The shrinkage depended on the product shape and the type of plastic used in injection melting temperature injection speed holding pressure and mold cooling. Different surroundings during the injection resulted in differences shrinkage so the exact shrinkage value hadn’t been known. This was the cause of Try out and error work that produced Injection products that were not in correct size. This research aims to find the shrinkage percentage based on the ASTM D955 standard test method from high density polyethylene (HDPE) which has partial crystalline structure and high shrinkage. The results were as follows: The specimen size 60x60 mm shrinkage was at 2.57 percentage and with 2 mm thickness the shrinkage was 3.60 percentage. The specimen size 12.7x127 mm shrinkage was between 2.76 percentage and 2.91 percentage with 3.20 mm thickness the shrinkage was 2.48 percentage. For the 100 mm circular specimen the shrinkage was from 4.35 to 4.39 percentage and with 3.20 mm thickness the shrinkage was 2.56 percentage

The design of plastic injection mold requires precision and efficiency of the injection. Therefore mold design engineers need to determine the size location and number of the gates to fit the length of the plastic flow in the work piece so that when the injection mold is built they’ll get the complete and specified specimen. This research was conducted to study the influence of injection flow channel thickness affects the flow index. Poly ethylene high density High density polyethylene HDPE was used in the experiments. The flow of plastic was Spiral Test according to ASTM: D 3123-94 with rectangular cross-sectional area of 6 mm. wide 6 mm. pitch. It was found that the thickness of the flow channel at 0.51.01.5 and 2.0 mm. which has the best flow rates at the best injection speed at 25% the injection pressure at 30% and the flow distance of 52 116 238 and 299 mm respectively with the plastic melting temperature between 190 C and 220 C.