CNC - Some new ideas, a plan, disaster!
Today’s plan was to get a number of test items, and start using them to test actually milling. This would be awesome - see some actual routing done.
I went into town, and bought a few items. But first my ideas…
I decided that at some point it will seem cumbersome to keep the point to point wiring I’ve set up for the Arduino GRBL ports to the system. My initial idea is to take a protoboard, and solder a DB25 + appropriate connections on it.
The Camera Plan
I have a mad idea that I could use a simple web cam mounted rigidly onto the Z gantry to seek some fiducial marks - a simple concentric circle pattern with a cross or something to indicate a few things.
First - one type to indicate a position on the bed, and secondary to indicate a position on the job. This way, homing/centring could be done using these.
This would mean some kind of PC or rPi based tool to seek the fiducials by reading the camera, and stream relative gcode to grbl to get it lined up. It could then hand control to a standard gcode streamer tool instead to start a job.
Even better - if the fiducials could be made so on a pcb it went all the way through, the board could be flipped and lined up again on the other side - perhaps giving the precision to do double sided and through holes/vias without trouble.
I bought myself a bag of balsa bits and some sheets of foamcore from the Hobbycraft. They had other woods, no plastics - but this would be a start.
At the local maplin, I got a cheap USB webcam, some heavy duty cable ties to strap it on, an arduino protoshield, a DB25 connector, some single sided, and double sided copper clad board.
I won’t use it all in one session - but clearly enough to have fun with.
I started with a balsa block.
The first thing was to select the right kind of tooling - the CnC documentation suggested a fluted bit for wood, although it may be overkill for the balsa.
Attaching the bit was a little tricky - but I got that attached. The next thing (and I’ve done this in the wrong order) was clamping it…
I had a bit of trouble clamping the piece to the T-Slots of the machine. The nuts supplied did not fit at all in the T slots - they couldn’t be slid in. I used the plates slotted around to hold the part firmly - but I will have to find some T-slot nuts of better fit or quality to replace those in the box.
I positioned the spindle manually over the job, then connected it up to the computer, powered it up and started the gcode streamer. I loaded the file ready to send. I was going to use the circle test I had yesterday - and let it cut a small circle out of the balsa.
I powered up the spindle - leaving it on the lowest setting, and then it stopped turning at all. Then smoke - the horrible smell of burning electronics.
Disconnect the PC, then the power and turn it all off. Somehow the spindle had blown something - perhaps the slow speed means it wasn’t turning and was current shunting. It had blown a fuse in the main board, and replacing that still didn’t get the spindle going. The steppers and their controllers seem fine.
I now need some other way to control the spindle - or to replace that power board. Time to take a little break and think - I can always solder together that shield too.
Next step may be to test which part in the spindle speed controller is damaged - and replace that. My likely candidate is the FET.