A New Approach to Improve Dimensional Stability and Decrease Cycle Time in Injection Molding

A New Approach to Improve Dimensional Stability and Decrease Cycle Time in Injection Molding

Bibliographic Details
Main Author: Mulyana, Rachmat
Language:English
Published: The Ohio State University / OhioLINK 2013
Subjects:
Engineering
Industrial Engineering
Polymers
Injection Molding
Polymer
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=osu1366893478
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spelling ndltd-OhioLink-oai-etd.ohiolink.edu-osu13668934782021-08-03T05:22:45Z A New Approach to Improve Dimensional Stability and Decrease Cycle Time in Injection Molding Mulyana, Rachmat Engineering Industrial Engineering Polymers Injection Molding Polymer In this dissertation, we present a novel injection molding approach using water containing plastic pellets to reduce the cycle time and improve the dimensional stability of parts without any equipment or mold modifications. A small amount of water was pressurized into pellets pre-mixed with water carrier particles such as highly porous activated carbon or tubular-shaped nanoclay. Most of the experiments were done with thermoplastic polyolefin (TPO), but Polystyrene (PS) was also tried. The need for water carrier particles depends on the polymer’s hydrophobicity and glass transition temperature (Tg). We found that in the case of PS, water could not be pressurized without using a water carrier. In the case of TPO, water could be pressurized without the need of a water carrier, however using a water carrier improved the process stability and consistency as well as increased the shelf life of the pressurized pellets. Our results showed that the cycle time could be drastically reduced with substantially reduced surface sink mark and part warpage without any adverse effects on mechanical properties. The evaporation of water during molding results in internal cooling; which led to a reduction in cycle time. However, this phenomenon by itself is not enough to explain the reductions of cycle time obtained. It is postulated that reduction in cycle time is also due to the improved contact between the part and the mold during cooling as a result of lower part shrinkage. As the water changes to gas during cooling, bubbles form in the center of the part contributing to lower shrinkage and thus improved mold contact. Complete filling of thin parts could also be achieved at a lower packing pressure in the presence of water, this is partially due to heating of the mold walls ahead of the leading edge as the water leaves the advancing plastic at the low front and condenses on the mold wall. This was supported by the measured temperature rise at the mold surface in the early stage of the molding cycle. The other factor contributing to the easiness of flow is the decrease in viscosity of the polymer due to the presence of water. Comparison of our approach to Super Critical Fluid Molding (SCFM) shows similar benefits without the need to modifying the equipment. Results also show that a small amount of water has a greater effect on warpage than supercritical nitrogen. As in SCFM, flow marks are present on the surface of the parts, which is a detrimental aspect of both processes. We discuss how this flow marks can be hidden by the use of In-Mold Coating (IMC). 2013-08-22 English text The Ohio State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=osu1366893478 http://rave.ohiolink.edu/etdc/view?acc_num=osu1366893478 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection NDLTD
language English
sources NDLTD
topic Engineering
Industrial Engineering
Polymers
Injection Molding
Polymer
spellingShingle Engineering
Industrial Engineering
Polymers
Injection Molding
Polymer
Mulyana, Rachmat
A New Approach to Improve Dimensional Stability and Decrease Cycle Time in Injection Molding
author Mulyana, Rachmat
author_facet Mulyana, Rachmat
author_sort Mulyana, Rachmat
title A New Approach to Improve Dimensional Stability and Decrease Cycle Time in Injection Molding
title_short A New Approach to Improve Dimensional Stability and Decrease Cycle Time in Injection Molding
title_full A New Approach to Improve Dimensional Stability and Decrease Cycle Time in Injection Molding
title_fullStr A New Approach to Improve Dimensional Stability and Decrease Cycle Time in Injection Molding
title_full_unstemmed A New Approach to Improve Dimensional Stability and Decrease Cycle Time in Injection Molding
title_sort new approach to improve dimensional stability and decrease cycle time in injection molding
publisher The Ohio State University / OhioLINK
publishDate 2013
url http://rave.ohiolink.edu/etdc/view?acc_num=osu1366893478
work_keys_str_mv AT mulyanarachmat anewapproachtoimprovedimensionalstabilityanddecreasecycletimeininjectionmolding
AT mulyanarachmat newapproachtoimprovedimensionalstabilityanddecreasecycletimeininjectionmolding
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