Changing bits during a job

I鈥檝e read & completed the tutorials in BobCAD/CAM. I did a dry CNC run that used only one bit/cutter. My Longmill ran continuously from start to finish. It occurred to me what if the job required more than one bit. Does the controller know this via the G code and stops automatically to change bits or does one have to manually pause the job? Can this be programmed in when creating toolpaths in CAM?

When you set up the job you choose the bits you want to use for that job. If you look at the latest video Andy did in Camlabs you will see how he did this in that program. I will describe it in basics terms here for you. Each step in that roughing pass to pocket to finish requires a different bit on the right side of that interface. If you input info in that area the program knows you want a bit change. It will stop the cut process at each point and wait until you hit start to go on cutting. Then you have to go and reset 0 for each bit on your job on a point in the job. Look at his video to a full explanation.

@SDS I believe I just spoke with you about this over the phone but I鈥檒l also post the answer here so that anyone else can use it as reference. The LongMill operates off the open-source GRBL firmware, which is an easily accessible and community built code-base which enables our control box to interpret g-code files and turn that into motor movements to carve out your project. This means that the functionality of the machine is also dictated by the functionality of the GRBL firmware. Since GRBL has been built around serving hobbyist machines, the community building it hasn鈥檛 put much time into supporting tool changing commands, hence it鈥檚 not available by default.

Usually our approach to using multiple cutting tools in a single project is to split each tools toolpath into separated, numbered g-code files. This way you can run one file, wait completion, switch the tool out, re-calibrate the z-height (at minimum since the new tool height will be different), and run the next g-code file. This is what Andy demonstrates in the above video.

Another trickier option is that even though the Firmware doesn鈥檛 support the tool change commands, the interface software you use (UGS is an interface software) does have the ability to intercept that tool change command and execute the change on its own. I only know of one software that can do this, and I鈥檝e never tested it so try at your own risk, but it鈥檚 bCNC and you can find their documentation on how to get it working here: Tool Change 路 vlachoudis/bCNC Wiki 路 GitHub

This is another discussion that I found on possibly introducing a macro into an interface software to deal with tool changes as well: Manual tool change for GRBL 路 Issue #118 路 cncjs/cncjs 路 GitHub

Once again, not certain on the success of these solutions as I have yet to try them personally. I鈥檒l let you know if I鈥檓 able to try them out successfully :+1: