The screw is the core equipment of plastic extruder equipment, it needs direct contact with plastic raw materials and will bear high temperature, high pressure, and high shear force working environment for a long time. So our manufacturer of screw quality requirements will have a high standard, for the production of different plastic products we have different screw requirements, but for the basic manufacturing quality requirements of the screw or some, the specific content is as follows:

1. The screw of the extruder needs to work in a high-temperature environment, high friction, and certain corrosion environment for a long time, so we need to choose alloy steel with small thermal deformation, wear resistance, and corrosion resistance for manufacturing. Screw manufacturing materials are usually made of 38CrMoAlA alloy steel,40Cr steel, or stainless steel, but sometimes the screw is replaced by 45#steel if it is repaired.

2. Before the extruder screw is manufactured, round steel can not be simply used for production. To ensure the strength of the final screw, an alloy steel blank formed by the forging method is needed.

3. After machining the screw blank, the outer circle accuracy of the screw should meet the requirements of grade 8 precision quality(GB180-79).

4. The extruder screw is a kind of high-precision parts that need to rotate, so there are certain requirements for the concentricity of the outer circle of the screw and the drive shaft. Generally, we need to make the coaxiality error of the outer circle of the screw thread on the working shaft surface and the connecting part of the drive shaft should not be greater than 0.01mm.

5. Screw surface roughness is also a great requirement, which screw thread part of the working surface roughness Ra value: thread two sides should not be greater than 1.6μm, thread bottom and outer circle should not be greater than 0.8μm.

6. To produce different plastic products, sometimes for various reasons, we also use low-carbon alloy steel to manufacture screws, but many properties of the screw working surface made of low-carbon alloy steel are insufficient. To solve this problem, the screw thread surface needs nitriding treatment, which can greatly improve the hardness of the thread working surface and corrosion resistance, and wear resistance, at this time need a nitriding layer depth of 0.3~0.6mm, surface hardness of 700~840HV. Brittleness is not greater than grade 2.

7. To do a good job in temperature control, some extruders sometimes drill holes in the core of the screw through cooling water or heating oil. It is necessary to conduct a 0.3mpa water pressure test outside the connection of the inner hole of the screw, and water leakage is not allowed for 5min.

The above is about the basic manufacturing quality requirements of the screw used in plastic extruders. If you need more information, you are welcome to inquire.