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Evaluating injection screws for better color mixing

Evaluating injection screws for better color mixing

Product catalog summary

Abstract: The study investigates the impact of screw design on color mixing in injection molding, focusing on variables such as screw speed, melt temperature, and backpressure. The research aims to enhance color dispersion by optimizing screw design.

Introduction: Screw design is crucial for achieving proper color mixing and melt homogeneity in injection molding. It influences melt temperature, recovery time, and color dispersion, potentially reducing scrap rates and cycle times.

Equipment: The study utilized a Toshiba Model ISS 85 injection molding machine with a clamping force of 82.6 tons and a screw diameter of 36 mm. Four different screws were tested, each with unique designs and compression ratios, to evaluate their performance in color mixing.

Resins: Four resins were used: PolyOne LDPE, PolyOne HDPE, PolyOne ABS, and Profax PP, each with different melt flow rates.

Experimental Procedure: Each resin was tested with each screw design. The machine was pre-heated, stabilized, and data was collected using a Fluke Data Acquisition System. Screw recovery time, temperature readings, and hydraulic pressures were recorded and analyzed.

Presentation of Data and Results: Screw number 4, a barrier screw with a patented mixer, showed the lowest screw recovery time and melt temperature, especially with Polypropylene and HDPE. Screw number 3 demonstrated excellent color dispersion, comparable to screw number 4.

Discussion of Data and Results: Screw design significantly affects processing parameters. A mixing section improves color dispersion, while a barrier screw enhances recovery time. The choice of screw design depends on the desired outcome and the material being processed.

Conclusions: 1) Barrier screws offer faster recovery times and lower melt temperatures. 2) Mixing sections enhance color dispersion. 3) Material type affects screw performance, necessitating specific designs for different resins.

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