Z axis error woes

[HankMcSpank]

Talk about a bad run of luck ....first Z woes - I replaced the stepper board which sorted this aspect ...but then Y axis woes, which I had thought was down to bad A3977 IC holder missing steps ...swapped out the IC holders which was no mean feat...these Allegro A3977 IC holders are QFP44 & soldered in on both sides of the board ......top tip- use bismuth rich solder - I bought some here a couple of years a go http://www.carnmetl.demon.co.uk/ (he makes it manually himself!) ...this type of solder stays molten long enough to flood all 44 pins - also I put a hot air gun perched above to help keep it molten... yank out the IC holder then clean up the pads with copper braid & liquid flux (consider this method a cheapskates hot air rework station!)

But after swapping out the IC holder, my Y axis was *still* missing steps! Seriously, I was getting zany 'all over the shop' results when moving back/forth 5mm on the Y axis.

The cause?

The grub screws on the motor coupling weren't quite tight enough ...which meant the Y stepper motor was occasionally slipping vs driving the leadscrew (which I guess is a mechanical version of 'missing steps'!) ....after tightening it up, now I've got superb repeatability at least (as measured on a dial gauge)

So a warning - if you buy/own a Sabel 2015 or Panther 2015 (same machine...there are a few variants out there) ...make sure all the motor coupling grub screws are nice & tight...prefereably with thread lock applied!

Also I've now got rid of my Chinese TB6560 board ...so finally feel that the my CNC demons - for now - have been exorcised!