Add-on CNC build log

[bikepete]

On reflection I'm going with the original design (double beams at the bottom) but I'd better do it properly with epoxy between the main joints. I'll see if I can machine the surfaces where the column intersects the base beams to a tight sliding fit, too - when clamped this should lock up solid.

Not much else new, still cleaning up the ends of the beams, takes a while for each cut:


And sorted out cable entry to the Z stepper: small diecast box off ebay with a rather crude cable clamp bolted on and a hole drilled in its bottom face for the motor cables, then epoxied onto the stepper:


I used 0.75mm^2, four core SY cable for this - motor is stationary on this axis so won't be flexing repetitively (CY cable usually preferred for that). I know 1.5 mm^2 is usually recommended for stepper wiring but that's getting a bit fat to go into the XLR plugs neatly. Using this calculator: ePanorama.net | Audio | Video | Circuits | Electronics Design and assuming 5A current max and 2m length max (will be shorter) gives under half a volt dropped due to cable resistance... acceptable I think, and they also say 0.75 is good for 6A in instrument cables.

Pleased with the cable labelling at the plug end - printed text onto self-adhesive mailing labels on the laser printer, cut to size and wrapped round the cable. Then protect with 1/2" heat-shrink tubing. Works a treat: