1. The height of the slide rail should be at least 1/3 of the height of the slide to ensure the stability and smooth sliding of the slide.
2. Pay attention to the opening of lubrication grooves where there is sliding friction. In order to prevent the outflow of lubricating oil, it is not advisable to make the grooves "open", but should be "closed". Generally, it can be milled directly on the milling machine with a single-piece cutter.
3. The cavity of the fixed mold core is generally cut by wire for the small mold, which can improve the accuracy of the mold; while the cavity of the larger mold is generally processed by milling, pay attention to its verticality during processing, and to prevent assembly , The mold core is not in place, the periphery of the mold frame should be milled to a depth of 0.2 with a milling cutter.
4. The interpenetration between the insert and the mold core, the mold core and the mold core, and the mold core and the mold frame should generally add a 1° inclination to prevent bumps during assembly.
5. The length tolerance of the positioning part of the insert is -0.02, the size tolerance is -0.10, and the corresponding positioning tolerance of the mold core is +0.02.
6. The tolerance from the bottom of the C-angle to the C-angle is +0.01 to prevent burrs from running.
- The main part of the main body mold uses NAK80 material, and the inserts, tips, etc. use SKH9, SKH51 (material treatment: chamber treatment, or unnecessary) materials, and VIKING materials can be used if necessary.
8. After drawing the parts, the position and size of the slider should be determined first to prevent interference and insufficient strength, and then determine the mold size.
9. The size tolerance of the insert is set to -0.01, and the corresponding tolerance of the insert hole on the mold core is +0.01.
10. The sharp corner part of the line-cut square hole on the die core is excessive with R0.20, and the corresponding entry part is also R0.20, which corresponds to the influence of the wire diameter during the line-cutting, and at the same time, it can prevent the sharp corner from being worn out, which will produce benefits. side.
11. The small pit size corresponding to the positioning bead is generally a tapered hole with a bottom diameter of φ3 and an included angle of 90°-120°.
12. The draft angle of the fixed side should be greater than that of the movable side, so that the release can stay on the movable side; and it can prevent the deformation of parts, especially the parts with thin walls and long parts that are easily deformed. The fixed side is easy to pull unevenly on it. Warp the part or leave it on the fixed side.
13. For parts with large side core pulling force and strict parts accuracy requirements, it is best to adopt a secondary core pulling structure.
14. The inclination of the oblique tip + 2°= the inclination of the compression block (generally 18° or 20° or 22°).
15. When the mold is assembled, the following habits should be cultivated:
a. Use an air gun to clean the surface of the mold core, mold cavity, inlet, runner plate, and parting surface.
b. Before assembling, polish the surface of the mold core, mold cavity, insert, and parting surface with oilstone, so as to smooth the tang during assembly.
c. Pay attention to clear the corners to prevent interference and bruises.
d. Before assembling, you should consider how to proceed.
16. The side compression block of the large mold core should be designed to be 0.5-1.0mm on the parting surface after locking to prevent interference.
- PC+GF20 shrinkage rate 3/1000
18. The POM shrinkage rate is normally 20/1000, but sometimes it can reach 30/1000 locally.
19. In order to prevent the latent gate from scratching the parts when the parts are ejected, a wedge-shaped block is added to the runner 2-4mm away from the latent gate, the height is about half of the runner, and the included angle is 10° on one side. The gate is broken when it is ejected.
20. The main runner pull material well, adopts an inverted cone with a depth of 8-10mm, an included angle of 10° on one side, and a width of the top diameter of the runner; this advantage is to prevent the pull material that is ground into a wedge on one side from being ejected. When hooking the runner, resulting in poor release.
21. There are two types of shutters:
1. Made of rubber, the center screw adjusts the deformation to adjust the tension.
2. Made of spring steel. Its function is to delay the mold opening time of the movable side and the fixed side, and it is applied to the small nozzle mold.
22. In order to ensure that the ejector pin and diagonal pin of the mold are reset, some molds are equipped with an early return mechanism (the female is installed on the 108 plate, the male is installed on the 102 plate, and the male is similar to the ejector pin, and the bottom is blocked with a headless screw. , Generally arrange two) or micro switches (between the 108 and 109 boards [installation components]).
23. Considering the screw length of the injection molding machine when clamping the mold, you need to pay attention to the thickness of the upper and lower fixing plates. If necessary, the four corners should be milled lower. At the same time, in order to improve safety, the upper and lower fixing plates can be adjusted according to the position of the holes on the injection molding machine. , Drill four bolt holes.
24. The forming end of the inclined pin has a straight face, which is generally 4-6mm long. In order for the inclined pin to slide between the 107 and 108 plates when it is ejected, the bottom should be poured with an R angle of 0.5mm-1mm.
25. For appearance products that require biting, the design of the draft angle needs to consider the degree of biting, so as not to cause appearance strain. For some protruding parts, the cross-section will become larger after the biting is considered, and the actual processing should be smaller than 0.02-0.03 on one side.
26. Considering that the fixed side and the movable side will form a gap when the mold is closed, the fixed side is 0.03-0.05 smaller than the movable side.
27. In molds with sliders, sometimes it is necessary to open an oil groove on the inclined surface where the slider on the slider and the compression block are against; in addition, if the forming is not affected, the oil groove is set on the upper surface of the template than in the slippery surface. The oil groove at the bottom of the block has higher processing efficiency.
28. The parting surface should not be selected on the surface where there are requirements.
29. The shrinkage rate of adding fiber is 1-2 parts per thousand as small as the flow direction, which is large perpendicular to the direction of flow; without fiber adding, the opposite is true.
30. The shrinkage rate of the addendum circle is 1-2 thousandths less than the shrinkage rate of the root circle.
31. After the mold has been used for a period of time, it needs to be shaped and repaired. In the process of repairing the mold core, try not to use oilstone, because repeated use of oilstone will deform the mold; it is best to use shaved cork or soft bamboo chopsticks.
32. In molds with sliders, four support bars should be added between #102 and #103 plates.
33. When forming the parts with the inside and the outside of the bread and the core, the secondary core pulling mechanism should be considered to avoid difficult demoulding and damage to the parts; if the input is on the fixed side or the slider, it is often pulled in first ; If the inlet is on the movable side and is broken against the fixed side, the counterbore of the inlet can be made deeper, and the parts should be pushed out first, and then out of the inlet. If it is not broken, it should be removed first, and the corresponding mold structure should be changed.
34. If the broken surface between the fixed side and the movable side is a plane that is not perpendicular to the mold opening direction, it should be designed as an inclined surface to reduce the possibility of flash formation due to abrasion, and at the same time, it will form a pre-break when it is broken. When designing, the length direction should be designed to a positive tolerance of +0.02, but it should be noted that when the fixed side and the movable side have a demolding slope, be careful to consider the difference between the fixed side and the movable side. The direction of the demolding slope of the moving side is opposite, and the broken slope will form a joint that does not match the original design of the part. If it is not considered properly, it will also cause burrs or breaks that are difficult to eliminate.
35. When the fixed side needs biting, the external dimension of the fixed side should be based on the degree of biting, and the design should be 0.03-0.05mm smaller on one side.
- The electrode is generally polished with 1000 sandpaper, but the appearance electrode needs to be polished with 1200 or more sandpaper; the mold core is polished with 1500, but the mirror surface is required to use 3000 sandpaper, and finally diamond paste and absorbent cotton are used for polishing. throw. When compounding, use 400 sandpaper first, then 800 sandpaper. However, the Japanese molds seem to have used 1000-1200 sandpaper for polishing.
37. After the plastic gear is formed, the measurement of the gear parameters is mainly the addendum circle and the cross-tooth thickness. If the two gears are too tight or too loose, it will affect the transmission; there is a special measuring instrument for the measurement of the cross-tooth thickness.
38. In the mold design, if the thickness of the parts is uneven and the gates of the parts are evenly distributed, uneven pouring is likely to occur. For example, Tian Jingdong's 0004 mold.
39. Although the gear made of PC+30GF is better in terms of forming size, generally four pieces in one mold, but its rigidity and wear resistance are not as good as PBT+GF30. Therefore, although the size of PBT is not easy to control in terms of forming, There are only two molds, but quality-oriented manufacturers like Olympus still choose quality in the face of quality and cost.
40. In the mold design, in order not to affect the use of the parts, it is often necessary to recess a piece on the surface of the part, so that the gate cut residue is lower than the surface of the part, and the depth of the recess is as shallow as possible under the premise that the gate residue is lower than the surface of the part. Generally 0.3-0.5mm, too deep will affect the size of the forming, such as Tian Jingdong's 0004 mold and Yi Xiangcheng's 0026 mold.
41. In order to improve the filling performance of the parts farther away from the gate, air escape grooves can be opened in these parts to increase the entry; this point should be especially considered before designing. When determining the structure, there should be such a concept: try to The pressure and temperature of each part are constant when the fluid flows in the cavity.
42. For molds with thin parts and difficult to form, such as Wang Feng's 0001 and 0002, the forming performance can be improved by increasing the gate, but it is not the larger the better. If the gate is too large, the gate will be torn off the part when it is cut. Some meat forms a pit, and at the same time, the orientation of the parts will increase and it will be easily deformed. Therefore, the point gate should be ¢0.5-1.2mm.
43. In EDM, the discharge gap is directly related to the machining accuracy (generally considered to be 3:1).
- The inclination of the compression block of the large mold core is 1°, 3°, 5°
45. In order to facilitate the ejection of the inclined pin, the inclined pin should be designed to be 0.1-0.3mm shorter than normal, that is, the part of the meat is 0.1-0.3mm thicker than normal.
46. When designing a mold, you should first consider the processing technology of the parts, try to avoid the use of electric discharge and wire cutting, and try to consider the use of milling machines and grinders, because in terms of processing cost, processing accuracy and processing time, the former are not comparable. The latter, although the accuracy of slow-moving wire cutting is good.
47. The design should avoid the simple shape, but the large-area planar discharge is time-consuming, the accuracy is difficult to guarantee, and the fitter's work load is increased.
48. When designing, we should try to avoid the step-shaped upper and lower mold core design that requires the surface and the surface to fit each other, which is often difficult to process. The WeChat public account of Xiaosa Online School is dry goods!
49. The disadvantage of ultrasonic polishing is that it is easy to distort the shape of the mold surface due to the inaccurate grasp of the hand feeling.
50. When the mass production requirement of the mold is 10000-15000/month, the material of the mold core is NAK55.
51. A good injection molding machine can adjust the parameters to perform more than 5 segment injections. For example, the first segment can be set to fill the runner; the second segment is one-third of the filled parts; the third segment is Fill one-half of the parts...wait. Therefore, the problems in injection molding can be solved by analyzing the filling conditions of the parts under these conditions.
52. For some parts that are difficult to mold, or have requirements on the surface, or the accuracy of some parts is difficult to meet the requirements in the previous few trial molds, consider using multi-stage injection molding during mold trial.
53. Both Japanese and Taiwanese injection molding machines can perform multi-stage injection molding, but generally speaking, Taiwanese injection molding machines can change the injection speed and injection speed. . . . . In addition, the injection pressure can be changed.
54. The determination factors of the cavity number of the mold are: the forming cost of a single part, the average mold making cost of each part, the precision requirements of the parts, and the difficulty of mold making.
55. Molding with corrosive resin is to choose corrosion-resistant materials for the mold material, or make anti-corrosion treatment on the mold surface; when molding resin containing high-strength filler materials such as glass fiber, the mold parts must have corresponding hardness.
56. The distance between the water pipe and the mold core should be greater than 4mm.
57. If it is estimated that the molding of the part is difficult and the molding pressure needs to be increased, the strength of the mold should be considered in the design, the strength of the mold core should be increased, the support column should be increased, and the tolerance between the bonding surfaces should be paid attention to.
58. The forced demolding mechanism should not be considered in the design of precision molds, otherwise it will have a great impact on the mass productivity of the mold, the accuracy of the parts, and even the surface of the parts.
59. In the mold design, from the perspective of cost and manufacturing, try to avoid the slider and the oblique tip mechanism.
60. If there are only 15-20 mold cores left after the milling machine is processed, and two to four pieces per mold, even the sharp-angled electrodes can generally be coarse and fine.
61. When placing complex curved electrodes with coarse electrodes, 0.06 should be reserved in X and Y directions, and 0.07 or more should be reserved in Z directions. Finally, fine electrodes are used for processing.
62. The discharge of sharp-angled, semi-circular and hemispherical electrodes requires special attention.
63. The mold opening stroke of the small nozzle mold is determined as follows: A. 101A plate and 102 plate de-runner stroke is calculated as: runner length + manipulator (40-60mm); B. 102 plate and 103 plate part-off stroke is calculated as ：Parts + manipulator (70mm)
64. For the parts that are difficult to remove during mold assembly, such as the pressure block, the runner plate of the small nozzle, the mold core, etc., it is necessary to drill the lifting screw holes; however, sometimes for the sake of simplicity, you can use the two clamping screws on the opposite corners. Drill through the hole and tap through to unscrew the lifting screw.
65. Molds that require good concentricity but cannot be made on the fixed side or the movable side at the same time. If the size of the mold core allows, the fixed side and the movable side should be designed with a male and female conical guide mechanism to ensure molding. The concentricity of the position at the time. Such as 9018, 9026, 0004, and 0032 roll molds are all added with #251 inserts.
66. For molds with a large number of moldings, consider the selection of the mold base (P20 can be considered) and the selection of the slider (P20). At the same time, the mold can be installed on the side block.
67. When using a grinder or milling machine to process a thickness less than 5mm and a length greater than 50, that is, a length-to-thickness ratio greater than 10, such as oblique tips and other mold parts, you should pay attention to the deformation during processing.
68. Sometimes the mold cavity used to place the mold core is too deep and the cooling ring must be opened. If the knife is directly used to process the cooling groove in the mold cavity, the knife is often not long enough. Then, you can consider opening the cooling groove in the mold. However, it should be noted that the cylinder in the middle of the cooling groove should be slightly larger than the inner diameter of the cooling ring, so that the cooling ring is not easy to fall out of the cooling groove. (Note that because the cooling water passes from the inside, the inner diameter of the cooling ring should be close to the mold wall when designing; if the cooling water passes from the outside, the outer diameter of the cooling ring should be close to the mold wall during design. Don't do it the other way around, otherwise it will cause oil leakage)
69. The inlet and outlet temperature of the cooling water should be kept as small as possible. Generally, the mold should be controlled within 5°C, and the precision mold should be controlled within 2°C.
70. The center distance between the water channels is generally 3 to 5 times the diameter of the water channel, and the distance between the outer circumference of the water channel and the surface of the mold cavity is generally 10-15mm.
71. For molding resins with large shrinkage rates such as polyethylene (PE), it is necessary to install a cooling circuit in the direction where the product shrinks.
72. When there is an array of cooling circuits on the mold, the cooling water should first pass into the part close to the main runner. (How to understand?)
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The material of the inclined tip is generally required to be relatively hard (use SKH9 or STAVAX). At the same time, in order to improve mass production, a wear-resistant plate (SKS3 material) is added between the bottom of the inclined tip (#106 thimble plate and #107 thimble fixing plate). The same thickness as the bottom of the thimble.
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Generally, the amount of depression of the product is less than 3%, and almost all can be used for forced demolding. If it exceeds a certain range, the finished product will be scratched or even damaged during demolding. The amount of depression is also easy due to the material, soft materials such as PP, NYLON can reach 5%, while PC, POM, etc. can only be between 2.5-3%.
75. The safety distance of the slider is generally 1.5~5mm.
76. There should be a small flat surface (about 0.8mm) at the root or top of the plastic thread for easy demolding after molding and not easy to damage the surface of the threaded part.
77. The tolerance of the spacer plate is generally +0.1mm. If the pressure of the mold is large, a support column needs to be added. The tolerance of the support column is generally +0.02 0.03mm, which is 0.02 0.03mm thicker than the spacer plate after assembly . This is considered The reason is: the surface of the support column (S45C or S55C) is harder than the template after quenching. After a period of use, the template will sink to compensate for the tolerance. If the support column is 0.1mm thinner than the spacer plate, the deformation of the #103 plate caused by the pressure during injection will magnify the mold core, resulting in a bend of more than 0.1mm, resulting in burrs.
- PD613 (better than SKD11), PD555 (better than SUS 420 J2) and NAK 101 (better than SKD11), etc. The maximum deformation of heat treatment is 0.065/50, which has high wear resistance, high corrosion resistance and high Mirror surface processing, suitable for processing precision molds.
79. Exhaust grooves are often set around the parting surface and runners. The outer side of the general mold exhaust groove is generally 0.5mm deep, and the side of the part is 0.02mm; while the outer side of the precision mold exhaust groove such as the front and rear cover body of the target camera It is generally 0.07-0.1mm deep, and 0.007-0.01mm on the part side.
80. In order to ensure a good fit between the movable side and the fixed side, the parting surface is generally 0.02mm higher than the template; and the four corners of #103 are often milled with C10-20 deep 0.5-1 gaps to ensure # 102 and #103 do not interfere.
81. Like polyacetal (polyacetal) finished product dimensional tolerance is about ±0.2%, the number of mold cavity increases by 1 to allow an increase of about 5%. The 8 cavity increases by 1.4 times, up to ±0.28%.
82. Use Kennametal ¢16 small blade (KCM25) to cut NAK80 material with a depth of 0.4mm, width of 2/3 of the knife diameter, linear speed 55m/min, 0.5mm/rev, and air cooling, which is more suitable.
83. In the grinding machine processing, 0.5mm grooves can also be ground.
84. The surface of the return tip is only about 0.5mm thick and is hard, while the inside is soft.
85. When finishing the plane, STEP generally adopts 2/3~4/5 of the tool diameter, and slow-moving.
86. The tolerance of the sliding block groove is -0.01 and +0.01.
87. Before designing, coordinate with the customer on the drawing surface (determination of parting surface, determination of thimble position, disposal method of inverted groove, gate position and shape, relationship between meat thickness and shrinkage, tolerance size, etc.) ) Is very necessary, it is very necessary to further understand the customer’s design intent and increase the design hit rate. This is the concept that the designer should establish first, and the designer cannot make his own claim.
88. Hot runners are generally suitable for mass production of plastic molds of more than 240,000 pieces.
89. For molds such as 9029 and 0031 that use latent gates, the straight end of the glue inlet is often round or flat, and then a round or flat thimble is used for ejection, but because the thimble is small and the glue inlet is long If there is no demolding slope at the glue inlet, the parts will often eject poorly or break the thimble when ejected. Therefore, the demolding slope should be 0.5°~1° for ejection.
90. Like the cg5375f1 back cover of Olympus, it is made of PC material, one mold, one point gate mold, and the injection pressure reaches 200MPA when using the Sumitomo 75-ton molding machine.
91. For molds with a relatively large runner, the part that acts as the cold material should be lengthened accordingly. For example, the end of the runner like 0039 is lengthened by 14mm after the first mold trial.
92. When designing large molds, you should consider the design of the exhaust groove. It should not be specified after the mold trial. According to experience, generally use a milling cutter or grinder (depending on the accuracy of the mold) around the mold to process it. The shallow groove of a week has a depth less than the overflow value of the plastic.
93. For the insert with C-angle, if the C-angle part is just connected to the mold core, in order to prevent burrs from appearing on the part, the length tolerance from the bottom of the insert to the C-angle should be +0.05, as shown in the figure:
94. In electrical discharge machining, the required mold surface roughness is 7um. The general surface roughness in precision molds is 4um, and the surface roughness of molds with high appearance requirements is 2um.
95. The order of mold material should generally be 3~5mm larger than the maximum size required.
96. As far as possible, do not use the fixing method of the back lock screw for the material pulling pin, because this method will produce stress and make the material pulling pin easy to break. The better way is that the material pulling pin can move freely.
97. Wire cutting generally produces a 0.2mm R angle at the sharp corners. In the mold design, when you encounter the position that requires wire cutting (into the hole, square thimble hole, etc.), you must consider the influence of this R , So as to avoid problems such as flash and burrs.
98. The fitting part of the sliding block and the mold core should generally be designed with a single-sided slope of 2-3°, which can avoid wear and facilitate the generation of preload.
99. The thickness of the coating is generally 0.02 0.03mm on one side , and the polishing amount of the mold is generally .02 0.03mm on one side . This must be considered in the selection of the product design and the matching size of the mold design.
100. The fitter's technique is very important when fitting in. It is best to flow slowly. When the insert is inserted into the cavity 1/4 of the depth, there should be no looseness.