Gas Injection Molding Technology Using Highly Fluid and Flame Resistant Material

In response to the drop in the prices of multifunction devices and printers, there is an urgent demand to reduce costs in all areas of manufacturing for multifunction devices and printers, including construction and materials. One way to efficiently reduce the cost of plastic parts is to make the parts thinner. Fuji Xerox has developed a molding technology (called the gas injection method) that uses a highly fluid and flame resistant material. This method enables both the thinning of plastic parts and the improved quality of appearance and features (such as flame resistance, intensity, and precise shapes).

In the gas injection method, plastic is first injected into a mold. Then highly pressurized gas is injected into the melting plastic in the mold and released to create hollow areas in the plastic. This method can reduce such defects as sink marksNote1 and warpage, and makes parts thinner and lighter by making the parts hollow, resulting in significant cost reduction.

The conventional gas injection method that injects gas into the entire part, however, poses the problem of not enabling control of the thickness of parts, thereby adversely affecting both flame resistance and safety (Fig. 1).

Fig. 1: Conventional Gas Injection Method

In order to maintain a stable thickness in the areas to be thinned, Fuji Xerox has developed the following.

  1. Highly fluid and flame resistant plastic material
  2. Gas path that enables the stable injection of gas by using such basic structures as the ribs and corners of parts, without creating a new channel or changing the shape of parts
  3. Mold management method
    Thanks to these new developments, flame resistance is stabilized and the advantages of injecting gas can be utilized to improve the quality of appearance and reduce warpage (Figs. 2 to 4 and Photo 1).

The gas injection molding method developed by Fuji Xerox significantly stabilizes the thickness of the thinned areas, which affects both flame resistance and safety, and also achieves the following by using highly fluid and flame resistant material:

  1. Stabilizing the quality and reducing the weight of plastic parts by injecting gas
  2. Reducing the amount of materials used and the processing time by thinning the parts
  3. Increasing the precision of the shape of parts by reducing such defects as warpage
  4. Facilitating management of flame resistance by controlling the thickness of hollow areas in the parts
  5. Improving the quality of such external parts as thinned large covers by adopting highly fluid material

This molding method is currently being used to create many of our plastic parts, such as external covers, large internal parts, and highly precise functional parts.

Sink marks are dents or distortions that form due to the shrinkage of plastic. This phenomenon is common among synthetic resin products made by injection molding.

Fig. 2: Fuji Xerox's Gas Injection MethodFig. 2-1: Three Dimensional Figure

Photo 1: View of the Backside of a Molded PartFig 3: Cross-sectional Surface of Molded Rib A
Fig. 4: Cross-sectional Surface of Molded Corner B

Visualized sample of gas injection into clear plastic (photo) and the sectional view of the hollow areas of parts
(Fig. 3 shows the lower area of a rib; Fig. 4 shows the lower area of a corner.)