The basic principles of two-color mold design, if you don’t understand it, it’s really bad design!

 Basic principles of two-color mold design:

(1) Do 1 time for hard glue and 2 times for soft glue;

(2) Do one time for transparency, and two times for non-transparency;

(3) Plastic with high molding temperature should be done once, and plastic with low molding temperature should be done twice;

The above is the basic principle of making two-color molds, otherwise the mold will be in vain; in addition, try to use sealant sealant instead of inserting sealant sealant when sealing, even if it is recommended that customers modify the product, they must use sealant sealant as much as possible;

2. The guide post and guide sleeve of the mold base must be symmetrical up and down, left and right, and the front and rear molds must be symmetrical.

3. The rear mold should be rotated 180 degrees, and the front mold should not move.

4. The product spacing must be based on the nozzle spacing of the injection molding machine. The nozzle spacing of some two-color injection molding machines abroad is adjustable, and some are not adjustable, and the domestic ones are not adjustable.

5. Two independent ejection systems, and two ejector pins. The two products of the rear mold are the same, and the thimbles are the same, which is a rotation relationship, and must not be made into a translation relationship.

6. The thimble plate can only be reset by the spring, not by the screw, because the back mold needs to rotate.

7. The side locks must be on the four sides of the mold center, and the front and rear molds are symmetrical, otherwise the rear mold will not match the front mold after rotating 180.

8. If the distance between the injection point and the nozzle of the injection molding machine is different, the hole of the ejector pin should be made into a waist shape, because the distance between the ejector pins of the injection molding machine cannot be adjusted. Note that most injection nozzles of domestic two-color injection molding machines are not adjustable.

9. Pay attention to the direction of the parallel nozzle of the injection molding machine provided by the customer, whether it is the x-axis or the y-axis, so as to determine the layout of the product ranking.

10. The direction of water in and out must be on the side of the sky and the ground, and the in and out of each circulating water must be on the same surface. It is not allowed to enter the water from the sky and the water to the ground side, because the back mold needs to rotate 180 degrees, so pay attention to the mold base The size should not exceed the height of the outlet tank of the injection molding machine, otherwise the water cannot be transported.

11. The product of the first injection should be placed on the non-operating side, because the product must be rotated 180 degrees for the second injection after the first injection, and it should be turned to the operation side for easy access to the product.

12. The coding position of the export mold should be on the operating side and the non-operating side, not on the heaven and earth side, because their products must be fully automatic.

13. Notes on the parting surface: the parting surface of the rear mold should be the parting surface obtained by merging the two products; the parting surface of the front mold should be a single product, and the combined product is not acceptable parting surface.

14. The tolerance of the front and rear flanges is minus 0.05mm, the distance between the two flanges is plus or minus 0.02mm, the gap between the top rod and the hole of the top rod is 0.1mm on one side, and the center distance tolerance of the front and rear mold guide sleeves and guide posts is plus or minus 0.01, the four sides and the depth of the mold frame must be toleranced, otherwise when the rear mold is rotated 180 degrees, there will be a batch front due to inconsistent height. The frame depth tolerance is minus 0.02mm.

15. If the mold base has been processed in the mold base factory, when the factory wants to process the nozzle and the ejector pin hole, the number should be taken based on the center of the distance between the four guide posts and guide bush holes, otherwise the deviation is too large and it is easy to get stuck dead mold. When ordering the mold base, it should be indicated that it is a two-color mold base, the four guide posts, guide sleeves and frames are symmetrical, and the rear mold can be matched with the front mold after rotating 180 degrees.

16. If it is a two-color rear mold rotation, it is much simpler. The two front mold cores are the same. After the hard plastic is injected on one side, it is rotated 180 degrees (note that the product cannot fall when turning, and the gate can be separated automatically), and turn To the other side and then inject soft rubber, injecting hard plastic does not need to arrange thimbles, just place the core on the side of the soft rubber, and pay attention to shrinkage, if the soft rubber completely entangles the hard rubber, you only need to put the hard rubber Shrinkage, if the contours meet, the hard and soft rubber will shrink.

17. If it is a two-color mold for a set of molds, it is a straight barrel and a 90-degree barrel for glue injection. It does not need to be rotated, and only one core is needed. The separation method of soft glue and hard glue depends on the position seal. glue.

18. The two shapes of the cavity are different, and one product is molded respectively. The two shapes of the core are exactly the same.

19. After the front and rear molds of the mold are rotated 180° from the center, they must match. This checking action must be done during design.

20. Pay attention to the positions of the thimble holes, the minimum interval is 210mm. For large molds, the number of ejector holes must be appropriately increased. Moreover, since the thimble attached to the injection molding machine itself is not long enough, we must design an extended thimble in the mold, and the thimble is about 150mm longer than the bottom plate of the mold base.

21. Two positioning rings must be designed on the bottom plate of the rear mold.

22. The total thickness of the front formwork panel plus plate a cannot be less than 170mm. Please carefully check other reference data of this type of injection molding machine, such as maximum mold thickness, minimum mold thickness, distance between ejector pin holes, etc.

23. The depth of the front sprue should not exceed 65mm. The distance from the top of the sprue on the upper side (big nozzle) to the center of the mold base is not less than 150mm.

24. When designing the cavity for the second injection, in order to prevent the cavity from inserting (or rubbing) the glue position of the product that has been formed for the first time, you can design a part of the void. However, the strength of each sealing position must be carefully considered, that is, whether there will be plastic deformation under high injection pressure during injection molding, resulting in the possibility of a batch front in the second injection molding;

25. During injection molding, the product size of the first injection molding can be slightly larger, so that it can be pressed more tightly with another cavity during the second molding, so as to achieve the effect of sealing.

26. Before closing the molds of plates a and b, should you pay attention to whether the slider or lifter of the front mold will reset first and crush the product? In this way, a way must be found to close the mold on plates a and b first, and then the slider or lifet of the front mold can be reset.

27. The water transportation arrangement of the two cavity and core should be as full as possible, balanced and the same.

28. In 99% of the cases, the hard rubber part of the product is injected first, and then the soft rubber part of the product is injected. Because the soft glue is easy to deform.

29. Pay attention to whether the movement of the plastic will impact the product that has been formed in the first time during the second injection molding, causing the glue position to deform? Assuming this is possible, we must find ways to improve it.

30. The position of the gate must be carefully selected for the two-color mold. It is best to choose latent glue feeding for a product, so that the product and flow channel can be automatically cut off. When latent glue feeding cannot be used, three-plate mold or hot runner mold can be considered. If the primary material is a dot gate, it must be made of wave Aberdeen to avoid touching the secondary material due to the residue of the first gate.

31. Two-color injection molds often use rotary injection molds. The punch/die at the two positions of the rotary injection mold requires the same size and precision, and a good fit with the die/punch. When the ejection and ejection mechanism on the two-color injection molding machine cannot be used, a hydraulic ejection and ejection mechanism must be installed on the rotary table.

32. Two-color mold injection molding usually uses the same plastic of different colors, or two different plastic raw materials. At this time, it is necessary to consider the interface effect of the two materials, the difference in shrinkage rate, and the processing parameters.

Two-color injection molding products are generally made of ABS, PC and other hard plastics combined with TPE soft plastics. Due to the relationship between cost or application, it is necessary to fully consider that the two materials used may not have good adhesion and fusion. There are many problems such as the mold treatment of the junction between the joints (generally there will be embossed texture or the need to make a mold sealing groove) and the thickness of the material! In order to make the two plastics "stick" tighter, the "stickiness" between the materials and the roughness of the mold surface must be considered. There are special tpu materials for two-color injection molding; and the smoother the surface of the mold, the tighter they "stick.

33. Generally speaking, the shrinkage rate of the two-color mold depends on the primary material. Because the primary material has already supported the contour of the plastic product, the secondary material will not shrink more. As for how to determine the primary material and secondary material, there are many factors to be considered, such as the fluidity of raw materials, the shape of plastic products, and so on.

34. Pay attention to the positioning of the front and rear moulds; the slope drop of all penetrations and breaks should be as large as possible, more than 0.1mm.

35. When abs/pc, abs/pc abs, abs/pmma two-color injection molding, it is necessary to inject pc, pc abs or pmma with higher temperature first. If it is a transparent shell mold, most of them use an inverted mold structure.

36. Transparent large two-color injection molding is a place that needs attention for structural design:

a. The reservation of the gate position must be agreed with the mold factory in advance;

b. The thickness of the material is recommended to be transparent over 0.8mm and non-transparent over 0.7mm. Non-transparent materials should be light-colored as much as possible. When there are LED lights, pay attention to shading;

c. The width of the parting surface of the transparent part is the same as that of the hole. The width is recommended to be 0.5mm.

d. The thickness of non-transparent parts is limited, and the upper ribs and other structures should be between 0.5-0.6mm as much as possible to avoid shrinkage;

e. At present, it is not recommended to do two-color injection molding with a main lens. The cost of the mold and the product is too high, and there are considerable requirements for the equipment and technical level of the mold manufacturer. If it is done, the other party needs to provide a detailed solution for the entire process For evaluation, all links in the middle need to be reviewed;

f. For large-area two-color injection molded parts, two key tests are drop and thermal shock. In these two tests, transparent and non-transparent parts are easy to separate. Cold and heat shock -40 -65, time 48 hours.

g. Simplify the structure on the two-color parts as much as possible, and make the complicated ones on the matching parts. The rib width of the non-transparent parts should be 0.5-0.6 as far as possible to avoid shrinkage