Friday, 31 August 2012

CNC drilling machine - testing everything

This is one of the most exciting blog posts for a while. After working on the CNC drilling machine as part of the BuildBrighton £50 CNC challenge for a few weeks, we're actually at the point of putting software, hardware, nc drill parsing and motor controller all together and actually trying to cut a PCB.

Actually, we don't have the drill part running yet - but this test shows actual movement, and we've used a laser dot in place of a drill head. But it shows a (sort-of) working CNC machine....


Instead of jumping in at the deep end and trying to draw a complex PCB (the printed pattern on the paper) we started off with a simple square. But as you can see from the video, we deliberately drew (and mounted) the square on an angle, to simulate mounting a PCB on the cutting bed on a wonky angle.

The software takes care of the rotation and follows the dots.
The first few seconds of the video show the machine being calibrated - the software prompts you to place the cutting head over a hole, record this location, then move the head to a second hole. This is what you see as the head travels diagonally across the board at the start (and the slight delay in the finer movement is us changing some parameters on the PC to reduce the jog step size).

The software then works out the cutting path (in this case, a simple down-across-up type pattern) and sets the motors spinning!

It's interesting to note that the cutting head doesn't necessarily follow the "lines" between the dots (if the dots were on the corners of a square for example), since it is a point-to-point machine, rather than a line follower. We'll try to demonstrate this more clearly in a later post.
But for now, sit back and enjoy our first CNC test.

It's not bad. It's not perfect - we need to take out any backlash in the gears (the motors themselves have quite a bit of "slop" on the spindle because of the internal gearing) to get greater accuracy but as an initial test - and particularly the handling of skewed boards - we're quite pleased with progress so far!

Next time we hope to actually cut (or maybe just draw felt-pen dots on) something.....