Effective Web Cam Server Suite 1. Historical perspective of CAM. CNC milling machines have of course been developed based on conventional milling machines, where the tool is moved through the material by operating a hand wheel for each of the available axes (X, Y, Z, ...). The basis of adding NC (Numerical Control) is very simple: replace the hand wheel by a positioning motor and add some electronics (the NC controller) to control the position. Nowadays many conversion kits are available to perform such operation. The first NC controllers were very simple: no user-interface, just an option to read the toolpositions to go to from a punched 2. The position of CAM Software in the process. In order to manufacture a part, nowadays typically three different software programs are used (see the illustration above): - First the CAD software to make the design of the part - Next de CAM software to calculate the toolpaths based on the design, compensating for the cutter’s geometry, adding feedrate and spindle commands, etc - Third the control software to read the toolpaths and let the machine actually move along these paths. This subdivision of tasks by three different programs is the same for both 2D and 3D applications. The Control software comes with the milling machine, while in contrast the CAD and the CAM software have to be bought separately. In case an NC controller with built in special purpose computer is used, the Control software is integrated. In case of a PC the Control software has2 to be installed, still it ’belongs’ to the machine as the machine cannot function without the Control software. Do note that many lowcost CNC machines are delivered with MS Dos based Control software, as the realtime control needed for machining is difficult to program under Windows. Communication between the three programs is done using files. From CAD to CAM the design is transferred using a file format for geometry data exchange. For instance file types like IGES, STL and STEP for 3D, DXF for both 2D and 3D, and Postscript and HPGL for 2D applications. These are standard formats that in most (!) cases can be used without any special configuring needed. Much more can be said about these file types. Perhaps an idea for a next article of the month I won’t add any explanations here. Communication from CAD to Control software is done using NC program files, for which many formats do exist. In most cases the format will be a (minor) variation on the ISO / DIN G-code format. 3. Types of CAM software. Many different CAM software packages are available, showing large differences in price. It is a very difficult job to get a clear view about each system’s capabilities and it’s price/performance ratio. The CAM software comparison table on this website is a great help, still only doing some real-life testing gives good evaluation information. To give some guidelines for choosing, two basic categorizations can be made.
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