MoldMaking Technology

NOV 2018

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8 MoldMaking Technology —— NOVEMBER 2018 EAB MMT EAB member Andrew Garstkiewicz of GE Appliances, a Haier Co., offers sage advice on design-for-manufacturing (DFM) analysis. One key aspect of plastic part manufacturing is that of a proper DFM analy- sis, starting as early in the design process as possible. A good DFM analysis should be made by someone who has some knowledge of the part function and of the material that has been selected. The following steps are the responsibil- ity of the designer. With the following information in hand, the DFM analyst should be able to dissect the CAD model and the part-design intent to provide good feedback to the designer about the feasibility of the design and subsequent mold that will produce the parts for the intended tool life: • Maintain a uniform wall thickness for the main form of the part, except for supporting structures such as ribs, bosses, etc. • Be aware that thickness variances that are greater than €‚ percent of the nominal thickness of the main form can cause issues with cosmetics as well as the ƒinal shape. • Spread thickness transitions from across the form of the part over three times the thickness difference in the variation. • Utilize ribs and gussets versus adding thickness to add structure to the form. • Ensure that the maximum thickness of the rib is no more than ˆ‚ percent of the thickness for non-cosmetic thermoplastics to strengthen part form (with ribs, gussets, etc.) or to integrate other features into the form. This must include radii and true intersection thickness against the main-form wall stock. • Ensure that the thickness of the rib is less than ‹‚ percent of the nominal thickness for cosmetic surfaces that comprise the form. This must include radii, too. (This, of course, can vary somewhat because of proximity to the gate and because amorphous resins shrink relatively less than semi- crystalline resins.) • Add radii to intersections of form to structure as well as structure to struc- ture. A small radius goes a long way to reduce stress concentrations. • Prepare for and apply adequate draft on the form and structure of the part. Ejection forces on the part from the mold should be low to prevent deforma- tion, and proper draft will directly affect these forces. • Understand and prepare for gate location or locations with respect to manu- facturability, strength of form and structure, cosmetics and the ƒinal part cost. • Consult with colleagues and industry professionals that have depth of knowledge in all the above considerations every time. Speak with them early in the design phase to maximize beneƒits and realize lower costs. All the above will go a long way to obtaining a valuable DFM analysis that leads to smoother tool builds and trials and optimized production life. Effective DFM Analysis Andrew Garstkiewicz Senior Advanced Manufacturing Engineer GE Appliances, a Haier company Louisville, Kentucky 502-387-1259 EDITORIAL ADVISORY BOARD (EAB) The EAB enhances the standing of the publication and strengthens its professional integrity through the active involvement of its members. The Board represents all aspects of the mold manufacturing industry with a balance of moldmakers, molders, original equipment manufacturers and academia, and various moldmaking segments and job functions. A member is selected based on his or her experience and knowledge of the moldmaking industry to serve a three-year term. Kylee Carbone Director of Talent Development Westminster Tool Plainfield, Connecticut 860-564-6966, ext. 244 Will J. Cipkar Technical Sales Crest Mold Crest Thermal Technology (CTT) Division Ontario, Canada 519-737-1546, ext. 117 Andrew Garstkiewicz Senior Advanced Manufacturing Engineer GE Appliances, a Haier company Louisville, Kentucky 502-387-1259 Ryan Katen President and General Manager Micro Mold Company Inc. Erie, Pennsylvania 814-838-3404, ext. 238 Tim Krieger President Krieger Craftsmen Inc. Grand Rapids, Michigan 616-735-9200 Gabe Meldrum Plant Manager International Mold Corp. Clinton Township, Michigan 586-783-6890 Gerardo Miranda (Jerry) Global Tooling Manager Oakley Foothill Rand, California 949-900-7785 Francine Petrucci President BA Die Mold Aurora, Illinois 630-978-4747 Ryan Pohl Founder Praeco Skills LLC Grand Rapids, Michigan 616-951-2133 Rich Stueber Engineering Manager NyproMold Instructor, Lake County Community College Clinton, Massachusetts 847-855-2252

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