What are the structural characteristics of the mandrel head?

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The structure of mandrel head is shown in Figure 6-4. After the plastic melt is compressed by the neck of the machine, it flows to the mandrel and is disposed into two strands of material flow, and flows 180 respectively along the mandrel to both sides. After that, rejoin at A. The combined material flow wraps the mandrel, flows along the circular path of the head to the die opening and is extruded in the form of a thin tube blank, and is blown into a film through compressed air.

The advantage of mandrel type handpiece is that the handpiece has less memory material and only one material flow Fusion line, which is not easy to cause plastic overheating and decomposition, and has simple structure and easy disassembly and assembly, it is more suitable for blowing pvc film. The disadvantage is:

(1) The material flow rate in the nose is not equal, which can make the film thickness uneven.

(2)The material flow is easy to cause uneven thickness of the film.

(3)The mandrel is prone to misalignment (Mandrel and die different Shaft).

(4) It is difficult to control the gap between the die opening of the mandrel head. If the gap is too large, in order to reach the set film thickness and folding diameter, the drafting ratio and blowing ratio must be increased, which will cause difficulty in operation; If the gap is too small, the back pressure in the handpiece is large, which reduces the output. The general clearance is 0. 1-1. 2mm.