Nissei Developed the Vacuum Material Supply System "Gas Cleaner" Which Saves Waste of Injection Molding Cost
March 2002 [News Release]

Nissei Plastic Industrial Co., Ltd. has been grappling with the in-house development of all sorts of peripheral equipment for injection molding machines, as molding support systems of injection molding machines, the company's main products. As part of the above, the company recently has developed and started overseas sales of a vacuum material supply system "Gas Cleaner" that reduces molding defects, caused by oxidation (discoloration) and burning (black spot) which are generated during injection molding, and mold contamination, so that waste of production cost is eliminated.

This "Gas Cleaner" is installed on the material feeding portion of injection molding machines (at the upper part of an injection mechanism). Air (oxygen), mixed into resin during melting and metering, and gas, evolved out of molten resin, are sucked up and discharged by a vacuum pump. As a result, molding defects, caused by air and gas, and mold contamination are sharply reduced.

This system is composed of a hopper-side shutter, a material feed shutter, a vacuum pump, a sealing-unit at the rear of a screw, and a controller. The features of an original shuttering/sealing mechanism and an operation method (Patent Pending) are as follows:
  1. It can be installed on an injection molding machine currently in use without changing screw and barrel.
  2. It can be used also for recycled materials.
  3. It can also be used for glass fiber reinforced resin.
  4. Maintenance of the system is easily conducted.

Following effects are expected through using this system:
  1. By means of discharging gas generated of molten resin;
    (1) Deposit adhering to molds reduces, and the cleaning period can be greatly shortened.
    (2) Molding defects due to deposits can be reduced.
  2. By means of discharging air;
    (1) Molding defects such as oxidation (discoloration) and burning (black spot) can be reduced.
    (2) Molding defects such as silver streak due to entry of air bubbles can be reduced.
  3. The number of cleaning times for maintenance of a screw can be curtailed.

This system has been monitored through practical molding at a customer's plant site, and the results of evaluation are as follows:
  1. Reduction of defects caused by oxidation and black spot.
    In the molding of connectors using polyamide resin (PA66) as a raw material which is apt to generate burning;
    * A fraction defective was 7% in a case that the system was not used.
    * A fraction defective was 0.5% in a case that the system was used.
  2. Reduction of mold contamination.
    In the molding of electronics-related parts using PPE resin (polyphenyleneether) as a raw material which is apt to cause mold contamination;
    * In a case that the system was not used, in order to obtain products of good quality, it was forced to stop operating a molding machine every four hours and to wipe off the stains stuck on the surface of a mold. Moreover, the mold had to be taken off for cleaning after continuous two-day-molding.
    * In a case that the system was used, products of good quality were molded without wiping off the surface of a mold for eight days with twenty-four straight hours of operation.

Therefore, this system is most suitable for polyamide resins (nylon, PA66, PA6T), which are being used for molding of connectors and are apt to cause burning, and electric/electronics related parts and automotive parts made of alloy-base resins which annoy molders with mold contamination. Furthermore, it also achieves the beneficial effects on the molding of food, medical treatment related products, lenses and other products.

There are two models of the system conforming to the sizes of injection units of NISSEI's molding machines.

Model G1 G2
Injection unit 5A - 36A 50A, 71A
Screw diameter 22 - 56 mm 50 - 71 mm
Injection volume (max.) 280 cc/shot 560 cc/shot
Height of equipment 540 mm 630 mm
Dimension of controller (LxWxH) 825 x 350 x 710 mm
Power source 3-phase 200V, 50/60Hz
Motor output 1.05 kW


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