Introduction and Precautions about the two-color (2K) injection mold

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Introduction and Precautions about the two-color (2K) injection mold

May 11
14:52 2023

Two-color mold forming principle: Two-color injection mold is a product made of two different materials or two different colors of the same material. It is generally divided into two categories. One is the mixed-color two-color injection mold, that is, the two injection molding machine The nozzles alternately inject materials of different colors into the same mold cavity to form color products without obvious boundaries. For two-color products on the border, the first nozzle injects the material into a small cavity and then forms, and then the mold is opened but not ejected. The mold is rotated 180 degrees and then closed, and then the second nozzle injects another material into the existing The large cavity of the first material, so that after the two materials are glued together, the mold is ejected for the second time, and a complete two-color product is injected. A complete product is ejected once. Generally, one of the two materials of this type of mold has an important assembly relationship and the size requirements are strict, while the assembly relationship of the other material is not very important. Generally, it only meets the requirements of decoration, cushioning or feel, so generally this layer The material is placed in the secondary injection molding, and this type of mold is also a lot of molds used in the past, that is, two sets of molds are opened, one material is cast first, and then the other material is injected into another set of molds.

Two-color mold introduction

The injection molding machines of the double-layer two-color mold are all rotary injection molding machines, that is, the mold is fixed on a rotating disk, and the movable mold rotates 180 degrees every time the material is shot. The two injection nozzles of this injection molding machine are arranged horizontally or up and down. , and the maximum injection volume of the two nozzles is one large and one small, so we must pay attention to this point in the design, otherwise, if the cavity with a large amount of material is wrongly arranged on the nozzle with a small injection volume, the result may cause injection If the amount of glue is insufficient, the mold may be scrapped. In the process of involving this type of mold, always pay attention to its rotation of 180 degrees to smoothly close the mold and open the mold.

The production steps of the two-color mold: Conventional structure:

1. Two sets of mold bases have more common forming structures: the front mold is the same, and the rear mold is different (the second mold base is rotated 180 degrees and placed). Note: There are certain skills for fixing the mold on the injection molding machine; fix one set first and then fix the other set, mainly to adjust the movable mold part of the other set (the code mold must be closed with screws, and the code boy is generally not available). High requirements for flange size

2. Side nails: There is no deflection column.

3. The precision of the mold base is high, and it is generally shipped from Guangdong (there are more mold bases with Futerba).

4. Forming requirements: (1) primary glue, (2) secondary glue, (3) pre-pressing, (4) avoidance of air; shrinkage does not need to be considered (generally, the product is about 2MM after glue).

When one glue sealing is required, the forming surface sealing position and the first sealing glue position should have a preload of about 0.02~0.05MM; the width of the preload surface is about 2~3MM, and other positions should be avoided.

Precautions for two-color molds:

(1) 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 are symmetrical.

(2) The rear mold should be rotated 180 degrees, and the front mold should not move.

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

⑷Two independent ejector systems and two ejector sticks. 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 a translation relationship.

⑸ The thimble plate can only be reset with a spring, and cannot be forced to reset with a screw, because the rear mold needs to be rotated.

⑹ The side locks must be on the four sides of the center of the mold, and the front and rear molds are symmetrical, otherwise the rear mold will not match the front mold after rotating 180 degrees.

⑺If the distance between the injection point and the nozzle of the injection molding machine is different, the top rod hole should be waist-shaped, because the distance between the top rod of the injection molding machine is not adjustable. Note that most of the injection nozzles of domestic two-color injection molding machines are not adjustable.

⑻ 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.

⑼ The direction of the 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 in the sky and the water out on the ground side, because the rear mold needs to rotate 180 degrees, pay attention to the size of the mold base Do not exceed the height of the water outlet of the injection molding machine, otherwise the water cannot be transported.

⑽The product that is injected for the first time should be placed on the non-operation side, because after the first injection, the product needs to be rotated 180 degrees for the second injection, which is just turned to the operation side, which is convenient for taking the product.

⑾ The code 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 should be fully automatic.

⑿ Precautions for the parting surface: The parting surface of the rear mold should be the parting surface obtained by merging the two products as the rear mold; the parting surface of the front mold should be a single product, and the combined product should not be divided. Profile.

⒀ The tolerance of the front and rear flanges is minus 0.05mm, the tolerance of the distance between the two flanges is plus or minus 0.02mm, the gap between the top rod and the top rod hole is 0.1mm on one side, and the center distance tolerance of the front and rear mold guide sleeve guide posts is plus or minus 0.01 , Tolerance should be added to the four sides and depth of the mold frame, otherwise, when the rear mold rotates 180 degrees, the front will be generated due to the inconsistency of the height. Frame depth tolerance is minus 0.02mm. ⒁ If the mold base has been processed in the mold base factory, when the factory wants to process the nozzle and the top stick hole, the number should be taken based on the center of the spacing between the four guide post and guide sleeve holes, otherwise the deviation is too much, and it is easy to get stuck. mold. When ordering the mold base, it should be indicated that it is a two-color mold base, the four guide posts and guide sleeves are symmetrical with the frame, and the rear mold can be matched with the front mold after rotating 180 degrees.


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