1. Height of slider guide rail must be at least 1/3 of slider height to ensure stability of slider and smooth sliding.
2. Pay attention to opening lubrication grooves in locations with sliding friction. In order to prevent lubricating oil from flowing out, it is not advisable to make grooves "open" but should be "closed". Generally, they can be milled out directly on a milling machine with a single-piece cutter.
3. Cavity of mold core is fixed, and wire cutting is generally used for small molds, which can improve accuracy of mold; while mold cavity of larger molds is generally processed by milling, pay attention to its verticality during processing, and in order to prevent assembly during assembly , mold core is not in place, surroundings of mold frame should be milled to a depth of 0.2 with a milling cutter.
4. Interpenetration between mold core and mold core, mold core and mold frame generally need to add a 1° slope to prevent damage during assembly.
5. Length tolerance of seating part of insert is -0.02, size tolerance is -0.10, and seating tolerance corresponding to mold core is +0.02.
6. Tolerance from bottom end of insert with C corner to C corner is +0.01 to prevent burrs.
7. Main part of body mold is made of NAK80 material, and inlet and tip are made of SKH9, SKH51 (material treatment: chamber treatment, or not). VIKING material can be used if necessary.
8. After drawing part, you should first determine position and size of slider to prevent interference and insufficient strength, then determine mold size.
9. Tolerance of entry size is set to -0.01, and tolerance corresponding to entry hole on mold core is +0.01.
10. Sharp corners of wire-cut square holes on mold core are oversized with R0.20, and corresponding entry parts are also R0.20 to correspond to influence of wire diameter during wire cutting. At the same time, it can prevent sharp corners from being worn and causing overflow.
11. Small pit size method corresponding to positioning bead is generally a conical hole with a bottom diameter φ3 and an included angle of 90°-120°.
12. Draft angle on fixed side should be larger than that on movable side, so that release can stay on movable side; and it can prevent parts from deforming, especially parts with thin walls and long parts that are easy to deform. Uneven pulling force on fixed side can easily cause parts to warp or stay on fixed side.
13. For parts with large side core-pulling force and strict parts accuracy requirements, it is best to use a secondary core-pulling structure.
14. Slope of tip + 2° = slope of compression block (usually 18° or 20° or 22°).
15. When assembling mold, you should develop following habits:
a. Use an air gun to clean surfaces of mold core, mold cavity, insert, runner plate, and parting surface.
b. Before assembly, use a whetstone to polish surfaces of mold core, mold cavity, insert, and parting surface to facilitate smooth assembly.
c. Pay attention to cleaning corners to prevent interference and bruises.
d. Before assembly, you should consider how to proceed with subsequent work.
16. Side pressing block of large mold core should be designed to be 0.5-1.0mm below parting surface after locking to prevent interference.
17. PC+GF20 shrinkage rate 3/1000
18. Normal shrinkage rate of POM is 20/1000, but sometimes it can reach 30/1000 locally.
19. In order to prevent latent gate from scratching parts when they are ejected, add a wedge-shaped block 2-4mm away from latent gate in runner. Height is about half of runner and angle is 10° on one side to break gate during ejection.
20. Main channel drawing well is an inverted cone with a depth of 8-10mm, an included angle of 10° on one side, and a top diameter as wide as flow channel; advantage of this is that it can prevent pull material ground into a wedge shape on one side from hooking flow channel during ejection, causing poor release.
21. There are two types of switches:
1. Made of rubber, deformation is adjusted by screw in the center to adjust tension.
2. Made of spring steel. Its function is to delay mold opening time of movable side and fixed side, and is applied to small nozzle molds.

 

22. In order to ensure that ejector pin and oblique pin of mold are reset, some molds are equipped with an early return mechanism (female one is installed on 108 board, male one is installed on 102 board, male one is similar to ejector pin, and bottom is blocked with headless screws, usually two are arranged) or micro switches (between 108 and 109 boards [containing electrical components]).
23. When considering length of screw when clamping injection molding machine, you need to pay attention to thickness of upper and lower fixing plates. If necessary, four corners should be milled lower. At the same time, in order to improve safety, four bolt holes can be drilled on upper and lower fixing plates according to positions of holes on injection molding machine.
24. Forming end of oblique pin has a straight surface, which is generally 4-6mm long. In order for oblique pin to slide between 107 and 108 plates during ejection, bottom should have an R angle of 0.5mm-1mm.
25. For appearance products that require embossing, design of draft angle needs to consider degree of embossing to avoid straining appearance. For some protruding parts, cross-section will become larger after taking into account bite. During actual processing, one side should be smaller by 0.02-0.03.
26. Considering that gap between fixed side and movable side will be formed, fixed side is 0.03-0.05 smaller than movable side.
27. In a mold with a slider, it is sometimes necessary to open an oil groove on the inclined surface where slider and pressing block are in contact; in addition, if it does not affect forming, it is better to open an oil groove on upper surface of mold plate than on slider. It is more efficient to open an oil groove at the bottom of block.
28. Parting surface should not be selected at a required location on the surface.
29. Shrinkage rate of fiber-added is 1-2 thousandths smaller in flow direction and larger perpendicular to flow direction; opposite is true for those without fiber-added.
30. Shrinkage rate of tooth tip circle is 1-2 thousandths smaller than shrinkage rate of tooth root circle.