to stretch the available capacity up into the corners and moved bosses to provide more space.” Aarrowcast used temporary tooling to test out a final design iteration, but successfully pouring samples on the temporary tool material proved dif- ficult. A quality test casting was finally poured after 10 failed attempts. Testing at John Deere revealed the wall thick- nesses in the design weren’t sufficient for the application. More changes to the design were needed. “Tere was a lot to learn in this
casting process,” said Jack Smith, Aar- rowcast vice president of operations. “It is not your everyday casting, and the methods we have applied to the part were new for us.” After adjusting the design for
thicker walls, Aarrowcast produced successful test samples using a semi- permanent tool. Te key to pouring good castings was adjusting gating practices for low velocity flow of molten metal at the gates. Aarrowcast uses
pressurized gating for in-mold ductile iron treatment. Simulations of typical gating practice showed flow at the gates for the oil pan to be at a rate of 70 in./ second. Aarrowcast engineers slowed the flow 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 castings and too much rework. Te 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 finite element analysis data as a guide. Tis 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 filling surface defects in the casting,” McKee said. Aarrowcast worked with the CCOE and John Deere Product Engineering to define the acceptance criteria that ultimately helped achieve higher throughputs. “Tis 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 finishing.” 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
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