Appliance Design - January 2009 - (Page 29)

PLASTICS & PLASTIC PARTS Fig. 2. Illustration shows undrafted (left) vs. drafted (right) part/mold cross-sections. On left, arrows point to undrafted part surfaces that will scrape against the mold during ejection. thetics. Part of this simplification is designing parts that can be made in two-part, so called “straight-pull” molds. In some cases, however, part designs include unavoidable “undercuts,” features that would be entrapped in a straight pull mold. These can be produced using side-actions, cams that produce the desired feature and then withdraw as the mold opens to allow the part to be ejected. While side actions are useful, they increase the complexity and cost of production and should be avoided if possible. Why draft? In a straight-pull mold, any part surface that is parallel to the direction of mold opening will drag along the mold face as the mold opens, resulting in damage to the part. Similarly, two mold surfaces that meet parallel to the direction of mold opening can be damaged as the metal surfaces rub against one another during mold opening and closing. (Such interfaces are called telescoping, or sliding shutoffs.) To avoid damage to parts or molds, all of these surfaces must be “drafted.” Drafting angles surfaces away from the direction of mold opening so that the surfaces — part and mold or mold and mold — move away from one another as the mold opens. This eases ejection of parts during production, and eliminates the likelihood of damage to Solving Problems With manufacturing plants in both the USA and Vietnam, we ensure that supply disruptions do not occur. We Take the Hassle Out of Asian Sourcing Low Cost & On Time Fully Certiﬁed & Established Pre-Production Test-Runs Prototypes, Samples & PPAP Orders Plastic Insert/Over Molding, Welding, Crimping, Potting, and Electro-Mechanical Assembly here and around the globe! MGI Global can produce both High Production and Short obal b d Run orders at our facility in Vietnam without the headache. ders Viet V adache. For a quote, call or e-mail our sales specialists TODAY! Wiring Harnesses & Cable Assemblies CUSTOM CUSTOM Your Partner in Thermal Protection 1175 Alexander Court Cary, Illinois 60013 Ph: (847) 516-8080 Fax: (847) 516-0747 E-mail: sales@mgimfg.com www.mgimfg.com www.applianceDESIGN.com AD09084ther.indd 1 applianceDESIGN January 2009 AM 8/15/08 8:54:59 29 http://www.mgimfg.com http://www.mgimfg.com http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - January 2009

Appliance Design - January 2009 Contents Editorial Shipments/Forecasts News Watch Supplier Spotlights Commercial Appliances Plastics & Parts Electronics Motors Design Marts Association Report: NAFEM Advertiser’s Index

Appliance Design - January 2009

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