Some CNC users will modify an OEM post processor to try to get different tolerances or utilize a widget or add-on. While there are a large number of post processors out there, they aren’t all created equal. Screenshot provided courtesy of SprutCAM 15 All CNC Post Processors Are Not Created Equal This is a post processing window in SprutCAM where you select the post processor (on the left) and then the actual creation of the G-code (on the right). Being cautious and testing thoroughly is key to using any sort of custom-made CNC post processor. While it might be possible to develop a workable post processor for a homebrew machine, there are a lot of factors that need to be considered before you can call the G-code sound. If your machine is custom made, it either needs to be built to similar specs as an OEM machine with a retrofit controller or a custom post processor needs to be created (sometimes both). Oftentimes, this is because they are building a homebrew CNC machine in the garage or basement. Many folks who are adept with programming and know their way around G-code develop their own homebrew post processors for their machines. Screenshot provided courtesy of SprutCAM 15. This is a Post Processor Generator that SprutCAM provides that shows how it creates an actual post processor. So, you are essentially creating G-code from your CAM work for the controller to read. The machine takes direction from the controller, for example, PathPilot controls all of Tormach’s CNC machines. It’s best to think of the post processor as a communicator with the controller of your machine, not the machine itself. Even when two machines are very similar in size and capability, it is rare that the same post processor will work for two different make/model machines. Post processors act as a translator from your CAM to creating G-code that is specific for your machine make and model. Even if two different machines still use the standard Fanuc G-code (an industry staple), there are still nuances that can be affected in the G-code. Many things can change in the G-code between different types of CNC machines, like supported canned cycles, decimal place location (digits required before and after the decimal), line numbering, and even certain G and M codes. Simply explained, a post processor is a file that converts your CAM toolpaths into G-code for your specific machine. But before you can move from software to an actual machine, you’ll need a post processor. Once you’ve developed a viable idea on a napkin sketch, you need to jump into design using a CAD program, then develop your toolpaths and tooling requirements in CAM, and then you need to actually machine the part with a CNC mill. Well, modifying the post processor can solve these annoyances and output g-code the way you want them to.There is a lot that goes into taking an idea from concept to working part. I want it to move back out of my way so I can remove the part. Why not fly directly over to where the machine will start cutting? Also, most processors will have the machine return to X/Y zero when its finished. Why does it need to do that? It doesn't, it's just a waste of time. As an example, most post processors will perform a move to X/Y zero at the beginning of every file. You will likely want to modify a post processor to suit your specific needs. All CAM software will also provide some sort of documentation for understanding and modifying them. Most of them are fairly easy to read and understand. Post processors are just text files and can be opened and edited in notepad. Also, you will find that several post processors may also work. Mach3, LinuxCNC, and the CNC USB Control Software can all use the generic g-code post-processors available with every CAM program. ngc), whether or not line numbering is used, the pre-amble and post-amble, setup routines like coordinate system and path optimization, and what each of different classes (rapid, feed, arc, etc) of moves looks like. Post processors define inch vs metric, the file extension that the g-code is saved as (like. Some controllers, require line numbers, while others don't care if they have line numbers or not. Like for example, LinuxCNC wants to see a percent sign at the beginning and end of each program. A post processor is a language definition file used to modify generic g-code such that it can be used on a particular cnc machine.
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