of the theoretical profile diameter of the outer surface in the product drawing, the diameter of the second cylindrical surface is changed to the average diameter of the theoretical cylindrical surface to obtain the corrected cylindrical surface, and then the minimum distance between each actual measurement point and the corrected cylindrical surface is obtained, and this minimum distance is used as the correction deviation value;

[0038] Step 3: According to the correction deviation value of each actual measurement point relative to the correction cylindrical surface obtained in step 2, the part corresponding to the actual measurement point on the mold after the trial mold is corrected, and after the correction, the corrected part is smoothed to complete the mold repair.

[0039] A specific example is described below in conjunction with the accompanying drawings to help understand the technical solution of the present invention.

[0040] like Figure 1 to Figure 7 Take the brush holder product of the automobile window motor system shown in the figure as an example. The material of this product is PA66-GF30. Figure 1 As can be seen from the product diagram, the directions of the coordinate system X, Y, and Z are marked in the diagram. The plane formed by the X direction being perpendicular to the Y and Z directions is the coordinate system for product measurement, which is related to the mold repair direction for determining the size during mold repair. Figure 2 It can be seen that the product has 6 ribs distributed along the circumferential direction, which are marked as a1, a2, a3, a4, a5 and a6 respectively. The maximum shapes of these 6 ribs are all 6 cylindrical surfaces. The measurement method of the product is usually based on the customer's requirements. On the outer surface of the 6 ribs, at the positions of the first preset distance and the second preset distance from the top surface, one data is measured for each rib. By comparing each data with the theoretical data, the diameter deviation value can be known. Based on the actual measurement values ​​of these 12 points, a cylindrical surface is fitted based on the least squares method. The distance value between the upper and lower center positions of this cylindrical surface and the coordinate origin of the reference circle A in the same plane is the basis for evaluating the coaxiality. The difference between the maximum positive deviation and the maximum negative deviation of a cylindrical surface fitted based on the least squares method with respect to the actual measurement values ​​of these 12 points constitutes the actual value of the cylindricity. From Figure 2 and Figure 3 It can be seen that, taking these 6 cylindrical surfaces as the measurement object and comparing with the theoretical values, the product can only be judged as qualified if it meets the requirements of the three dimensions of diameter Φ, coaxiality with the reference circle A and its own cylindricality error at the same time. In this example, the theoretical cylindrical diameter of the outer surface of the 6 ribs of the brush holder product is Φ=15.6mm, and the tolerance requirement range is -0.08mm~-0.02mm, that is, the upper limit of the theoretical cylindrical diameter is 15.58mm, the lower limit is 15.52mm, and the average diameter is 15.55mm; in addition, in the coordinate position of the YZ plane, the concentricity tolerance of the product is required to be 0.1mm; the cylindricality tolerance requirement is 0.08mm. In addition, according to the customer's requirements, the positions of the 12 measurement points on the outer surface of the 6 ribs from the top surface are the first preset distance H1=1.75mm and the second preset distance H2=3.75mm.

[0041] According to the above requirements, the product after the first mold trial is measured, and the center of the reference circle A obtained by actual measurement is used as the coordinate origin (Y 基 =0,Z 基 = 0), and we get Figure 6 and Figure 7The plane coordinate values ​​of the 12 actual measurement points shown are the plane coordinate values ​​of the six actual measurement points (p1, p3, p5, p7, p9, p11) on the YZ plane at the first preset distance H1=1.75mm, and the coordinate values ​​of the six actual measurement points (p2, p4, p6, p8, p10, p12) on the YZ plane at the second preset distance H2=3.75mm, wherein the coordinate value of p1 is: (Y1=-5.3209mm, Z1=5.5344mm), and the coordinate value of p3 is: (Y3=-0.0779mm, Z3=7.7831 mm), the coordinate value of p5 is: (Y5=5.2322mm, Z5=5.7784mm), the coordinate value of p7 is: (Y7=5.4623mm, Z7=-5.5291mm), the coordinate value of p9 is: (Y9=-0.0239mm, Z9=-7.7448mm), the coordinate value of p11 is: (Y11=-5.3275mm, Z11=-5.5781mm); the coordinate value of p2 is: (Y2=-5.3006 mm, Z2=5.5126mm), the coordinate value of p4 is: (Y4=-0.0756 mm, Z4=7.7413 mm), the coordinate value of p6 is: (Y6=5.2127 mm, Z6=5.7572), the coordinate value of p8 is: (Y8=5.4332 mm, Z8=-5.4972), the coordinate value of p10 is: (Y10=-0.0221 mm, Z10=-7.7104 mm), and the coordinate value of p12 is: (Y12=-5.3102 mm, Z12=-5.5599 mm).

[0042] The first cylindrical surface G1 is fitted based on the least squares method, such as Figure 8 As shown. At this time, the diameter of the first cylindrical surface G1 is Φ1 = 15.462 mm, and the coordinate value of the upper circle center (Y 上 =0.0631mm, Z 上 =0.0079mm) and the coordinate value of the lower circle center (Y 下 =0.0508mm, Z 下 =0.0073mm), since the distance between the upper circle center and the coordinate origin is larger, the coordinate value of the upper circle center is used as the coordinate value of the center of the first cylindrical surface G1, recorded as: (Y=0.0631mm, Z=0.0079mm); based on these two coordinate values, the evaluated coaxiality is 0.1246mm, which exceeds the design requirements; and the first deviation value (pl1~pl 12 ) are: p1 1偏差 =-0.0156mm, p2 1偏差 =-0.0485mm, p31偏差 =0.0453mm, p4 1偏差 =0.0040mm, p5 1偏差 =-0.0159mm, p6 1偏差 =-0.0091mm, p7 1偏差 =0.0025mm, p8 1偏差 =-0.0376mm, p9 1偏差 =0.0220mm, p10 1偏差 =-0.0131mm, p11 1偏差 =0.0317mm, p12 1偏差 =0.0026mm; based on the maximum positive deviation p3 1偏差 =0.0453mm and maximum negative deviation p2 1偏差 =-0.0485mm, the actual value of the cylindricality is 0.0453mm-(-0.0485mm)=0.0938mm, which also exceeds the design requirements. The three largest points in the radial direction of all the 12 actual measurement points are fitted to a size evaluation cylindrical surface MAX with a diameter of Φ MAX =15.528mm. Although this value is acceptable, it is at the lower limit of the product diameter and may exceed the tolerance at any time.

[0043] The mold correction plan is as follows:

[0044] Step 1: Move the first cylindrical surface G1 to the coordinate origin at Y=-0.0631mm, Z=-0.0079mm, so that the center of the first cylindrical surface G1 coincides with the coordinate origin to obtain the second cylindrical surface G2, as shown in Fig. 9 At this time, the diameter Φ2 of the second cylindrical surface G2 relative to the first cylindrical surface G1 has not changed, Φ2 = 15.462mm, but the second deviation values ​​(p12~p122) of the 12 actual measurement points (p1~p12) relative to the second cylindrical surface G2 have changed, which are: p1 2偏差 =-0.0539mm, p2 2偏差 =-0.0867mm, p3 3偏差 =0.0523mm, p4 2偏差 =0.0111mm, p5 2偏差 =0.0641mm, p6 2偏差 =0.0391mm, p7 2偏差 =0.0411mm, p8 2偏差 =0.0010mm, p9 2偏差 =0.0136mm, p10 2偏差 =-0.0215mm, p11 2偏差 =-0.0178mm, p122偏差 =-0.0469mm.

[0045] In the second step, the diameter of the second cylindrical surface G2 after the center of the circle is moved is modified to the average diameter of the theoretical cylindrical surface diameter to obtain the modified cylindrical surface G3, as shown in Fig.10 The diameter of the corrected cylindrical surface G3 is Φ3 = 15.55 mm, and the corrected deviation values ​​(p1 3偏差 ~p12 3偏差 ), respectively: p1 3偏差 =-0.0979mm, p2 3偏差 =-0.1306mm, p3 3偏差 =-0.0083mm, p4 3偏差 =0.0329mm, p5 3偏差 =0.0201mm, p6 3偏差 =-0.0049mm, p7 3偏差 =-0.0029mm, p8 3偏差 =0.0430mm, p9 3偏差 =-0.0304mm, p10 3偏差 =-0.0655mm, p11 3偏差 =-0.0618mm, p12 3偏差 =-0.0909mm.

[0046] The third step is to correct the parts corresponding to the 12 actual measurement points on the mold after the trial mold according to the corrected deviation value obtained in the previous step, and then smooth the 6 rib positions after the corrected deviation value to complete the mold repair.

[0047] Theoretically, after the mold is repaired according to the final correction deviation value, the final deviation should be 0. However, in the mold repair process, in addition to the correct theory of the mold repair plan, there are still certain errors in the mold machining process and the product injection process. However, if the mold repair plan is correct, the impact of these errors is very small.

[0048] After the mold in this example was repaired according to the above three steps, the product of the trial mold after the mold repair was measured in the same way, and the following measurement results were obtained:

[0049] The plane coordinate values ​​of the 12 actual measuring points are: p1 (Y1=-5.4052mm, Z1=5.6219mm), p2 (Y2=-5.3907mm, Z2=5.6064mm), p3 (Y3=-0.0780mm, Z3=7.8008mm), p4 (Y4=-0.0759mm, Z4=7.7693mm), p5 (Y5=5.2169mm, Z5=5.7616mm), p6 (Y6=5.2108mm, Z6=5.7551mm), p7 (Y7=5.4542mm, Z7=-5.5210mm) , p8 (Y8=5.4571mm, Z8=-5.5214mm), p9 (Y9=-0.0239mm, Z9=-7.7400mm), p10 (Y10=-0.0222mm, Z10=-7.7515mm), p11 (Y11=-5.3553mm, Z11=-5.6073mm) and p12 (Y12=-5.3515mm, Z12=-5.6032mm), the diameter of the first cylindrical surface G1 fitted based on the least squares method is Φ1=15.5458mm, the first deviation value p1 of the 12 actual measurement points relative to the first cylindrical surface G1 1偏差 =0.0134mm, p2 1偏差 =0.0002mm, p3 1偏差 =0.0190mm, p4 1偏差 =-0.0085mm, p5 1偏差 =-0.0003mm, p6 1偏差 =-0.0110mm, p7 1偏差 =0.0045mm, p8 1偏差 =-0.0008mm, p9 1偏差 =-0.0195mm, p10 1偏差 =-0.0120mm, p11 1偏差 =-0.0153mm, p12 1偏差 =-0.0189mm; then get the coordinate value of the upper circle center (Y 上 =-0.0094mm, Z 上 =0.0113mm) and the coordinate value of the lower circle center (Y 下 =-0.0024mm, Z 下 =0.0073mm), since the distance between the upper circle center and the coordinate origin is greater, the coordinate value of the upper circle center is used as the coordinate value of the center of the first cylindrical surface G1, recorded as: Y=-0.0094mm, Z=0.0113mm; based on these two coordinate values, the coaxiality evaluated is 0.0295mm, which meets the design requirements. Based on the maximum positive deviation p3 1偏差=0.0190mm and maximum negative deviation p9 1偏差 =-0.0195mm, the actual value of the cylindricity is 0.019 mm -(-0.0195 mm)=0.0385 mm, which also meets the design requirements. A cylindrical surface for size evaluation is fitted with the three largest points in the radial direction of all the 12 actual measurement points, with a diameter of 15.5596 mm, which is also qualified.

Claims

1. A mold repair method for preparing a plastic product with a round shaft feature, characterized in that The following steps are involved: Step 1: For the outer surface of the circular axis of the reference circle marked in the corresponding product drawing of the product after the mold trial, a group of actual measurement points distributed along the circumferential direction are selected around the circular axis at positions with a first preset distance and a second preset distance from the top surface, respectively, and the center of the circular axis actually measured is used as the coordinate origin to measure and obtain the plane coordinate values ​​of each actual measurement point; Step 2: According to the tolerance requirements of the theoretical profile diameter of the outer surface in the product drawing, the coordinate origin of step 1 is taken as the center of the circle, and the average diameter of the reference circle marked in the product drawing is taken as the diameter to obtain the corrected cylindrical surface, and the corrected deviation value of each actual measurement point relative to the corrected cylindrical surface is obtained. The specific method of step 2 is as follows: Step 2-1: According to the plane coordinate values ​​of each actual measurement point, a first cylindrical surface is fitted based on the least square method, and the minimum distance between each actual measurement point and the first cylindrical surface is obtained, and the minimum distance is used as the first deviation value; Step 2-2: According to the fitted first cylindrical surface, obtain the coordinate values ​​of the upper center and the lower center of the first cylindrical surface; Step 2-3: Compare the distances between the upper and lower centers and the origin of the coordinate system respectively, take the center of the circle with the larger distance value as the center of the first cylindrical surface, move the first cylindrical surface so that the center of the first cylindrical surface coincides with the origin of the coordinate system to obtain the second cylindrical surface, and then obtain the minimum distance between each actual measurement point and the second cylindrical surface, and take this minimum distance as the second deviation value; Step 2-4: According to the tolerance requirements of the theoretical profile diameter of the outer surface in the product drawing, the diameter of the second cylindrical surface is changed to the average diameter of the theoretical cylindrical surface to obtain the corrected cylindrical surface, and the minimum distance between each actual measurement point and the corrected cylindrical surface is obtained, and this minimum distance is used as the correction deviation value; Step 3: According to the correction deviation value of each actual measurement point relative to the correction cylindrical surface obtained in step 2, the part corresponding to the actual measurement point on the mold after the trial mold is corrected to complete the mold repair.

2. A method for repairing a mold for preparing a plastic product having a round shaft feature as claimed in claim 1, characterized in that The actual measurement points at the positions of the first preset distance and the second preset distance around the circular axis are both 4 to 8.

3. A method for repairing a mold for preparing a plastic product having a round shaft feature as claimed in claim 1, characterized in that In step 3, after the portion of the mold corresponding to the actual measurement point after the mold trial is corrected, the corrected portion is smoothed.

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