pressurized gating for in-mold ductile iron treatment. Simulations of typical gating practice showed fl ow at the gates for the oil pan to be at a rate of 70 in./ second. Aarrowcast engineers slowed the fl ow to 25 in./second by stepping the gates for lower pressure. Depending on the engine, the oil
pan castings require up to 13 cores, all of which are manually set into the mold by Aarrowcast technicians. To ease coresetting, Aarrowcast adjusted the core locks and used seats for chaplets to facilitate core placement. But plant supervisor Mark Burmeister said train- ing also was integral to achieving tight tolerances. “It takes a skilled hand to put the mold together,” he said. After the oil pan had been in pro-
duction for a few months, Aarrowcast was discouraged by ongoing issues that resulted in too many scrapped cast- ings and too much rework. T e casting facility contacted John Deere’s CCOE for help. Jim McKee, manager of John Deere’s CCOE, stepped in to assist in resolving the issues. McKee worked to draft a critical
acceptance criteria document for the oil pan casting using fi nite element analysis data as a guide. T is document outlined where various imperfections could or could not be found on the casting, according to the applica- tion requirements. “We knew where high stresses were and where defects absolutely could not occur for salvage fi lling surface defects in the casting,” McKee said. Aarrowcast worked with the CCOE and John Deere Product Engineering to defi ne the acceptance criteria that ultimately helped achieve higher throughputs. “T is part has to be ultra clean
because it has to meet engine criteria,” Smith said. “But in some cases, we were putting too much work into the part than was needed in fi nishing.” Additionally, the machining strategy
was later adjusted to put all the machin- ing locators on the drag side of the mold where all the cores are set. Previously the locators were on both sides of the parting line and caused excessive part-to-part variation through machining. Now the part runs smoothly
Best-In-Class
Electronics Mount Aristo-Cast Inc. Almont, Michigan
Material: AZ91E-T6 magnesium. Process: Investment casting. Weight: 54 grams. Dimensions: 3.681 x 4.488 x
2.953 in. Application: Hand-held device used in aerospace.
• The component acts as a bracket to mount processing electron- ics and acts as a heat sink to manage the thermal load from all of the elec- tronics. It also ties the two halves of the housing together, preventing it from “oil-canning” under external pressure loads.
• The investment casting process provided the ability to combine many parts into one and lower part cost and weight.
May 2014 MODERN CASTING | 25
through Aarrowcast’s operations and machining processes, and both cus- tomer and suppliers are pleased with the results. “Aarrowcast is happy with the busi-
ness, and we are happy with their part of the business,” McKee said. “And now the machine shop is happy because they get consistency from part to part.” T e lessons learned from the col-
laboration on this project have not been lost on the metalcasting facility. T roughout development and into production, engineers from John Deere and Aarrowcast met face to face and electronically to work through several iterations with a goal of achieving sound metalcasting practices to meet the application’s requirements. “We probably would not be in
production if that level of eff ort was not put in up front,” Smith said. Olson can’t imagine not estab- lishing similar collaboration on future new projects. “Put it this way, if our customer doesn’t hold a design review with us, we’re holding it with them,” he said.
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