o I had to make some changes to the frame design. Not because of any design problems, but because there was a bunch of steel section in the scrap bin that was looking for a home.
Overall the new frame dimensionally the same as before, but now constructed from 25x25mm box. As the SBR16 rails have a 40mm mounting plate, I'm going to run two legnths of 25mm box along two sides.
The steel is all cut to size(ish, must learn to use saws better…) and ready to be welded. Was hoping to get that done today, but ran out of time. I've never welded anything before, so I did get a chance to do some practice welds today and it went pretty well!
I've also cut two 600mm lengths for the grantry, and made two feet out of 50x25mm section (the only bit of it lying around I could steel). I've drilled the holes for mounting to the SBR16UU bearing blocks, and I'll weld the legs onto the feet when I do the rest of the frame.
Current thinking is to use a bolt-on system for the gantry, so that it can be adjusted for squareness once all the other bits are in place. Not sure if this is a good idea or not yet.
Been looking at these bad boys and after some comments from a lovely chap called Kert (and not Ken as I original misread his name as!) over on Hackaday.io I reckon the mass of the gantry isn't going to be too much of a worry.
A bit stuck here. I love the price of the TB6600 drivers on ebay (around £11 per axis), but getting not so encouraging reports on their quality. There seems to be a few different board designs, though, so hopefully some more research will reveal one of them that works as advertised
The next option I've found is about 3x the price, using the CW4056 (or something like that) drivers. More thought/research needed.
Slower progress than I'd hoped, but still progress.