When the allowable ranges of temperature setting of the heating cylinder overlap

When a consecutive molding process with different types of resin is conducted, it is necessary to replace the resin in the heating cylinder. For example, if it is to replace POM (180 deg.C to 210 deg.C) with PP (160 deg.C to 250 deg.C), set the temperature of the heating cylinder to 190 deg.C and purge until the POM runs out. Pour PP while keeping the temperature of the heating cylinder at 190 deg.C and purge until it is completely replaced with PP.
After the resin in the heating cylinder is completely replaced, change to the PP molding temperature.

When the allowable ranges of temperature setting of the heating cylinder does not overlap

When a consecutive molding process with different types of resin is conducted, it is necessary to replace the resin in the heating cylinder. For example, if it is to replace PC (280 deg.C to 320 deg.C) with ABS (190 deg.C to 250 deg.C), set the temperature of the heating cylinder to 300 deg.C and purge until the PC runs out. Charge the resin PE (170 deg.C to 260 deg.C) where the allowable temperature setting range of PC and ABS overlaps with the temperature of the heating cylinder kept at 300 deg.C, and purge until it is completely replaced by PE.
After the resin in the heating cylinder has been completely replaced, change to the molding temperature of ABS, charge ABS and purge until no PE is remaining in the heating cylinder.

How to check the degree of resin substitution in resin exchange

To check the degree of resin replacement when replacing the resin, check the appearance, transparency, color tone, etc. of the resin discharged by purging. In addition, confirm the molten resin injected from the tip of the nozzle, and if there is no thin thread-like stripe in the molten resin, it can be judged that the resin replacement is completed. If thread-like stripes remain, replacement may be insufficient.

By applying the above knowledge, you can smoothly change materials when molding multiple materials with one injection molding machine. Wrong setting of these temperatures may cause damage to the injection molding screw.