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Design for Manufacturing (DFM) – CNC Machining

At Ktech, we work with our customers in the design process in order to help achieve the best functionality and aesthetics while keeping unit costs at a minimum. We plan our processes and machining methods with both Design for Manufacturing and Design for Assembly at the forefront.

Design for Manufacturing (DFM) and design for assembly (DFA) are the integration of product design and process planning into one common activity. The goal is to design a product that is easily and economically manufactured.

When considering design for manufacturability for CNC machining there are a number of factors that are paramount:

Material type: Better “machinability” = lower cost material removal

Some materials that we consider to have the best machinability include non-ferrous metals such as aluminum and brass, plastics such as delrin and peek, and steels such as 304 stainless steel. As materials get harder, denser and stronger, such as steel, stainless steel, titanium, and exotic alloys, they become much harder to machine and take much longer, which means longer cycle times and shorter tool life. A choice of material that is unnecessarily hard or tough makes a part less manufacturable. Most types of plastic are easy to machine, however some have additives such as glass which reduce the machinability.

Tolerances: Tighter tolerances = higher costs

One of the most significant contributing factors to the cost of cnc machined components is the geometric tolerances to which the features must be made. The tighter the tolerance required, the more expensive the component will be to cnc machine. When designing, specify the loosest tolerance that will serve the function of the component. Tolerances must be specified on a feature by feature basis. There are creative ways to engineer components with lower tolerances that still perform as well as ones with higher tolerances.

Design and features: The cost is in the details

As cnc machining is a subtractive process, the time to remove the material is a major factor in determining the cost to machine a component. The volume, shape and fine details of the material to be removed as well as how fast the tools can be fed will determine the machining time. What seem like simple features can make a part much more expensive to machine. Things such as small corner radius call outs at intersections, radius’s on outside corners instead of chamfers and undercuts can all add considerable cycle time when perhaps not necessary.

Material shapes and forms:

Metals come in all shapes and forms. The most common ones we cnc machine at Ktech are bar stock (round, square, rectangular, etc…) and plate. The size and shape of the component may determine which form of material must be used. It is common for engineering drawings to specify one form over the other. Bar stock is generally close to 1/2 of the cost of plate on a per pound basis. So although the material form isn’t directly related to the geometry of the component, cost can be removed at the design stage by specifying the least expensive form of the material.

Please contact us if you are interested in our CNC machining services!