100 mold design considerations?

2021/08/12




1. The height of the slider guide should be at least 1/3 of the slider height, in order to ensure the stability of the slider and smooth sliding.

2. Sliding friction position attention to open lubrication groove, in order to prevent the flow of lubricant, should not open the groove into "open", but should be "closed", generally can use a single blade in the milling machine directly milling out.

3.The cavity of fixed die insert, for small die, generally use line cutting, so as to improve the accuracy of the mold; while the cavity of larger die is generally processed in the form of milling, when processing, pay attention to its verticality, and in order to prevent the assembly, the die insert is not in place, the surrounding of the mold frame should be milled with a milling cutter 0.2 deep.

4. The interpenetration of the inlet and the mold kernel, the mold kernel and the mold kernel, and the mold kernel and the mold frame should generally add a slope of 1° to prevent bruising when assembling.

5. The tolerance of the length of the inlet part is -0.02, the tolerance of the size is -0.10, and the tolerance of the corresponding inlet of the die insert is +0.02.

6. The tolerance from the bottom to the C corner part of the entry with C corner is +0.01, to prevent the running edge.

7. Use NAK80 material for the main part of the body mold, SKH9, SKH51 (material treatment: chambering treatment, or not) for the inlet, tip, etc., or use VIKING material if necessary.

8. After drawing the parts, the position and size of the slider should be set first to prevent interference and insufficient strength, and then set the mold kernel inch method.

9. The tolerance of the size of the insert is set to -0.01, and the tolerance of the corresponding insert hole on the die is +0.01.

10. The sharp corner part of the square hole of the wire cutting on the mold kernel is R0.20 over, and the corresponding inlet part is also R0.20, in order to correspond to the influence of the wire diameter during the wire cutting, and at the same time, it can prevent the sharp corner part from wearing out and producing the beneficial edge.

11. The small pit corresponding to the positioning bead is generally a conical hole with a base diameter of φ3 and an angle of 90°-120°.

12. Fixed side of the extraction angle should be greater than the movable side, so that the departure from the shape to stay on the movable side; and can prevent the deformation of the parts, especially thin-walled, long pieces of easily deformed parts, the fixed side of the uneven pull on it is easy to make the parts warp, or stay on the fixed side.

13. For the side of the core force and the parts of strict precision requirements of the parts, it is best to use the second core structure.

14. The slope of the oblique tip + 2 ° = the slope of the compression block (generally 18 ° or 20 ° or 22 °).

15. When the mold is assembled, the following habits should be developed.

a. Use to clean the surface of die kernel, die cavity, inlet, runner plate and parting surface.
b. Use oil stone to polish the surface of die kernel, cavity, inlet and parting surface before assembling, so that the assembly can be smoothly tang.
c.Pay attention to clear the corner to prevent interference and bruising.
d. Before assembling, you should consider how to do the work later.

16. The side compression block of large mold kernel should be designed to lock the bottom 0.5-1.0mm in the sub-mold surface to prevent interference.

17. PC+GF20 shrinkage rate 3/1000

18. POM shrinkage rate is normally 20/1000, but sometimes it can reach 30/1000 locally.

19. To prevent the submerged gate from scratching the part when the part is ejected, add a wedge-shaped block 2-4mm away from the submerged gate in the runner, about half the height of the runner, with the angle of 10° on one side, for breaking the gate when ejecting.

20. Mainstream channel pulling material well, using 8-10mm deep, angle of 10° on one side, top diameter is the width of the runner inverted cone; the advantage of this is to prevent the single side grinding into the wedge shape of the pulling material in the ejection hooked runner, resulting in poor release.

21. There are two kinds of openers and closers.
1. made of rubber, relying on the center of the screw to adjust the amount of deformation, to adjust the tension.
2. Made of spring steel. The role of both: delay the mold opening time of the movable side and fixed side, applied to small water mouth mold.

22. In order to ensure whether the ejector pin and tilt pin of the mold are reset or not, some molds are equipped with early return mechanism (the female is mounted on board 108, the male on board 102, the male is similar to the ejector pin, the bottom is blocked with headless screws, generally two are arranged) or micro switch (between boards 108 and 109 [with electrical components]).

23. Considering the length of the screw when clamping the mold on the injection molding machine, it is necessary to pay attention to the thickness of the upper and lower fixing plates, and the four corners should be milled lower if necessary. Meanwhile, in order to improve safety, four bolt holes can be drilled on the upper and lower fixing plates according to the location of the holes on the injection molding machine.

24. The molding end of the bevel pin has a straight section, generally 4-6mm long, in order to slide smoothly between 107 and 108 plates when the bevel pin is ejected, the bottom should be poured 0.5mm-1mm R angle.

25. The design of the slope of the die pulling needs to consider the degree of bite to avoid the appearance of strains. For some protruding parts, the cross section will be bigger after considering the nibbling, so the actual processing should be 0.02-0.03 smaller on one side.

26. Considering that the fixed side and the movable side will form a broken difference, the fixed side is smaller than the movable side by 0.03-0.05 on one side.
27. In the mold with slider, sometimes it is necessary to open oil grooves on the slider on the sliding block against the pressing block on the sliding block; in addition, if it does not affect the forming premise, it is more efficient to open oil grooves on the upper surface of the template than to open oil grooves on the bottom of the slider.

28. The parting surface should not be chosen in the position where the surface is required.

29. The shrinkage rate of the added fiber is 1-2 thousandths in the flow direction, and large perpendicular to the flow direction; the opposite is true for the non-added fiber.

30. The shrinkage rate of tooth top circle is smaller than that of tooth root circle by 1-2 thousandths.

31. After using the mold for a period of time, it is necessary to carry out type repair, repairing the process of mold kernel, try not to use oil stone, because repeated use of oil stone will make the mold deformation; it is better to use chipped cork or soft bamboo chopsticks.

32. In the mold with slider, four support crutches should be added between #102 and #103 plates.

33. When forming parts with insert and mold kernel, we should consider the second core extraction mechanism to avoid the difficulty of removing the mold and damage to the parts; if the insert is on the fixed side or slider, often extract the insert first; if the insert is on the movable side, and the fixed side is broken, the sink hole of the insert can be made deeper, and the part will be ejected first when ejecting, then remove the insert. If it is not broken, the inlet should be taken off first, then the corresponding mold structure should be changed.

34. If the breaking surface between fixed side and movable side is not a plane in the direction of vertical mold opening, it should be designed as a beveled surface to reduce the possibility of forming flying edge due to friction, and also to form a pre-pressure when breaking to strengthen the fit of the two surfaces, the design should be designed with a positive tolerance of +0.02 in the length direction, but it should be noted that when the fixed side and movable side have a release slope, careful consideration should be given to the direction of the release slope between fixed side and movable side. However, it should be noted that when the fixed side and the movable side have a release slope, it should be carefully considered that because the fixed side and the movable side have the opposite direction of the release slope, a joint mark will be formed at the slope against the broken part that is not in accordance with the original design of the part.

35. When the fixed side needs to nibble, the shape size of the fixed side should be small 0.03-0.05mm on one side of the design according to the degree of nibbling.

36. The polishing of electrode is generally done with 1000 sandpaper, but the appearance electrode needs to be polished with 1200 or more sandpaper; the polishing of mold kernel is done with 1500, but those requiring mirror surface should be done with 3000 sandpaper, and finally polished with drilling plaster and degreasing cotton. When the matching into the sub, first with 400 sandpaper, then 800 sandpaper, but the Japanese mold into the sub seems to have used 1000-1200 sandpaper for polishing.

37. After the plastic gears are formed, the measurement of gear parameters are mainly the tooth top circle and cross tooth thickness, if the two gears are too tight, or too loose will affect the driveability; cross tooth thickness measurement has a special measuring instrument.

38. In the mold design, if the flesh thickness of the parts is not uniform, and the gates of the parts are evenly distributed, it is easy to produce uneven pouring. For example, Tian Jing Dong's 0004 mold.

39. Gears made of PC+30GF, although the size of the molding is better, generally can be four pieces in one mold, but its rigidity, wear resistance, etc. is not as good as PBT+GF30, therefore, although the size of PBT is not easy to control in the molding, only two pieces in one mold, but manufacturers like Olympus, who pay attention to quality, still choose quality in front 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 in the surface of the parts, so that the gate shear residue is lower than the surface of the parts, the depth of the recess to meet the premise of the gate residue is lower than the surface of the parts, the shallower the better, generally 0.3-0.5mm, too deep will affect the size of the molding, such as Tian Jingdong's 0004 mold and Yi Xiangcheng's 0026 mold.

41. In order to improve the filling performance of the parts far from the gate, it is possible to open an escape groove in these parts to increase the entry; this should be considered especially before designing, and when setting the structure, there should be a concept that the pressure and temperature of each part of the fluid flowing in the mold cavity should be constant as much as possible.

42. For molds with thin flesh and difficult forming, such as Wang Feng's 0001 and 0002, the forming performance can be improved by increasing the point gate, but not the bigger the better. Therefore, the point gate should be ¢0.5-1.2mm.

43. In EDM, there is a direct connection between the discharge gap and the processing accuracy (generally considered as 3:1).

44. The slope of compression block for large mold kernel is 1°, 3°, 5°

45. In order to facilitate the slant pin ejection, the design should be designed to make the slant pin shorter than normal by 0.1-0.3mm, that is, the part of meat is thicker than normal by 0.1-0.3mm.

46. When designing the mold should first consider the processing of the parts, try to avoid the use of electrical discharge and wire cutting, but try to consider the use of milling and grinding machines, because from the processing cost, processing accuracy and processing time, the former are not as good as the latter, although the accuracy of slow wire cutting is good.

47. The design should avoid simple shape, but also need a large area of the plane discharge, both time-consuming, precision and difficult to ensure, and aggravate the clamp workload of the clamp.

48. The design should try to avoid the step-shaped and need to face and face each other to fit the upper and lower die kernel design, which is often difficult to process. The mold people WeChat public number is dry!

49. The disadvantage of ultrasonic polishing is that it is easy to make the mold surface shape distorted because of the inaccurate grasp of hand feeling.

50. The mass production requirement of the mold is 10000-15000/month, and the material of the mold kernel is NAK55.

51. A good injection molding machine can adjust the parameters to perform more than 5 stages of injection, such as the first stage to fill the runner; the second stage to fill one-third of the part; the third stage to fill one-half of the part ......, etc. Thus, the problems in injection molding can be solved by analyzing the part filling situation in these cases.

52. For some parts that are difficult to mold, or have surface requirements, or some parts that are difficult to reach the required size in the first few mold trials, consider using multi-stage injection molding during the mold trials.

53. Both Japanese and Taiwanese injection molding machines can perform multi-stage injection molding, but generally speaking, the Taiwanese machine can change the injection speed and 。。。。。 In addition to the injection speed and , the Taiwan machine can also change the injection pressure.
54. The cavity number of the mold is determined by the molding cost per part, the average mold making cost per part, the precision requirement of the part, the difficulty of the mold making, etc.

55.Molding corrosive resin is the mold material to choose corrosion-resistant materials, or in the mold surface for anti-corrosion treatment; molding resin containing glass fiber and other high-strength filling materials, mold parts must have the corresponding hardness.

56. The distance of the water pipe from the mold kernel should be more than 4mm.

57. If it is predicted that the parts are difficult to be molded and the molding pressure needs to be increased, the design should consider the strength of the mold, increase the strength of the mold kernel, increase the support column, and pay attention to the tolerance between the laminating surfaces.

58.The forced release mechanism should not be considered in the design of precision mold, otherwise it will have great influence on the mass production, part accuracy and even part surface of the mold.

59.In mold design, from the cost and manufacturing point of view, try to avoid the slider and tilt tip mechanism.

60.If there are only 15-20 mold kernels left after milling machine, and two to four pieces in one mold, then even the electrode with clear tip is generally one coarse and one fine.


61. When placing the rough electrode of complex surface electrode, you should reserve 0.06 in X and Y direction, and 0.07 or more in Z direction, and then use the fine electrode to process.


62. Special attention should be paid to the discharge of sharp angle, semi-circle and hemisphere electrodes.

63. The opening stroke of small water outlet mold is determined as follows: A. The stroke of 101A plate and 102 plate off runner is calculated as follows: runner length + manipulator (40-60mm); B. The stroke of 102 plate and 103 plate off parts is calculated as follows: parts + manipulator (70mm)

64. Like the pressure block, small spout runner plate, mold kernel, etc. in the mold assembly difficult to remove the parts, it is necessary to drill lifting screw holes; however, sometimes for simplicity, you can drill through the two clamping screw holes on the opposite corner, tapping through to screw lifting screws.

65. require good concentricity but can not be done at the same time in the fixed side or movable side of the mold, if the size of the mold kernel allows, fixed side and movable side should be designed with a male and a female conical guide mechanism, in order to ensure the concentricity of the position when forming. For example, 9018, 9026, 0004, 0032 roller molds are added with #251 inlet.

66. For molds with large molding quantity, the selection of material for mold frame (P20 can be considered) and slider (P20) can be considered, while the resistant template can be installed on the side slick block.

67. When processing mold parts with thickness less than 5mm and length more than 50, i.e. length-thickness ratio more than 10, such as slanting tip, by grinding machine or milling machine, we should pay attention to the deformation problem during processing.

Sometimes the mold cavity used to place the die insert is too deep, and it is necessary to open the cooling ring, if you directly use the knife to process the cooling slot in the mold cavity, the knife is often not long enough, then, you can consider opening the cooling slot at the bottom of the die insert, but the point to note is that the cooling slot in the middle of the cylinder 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 slot. (Note, because the cooling water is from the inside, the design should let the cooling ring inner diameter and close to the mold wall; if the cooling water is from the outside, the design should let the cooling ring outer diameter and close to the mold wall, this point must not be reversed, otherwise it will cause oil leakage)

69. The temperature of the cooling water outlet and inlet should be as small as possible, within 5°C for general molds and within 2°C for precision molds.

70. The center distance between waterways is generally 3-5 times the diameter of the waterway, and the distance between the outer circumference of the waterway and the surface of the mold cavity is generally 10-15mm.

71. For molding resins with large shrinkage rate such as polyethylene (PE), a cooling circuit must be set in the direction of large shrinkage of the product.

72. When there are several cooling circuits on the mold, the cooling water should be passed to the part close to the main flow channel first. (How to understand?)

73. The material of the slant tip is usually hard (SKH9 or STAVAX), and in order to improve the mass production, add a wear plate (SKS3 material) between the bottom of the slant tip (#106 ejector plate and #107 ejector fixing plate) with the same thickness as the bottom of the ejector. Molders WeChat is all dry!

74. Generally, the amount of depression of the product is less than 3%, almost all of them can be used for forced demoulding, if it exceeds a certain range, the finished product will be scratched or even damaged when demoulding. The amount of depression is also easy to 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. The root or top part of the plastic thread should have a small plane (about 0.8mm), in order to make it easy to release the mold after molding, and not easy to hurt the surface of the thread part.

The tolerance of the spacer plate is generally +0.1mm, if the pressure of the mold is large, it is necessary to add the support column, the tolerance of the support column is generally +0.02~0.03mm, that is, the group is 0.02~0.03mm thicker than the spacer plate, the reason for this consideration is that the surface of the support column (S45C or S55C) is hardened than the template, and the template will be concave after using for a period of time. compensate for the tolerance. If the support column is 0.1mm thinner than the spacer, the deformation of the #103 plate during injection will be magnified on the die kernel, resulting in more than 0.1mm of bending, thus creating a burr.

78. PD613 (better than SKD11), PD555 (better than SUS 420 J2) and NAK 101 (better than SKD11) have a maximum deformation of 0.065/50 for heat treatment, which has high wear resistance, high corrosion resistance and high mirror finish, and is suitable for processing precision molds.

79. Exhaust slots are often opened around the parting surface and runners, and the outer edge of the exhaust slots for general molds is generally 0.5mm deep and 0.02mm on the side of the part; while the outer edge of the exhaust slots for precision molds such as the front and rear cover body of the object camera is generally 0.07-0.1mm deep and 0.007-0.01mm on the side of the part.

80. To ensure that the movable side and the fixed side fit well, the parting surface is generally 0.02mm higher than the template; and often in the four corners of #103 milling C10-20 deep 0. 5-1 notch to ensure that #102 and #103 do not interfere.

81. Like polyacetal (polyacetal) finished size tolerance is ± 0.2% or so, the number of die cavities increased by 1 tolerance of about 5%. 8 cavities is increased by 1.4 times, up to ± 0.28%.

82. Kennametal¢16 small insert (KCM25) cut NAK80 material 0.4mm deep per knife, 2/3 knife diameter wide, line speed 55m/min, 0.5mm/rev, air-cooled, more suitable.

83. In the grinding machine, the groove of 0.5mm can be ground.

84. The surface of the return tip is hard only about 0.5mm thick, and the inside is soft.

85. When finishing a flat surface, STEP generally takes 2/3~4/5 of the tool diameter, and the tool travels slowly.

86.The tolerance of slider slot is -0.01 and +0.01.

87. Before design, it is very necessary to cooperate with customers on drawing surface (determination of parting surface, determination of ejector position, disposal of inverted groove, location and shape of gate, relationship between flesh thickness and shrinkage, further confirmation of tolerance size, etc.), which is very necessary to further understand customers' design intention and increase the design hit rate.

88. Hot runner is generally suitable for plastic molds with mass production of 240,000 pieces or more.

89. For molds like 9029, 0031, etc. with submerged gate, the straight end of the inlet is often round or flat, and then the round or flat ejector is used, but because the ejector is small and the inlet is long, if there is no release slope at the inlet, poor ejection or broken ejector often occurs. Ejecting.

90. Like Olympus cg5375f1 back cover, PC material, one mold, one spot gate mold, injection pressure up to 200MPA when using Sumitomo 75 ton molding machine.

For example, the end of the main flow channel of 0039 was lengthened by 14mm after the first mold test.

92. Large molds should consider the design of the exhaust slot during the design, should not be specified after the mold test, according to experience, generally around the mold with a milling tool or grinder (depending on the mold accuracy needs), processing a week of shallow groove, the depth is less than the plastic overflow edge value.

93. The inlet with C corner, if the C corner part just meets the mold kernel, the length tolerance from the bottom of the inlet to the C corner should be +0.05 in order to prevent the appearance of burr on the part, as shown in the figure.

94. In the electrical discharge processing for general requirements of the mold surface roughness of 7um can be, precision mold in the general surface roughness of 4um, like the appearance of high requirements of the mold surface roughness requirements up to 2um.

95. The order of mold material should be generally 3~5mm larger than the required maximum size.

96.Try not to use the back locking screw fixing method, because the way will produce stress will make the pulling material tip easy to break, the better way is to pull the material tip can be more free to move.

97. Wire cutting will generally produce 0.2mm R angle in the sharp corner parts, in the mold design in the request to use wire cutting position (into the sub hole, square thimble hole, etc.), must consider the impact of this R, so as not to produce flying edge, burrs and other problems. Mold Daren weibo are dry goods!

98. The fitting part of the slider and the mold kernel should generally be designed with a slope of 2-3° on one side, which can avoid wear and tear and facilitate the generation of pre-pressure.

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, which must be considered in the selection of product design and mold design with the size.

100. Clamp in with into the son when the technique is very important, into the son to be able to slowly flow for the best, into the son into the cavity 1/4 depth can not have the feeling of looseness.