1. Differences in liquidity
Injection moulding requires high fluidity, especially for
thin-walled products and large-scale products. Extrusion
requirements are more relaxed, because extrusion is open, there is
no huge resistance of reverse die.
2. Melt Strength
Injection moulding is formed in the mold, which has geometric
limitations of the mold composition and does not require high melt
strength. Although extrusion moulds have geometric limitations,
they are not fully solidified after the exit moulds. In this free
state, they are sometimes not well formed due to low melt strength
(e.g. spinning).
Extrusion is often accompanied by subsequent free state processing,
such as hot forming, hollow blow molding, in these forming
processes there are often varying degrees of melt tension, if the
melt strength is low, it is easy to break. Therefore, injection
moulding generally does not require high melt strength, but
extrusion is generally required.
3. Export Expansion
Injection moulding generally has no strict requirement for export
expansion, and the export expansion of extrusion will cause great
problems. Therefore, the viscoelastic control of injection and
extrusion materials will be different.
4. Applicable raw materials
Squeeze:
Most thermoplastics and some thermosetting plastics, such as PVC,
PS, ABS, PC, PE, PP, PA, acrylic resin, epoxy resin and melamine
resin, etc.
Injection Molding:
Except for a few kinds of thermoplastics, almost all thermoplastics
can be formed by this method. Injection moulding can also process
some thermosetting plastics, such as phenolic plastics.
Characteristic comparison
Extrusion Molding
A. The production process is continuous, and the plastic parts of
arbitrary length can be extruded with high production efficiency.
B. The die structure is also simple, easy to manufacture and
maintain, less investment and quick effect.
C. The internal structure of the plastic parts is balanced and
compact, and the size is stable and accurate.
D. Except fluoroplastics, all thermoplastics can be extruded, and
some thermosetting plastics can also be extruded. By changing the
die of the machine head, the cross-section shape and size of the
product can be changed accordingly, thus various plastic parts of
different specifications can be produced.
E. It has wide application range, simple operation equipment, less
investment, quick effect, sanitary production environment, low
labor intensity, and is suitable for mass production.
injection molding
A. Plastic products of various shapes can be injected and moulded.
B. The structure and dimension of the products are more accurate
and the surface quality is better.
C. Injection products can be standardized, standardized and
serialized.
D. Simple operation, easy adjustment and renewal of moulding die,
fully automatic production can be adopted, high production
efficiency;
E. The investment of injection moulding equipment is relatively
large, the cost of mould manufacturing is high, and the process
conditions of product moulding need to be strictly controlled.
