Our group has chosen to work with CNC for rapid manufacturing of the shafts. This choice resulted from the time for production, cost of production, and ability to construct our parts. CNC is also fairly easy to use based on our knowledge base and the ease of having a CNC machine on campus. In comparison to standard machining, CNC is considered favorable for its accuracy, speed, and repeatability.

CNC is an integration of computer monitored feedback with a standard machining process. When machining with a CNC, a negative process, portions of a larger piece of material are removed to form the desired end product.
 
 

Before the CNC can begin production of a physical part, a computer model must be designed and sent to the machine. This is done with use of computer aided design such as ProEngineer or AutoCAD. During this process, the user must create a model that can be translated into virtual space and specify dimensions for this model. The created 3D model is exported to a computer aided manufacturing package. This package is often specific to the CNC machine to be used.

While exporting the model, the user specifies the physical properties of the material for producing the part. The user is also responsible for assigning the way the machine will manufacture the final part by defining: tool speed, tool path, cutter rate, feed rate, material hardness, and positioning. Once these variables are defined, they are checked to be sure that the final machined part will match the computer’s model. One concern for this portion of the process relates to the user’s ability to send a cutter into the machine’s assembly if there is a miscalculation of the tool path. This mistake would cost $40,000 due to destruction of the machine.

Finally, the piece is cut on the CNC. To accomplish this, the material must be held in place while the CNC cuts it. This is accomplished with use of clamps or chucks. Once the piece is in place, the machine is zeroed to a preset location to allow the computer to pinpoint a starting location. At this point the computer is prepared and is able to begin the cutting process.

In general, CNC machines are versatile. They have the ability to cut through many materials including hard rubbers, metals, plastics, glass, and composites. Beechman 4000 & 4500 series Desktop CNC Mills have a resolution of 0.00001" (0.000254mm) and 5000 & 5500 series mills have a resolution of 0.000025" (0.000635mm).
 
 
 

Links to other CNC pages:

Denford CNC Machining

Mercateach CNC Machining