China Mould English

Mould China

 China Mould

Date:2017-04-18 10:51:18

Injection molding defect and solution

Defects are most common things to arise in manufacturing process and can be in different form , with different effect and with different way of solution. Problem must be troubleshoot with an objective mind. The solution that solved a problem one day may not solve the same problem on another day. Due to the large number of parameters and the variability of these parameters plus the way of parameter interactions, many solutions may exist for a single problem. Likewise, many problems may be fixed by using a single solution.The solutions mentioned are possible solutions and must be tried out with safety in mind. Please always follow the material manufacturer and machine manufacturer's guidelines for safety.

Steel hardness play vital role in mold longevity ,avoid flashes at the ends and sides of the product and also avoid other kind of defects in mould.

High care should be taken while assembling molds, precise inspection of the all parts including cooling systems, hydraulic oil channel system , hot runner , mould plate, ejector pin, stripper, ejector block or slider system should be done.

These are some defects and there possible solution.

Short shot:

Molten Plastic is not reaching the mold cavity section

Possible solution:

Increase melt temperature,Increase mold temperature,Increase injection speed,Increase injection pressure if process is pressure limited,Check if the mold is vented in the area of short shots,Increase gate and runner sizes.


Molten Plastic is flowing into unwanted sections of the mold cavity.

Possible Solution:

Check for Mold shutoff and mold damage,Decrease melt temperature,Decrease mold temperature,Decrease injection speed


Plastic is shrinking as it cools but additional plastic cannot be for further compensation of the shrinkage.

Possible Solution:

Increase pack and hold pressures,Increase pack and hold times,Decrease mold temperatures,Decrease melt temperature


A differential cooling rate of the melt in two sections of the molded product

Possible solution :

Decrease melt temperature,Experiment with differential mold temperatures on the fixed and movable sides,Increase pack and hold pressures,Increase pack and hold times,Increase cooling time

Burn mark:

When air and gasses get trapped inside the mold cavity during plastic injection, the high pressure results in the dieseling of the plastic resulting in the burning of the plastic.

Possible solution:

Increase venting in the mold,Decrease injection speed,Decrease melt temperature,Decrease Screw Rotation Speeds


Usually occur with the parts are thick. The walls solidify and the plastic melt shrinks towards the wall and therefore sucks a vacuum void on the inside of the part.

Possible solution:

Reduce melt temperature,Reduce mold temperature,Reduce injection speed,Increase pack and hold pressures,Increase pack and hold times


Usually seen with the part is thick causing the injected plastic to ‘snake fall’ on to the cold mold surface and start freezing immediately. When the fresh plastic come in it does not blend well with the first material causing the jetting marks.

Possible solution:

Reduce injection speed,Increase melt temperature,Change gate location

Weld line :

The melt flow front is usually cold due to the exposure to the cold cavity. When two flow fronts meet as in a flow around a mold pin they do not fuse uniformly causing a weld line. Sometimes air can also get trapped in to form the defect.

Possible solution:

Increase melt temperature,Increase mold temperatures,Increase injection speeds,Increase venting

SINO MOULD is one of the leading company dedicated to design and manufacture of High qulaity injection mold along with providing magnificient service to the clients.

Rahul shah


Plastic Molding Service
Sino Moldings is a qualified Molding Supplier in China, offers good price Plastic Moldings worldwide.
China Plastic Molding company-SINO is Chinese Plastic Molding technologies innovator, Chinese Plastic Molding supplier and China Plastic Molding Company.
With advanced plastic Injection Moulding Process, Services & technology, Sinomould stands as a famous Plastic Injection Molding manufacturer and supplier in China.

Custom Molds


Sino Mould Co., Ltd
Add :
369# XinJiang Rd., Xinqian Street, Huangyan Taizhou, Zhejiang, China
P.C. 318020
Tel : 8613586015108
Tel : 86 576 84023777
Fax : 86 576 84018996


Web:  +8613586015108