What Role does Vacuum Setting Play in Pipe Production Line?

When the pipe comes out of the plastic extrusion machine, it is still a hot hose, and it can only be “locked” into qualified outer diameter, wall thickness and roundness by the final shaping process. The vacuum setting box is the equipment for this job. In many new projects, the pipes are either oval or the wall thickness is thick and thin, and the final problem is mostly in the vacuum setting section. When Beisu Machinery is debugging the pipe production line, it often takes a long time to straighten out the vacuum setting parameters first, and then smooth the extrusion afterwards. It is no use if the setting is not up to standard. This article explains the function of vacuum setting thoroughly according to the first-line experience.

The core role of vacuum setting in pipe production

Stabilize the outside diameter of pipes

After the molten material is extruded through the die, it is tightly attached to the inner wall of the sizing sleeve under the action of vacuum adsorption, and the outer diameter is fixed. When the vacuum degree is stable, the outer diameter of the pipe is stable. When the vacuum degree is high and low, the pipe diameter will fluctuate, and if the specification deviation is large, it will be directly judged as waste.

Control the uniformity of wall thickness

The vacuum setting box combined with the traction speed can make the thickness of the pipe wall tend to be consistent. If the traction is too fast, the pipe wall will be thinned, and if it is too slow, the local stacking will become thicker. The function of vacuum sizing is to give the material a uniform adsorption force, make the wall thickness distribution more uniform, and reduce the risk of stress cracking in subsequent processing.

Improve the surface quality of pipes

Vacuum adsorption makes the outer wall of the tube blank fully fit with the sizing sleeve, which can flatten the fine defects on the surface, make the outer wall of the tube smoother and reduce the concentration points of internal stress. For common pipes such as PVC, HDPE and PPR, the surface quality directly affects the pressure bearing and appearance inspection of the pipes.

The working principle of vacuum setting

vacuum adsorption and sizing sleeve cooperation

The inner wall of the vacuum setting box is covered with water suction holes and vacuum grooves, and negative pressure is formed after vacuumizing, so that the outer wall of the tube blank is adsorbed on the sizing sleeve. The dimensional accuracy of the sizing sleeve directly determines the outer diameter of the finished pipe, which belongs to the precision parts in the pipe production line and should be replaced in time after wear.

collaborative cooling of cooling water and vacuum

Cooling water is introduced into the setting box, and the tube blank is cooled while setting, so that the tube blank can be quickly hardened and set from the softened state. The water temperature and water quantity should be matched with the linear velocity. If the pipe is not cooled enough, it will be soft and easy to deform, and if it is cooled too quickly, it will easily produce internal stress.

Common vacuum setting fault troubleshooting in production

Vacuum degree can’t get up

First, check whether the vacuum pump works normally, whether the sealing ring leaks, and whether the inlet hole of the shaping box is blocked. This kind of problems often appear after changing specifications or long-term operation, and it is not complicated to investigate.

Water ripples appear on the pipe surface

Most of them are caused by vacuum fluctuation or uneven distribution of cooling water, so it is necessary to adjust the opening of vacuum regulating valve and check the wear of sizing sleeve.

FAQ

Q: Does vacuum setting have a great influence on the quality of pipes?

A: It has a great influence. The roundness, wall thickness and surface quality of pipes are basically determined by this process.

Q: What kind of shaping pipe does the vacuum shaping box mainly rely on?

A: vacuum negative pressure adsorption, matching with sizing sleeve and cooling water.

Q: Is the higher the vacuum degree, the better the pipe quality?

A: No, it is easy to strain the surface of the pipe if the vacuum degree is too high. It should be adjusted to an appropriate value according to the formula and line speed.

Q: How to deal with water ripples on the surface of pipes?

A: check the fluctuation of vacuum degree and the wear of sizing sleeve first, and then adjust the distribution of cooling water.

Q: What is the configuration of vacuum setting box in Beisu Machinery pipe production line?

A: vacuum pump set and sizing sleeve can be selected according to pipe diameter specifications and raw material characteristics to ensure stable sizing accuracy.

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