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Plastic Injection Molding Service
2021.04.21
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Plastic injection molding is designed especially for the mass production of plastic parts by repeatedly using the same mold. Consistent color, structure, appearance is the features for injection molded parts. Hundreds of thousands of custom parts are produced by machines, which speeds the production process and lowers the labor cost.  

 

img-Plastic injection parts from 2fprototypes

img-Plastic injection parts from 2fprototypes

img-Plastic injection parts from 2fprototypes

img-Plastic injection parts from 2fprototypes

img1-Plastic injection parts from 2fprototypes

img-Plastic injection parts from 2fprototypes img-Plastic injection parts from 2fprototypes img-Plastic injection parts from 2fprototypes

Plastic injection molding parts from 2fprototypes

 



 

Process of Plastic Injection Molding

 

Plastic injection molding is one of the oldest manufacturing ways. Its capability of volume-production is still the popular choice of large custom manufacturing. Plastic injection molding is the process that plastic is squeezed into the mold and then be shaped. The basic principle may be simple, but it is a very complicated process in reality. Many factors can change or destroy the quality. The quality and consistency of the final parts require the right equipment and rich experiences.
 
The plastic injection molding machine is made of a hopper, injection ram, heating device, mold, ejector pin, etc. Generally, the injection molding machine works horizontally. When choosing suitable plastic pellets, they will be poured into the heating system by hopper. Plastic pellets can be melted down into moldable liquid by the heating device that is created by the frictional action of the screw. The plastic liquid will enter the mold cavity by way of the runner system and mold gate. The whole process is known as an injection. The plastic will be molded and cooled after injection. The mold opens and drops the molded part and is then ready for the next injection. Depending on the mold lifetime, the injection molding process will be repeated over and over until the job is completed or the mold needs to be replaced.

 

Basic process of injection molding - 2fprototypes


Step 1: Add plastic materials(pellets) into the hopper
Step 2: Pellets will be heated and melted down in the barrel
Step 3: The heated plastic is injected into the mold through the nozzle
Step 4: Plastic is allowed to cool and harden in the mold
Step 5: The mold opens and ejects the parts

 

How the molded part is produced?


The whole process to produce a part is short. For large parts as shown in the video, there are additional mechanical devices to help pour the plastic pellets and take the molded part out to the transport tape. The first quality inspection will be performed at the end of the transport tape.



 

 

Plastic Material Property

 

Material

Color

Advantage

Disadvantage

Polystyrene/PS and modified polystyrene/HIPS

Transparency

Good fluidity for easier processing;
Good dimensional stability; Easier coloring;

High brittleness for poor shock resistance;
Can be scratched on the surface easily;
Poor acid resistance for crazing;

Propylene - butadiene - styrene polymers/ABS

Light yellow

The best electroplate ability among plastics;
The ingredient of butadiene improve the shock resistance greatly;
Good surface gloss;
Low shrinkage for reliable dimension;

Organic solvent intolerance, can be dissolved into emulsion when combining with ketone, ester, aldehyde, and chlorinated hydrocarbon

Polyformaldehyde/POM - Crystalline plastics

Milk white

Comprehensive mechanical performance;
High rigidity and hardness; Excellent worn resistance and self-lubrication;
Organic solvent tolerance;
Low moisture that can maintain stable dimension;

Low acid resistance;
Low adhesiveness;

Polyethylene/PE - Crystalline plastics

Translucent particles. It shows milk white in whole piece condition; The transparency falls with density growing, as known as HDPE(high density) and LDPE(low density)

Usually used for blow molding products;
Its chemical properties are reliable that can’t be dissolved into any solvent under room temperature;
Good toughness and extensibility even at low temperature;

Poor mechanical strength;
Low adhesiveness;
Scratch on the surface easily;

Polypropylene/PP - Crystalline plastics

Translucent

Lightweight;
High tensile strength;
Good formability;
Good wear resistance;
Shock resistance under room temperature;

High forming shrinkage(1.6%) that plastic part can be deformed and shrink easily;
Low adhesiveness;

Polyvinyl chloride/PVC

Translucent

It is soluble in cyclohexanone and dichloroethane;
The softness of range can be extended after plasticizer is added;
Good fire resistance;

High shrinkage of soft PVC(1-2.5%);
The PVC molecule absorbs water easily so that it needs to be dry before forming;

Polycarbonate/PC - Crystalline plastics

Transparency

The best plastic of shock resistance; Low forming shrinkage(0.05-0.7%) that the end-part is precise and the dimension is stable;
Burning slowly;

Can be dissolved in organic solvent such as alkali, ketone, aromatic hydrocarbon, etc.
Poor fatigue resistance;
Significant ESCR;

Polyamide/PA/Nylon - Crystalline plastics

Black, white

Good toughness;
Good wear resistance;
Good fatigue resistance;
Good self-lubrication;
Good self-extinguishment;
Good strength of extension;

High water absorption

polymethyl methacrylate/PMMA/Acrylic

Transparency

Burning slowly;
High transparency;
Forming easily;

Scratching easily




 
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