maintaining high castability to keep costs and scrapped castings down. To optimize the bracket for the hori-
zontal green sand casting process, the team had to design a bracket shape that would eliminate the need for multiple cores. As designed for the weldment, the part included several areas of back- draft. Dotson’s product manager Chris Witt guessed it would have taken four or five cores to produce the casting. “With some minor design changes,
The award winning casting replaced a welded bracket that fit on John Deere’s skid loader engines.
bracket’s piece price by 48% and the on-line scrap rate by 10%. The casting also fetched the 2010
AFS/Metal Casting Design & Purchas- ing Casting of the Year award.
From Liability to Benefit In the interaction between Dotson
and Deere that yielded the great sav- ings and reduced number of scrapped brackets, G&V Machine Co., Ixonia, Wis., played catalyst. Deere had a vague notion that its weldment needed to be produced in the metalcasting process. The machine shop not only knew what specific casting process would produce the part the company needed, it knew the right casting sup- plier for the job. Chris Griswold, G&V’s vice presi-
dent of manufacturing, said his team briefly considered a gray iron casting to achieve maximum cost reduction on Deere’s bracket, but the material would have been a liability in the high impact and vibration applica- tion of a skid loader engine. The design team settled on ductile iron for its strength. The team also knew the tight dimensional tolerances of a nobake cast part would be overkill for the bracket and that a green sand part would serve its purposes. Taking into account these factors,
production requirements of 7,000 pieces per year, and the weight and size of the component (10.7 lbs., 15 x
The 10.7-lb. bracket (in gold) attaches the alternator and air conditioner compressor to the skid loader engine.
26 Metal Casting Design anD PurChasing May/June 2010
6 x 5 in.), G&V knew the metalcaster for the job. “Dotson is very easy to deal with,” Griswold said. “The engineering and turnaround is very fast.” Armed with a CAD drawing of
Deere’s weldment, G&V brought Dot- son into the design fold early in the conversion process, seeking to opti- mize the benefits of metalcasting while
we knew we could make it more economically,” Witt said. “We reduced material so the part was naturally drafted, we worked toward a uniform wall thickness so there weren’t any areas that were hanging over, and we added draft to the base of the cylin- drical bosses.” The resulting design, positioned with the long axis vertical in the mold, required one core to produce a small slot for the engine’s throttle control. What’s more, the cast version of
the bracket was designed with angles and surface alignment that allow for accurate mounting surfaces and hole positioning and horizontal CNC ma- chining with one setup. Dotson also added a feed path to ensure the part’s bosses would be porosity free and a number of stiffening ribs to eliminate flexibility in the part and help it come through shakeout without damage.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68