How much does it cost to manufacture a part using MIM?
The optimal MIM part could be defined with the following characteristics:
- Length less than 100 mm
- Ratio length/width must be less than 5
- Weight can vary between 0.5 and 50 grams
- Wall thicknesses between a range of 0.5 and 15 mm
The most important factors in setting a cost for a MIM part are:
1. MIM part material
The choice of material significantly impacts the cost of the parts due to two primary factors:
- Material Cost: Stainless steels (such as 316L and 17-4PH) are generally more expensive, approximately 30% higher in cost compared to carbon steels (such as 42CrMo4 and FN08). The price difference can be attributed to the fact that stainless steels are around 10-15 times more expensive than raw materials in the form of bars or ingots.
- Sintering Process: The sintering process for stainless steels requires a slower rate compared to carbon steels. Additionally, stainless steels are sintered in a hydrogen atmosphere, while carbon steels are typically sintered in a nitrogen atmosphere. Moreover, carbon steels have a higher sintering rate, approximately 30-40% faster than stainless steels.
These factors should be taken into consideration when evaluating the cost and sintering requirements for different materials in the manufacturing process.
2. Size and configuration of the MIM part
The size of the parts is crucial as it impacts both the weight and the sintering capacity. MIM parts are processed in molybdenum trays measuring 200*200, and maximizing the number of parts per tray improves the cost efficiency of the continuous and batch furnace processes. Based on our historical data, the optimal size range for MIM parts is between 0.5 grams and 40 grams, although we have successfully produced parts weighing over 150 grams that offer cost advantages compared to other technologies due to their configuration and reduced machining requirements.
Equally important is the design of the part to accommodate the limitations of the technology and avoid secondary operations like machining, which helps reduce costs. It is crucial to avoid sharp edges and incorporate radii wherever possible to facilitate material injection, prevent segregation during injection, and minimize the occurrence of cracks after the sintering process. Ample space should be allocated for the injection point, and the walls should be homogenous to ensure proper material injection, considering that injecting steel powder presents inherent challenges.
Additionally, designing the part with suitable areas for settling during the debinding/sintering process significantly influences the cost. Flat support faces are preferred to avoid the need for special sintering supports, optimizing furnace load and cost efficiency. Lastly, for carbon or low alloy steel parts requiring heat treatments, careful consideration should be given to the placement of these treatments to prevent deformations or cracks that may result from the thermal processes.
by saKudarte