Design of the extrusion port of the rubber extruder

The mouth should have a certain cone angle, the inner port of the mouth should be large, and the port diameter of the glue outlet should be small. The taper angle is large, the extruded semi-finished product is smooth and dense, but the shrinkage rate is large.The inside of the mouth should be smooth, streamlined, without dead ends and without eddy currents.In some cases, in order to prevent the scorching of the rubber, the rubber mouth can be properly opened at the edge of the mouth.For the rubber compound with high hardness and short scorch time, the mouth shape should be thinner; for thinner hollow products or products with more reclaimed rubber content, the mouth shape should be thick.

The follow is the list

• The specific design of the mouth shape

• Extrusion process

The specific design of the mouth shape

To master the design of the mouth shape, we must first understand the expansion rate of the rubber compound. There are many factors that affect the expansion rate of rubber compounds:

(1) rubber species and formula: Different rubber species have different extrusion expansion rates;

High rubber content and large extrusion expansion rate; inorganic filler expansion rate is smaller than carbon black.

(2) Plasticity of the rubber compound: the greater the plasticity of the rubber compound, the smaller the extrusion expansion rate;

(3) Head temperature: the temperature of the head is high, and the extrusion expansion rate is small;

(4) Extrusion speed: the extrusion speed is fast and the expansion rate is large;

(5) Specifications of semi-finished products: large semi-finished products have a small expansion rate;

(6) Extrusion method: When the rubber tube blank is extruded with a core, the expansion rate is smaller than that of the coreless extrusion.

Because there are many factors that affect the extrusion expansion, it is difficult to design the mouth shape successfully at one time. It needs to be tested and corrected at the same time, and finally the desired mouth shape is obtained.

Extrusion process

Shrinkage and quality problems of extruded semi-finished products

one. Factors Affecting the Extrusion Process

1. The composition and properties of raw rubber

(1) Appropriate selection of raw rubber varieties. Among the commonly used rubber varieties, the shrinkage rates of SBR, CR and IIR are greater than those of NR and BR.

(2) Add reinforcing filler to reduce the rubber content of raw rubber and reduce the elastic deformation of the rubber. The particle size of carbon black has no effect on the shrinkage rate of the compound, while the structure and dosage have a significant effect on the shrinkage rate. The higher the structure of carbon black and the larger the dosage, the smaller the extrusion shrinkage rate; the anisotropic particles with low reinforcement (such as clay, magnesium carbonate, etc.) have a smaller extrusion shrinkage rate.

(3) Adding reclaimed rubber to the rubber compound can increase the fluidity and reduce the shrinkage rate.

(4) Adding ointment softener to the rubber compound can play a lubricating role, reduce the shrinkage rate and make the surface of the product smooth.

Seahawk Machinery have more than 18 years of experience in producing and exporting different kinds of rubber and plastic machinery. With advanced technology and experience, we produce rubber and plastic machines.