How is material cost calculated for sand cast parts in DFM Concurrent Costing?

In a DFM sand casting analysis, two entries on the process chart can contribute to the total material for the process: Mold core and Cast part. (There can be more than 1 Mold core entry; or there can be no Mold core entries.) The material cost for the Mold core entry(ies) is made up entirely of the cost of core sand used in manufacturing the core. Normally, when manufacturing sand cores, there is very little scrap material generated that cannot be recovered and reused.

The remaining material cost is attributed to the Cast part operation, and is made up of three different cost components. The first is the original cost of the part material used to cast the part. The sand casting process itself typically generates quite a bit of scrap due to the material used in the required pouring cup, sprue, runners, and various risers. It is quite common for the amount of material required during sand casting to be two or three times the amount of material contained in the actual part. In reality, the amount of material required depends rather heavily on the envelope dimensions of the part and the depth of the part in the forming direction. It is a good idea to double-check the envelope dimensions when you import dimensional data from CAD, and to make certain that the correct forming direction has been chosen.

The second cost component is the recovery of scrap material. This will tend to reduce the material cost calculated by the software. The extra material in the pouring cup, sprue, runners, and various risers can be recovered and it is assumed that this material is recovered at a scrap value entered into the software responses. For instance if the scrap value is 1/15 the original value of the material, this means that about 93% of the original value of that scrap material is not recovered after the part is trimmed, increasing the material cost to a value which is significantly larger than the value calculated when simply multiplying the weight of the part by the material cost. (DFM Concurrent Costing applies the value of scrap similarly for other process models.)

The final component is the cost of using the mold sand, which has a finite life. All three of these costs are added together to yield the final material cost for the sand cast processes.