eprintid: 182
rev_number: 4
eprint_status: archive
userid: 6
dir: disk0/00/00/01/82
datestamp: 2008-10-13
lastmod: 2015-05-29 19:48:52
status_changed: 2009-04-08 16:55:28
type: report
metadata_visibility: show
item_issues_count: 0
creators_name: Lewis, Greg
contributors_name: Frigaard, Ian
contributors_name: Huang, Huaxiong
contributors_name: Wu, Jinbiao
contributors_name: Lewis, Greg
contributors_name: Myers, Tim
contributors_name: Stockie, John
contributors_name: Westbrook, Rex
contributors_name: Ceko, John
contributors_name: Bejanov, Boyan
contributors_name: Carrasco-Teja, Mariana
contributors_name: Javidnia, Hooman
contributors_name: Krakovska, Olga
contributors_name: Shakoori, Azar
title: The Effects of Impact on Design Features
ispublished: pub
subjects: other
studygroups: ipsw8
companyname: Husky Injection Molding Systems
full_text_status: public
abstract: This report concerns with finding a simplified model for an injection molding machine, which consists of a hydraulic piston that forces some molten metal into a mold.

The model currently used by Husky ignores all effects except the deformation of the piston and housing, which is assumed to be elastic. The impact is modelled using a mass-spring system, where the force of impact is obtained for a given impact velocity, system mass and pre-calculated “spring” constants for the impacting bodies. In order to determine the importance of the presence of the hydraulic fluid, the compressibility of the molten metal, and the leakage past the screw tip, we will assume that the deformation of the piston and housing can be ignored. However, in order to make quantitative predictions of the impact forces, it is necessary to include the effects due to the compressibility
of the machine parts. Thus, we also investigate a model that, like the current Husky model, uses a mass-spring system to incorporate the elastic deformation of the piston and the housing.
problem_statement: The system of interest is an injection molding machine consisting of a hydraulic piston that forces some molten metal into a mold. The injection piston itself consists of a flange (the tail end), a piston rod, and a screw that is attached to the tip of the piston rod. A variable hydraulic force, that is applied to the piston, attempts to keep the piston moving at a constant velocity, where a force can be applied. A molten metal (e.g. a magnesium alloy) is injected into a mold. In normal operation the piston screw, travelling at the prescribed velocity, will impact the molten metal that has been injected into the mold and force the molten metal to completely fill the mold. The whole machine is symmetric under rotation about the lengthwise axis of the piston.

It is desired that the machine be designed for (essentially) infinite life. Therefore, design features must be specified so that the machine can withstand the repeated strain on the piston due to the impact of the piston screw on the molten metal. In addition, in the event that there is an insufficient amount of material in the mold, the piston may “bottom out”. That is, the flange of the piston may impact the housing at full velocity. The machine must also be designed to withstand such impacts.

In order to efficiently engineer the machine, it is necessary to understand the effects of impact on design features. At present, these effects are verified using a transient finite-element analysis (FEA). However, an FEA is not only time consuming but the company’s FEA resources are limited. Therefore, a simplified model, that could be used by a designer to obtain a first pass type of analysis, is desired. Once appropriate design features are obtained using the simplified model, they can be verified using an FEA.
date: 2004
date_type: published
pages: 15
citation:   Lewis, Greg  (2004) The Effects of Impact on Design Features.  [Study Group Report]     
document_url: http://miis.maths.ox.ac.uk/miis/182/1/husky_injection.pdf