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The rubber extruder is the basic equipment in the rubber industry and one of the key equipment affecting product quality. It plays a very important role in the production process of tires and rubber products. If you are also interested in learning about rubber extruder, you can read on.
Here is the content list:
- What are the flow conditions in the extrusion section?
- What are the factors that affect extrusion expansion?
- What are the general principles of lip design?
What are the flow conditions in the extrusion section?
Downstream: Because the rotation of the screw of the rubber extruder promotes the flow of the rubber along the thread groove to the direction of the rubber extruder’s nose, it promotes the extrusion of the rubber, which is also called squeeze flow. Its speed distribution is approximately linear, with the maximum speed on the surface of the screw and approximately zero on the inner wall of the barrel. Downstream is beneficial to extrusion output.
Reverse flow: caused by the resistance of the rubber extruder’s nose to the rubber, also known as pressure reverse flow or reverse flow. The rubber material flows backward along the screw channel along the pressure gradient. Backflow causes a decrease in extrusion output.
Leakage: The gap between the screw peak and the inner wall of the barrel is caused by the resistance of the rubber extruder. It is opposite to the downstream direction, which causes the extrusion output to decrease.
Circulation flow: also known as crossflow, due to the flow caused by the pushing action of the rubber extruder screw when it rotates, it becomes a vertical direction with the downstream flow, which promotes the mixing of the rubber, and does not affect the output. Circulation plays a role in the mixing, heat exchange, and plasticization of the rubber material.
What are the factors that affect extrusion expansion?
(1) Process factors: mouth shape, mouth shape (plate thickness) wall length, rubber extruder’s nose mouth temperature, extrusion speed, etc.
(2) Formulation factors: types, dosages, the plasticity of raw rubber and compounding agents, etc.
Generally speaking, the plasticity of the rubber is small, the rubber content is high, and the extrusion speed is fast. When the temperature of the rubber and rubber extruder’s nose and mouth is low, the expansion rate (or shrinkage rate) of the extrudate is large.
What are the general principles of lip design?
(1) According to the flow state and extrusion deformation analysis of rubber extruder’s rubber compound in the mouth, determine the difference between the cross-sectional shape of the mouth and the cross-sectional shape of the extruded semi-finished product and the expansion degree of the semi-finished product;
(2) The size or width of the rubber extruder’s orifice should be compatible with the diameter of the rubber extruder’s screw. When extruding solid or round semi-finished products, the large orifice of the orifice should be 1/3 to 3/4 of the screw diameter. For flattened mouth shapes (such as tread rubber, etc.), it is generally 2.5 to 3.5 times the diameter of the screw.
(3) The mouth shape must have a certain taper angle, the inner port shape of the mouth shape should be large, and the rubber outlet port diameter of the rubber extruder should be small. The cone angle is large, the pressed semi-finished product is smooth and compact, but the shrinkage rate is large.
(4) The inside of the mouth shape should be smooth, streamlined, without dead ends, and no eddy currents.
(5) In some cases, to prevent the scorching of the rubber, the rubber opening can be properly opened at the edge of the rubber extruder.
(6) For rubbers with higher hardness and short scorch time, the mouth of rubber extruder should be thin; for thinner hollow products or products with more reclaimed rubber, the mouth of rubber extruder should be thick.
Qingdao Huicai Machine Manufacture Co., Ltd developed a rubber extruder. The quality of rubber extruder is guaranteed by our company after testing, so it is very cost-effective. If you also need this product, you can contact us.