Common quality problems and solutions for large blow molding products

Update:28 Jan 2021

Common quality problems and solutions for large blow molding products

Large blow molding products often have some problems in operation. According to user feedback, we have found out the questions that users consult more. In order to let users better understand, today we will list the common problems of blow molding products and answer them. , For our study and reference, the following is a summary of 6 common problems and solutions for hollow blow molding machines:

1. Uneven cooling of blow molded products


1) Uneven cooling results in warping, bending, and tilting of the bottleneck.


1) The temperature control of the blow molding mold can be set. The temperature of the mold is related to the material. Therefore, Yankang Plastic Machinery is designing the cooling tower of the blow molding machine, using polypropylene material, increasing the spray area, and rotating the water or pipe type. Water distribution can better complete uniform water distribution and enhance cooling effect.

2. Uneven wall thickness of blow molded products


1) The drape of the parison.

2) The diameter of the longitudinal cross-section of blow-molded products varies greatly.


1) Lower the temperature of the preform, choose a resin with a low flow rate, and adjust the control equipment of the preform.

2) Use bottom blow molding.

3 There are black spots or stripes on the surface of blow molded products


1) The inflation speed is too slow.

2) Improper mold exhaust.

3) Lack of inflation air pressure.

4) Mold leakage or condensation inside the mold.


1) Improve the inflation speed.

2) Add vent holes and frost the mold preform.

3) Improve the inflation pressure.

4) Repair the mold and adjust the cooling temperature to above the "dew point".

4 Blow molding products have too much burrs


1) Passivation of mold clamping edge.

2) The mold is inflated and the film locking pressure is too low.

3) Premature inflation is too early.

4) When inflating, the parison is deflected.


1) Trim the knife edge of the mold.

2) Increase the film locking pressure and properly lower the inflation air pressure.

3) Adjust the inflation time of the preform.

4) Proofread the center position of the parison and blowing rod.

5. Difficult to demold blow molded products


1) The cooling time is too long and the mold temperature is too low.

2) The mold design has flaws, forming burrs on the outside.

3) Mold device error.


1) Shorten the inflation time and increase the mold temperature.

2) Adjust the mold to reduce the depth of the groove, the slope of the convex rib is 1:50 or 1:100; use a release agent.

3) Re-install the mold and check the installation orientation of the two mold halves.