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China Overmolding, Two-shot molding

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China Overmolding, Two-shot molding
Click number:- Release time:2019-08-22

Overmolding is an injection molding process, Overmolding is also called 2 times injection molding in China. Compared with the third-party material bonding, overmolding process makes the process faster and more cost-effective, it has been widely employed in plastic design.

Over molding are categorized into 3 types: insert molding, double shot molding, co-injection molding.

Overmolding JPG

Insert molding: The most commonly used to mold soft elastomers to rigid plastics, insert molding is the most economical way to do overmolding. In the insert design, the hard segment has been separated into tools in advance, and then eject the soft materials in.

Elastomers are adhesion bond, which can be mechanical locks, chemical and other methods. In order to achieve chemical adhesion, the elastomer must be sufficiently heat to melt the surface of the hard segment to achieve chemical bonding.

Two-shot molding: This over molding process requires two injection molding machines. Hard segment is injected first, and then led by the elastomeric mold to the injection molding machine, finished the process of hard segment into the elastomer injection. Heat substrate is usually semi-solid, gel state. These molds can be designed and shaped projecting laterally of the hard segment on the substrate. This can achieve a stable mechanical bond.

Co-injection molding: In co-injection molding, while the hard substrate and the elastomer is injected into the same mold, compatibility between materials is essential, it must be carefully controlled.

Co-Injection is very expensive and difficult to control; it is used least comparing with other 2 method. However, because the hard and soft substrates elastomers in a fully molten state, it provides the best bonding between soft and hard parts, the molded parts quality is also the best.

Overmolded parts take longer to cool than single shot injection molded part, and cooling systems are less effective. The insert acts as an insulator and heat is less efficiently extracted from the part. However, optimising the cooling system can help reduce the cycle time.

Two-color mold and Over mold difference

Co-Injection is very expensive and difficult to control; it is used least comparing with other 2 method. However, because the hard and soft substrates elastomers in a fully molten state, it provides the best bonding between soft and hard parts, the molded parts quality is also the best.

 A. Two-Shot Mould.  Two resins to be molded in one injection molding machine, forming in two times, the two different color parts are produced out in one cycle time, one injection process. It is also called two resins injection molding, normally need one set of injection mold, but certain injection molding machine, the double color injection machine.Two-color mold

B. . Over mold (2 times forming) : Two resins to be molded in one injection machine or two different machines, parts forming in twice; The operator will take out part from one mold, then put it into another mold for the second injection molding process. So, it needs 2 molds to finish the over molding process, normal injection machine can finish the process, no need for specific double color machine.

二、Two-Shot Mould and double color mold overview

 For the design of the over mold, need to take more attention on the location of hard plastic part, has to be reliable and perfect fit with the soft part with slope holes to avoid the warpage. The double color molds is becoming more and more popular nowadays. It can make the part appearance more beautiful, change color easily without painting, however it costs higher, request higher design technical skills.

三、Differences between the double color injection molding and overmolding

 The real double molds, after finishing one shot run, can turn over 180 degree, ie, the same molds base, the different cavity and core side. It is efficient, low cost during mass production. If the parts quantity requested is very high, we suggest not to consider the over molding due to the injection timing and defective rate

For Overmolding, it needs to take one part of the product out from one injection machine , then put on other injection machine for production another part. It takes longer time and cost higher comparing with the double color injection molding during large quantity production. But it can be considered if the production quantity is low. 

HKY Mould are China overmolding, two-shot molding company, Good at Fluent technical English communication with excellent project management, Only A few of companies have this service in China.


【Paper label】:Overmolding Two-shot molding
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HKY Mold Technology Co., Ltd

HKY Mold Technology Co., Ltd

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