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A Preliminary Study of Using Plastic Molds in Injection Molding

Bartlett, Leah Paige
http://orcid.org/0000-0001-5223-4472
http://rave.ohiolink.edu/etdc/view?acc_num=osu1509440406290043

Abstract Details

2017, Master of Science, Ohio State University, Industrial and Systems Engineering.
Two critical aspects of 3D printed tooling are studied in this thesis: tool survivability and mechanical properties of the molded parts in reference to the ones molded on metal molds. Understanding tool survivability is a critical requirement for implementing 3D printed tooling in industry. The tool must be able to withstand the heat and pressures during the injection molding process. Tool survivability was analyzed in this thesis experimentally and with simulations. Two ribs of different aspect ratios were printed on a tool insert and used in a mold assembly. The aspect ratio was changed by doubling the rib thickness while maintaining the same height. The ribs were tested individually under varied flow rates. Experimental results showed that the thinner rib failed after the first shot. The thicker rib did not fail after the first shot; instead, it failed after several shots possibly due to the increase in temperature with consecutive moldings. It was found that the thicker rib did not fail when the mold open time was set to four minutes. This allowed the temperature on the rib surface to not exceeded the heat deflection temperature for the mold material. Simulation was used to evaluate the net force on the rib surface during the filling stage due to the pressure difference and its effect on the Von Mises stress at the base of the rib. It was found that if the Von Mises stress obtained from an FEA simulation was larger than the yield strength of the Digital ABS tool material, it is predicted to fail at the first shot; If the Von Mises stress was not larger, the rib was predicted not to fail on the first shot. It was found that mechanical properties for parts molded in plastic 3D printed molds were similar to the ones molded in metal molds with the exception of ductility. Parts molded in plastic molds in general have a much lower ductility than the ones molded in metal molds. The effect of mold and melt temperature, filling speed and material residence time in the injection barrel on ductility was evaluated, for both, a semi crystalline and an amorphous material. Finally, the effect of mold surface finish on ductility was studied. Results found that the significant parameters affecting ductility were mold and melt temperature, crystallinity and injection speed. By adjusting the above mentioned process parameters the ductility of parts molded in a plastic tool could be increased to similar values to the ones molded in metal molds for amorphous materials. For semi-crystalline materials, the ductility can be increased but it can not be made similar to the ductility of parts molded in metal molds.
Jose Castro, Dr. (Advisor)
Allen Yi, Dr. (Committee Member)
Rachmat Mulyana, Dr. (Committee Member)
96 p.
Engineering; Industrial Engineering
Stratasys PolyJet; 3D Printed Tooling

Recommended Citations

Citations

  • Bartlett, L. P. (2017). A Preliminary Study of Using Plastic Molds in Injection Molding [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1509440406290043

    APA Style (7th edition)

  • Bartlett, Leah. A Preliminary Study of Using Plastic Molds in Injection Molding. 2017. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1509440406290043.

    MLA Style (8th edition)

  • Bartlett, Leah. "A Preliminary Study of Using Plastic Molds in Injection Molding." Master's thesis, Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1509440406290043

    Chicago Manual of Style (17th edition)

osu1509440406290043
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This open access ETD is published by The Ohio State University and OhioLINK.