CNC Machining Parts Design Guide-Material Selection

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6月 3, 2016
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7月 4, 2016

CNC Machining Parts Design Guide-Material Selection

Material is very important in determining the function and cost of the part. The designer must define the important material characteristics to the design – hardness, corrosion resistance, chemical resistance and heat treatability etc. Shank Machining can produce with a wide variety of metal and plastic materials,except the materials listed below, as well as other materials upon request.

The material blank is the size of the material that will be used to create the finished part. For example, if the finished part dimensions are 3.5” long x 2” wide x 1” tall, then the raw material blank size should be 3.75” long x 2.125” wide x 1.125” tall at least. Material blank thickness is another area that should be considered during the design process.

An easy way to follow is to account for a blank that is a minimum of 0.125” larger than the part size. For example, if the dimension of the final products is 1” x 1” x 1”, then the blank for the part would be 1.125” x 1.125” x 1.125” to allow for the variations in the raw material. When design the part, if the final dimensions is 0.875” x 0.875” x 0.875”. This way a standard 1” x 1” x 1” block could be ordered and save some material cost versus a larger starting blank.


Shank can offer different metals for CNC machining:
• Aluminum
• Brass
• Stainless Steel
• Alloy Steel
• Other Custom Materials
Normally, softer metals, for example aluminum and brass, as well as plastics can be machined easily and less time will be taken to remove material from the part blank. Harder materials, like stainless steel and alloy steel, must be machined with slower speed and smaller feed rates, the processing time will be longer than softer material. As a general rule, machining with aluminum will be about 4 times faster than alloy steel, and machining with stainless steel will be as half fast as alloy steel. The type of material is a critical part in determining the overall cost of the part. For example, 6061 aluminum bar stock is approximately half the price per pound of aluminum plate, and the cost of 7075 aluminum bar stock can be 2 to 3 times than 6061 bar stock. 304 stainless steel costs about 2 to 3 times what 6061 aluminum costs and is about double to 1018 carbon steel. According to the size and geometry of the part, the material cost can be a significant portion of the overall price of the part.


Shank can provide parts with following plastics for CNC machining:
• Acrylic
• Delrin
• Nylon
• Other Custom Materials
Plastic material is a more economic choice to metals if the rigidity of metal is not required. Polyethylene is easy to machine, and the cost is about 1/3 of 6061 aluminum. In general terms, ABS is about 1.5 times expensive of Acetal, Nylon is approximately 3 times expensive than Acetal. Although plastics could be a cost effective material, but tight tolerances can be harder to produce with plastics, and the parts could warp after machining because of the stress created when material is removed.