What is a postprocessor? – Alphacam #35

 What is a postprocessor?


What is a postprocessor and what is it applicable to CAM systems? Why is there always a postprocessor topic talking about CAM systems?

The postprocessor is an external application that translates the toolpaths into a machining program adapted to the selected machine. That’s how it can be called in one sentence. In CAM systems, we generate tool paths based on existing geometry. These are 2D drawings or 3D models. So it is just some graphics. When defining machining strategies, we set the machining parameters for a selected strategy and also get graphical representations of the toolpaths.

The drawing or models in the CAM system are oriented in relation to the origin of the coordinate system defined in the CAM system. And the toolpaths are generated in relation to this setup, based on a 2D drawing or a 3D model. This coordinate system determines the base on the machine. And we must set the base on the machine in the same place (relative to the model) in which the origin of the coordinate system was generated during the generation of tool paths.

The graphical representation of the toolpaths alone will not help us in starting the machining (it is very useful, because we can, for example, check the machining simulation, which can help in catching potential collisions).

These paths need to be presented in some way in a format that we read on a CNC machine. So we have to change what we have on the screen into a machining program, a text file.

And here a postprocessor comes to help. The postprocessor is a kind of translator that translates the tool path we have prepared in the CAM system into a machining program understandable for a CNC machine tool.

The postprocessor also solves another problem. Each machine in the workshop may have a different control system, i.e. each one needs a machining program in a different format. And so in the case of manually writing programs or writing them from the machine desktop, if we would like to start machining the same part on several machines, then for each of them we would have to write separate programs. It would be time-consuming, even with the use of macros or subprograms. Having a CAM system, we create one program, and the postprocessor will generate the appropriate code for the selected machine. Of course, we can have one CAM system, but we must have a postprocessor for each machine, for any control system.

Which is convenient. We make ourselves independent of the machine manufacturer. We do not have to have machines from one company. And a CNC programmer does not need to know exactly each of the control systems. All you need to do is learn about the CAM system. In the CAM system, it prepares a machining program and generates a code for the selected machine. When there is a need to transfer the program to another machine, it takes a moment. All you need to do is generate the machining program once again by selecting a different postprocessor.

In summary, a postprocessor is an application that will process the tool path from the CAM system into an NC program in the format of the selected machine. Each type of controller requires a separate postprocessor, but we only need one CAM system. And the price of the postprocessor is usually much smaller than the price of the CAM system. We do not need to get to know each control system accurately to generate correct NC programs.

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