The most important factors in setting a cost for a MIM part are:
The MIM process does not have such an important variety of materials as other metal forming technologies. In the case of the Ecrimesa Group they are materials with commercial catalytic debanding.
The list of materials we can offer are:
The type of material has an important influence on the cost of the parts for two main reasons:
- Price of the material, which is more expensive in stainless steels (316L-174PH) than in carbon steels (42CrMo4-FN08), around 30%. In relation to the price of the materials, they are 10-15 times more expensive than the material coming from bar or ingot to melt.
- Sintering process, that must be at a slower rate in stainless steels, and in hydrogen atmosphere compared to carbon steels that are normally sintered in nitrogen atmosphere and with a sintering rate 30-40 % higher.
2.- Size and configuration of the part
The size is important, as it influences the weight mentioned above, as well as the sintering capacity, since the parts are processed in molybdenum trays of size 200*200 and the greater the number of parts that can be processed per box, the better the cost of this process, both in continuous furnace and in batch furnace.
According to our records, the optimum sizes of MIM parts are between 0.5 grms and 40 grms, although we have parts above 150 grms that, due to their configuration and the machining savings obtained, are profitable compared to other technologies.
On the other hand, and no less important, is the design of the part in order to adapt it to the limitations of the technology, to avoid secondary operations such as machining and to reduce its costs.
Roughness – Ra0.8Ra1.2
It is very important that the parts are not designed with sharp edges, and that they have as many radii as possible to facilitate the injection of the material, to avoid segregation during injection and to prevent cracks from appearing after the sintering process.
Likewise, they must have space for the placement of the injection point and homogeneous walls for a correct injection of the material (since it must be taken into account that steel powder will be injected with the difficulty that this entails since it is not an easy material to inject).
Designing the part with adequate areas for the part, to settle during the debanding/sintering process, also has a very important influence on the cost, since in case of not having flat support faces it forces to use special sintering supports, reducing the load on the furnaces and therefore not maximizing the cost advantage.
Finally, for carbon or low alloy steel parts that require heat treatments, it is of special importance to establish adequate placements for the performance of these heat treatments in order to avoid deformations during the heat treatments, or cracks generated by the heat treatment on the part. The Ecrimesa Group has its own facilities for heat treatments and adapts them to the requirements of the parts in order to maximize the cost and quality of the part.
Making a comparison between MIM and Microfusion of a potential part:
For an annual consumption of 45,000 pieces/year the cost study would be:
Estimating the amortization of the tooling on the first 45,000 pieces, the result would be:
To learn more about this technology at Ecrimesa Group: