Evaluating a Sheet Metal-Composite Cam Am System
Cam Am systems are used to take electronic part drawings (CAD files), process and 'nest' them onto sheets or rolls of material and convert the resulting nesting layouts to a series of coordinates and machining instructions, known as CNC programs so that the part can be accurately and effectively machined on a specific machine tool. The resulting code is sent electronically to the machine tool, ready for machining. These CNC programs are very specific to each particular CNC machine technology and machine controller.
There are several stages to creating a CNC program, starting with the definition (drawing) of component geometry if CAD facilities in Cam Am system are being used, or with importing and 'healing' of component geometry which was created in an external CAD or unfolding software. Once the correct component geometry is available within the Cam Am system, tooling and/or profiling/cutting information needs to be added. Depending on the Cam Am system in use, this can be done interactively, automatically or in some combination of both. This information differs from machine to machine and across machine tool technologies in use.
Once all of the machining information has been applied to components the next task is to 'nest' them - squeezing as many components on the sheet or a roll of given size as possible. A nest might consist of the same parts or a mixture of different parts, and can be classified as either rectangular or 'free form' (true shape). Rectangular nesting, as the name suggests nests each component as if it were a rectangle, which will result in a significant waste of material if you are cutting many irregular shapes. With rectangular nesting parts may be nested at different angles, but are usually nested at 0 and 90 degrees. Free form nesting offers the best material yield by being able to nest parts at any angle and also taking advantage of any scrap material within larger components, such as cut-outs, etc. Depending on the level of automation within a particular Cam Am system, the placements of parts will either be a manual or automatic process (or could be a combination of the two).
Manual nesting for dissimilar components is often performed by dragging and dropping parts on the nest, also known as bump nesting. Unless the operator is very skilled, this process can result in significant material waste, and in any case is invariably a very slow process. Because of this, many companies currently produce so called 'static' nests, which were created manually and are regularly re-used. The problem with this is that all of the parts will be produced each time a particular nest is run on the machine, regardless of whether they are all needed or not. 'Dynamic automatic nesting' on the other hand allows for unique nests to be created as and when required, providing a 'Just In Time' approach whilst retaining high material efficiency. This of course is especially important when processing expensive materials.