Overmolding & 2k Molding

The same type of material of different colors is usually used for two-color
injection overmolding（or 2k injection molding）so that the bonding strength
of the first color and the second color plastic is the best, but due to the
functional requirements of the product, the performance difference of the
two materials actually used may be very big, if the elastomer is injected
into the surface of a rigid material, the most difficult thing to solve
during 2k moulding process is the delamination and shedding of the bonding
surface of the two materials.

OVER-MOULDED 2K MOLDS FOR SALE

Water Proof Plastic Enclosure Mold
The product will be made by two times, which will inject the second piece
after finishing the first piece in the other mold and different injection
machine, normally will be no specific request for 2 different pieces
injection time, injection machine.

Drip Tip Mold
The two-color molding will be made in one same injection machine at the same
time by 2 times injection, with 2 injection barrels and 2 different
injection gates by 2 different molds, but the product will be picked up one
time, it will request 2 molds in one specific 2k injection machine to finish
final injection.

2K Mold
This mold will be put with a movable core on gate position of the core side,
the movable core is pushed to the rising position when injecting the first-
color material, and the first color part is solidified, After that, the
movable core return back through the action of the hydraulic device, at this
time, another barrel injects the second color material into the space left
by the retreat of the core, the mold is opened and the part is taken out
after finishing one injection after it's solid.

Material Selection For 2K Plastic Injection Moulding
In addition to meeting the requirements of product function and appearance
in the material selection of two-color products, whether the adhesion
between raw materials can be solved well will be related to the success of
two-color products in 2k moulding process is also the difficulty of 2k
moulding technology.

The following four points should also be considered in the selection of
materials for two-color injection molded products:

1. In terms of the effect of the bonding surface, if the force of the
bonding surface of the two materials cannot be enhanced by the structure,
the bonding performance between the selected materials is better, the
material has good adhesion performance, the bonding surface layer has a
large force, and it is not easy to delaminate and fall off.

2. In terms of shrinkage rate, if the two-color injection molded product is
prevented from falling off and delamination through structural embedding or
wrapping, it should be noted that the thermal shrinkage rate of the two
materials cannot be too different, and try to match the shrinkage rate
completely. Generally, the shrinkage rate of the first color material is
slightly smaller.

3. In terms of processing parameters, for the two-color plastic injection
overmolding process, because in the 2k injection molding process, although
the two injection cycles are relatively independent, the entire injection
cycle time is the same, so it is necessary to focus on controlling the
injection time of the two-cavity injection cycles, cooling time and pressure
holding time, so as to ensure that the product can be produced normally; at
the same time, it is also necessary to control the injection volume,
injection speed, and mold temperature, this is because in 2k plastic
injection moulding, changing the injection volume and mold temperature can
make the degree of mixing of the plastic part or the thickness of each layer
occur. Change, and whether the injection speed is appropriate or not, will
directly affect whether the melt may have turbulent flow or cause the outer
layer of the plastic part to rupture during the flow process.

4. In terms of temperature difference, it is necessary to avoid too much
temperature difference between the two-component materials.

2K Molding Design Guide
Structural design is the most important part of 2k molding product design,
the structure design of the product should not only consider the function of
the product but also consider whether it meets the processing conditions and
the complexity of the processing mold, in the design of two-color injection
products, in addition to the issues to be considered for ordinary injection
products, the following aspects should also be considered:

1. The quality ratio of the two materials: since the injection time is
related to the injection volume, the coordination of time is also related to
the product design. To control the injection volume ratio, the difference in
the injection quality between the two cavities should not be too big.

2. Product structure shape design: in order to increase the 2k moulding
product's fusion strength, the measure in the product structure design is to
increase the contact area of the two parts. For example, if possible, the
contact area of the two parts can be enlarged through the non-joining
surface, and concave and convex grooves can be designed around the small
cavity products (which can be generated by forced demolding, and the depth
can reach 2mm).

As professional 2k molding factory, we will do our best to provide more
types of related products for sale, if you have needs, please contact us.

As one of injection molding manufacturers, we will do our best to meet all
the needs of customers.

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