Step 19: CNC Finished?

posted in: Construction CNC DIY | 0

Well, after all this steps, I could say that the CNC is almost finished, couldn’t I? I could say than Yes, at least the phisic part of it. What I still need is to learn a bit more of the program, LinuxCNC, what for someone without experience is a little bit complicated, and I still need to learn more about part origin, machine origin, tool compensation, etc… Also, i must to customize with the tools I have, my drills, diameter, lenghts, etc…

The learning process in a CNC machine, as in all kind of projects, must have an order: first easy things, and after more and more complicated. I started learning to move axis in a manual way. In the Manual Control tab of LinuxCNC, I can control the movement with keyboards arrows and setting up the velocity in mm/min. Up to here, all in order. It moves as it must, and the dimensions are correct (I already set up the motors in the program, selecting the frequency, maximum velocity, etc.. as well as the enter and exit pins of the motors and limit sensors)

Next step is to import the G-Code I’ve generated, and that my CNC do what I want. I drew my name in CATIA, and programmed it to keep the letters lines. Up to here, easy. I generated the G-Code and import the txt to the Linux. Previously I installed a pen where the tool should be.

Now comes the good thing: The piece has an origin, that the program puts in the machine origin. I will explain. The LinuxCNC generate a volume that belongs to the working volume that I already defined. In one corner is the machine origin, and LinuxCNC place the part origin over this point. That can generate a problem: If when we draw the piece we place the stock’s corner just in this origin, there will be for sure some tool paths that will go out from the working volume, and LinuxCNC will identify this as an error. But there is an appropiate tool that consist in move the part and the part origin in the three axis where we want. But this must be done with the center of the tool just in the origin, if not, the displacement will be cumulative .

Taking this in account, we can keep drawing the pieces and put the origin in the correct points. Next, we must to have clear the compensation tool concept. We must to fill the tool table in the LinuxCNC, at least the tool number, diameter and the most important, the lenght. Of course, the number in this table must be the same than we set up in CATIA.

When we execute the program, we will execute the G43 code, that basically will do the next: read the tool table, and according the tool number after the G43, will apply the compensation according the lenght we wrote. It cost me a lot of time to have clear, but when i realised of how it works, i knew it was something fundamental.

With all this concepts learned, in an autodidact way, i was able to draw with my machine. I’ve uploaded the next video where you can see the results (I’m proud of this moment!!)

Continue with Step 20: First machinings