Layering CAD files for CAM

The most widely recognized formats for 2D geometry are .DXF and .DWG (AUTOCAD application), and the majority of the NC programming tools recognize them. In fact the CNC interface for 2D machining is adapted to these to formats and they generate NC code automatically. Other formats types like .IGS and .STEP are used also in 3D machining applications. CAM users can easily use these formats in programming? The answer is not so easy. There are two cases: in first case the CAD user and the CAM user design their programs within the same CAD-CAM platform. The CAM user has the advantage uses the CAD data without any conversion to neutral format (.DXF, .DWG, .IGS, .STEP). The CAM software recognizes the CAD software files and there is a one-way dependency between them. Changes made in the initial CAD file can easily been updated in the corresponding CAM file. In the second case the CAD and CAM software are items of different CAD/CAM platform. Here CAD files must be converted to neutral CAD data which are recognized by the CAM software. In this case the CAM user must manipulate a lot the CAD files because many features are useless for programming.

CAD drawing files include much information like dimensions, notes, surface roughness, axis, geometric tolerances, detail views and others. All these information are not needed in order to create a NC program. The basic information is the part’s geometry (lines, holes, and splines) which is converted to tool path. Latest CAD software has their drawing formats and conversion to .DXF (or .DWG) formats produces drawings with many unorganized features: there are not blocks, layers, the dimensions and notes are broken, layers do not exist. The CAM user has to erase one by one the useless features, spending time (erase carefully). This is the half the truth because CAD programs have configurations settings that control the CAD conversion. The CAD user must perform layering in drawings. Layering means to organize each group of features in a layer inside the initial drawing. This action could be manual or automatic (depends on CAD program possibilities). In manual mode the CAD user creates a new layer with the dimensions, another one with the notes, with the surface roughness, and so on. In automatic layering each time a feature is created it is included by the program to a layer. At conversion options configuration the export of structure as layers (or as blocks in some CAD) must be selected.

Converting 3D model to .IGS format is much simpler since the final file is geometry (solid or surface), although there are a lot configuration options which refer to secondary arrangements.