Once the part has been designed using conventional mechanical design methods (structural analysis, FEA, fatigue study, etc.), the part is manufactured using the following method.
1. Create a solid 3D model of the part to be produced. Any standard CAD format is acceptable.
2. Import the solid model into the CAM (computer aided manufacturing) software. (this demonstration uses MasterCAM)
3. Input the raw material stock size and set the part’s coordinate origin.
4. Input the necessary information for each tool used in machining the part features. Typically, a tool library will exist, which is simply a database of tools and their related parameters.
5. For each part feature, select the appropriate tool from the library and set the parameters necessary for machining that feature. Typical parameters include spindle speed, depth of cut, feedrate, number of passes, tool path pattern, etc.
• CNC manufacturing offers advantages on two types of parts: (1) simple parts that are mass produced and/or (2) complex parts with features requiring multiple axes of simultaneous motion. For simple parts in low quantity, it is often quicker to produce the parts on manual machines (as in lab).
• CNC does not inherently imply increased part accuracy. An old CNC with a lot of hours of use will produce less accurate features than a new quality manual machine and vise-versa; so don’t automatically associate higher accuracy with CNC machines. (Accuracy has more to do with machine design, component selection and mechanical wear.)
• Modern CNC machines offer increased productivity due to stiffer machine and spindle designs, more powerful motors, high pressure coolant (up to 1000 psi) that floods the cutting zone, automatic tool changers, digital workpiece and tool probing, and/or horizontally mounted spindles.
• Downsides to CNC machines are higher initial cost, larger space and electrical requirements, increased maintenance cost, required programming skillset and their inherent complexity means there’s a higher probably of component failure during the useful lifespan.