. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PurChasing POints
Working With the Design Team Bob Mueller Jr., P&H Mining Equipment, Milwaukee, Wisconsin
yond expectations, and is delivered on time at a fair price. But how do we work together to ensure we obtain these goals when dealing with an engineered cast product? The answer starts early in the
T
design process. The engineering team must involve the purchasing agent and the potential supplier prior to releasing drawings. These supplier design review meetings are critical to minimizing costs. In far too many instances, engineer- ing designs a part with costs as an afterthought. From a purchaser’s perspec-
tive, we must work with the en- gineering department to become involved in the design process earlier, when significant oppor- tunities exist to control costs. If this process is ignored, any future cost reduction efforts will require elevated costs and time. What’s more, the engineering department may at that point be reluctant to change an aspect of the design that is work- ing for them, arguing that “if it’s not broke, don’t fix it.”
Casting Cost Drivers Your casting suppliers can assist
your engineering team in identify- ing the high cost drivers associated with cast components. Cores (used to create hollow spaces inside metal castings), soundness requirements and the pattern setup associated with meeting those requirements, proper material selection, and machining requirements all are large cost drivers in metal castings. The need for cores is directly related
46 Metal Casting Design & PurChasing
he goals of engineering groups and those in the procurement role are similar. We all want a part that meets specifications, performs be-
to casting design, and in many cases, it can be eliminated by altering the design of the part slightly, or through the use of off-set parting lines in the pattern design process. In the case of castings made in the nobake sand casting process, cores can be eliminated through the use of loose pattern pieces. By focusing on the castability of the part, you can turn an expensive, complex casting into a cost effective design.
How can I work with my design team to ensure that the cost of my cast part is minimized, while the design considerations are maximized?
Feeding requirements also can be
reduced through initial design review meetings. Areas of a casting with isolated hot spots (sections that are slow to solidify and must be “fed” with fresh metal to avoid defect formation) can be modified in such a way that they are fed from other areas of the casting through directional solidifica- tion, rather than through a riser (an external cavity placed on a pattern solely for this purpose). It is also important to discuss with
the engineering team the level of sound- ness required for the component. In many instances, a high soundness level is specified, but in reality, a far lesser degree is required for the application. In most cases, this is due to a lack of understanding by the engineering staff.
Another key cost driver is the mate-
rial selection for your cast component. In the case of steel castings, you may be able to eliminate the need for a higher alloyed material in lieu of a low-alloyed, heavily heat-treated part. This evaluation will depend on the ap- plication of the part, material section size and the desired mechanical prop- erties. Provide your supplier with your mechanical property requirements, and ask that they provide you with the alternatives they have available to meet those requirements. Using a material grade that the metal casting supplier regularly pours, ver- sus a special grade that requires minimum order quantities, also will help cut costs. Reducing the amount of ma-
chining on your part can play a significant role in reducing overall costs. Providing raised bosses and profiling individual surfaces will help lessen machine cycle times and therefore costs.
Lifecycle Costs When you are early in the design
phase, anything is possible. Throughout the design review process, it is critical that both you and your supplier fully understand the end-use of your prod- uct, including any assembly that takes place. Also, servicing or changing out the component may play a role in reduc- ing costs. Opportunities to add features or provide end-users with advantages during change outs or preventive main- tenance cycles can achieve a significant cost advantage. In the end, the final cost of your
cast components will come down to how well your company and your suppliers interact.
METAL
Bob Mueller Jr. is a procurement special- ist working with raw materials for P&H Mining Equipment, Milwaukee, Wis.
July/august 2010
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