8 Causes and Solutions for question of Plastic Extrusion

I think you should have the situation that there are some irregular products in the process of producing plastic profiles?

According to our experience from engineers, we concluded some causes of abnormal phenomena in plastic profile extrusion and solve solutions.

No. 1 Fluctuation of raw material feed

  1. Possible causes,

1) poor flow of raw materials.

2) raw materials are prone to form a cavity in the centre of the hopper attached to the wall to hang, bridging stagnant materials.

3) The temperature of the feed is too high.

4) The bottom of the hopper humidity is too high.

  1. Solution,

1) Use a dry mix of PVC with appropriate fluidity.

2) Install stirring feeder to prevent bridging, check frequently and deal with it in time.

3) pass cooling water through the feeding section to cool or reduce the temperature of the filling section.

4) Remove the wet material from the hopper to keep the hopper dry.

No.2. Profile bending

  1. Possible causes.

-1) the whole line is not straight.

-2) improper cooling method.

-3) abnormal vacuum cooling water channel.

-4) head; unreasonable runners and gaps, large wall thickness disparity

-5) too fast extrusion speed

-6) unsynchronized upper and lower tracks of the traction machine

-7) uneven die assembly.

-8) unbalanced resistance on each forming surface of the shaping die.

  1. Solution ideas.

-1) adjust the production line to keep it in a straight line.

-2) strengthen the cooling of the wall thickness part and reduce the water temperature.

-3) Check the vacuum cooling system to normal.

-4) amend the flow channel and wall thickness to uniform discharge.

-5) reduce the extrusion speed

-6) check and adjust the synchronized operation of the upper and lower tracks of the traction machine

-7) align the die with the levelling centre after installation

-8) Clean up the setting pattern or carry out maintenance professionally.

No. 3 Local shrinkage marks

  1. Possible causes.

-1) slow resin activity at the mouth mould tendon and stretching of the tendon groove.

-2) improper vacuum operation or inappropriate vacuum control.

-3) High cooling water temperature.

-4) Local cooling is too fast.

2, solution ideas.

-1) clean up the mouth mould to amend the mould so that the flow rate at the tendons in the mouth mould is accelerated or the traction speed is reduced.

-(2) adjust the vacuum level or use a chucking tool to poke small holes in the material before the billet enters the shaping mould, so that the profile is released to strengthen the vacuum adsorption.

-3) lowering the water temperature to improve cooling efficiency

-4) turn off the local cooling water.

No.4 Large shrinkage after profile

  1. Possible causes.

-1) high traction speed.

-2) insufficient cooling of the shaping die.

-3) high temperature of the machine head.

2, solution ideas.

-1) adjust the traction speed.

-2) improve cooling efficiency

-3) reduce the temperature of the head.

No. 5 Product size and thickness are sometimes large and sometimes small

  1. Possible causes.

-1) Fluctuation of feeding material.

-2) irregular heating of the electric heating ring.

-3) unstable traction surface, slippage of traction motor or speed fluctuation.

-4) uneven mixing of the material.

-5) changes in the mould gap.

-6) material stagnation in the die head.

  1. Solution ideas.

-1) use of dry mixed PVC powders with appropriate fluidity.

-2) Overhaul the electric heating ring.

-3) check the tractor belt, whether the transmission is slipping, whether the products on the track are sliding and whether the clamping is appropriate.

-4) Checking that the mix is uniform.

-5) check and repair the mould trial clearance

-6) Clean up and reassemble the machine for inspection.

No.6, the end of the product is cracked or jagged

  1. Possible causes.

-1) poor plasticization of formulation components.

-2) low temperature of the mouth mould.

-(3) the local temperature of the mouth mould is low.

2, solution ideas.

-1) check and adjust the formula.

-2) increase the temperature of the mouth mould.

-3) avoid small stimulation of the mouth mould.

No.7. Fusing marks appear

  1. Possible causes.

-1) bad design of the mouth mould structure.

-2) inconsistent raw material matching and forming conditions.

  1. Solution ideas.

-1) make the material flow in the mouth mould uniform.

-2) increase the front end head pressure.

-3) increase the length of the shaped end of the head

-4) set up a material pool behind the mould core holder

-5) increasing the resin flow path at the resin inlet

-6) reducing the external lubricity of the mix

-7) using materials with a low melt viscosity

-8) increasing the body temperature and lowering the mouth die temperature

-9) Reducing the extrusion speed.

No.8. Spots, base eyes or bubble-like projections on the surface or inner wall of the profile

  1. Possible causes.

-1) impurities mixed with raw materials.

-2) high moisture or volatile matter content in raw materials.

-3) Excessive stacking time of the powder.

-4) low temperature of the machine body and high temperature of the head.

-5) poor thermal stability of the material.

-6) Extrusion speed is too high.

  1. Solution ideas.

-1) check the source of impurities in order to remove them.

-2) Dry the raw material to reduce the moisture content