Two Color Injection Molding Machine Manufacturer & Supplier in China

Multi-component injection molding technique is now widely used reach highend molding products which can catch customers atractive and pay for a higher price. Due the multi-shot injection molding can bring down the manufacturing cost of mass production but offer better functions and using experience.

Today, with one-step multi-material injection molding process has become an effective solution for innovative products in almost all industries, from automotive to construction, packaging, medicine, household products, electronics and home appliance, etc

Multi-component Injection Molding method are types of plastic injection method that allows two or more different plastic materials to be produced within the same injection moulding process. There are different injection methods according to the part design and requirements.

What Are Types of Multi-component Injection Molding Methods?
There types of multi-component injeciton molding in total up to today. It depends on how many injection screw & barrel sets:
1. Double shot injection moulding (2k injection molding)
2. Triple shot injection moulding (3k injection molding)
3. Quadruple shot injection moulding (4 color injection molding)

Below we will talk more details about double shot injeciton moulding methods for better understanding. We will separately talk for the working princle of injection unit and mold clamping unit.

The following table will show you how multi-component moulding`s injection unit works:

Injection Mode	Injeciton Mode Description	Injeciton Molding Reference Picture
1. Parallel	Parallel Double Injection construction
2.Right Angle – Horizontal	Side Injection + Back Injection
3.Right Angle – Vertical	Side Injection + Top Injection
4.Piggyback Injection	Side Injection + Oblique Injection
5.Opposite Injection	Opposite Double Color Injection

Now, we will discuss how the plastic mold works for multi-shot injection moulding process:

 

Mold Moving Mode	Mold Moving Specification	Mold Moving Reference Picture
L shape Shoting （Core-Back Process）	In the core-back process, the core that is pulled back on the moving side of the mold creates space in the mold cavity for the second material in the second stage of the process.
Rotary Table (180° Index Plate Process)	Rotary table two shot injection molding process is one of the most important multi injection molding method. the moving side of the mold is rotated with 180°. The geometry of the product to be molded can only be changed by the thread of the mold. It begins by injecting the plastic melt into the primary cavity of the 2-chamber mold. Then the rotating plate is rotated 180 degrees and the primary molding is moved to the secondary cavity. Finally, another plastic melt is injected into the 2nd cavity formed inside the mold on the part formed by primary molding. It is possible to perform more than 2 injections in the same mold according to the requirements
Rotary Core Process	Suitable for production processes that require the same geometry on both sides of the mold cavities. This method provides considerable freedom for part design.
Vertical Rotation Method Stack-turning mould Method	The mold cavity of the group of plates in the middle faces both directions. In order to use different materials or colors, the closing process takes place when the mold turns 180 ° thanks to the cores used during the first injection, and the sections left blank by the cores during the first injection are filled in during the second injection.

1． The differences in mold structure (one cavity mold as an example)

-Single plastic mold just has one cavity,core, one center injection gate and ejection unit.

-Two-color plastic molds can be understood as composed of two single molds， there are two of the same cores and two different cavities,and two center injection gates and two ejection units

2.The different in injection molding machine

-Normal injection molding machines only have one screw and one barrel

-Two injection molding machine has two screws,barrels, some two-color injection molding machine has a rotary platen or rotary shaft core.

How does two color injection molding work?

There are several types of two color injection molding, rotary table bi injection molding, and rotary shaft two-component injection molding, rotary table injection means after finishing the injection of the first color, then the mold will rotate 180°through rotation of the machine’s plate need rotate , the first color will be rotated to the other side for the second injection.

Sandwich injection molding is an additional barrel added to a traditional plastic injection molding machine to form an independent double barrel with special design nozzle, during the injection process, this double barrel can concurrently inject two types of molten plastic, via the same nozzle into the mold to achieve double material simultaneous injection. The outer layer of the mixed molten plastic is called the skin material, while the inner layer is called the core material.

By matched with special design nozzle，sandwich injection molding machine might produce the special flowered & multilevel colors，thus to create high values-added products while keeping the costs down and creating the additional profit.

Sandwich injection molding advantages over traditional injection molding：

• For products with different outer and inner layer materials, the traditional two-step insert molding becomes one-step.
• The different color combinations give old products(molds) new life.
• Low-viscous materials can be used as core materials to reduce injection pressure.
• Sandwich injection molding machine can also produce single color which provides a multi-function and flexible molding method, increasing the processor’s capability to produce high-quality and low-cost products.
• Recycled and low-quality materials can be used as core materials to reduce production costs.
• High-quality materials with anti-magnetic interference properties and high surface quality can be used as skin materials to increase product utility.
• Appropriate core and skin material combinations can reduce the residual stress and increase product hardness.

The sandwich injection moulding`s most applications advantages:

Core material (inside)	Skin material (outside)	Sandwich Injection Moulding Advantages
Recycled material	Virgin (Brand new) material	Material cost saving
Foamed polymer	Smooth surface / soft feeling	Material cost and weight saving
Glass filled polymer	Paintable surface	Increased stability and strength
Colored material	Transparent material	Decorative effects / value added to products
PE weld able	PA not weld able	Combination of characteristics

What is two-color injection mold:

two-color injection mold is a mold in which two plastic materials are injected on the same injection molding machine and are molded in two times, but the product is only released once. Generally, this molding process is also called two-component injection molding, which is usually completed by a set of molds and requires a special two-color injection molding machine. Two-color molds are increasingly popular in the market. This process can make the appearance of the product more beautiful, and it is easy to change the color without spraying, but the cost is expensive and the technical requirements are high.

The advantages of two-color injection molding molds are as follows:
1. The product has high precision and stable quality.
2. Good structural strength and durability.
3. Small matching clearance and good appearance.
4. The cost is greatly reduced.

The mold materials are similar, pay attention to the following points when designing:
1. Basic principles of two-color injection mold design:
(1) Do 1 time for hard glue and 2 times for soft glue;
(2) 1 time for transparent, 2 times for non-transparent;
(3) The plastic with high injection molding temperature is done once, and the plastic with low molding temperature is done twice;

2. The mold base guide column and guide sleeve must be symmetrical up and down, left and right, and the front and rear molds are 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 foreign two-color injection molding machines is adjustable, some cannot be adjusted, and domestic ones are not adjustable.

5. Two 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.

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

7. The side locks must be on the four sides of the center of the mold, and the front and rear molds are symmetrical. Otherwise, when the rear mold is rotated 180 degrees, it will not be in line with the front mold, which is not good.

8. If the distance between the injection point and the nozzle of the injection molding machine is different, the hole of the top rod should be waist-shaped, because the spacing of the top rod of the injection molding machine is not adjustable. Note: Most of the 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, which 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. The water cannot be in the sky and the water out on the ground side, because the rear mold has to rotate 180 degrees, pay attention to the mold base The size should not exceed the height of the water outlet of the injection molding machine, otherwise, the water cannot be transported.

11. The 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.

12. The code mold 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.

13. 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, not the combined product. Parting surface.

14. 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, tolerances 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 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 top stick hole, the number should be taken based on the center of the distance between the four guide post and guide sleeve holes, otherwise the deviation is too much, and it is easy to jam. Dead mold. When ordering the mold base, it is necessary to indicate 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.

16. If it is a two-color mold for a set of molds, it is a straight barrel, a 90-degree barrel to shoot glue, no need to rotate, only one mold core, the separation method of soft glue and hard glue depends on the line sealing. glue.

17. The two shapes of the cavity are different, and a product is formed separately, while the two shapes of the core are completely the same.

18. After the front and rear molds of the mold are rotated 180° from the center, they must be matched. When designing, this check action must be done.

19. Pay attention to the position of the thimble holes, the minimum interval is 210mm. For large molds, the number of ejector holes must be appropriately increased, and since the ejector pin attached to the injection molding machine itself is not long enough, we must design a longer ejector pin in our mold, and the ejector pin grows out of the bottom plate of the mold base by about 150mm.

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

21. The total thickness of the front mold panel plus the A board should not be less than 170mm. Please carefully check other reference data of this type of injection molding machine, such as the maximum die thickness, the minimum die thickness, the spacing of the top stick holes, etc.

22. The depth of the front SPRUE should not exceed 65mm. The distance from the top of the upper side (large nozzle) SPRUE to the center of the mold base is not less than 150mm.

23. When designing the cavity for the second injection, in order to prevent the cavity from inserting (or scratching) the glue position of the product that was molded for the first time, a partial void can be designed.

24. 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 to achieve the effect of sealing.

25. The water transport arrangement of the two cavities and the core should be as sufficient as possible, and should be balanced and the same.

26. For two-color injection molds, the gate location must be carefully selected. It is best to choose latent glue feeding for a product, so that the product and the runner can be automatically cut off. When latent feeding cannot be used, three-plate molds or hot runner molds can be considered. If the primary material is a point gate, it should be made a wave to avoid hitting the secondary material due to the residue of the primary input point.

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

28. Two-color injection mold injection molding, usually the same plastic with different colors, or two different plastic raw materials. At this time, the interface effect of the two materials, the difference in shrinkage rate, and the processing parameters should be considered.

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

30. Pay attention to the positioning of the front and rear molds. The inclination drop of all insertion and breaking surfaces should be as large as possible, which should be more than 0.1mm.

Why Two-color Injeciton Mold Cost Higher Price?

After reading this, do you feel that the two-color mold has certain technical difficulties? Two-color molds are also expensive, so what are the reasons for their high price?

Anyone who knows molds knows that more people choose two-color molds than single-color molds. There are many factors, and the two-color mold itself has a lot more than the single-color mold. Not only because of the single color or the price, the fixed cost input makes the two-color mold and the single-color mold different, but the most important thing is the technology. The two-color mold is much more generous and beautiful in appearance, thereby enhancing its own value and realizing the value of its shape. And it is also conducive to better color, without having to spray too much. Of course, in total, the cost will be high, and the market price will also be high. In addition to these, two-color molds are also much more technically demanding than single-color molds. Let’s take a look:

The requirements for the front and rear molds of the two-color mold are the same, and the processing requirements for the mold base are high. According to the requirements of the product, data control will be carried out on the panel thickness of the mold and the distance of the holes, and during the second injection, pay attention to the glue position of the first molded product, and do not let part of the nostrils. There is also the strength of the glue position in each place. The two-color mold is made of two materials or a mixture of multiple materials, and the color is also very bright and beautiful. The choice of the two materials is also very particular, requiring a good combination and strength requirements. In order to ensure this, combined experiments can be carried out to ensure that there is no error before mass production, because that is the reason why its technical requirements are relatively high.

Although the single-color mold is relatively simple in operation and technology, it is also simplified. The traditional mold industry is also used more, the cost input is less, and the natural price will be different from the two-color.

2-Shot Overmolding is an injection molding process where two materials are molded together. Types of overmolding include two-shot sequential overmolding, multi-shot injection molding or insert overmolding.

Below is the brief specification of these three types over-molding for study:

• Two-shot sequential over-molding is where the molding machine injects the first material into a closed cavity, and then moves the mold or

  cores to create a second cavity, using the first component as an insert for the second shot using a different material.

• Multi-shot injection molding injects multiple materials into the cavity during the same molding cycle.
• Insert overmolding uses a pre-molded insert placed into the mold before injecting the second material.

Any interest for Double Shot Overmolding injection machines, please click any picture below:

Double Injection Molding Machine

Double Injection Molding, sometimes known as 2 material 2 shot molding or 2K molding, is an innovative manufacturing process used to produce complicated molded parts from two different materials. Through a highly specialized and automated process we carefully control the injection of multiple materials, including two different kinds of resin, into a single, multi-chambered mold.

Double Injection in performed on one machine that is programmed to perform two injections in one cycle. In the first cycle, a nozzle injects plastic into a mold. The mold is then automatically rotated and a different type of plastic is injected into the mold from a second nozzle.

 

Double Injection Molding optimizes co-polymerization of hard and soft materials to create powerful molecular bond. The result is a single part with production and feature advantages. It can be used for a variety of product designs across all industries. It also allows for molding using clear plastics, colored graphics and stylish finishes which improving your product functionality and marketplace value.

Double Colors Molding Product Samples