It was so long ago I can't remember, or find, if I posted a build log for the initial CNC conversion of my milling machine. All I did was made some quick stepper motor mounts for the existing ACME screws and quill feed. It works, but clearly it's not ideal and has plenty of backlash, so time to add some ballscrews and eliminate the backlash using the usual system of two nuts and disc springs.
I've done Y, should get a bit more travel than the original 145mm (or actually 141mm because the original was assembled incorrectly):
That's the old motor mount - I need to replace it with something stronger that doesn't look like a grandfather clock. I've left it like that for now so I can use the Y-axis, as it's tricky to make parts with only one axis working...
I've machined the ballscrew for the X-axis, threads on both ends so I can tension it between angular contact bearings. Long bit for the pulley and room for a dial so I can still use it manually. Annoyingly I accidentally dug the tool where the bearing goes, but it's a good fit so it's only aesthetic damage.
Here's the ballnut mount for X, which is the same system as Y, so two nuts and a belleville washer to preload one of them against the other and eliminate the backlash:
Things to do:
Acquire and machine Y ballscrew so it's the right length.
Mill a bit more off the X ballnut mount to get it closer to clearing the table.
Decide how to take 1-2mm off the underside of the ends of the table to clear the ballnut mount. CNC router might do it, if not I guess I need to get an angle grinder.
Make bearing and motor mounts for X.
Make everything for Z.
Here's some pictures of the quill:
The front face is machined, albeit roughly, so looks like I'll be able to use that to mount the Z-ballscrew...
If you want an angle grinder give me a shout ..Clive
Aldi have some in £18 each, picked a couple up today.
Mind you if you want it milling off give me a shout.
Last edited by John S; 07-09-2013 at 10:41 PM.John S -
Thanks for the offers. Turns out my CNC Router is happy enough cutting cast iron so I'm just using that now. I'm using a 6mm single flute cutter, as they take about 5 mins to regrind if it's damaged. I've set it to 1mm doc, 70% stepover, 250mm/min at 4000rpm and it seems fine. Going to take an hour to take 3mm off both ends of the bed, which isn't too bad.
I've made the motor and bearing mounts for the X-axis, so once this bed is milled it should all fit together...
Last edited by Jonathan; 21-09-2013 at 02:47 PM.
I've assembled the X-axis now:
Unfortunately I'm still waiting for the pulleys to arrive, so I've temporarily put some spare XL pulleys I had lying around on it. Since using the pulleys I had means the bigger pulley had to go on the motor, it's currently 30:14 ratio so it'll currently go silly fast - over 10m/min!
Oddly there's still 0.02mm (0.0008") of backlash... not sure what's causing it yet, I'm hoping it's just the pulleys so I'll look into it further when I've got the new ones.
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