Kit's Machine

[Kitwn]

When I built my first Heath Robinson machine the choice of controlling software seemed to be between MACH3 which almost everybody was using and LinuxCNC which was free. I went with LinuxCNC running on an old Windows XP era machine built from the best bits from a couple of dust-gatherers I obtained for $20 the lot by advertising on our local ‘Buy-Sell-Swop’ group on facebook. This is still working well.
The original $25 Chinese breakout board is still working though I did have some fun with noise pickup when changing from using mechanical microswitches to proximity switches for limits and homing. That fun and games is documented elsewhere on the forum.
Four 1.9Nm stepper motors and DM452T digital drivers from Stepperonline provide the motive power. These are way superior to the TB6600 based drivers I originally used, the motors being much quieter and cooler in operation.
Power comes from a pair of 36V 10A switch mode supplies, one for the two X axis motors and one for Y and Z. I have had no problem with SM supplies as long as the rated current is well above the total peak current required by the motor drivers. If I were starting again I’d use a higher voltage linear PSU and drivers to suit but I can still rapid at 9m/min with this arrangement.
The electronics is mounted on an MDF baseboard housed in an old PC case. It isn’t exactly pretty but functions just as well as a more expensive, professional looking box costing more than a case (or two) of fine Western Australian Shiraz. 5V for the BoB and 12V for fans is provided by the original PC power supply.
The VFD for the 2.2Kw water cooled spindle is mounted on the wall rather than in the box. Partly because the box isn’t big enough but also because I know from professional experience that poor cooling airflow is death to solid state power electronics so I wanted it where it can breathe freely.
Water cooling for the spindle is provided by a tub full of about 15l of distilled water with a 240V submersible aquarium pump.

[Doddy]

5V for the BoB and 12V for fans is provided by the original PC power supply.

Kit, you're one person on here that I really wouldn't want to teach how to suck an egg. But that picture of your BoB - firstly addresses on solution that crossed my mind - you're trying to smooth the supply to the BoB with that cap hanging off the PSU (I would suggest a low esr cap in parallel with the floating electrolytic - but there'll be enough of that on the board anyway)... so that's all good. But, the one thing that does worry me is I can't see any isolation on the BoB (in the form of opto-isolators). It could be a different package that I'm used to - but the geographic positioning of devices on the board doesn't appear to support that. You say you're using relays on the inputs - I can't see the detail of this in the figure, but assume you're using a NC or NO contact?, hopefully you have it that in the non-triggered state the input is hard-tied to ground? (i.e. not floating?). Have you the connectivity to use a C/O contact between 0V and 5V, so the inputs are hard-tied in both states? Also, I've experienced so much crap with proxy diagnosis of noise on BoB inputs that I wouldn't now entertain any without opto-isolated inputs. Not for the galvanic isolation, but simply it's good to have a device that needs proper current flowing to switch, rather than the usual HCT high-impendance inputs. From the UK I'd be throwing 6 quid at China for a cheap replacement BoB to trial.

Again - I'm confident you know what you're doing, and you sound like you're addressing this top-down with removing noise from source, just worth conisidering going bottom-up and looking at the noise susceptibility on the signalling to the PC.

UCCNC, btw, is the way forward :)