Grandshine Injection Over Mold Service

Grandshine has more than 20 yeas experience of over mold. We are China top 10 experts in over mold filed in China. All our over mold plastic parts have perfect performance and will not shutt-off and the joint of the two materials is very smooth.Our over mold plastics products were applied in United Airline service device,Samsung retail device and Square payment devices etc. Over mold is also called 2 times injection molding,it means to apply one material onto another material. Here two color pistol grip, utilizes TPU injected onto PC material.Two types material should form a bond and offer functional performance. Compared with the third-party material bonding, over mold process makes the process faster and more cost-effective, it has been widely employed in plastic design.

Regarding over molding mold design,we must take shrinkage into consideration due to two different plastic materials.Two material both have their own injection gate and runner systems. And the wall thickness of over mold should be as uniform as possible in order to have the shortest cycle time. In the range from 0.7mm to 2mm will ensure very good bonding of two materials in most over molded applications. But if final part requires the use of thick, then they should be cored out to manimize shrinkage problem and to reduce the part weight and cycle time.

Grandshine provide oem odm injection over mold co-mold service and manufacture all kind of co-mold products. Our engineer team can help you design mold structure in free. Welcome to visit our factory and work together for insert injection molding.

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Why Grandshine Is Your Professional Over Mold Products Supplier?
) 20 years experience in custom plastic injection mold and products development.
) Engineer teams’ technology were from Japanese mold and Taiwan mold Technology.
) From Product design to molding to production one-stop product development service.
) ISO9001:2015 and ISO14004:2015 Quality System and BSCI social audit certificate.
) You can custom your own products from Grandshine.

Specification :

Mold Base:

 LKM, HASCO, DME or your requirement

Mold Material:

P20, H136, 718, 1.2344, 1.2738 and so on



Product Material:

PC/ABS, ABS,TPU,TPE,TPR, PA66, POM or other.

Runner :

Cold/Hot Runner

Gate Type:

Side gate, Sub gate, Pin point gate, Edge gate etc

Mould Weight:


Injection Machine Type:


Standard for Product:

Appearance for graining MT(Mold Tech), YS, HN Series The Way of Color Contrast for Plastic RAL PANTONE


 ISO 9001:2015 Certificated



Here Are All Information You Care About Product Development

Take a look at products description below. If you still have questions,feel free to contact us email or whatsapp.

There Are Two Main Techniques For Over Mold

1.One is two-color injection molding, that is, two-component molding, which is realized in the two-color injection molding machine. First, a material is injected into the product, and then the product is jumped into the corresponding mold cavity of another plastic injection cylinder by the mold flip in the two-color machine. Injection molding machine is double cylinder, double mold cavity, injection process is two kinds of material products at the same time, but a cavity products will be used as inserts into the next cavity.

2.The other is two-step injection molding (that is, secondary co-mold ). In an injection machine, a part of a material is formed first, and then the molded part is put into another mold as an insert, and then a second material is injected.

The method of Over mold (Co-mold)

Over mold (Co-mold) can have a physical snap method and a chemical method

1. The physical method relies on the buckle design, the surface roller, the surface tapping, and then injection molding on the second material to achieve Over mold (Co-mold). The feature of this method to achieve material adhesion is that the physical connection part has a strong adhesion, while the parts outside the physical connection part have almost no adhesion.

2. The chemical method relies on the molecular affinity between the two materials and the bond force of the chemical bond to bond the two materials together to form a single component, two or even a variety of components.

Although physical snaps and chemical bonding methods are often used together in practical applications, it is clear that achieving chemical bonding between two materials is the more robust and design-preferred method.

Two-color Injection Molding Process Requirements

1. Double shot design of soft and hard plastics. There must be a certain temperature difference between the melting point of the two materials. The general recommendation is 60 degrees, and the recommendation is at least 30 degrees. Generally, the first shot is PC or PC/ABS, and the second shot is TPU or TPE. The thickness of PC is 0.6-0.7mm, and the thickness of soft plastic is above 0.4mm.
Try to widen the contact area, do grooves and so on to increase the adhesive force, or the first shot using core withdrawal, the second shot part of the material injection into the first shot inside, the first shot mold surface as rough as possible

2. Transparent and non-transparent Over mold designs
The Over mold design of the small lens
The first shot is non-transparent, the second shot is the lens, the first shot is as high as possible with pc melting point, the second shot is PMMA.

Decoration Transparent and non-transparent Over mold design

The first shot is non-transparent material, the second shot is transparent material, non-transparent material is commonly used PC material temperature, the second shot transparent material PMMA or PC. PC needs to be sprayed with UV to protect, PMMA can choose UV or strengthen, such as the surface of the character must choose UV.

TPU Material Selection For Over Mold Co-mold

If it is TPU over mould on PP, the hardness of TPU should be about 65A-75A. TPU over mould on PC, TPU over mould on PA6, TPU over mould on PA66, TPU over mould on ABS, TPU over mould on PC/ABS, the hardness is higher. 75A-85A is recommended.
In general, TPU over molding doesn’t have any problems! The temperature increases, and then pay attention to the plastic parts have not played release agent! Is the plastic surface of a product over mold smooth? If it is sand, be sure to polish it

TPU over mold is actually a kind of TPU secondary injection molding, the product body generally includes (hard plastics such as PP, PC, PC/ABS, POM, PA6, PA66, ABS, PS, etc.) and co-mold soft plastic TPU, in the mold manufacturing, the first production of hard plastic body, The main hard plastic mold is designed according to the normal design procedure. The design of the soft plastic TPU mold of co-mold should take the hard plastic finished product as the reference, and there is no need to put shrinkage. The back mold part is consistent with the hard plastic body, while the front mold has the over mould shape. Then put the hard plastic body into the co-mold mold for soft plastic injection molding production.

When designing TPU over mold, we should first pay attention to the shrinkage problem. The external parts do not shrink, and then it is a design scheme. The empty place is as empty as possible to facilitate the putting of the external parts and reduce the cost of the mold. over mold should pay attention to the strength of the skeleton to prevent deformation after over mold;

Why Does TPU Over Mold On PC Break?

Why does TPE over mold on PC break? Does tpu over mol break or does PC break. The problem should be that the PC parts are mostly cracked.

1. Crack (rupture) of PC parts
Cracking of PC(polycarbonate) is a common problem. PC parts are easy to crack, mainly due to the internal stress of the parts. The forced molecular orientation occurs during the molding of PC materials, but after the molding cooling, due to the existence of benzene ring structure with poor flexibility, the molecular orientation is very difficult. Therefore, when the PC parts are forming, the solution orientation measures are not handled properly, such as the mold temperature setting is low, the cooling and pressure holding time is not enough, so that the molecules can not fully relax and reconcile the orientation, then the formed products will have internal stress, when the internal stress reaches a certain degree (greater than when the cracking force), the PC parts will have cracks.

When TPE and TPR are used for secondary injection molding over mold on PC, because there is a large internal stress inside the PC parts, the destructive effect of this internal stress just appears at the time of over mould TPE, or when TPE over molding is used, part of TPE over molding is larger. During the over mould molding, TPE shrinks and the thickness of PC parts is thin, which leads to the cracking of PC parts.

Solution: PC molding using high die temperature, appropriate extension of pressure and forming cooling time, reduce or eliminate the internal stress.

2.TPE/TPR over mould cracking
TPE, TPR over mould PC, TPE rupture (tear), which usually occurs after the over mould has been formed for some time. TPE and TPR cracks are mainly caused by the poor aging resistance of TPE and TPR and the aging cracking of TPE materials.

Solution: TPE and TPR products with excellent aging resistance are used to improve the aging and cracking resistance of materials.

Different Hard Plastic Co-mold.

1.PP co-mold
PP is a plastic with very weak polarity, very close to the polarity of SEBS TPE. Therefore, over mould PP, conventional TPE formula can be used directly, without adding polar modifiers. Although PP co-mold TPE is the most common type, the secondary injection molding temperature is also very important. Sufficient injection molding temperature must be used to ensure the fluidity of TPE and rapid co-mold PP. The injection molding temperature should be able to ensure the rapid formation of a fusion layer on the surface of PP plastic, which is conducive to the adhesion of TPE and PP. And not in the injection molding to PP plastic parts thermal deformation. Note: SBS is not recommended as the modified base material of TPE for PP encapsulation.

2. ABS and PC over mould
ABS and PC are weak to medium polarity plastics, and there is a certain polarity difference with TPE. By adding a modifier (TPU) into the formula, the polarity of TPE can be improved, thus improving the adhesion of TPE with ABS and PC. In addition, the temperature of secondary injection molding is recommended to be 180~230℃, which can be adjusted according to the actual processing situation.

3. PBT, PET co mold
PBT and PET are semi-crystalline plastics, similar to ABS and PC in polarity. PBT melting point 220℃, PET melting point can be up to 260℃, TPE needs to have a higher melt temperature. Therefore, the secondary injection temperature of TPE co-mold PBT and PET is higher than that co-mold ABS and PC. Gluing is more difficult.

4. PA6 and PA66 double injection
PA6 and PA66 are semi-crystalline strong polar plastics, which require high temperature and energy to form a fusion layer on the hard plastic surface. The melting point of PA6 is 240℃ and that of PA66 is 260℃. To form a strong bond, a higher melting temperature of TPE is required. Generally, TPE adhesive PA6 has a secondary injection temperature of 230~250℃, and TPE adhesive PA66 needs a temperature of 240~270℃. In addition, PA6 and PA66 are easy to absorb water, which are adverse factors to co mold bonding.

5. POM over mold
POM’s over mold. Although the melting point of POM is not high, only 180℃, due to its high crystallinity, high energy is needed to form the fusion layer on the surface of over mold. Meanwhile, due to the self-lubricity of POM, it is not conducive to the rapid co-mold of TPE material on the surface of POM hard plastic parts.

Finally, make an induction and supplement. The second injection molding of TPE and PP,ABS,PC,PA and other plastics, the quality of adhesion, depends on the TPE formula and the appropriate over mold glue process. In addition, for high melting point plastics such as PA6, PA66 and PBT, the hardplastic parts should be preheated before the secondary injection molding, which is conducive to the adhesion between TPE and hard plastics. During the secondary injection molding, high injection temperature (limited by the non-degradation of TPE) and high rate of fire are adopted to allow TPE to have as much energy and time as possible to achieve cladding and fusion with hard plastic parts such as PA6, PA66 and PBT, thus forming a good bond

Moulding Manufacture To Ensure Your New Product Quality

Only one good quality plastic injection mold can manufacture top quality products. You may have experience that your products quality can’t be improved no matter how do you try. The main issue is you are not professional in a good quality mold manufacture or you select the cheap mold supplier instead of professional mold factory.

Currently we have 50 experiened mold makers engineers, most of the them have 15years experience in plastic injection molding industry,most of them learn from Japanese mold factory and Taiwan mold factory.We are able to provide 60-80 sets of injection molds per month.We introduce latest technology continuously and equipped the most advanced mold manufacturing facilities, we have full in-house plastic injection mold manufacturing, injection molding, painting, assembly capacity, our equipment includes but not limited to: 6 sets of CNC, precision 0.005mm; 16 sets of EDM, 9 sets of slow wire cut, 25 sets injection molding machines range from 120 Ton to 800Ton.We have experience to manufacture plastic part for Tesla car.

We are Chinese top 10 experts in over-mold field in China. All our over-molding products have perfect performance and will not shutt-off and the joint of the two materials is very smooth.Our over-molding plastics products were applied in United Airline service device,Samsung retail device and Square payment devices etc. Over-molding is also called 2 times injection molding,it means to apply one material onto another material. Here two color pistol grip, utilizes TPU injected onto PC material.Two types material should form a bond and offer functional performance.Compared with the third-party material bonding, over-molding process makes the process faster and more cost-effective, it has been widely employed in plastic design.

If you want to manufacture good quality products,good mold is the first step and Grandshine is your best choice of product development and mold manufacturer.

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