Reading more and more post I find my self thinking o's##T what have I let my self in for
I really thought 20 mm rails for the bed would be more than ample to carry the weight of the whole cnc machine
two 20 mm rails (made from 304 stainless steel) and four bearings mounted on the 90 degree side of 40/80 profile aluminium extrusion
and a centre ball screw (centre of the bed) 0f 16 to 20 threaded bar
where on earth do you all get your aluminium from as I have ordered of ebay, it arrived today so bent it is unusable
James & Luke
The reason I advised using the bigger bearings is not directly due to the higher load ratings. It it because they have 5 rows of ball bearings, not 4. This seems to make them have a lot less play than the <=20mm bearings. So I'm not saying you have to get the 25mm bearings, just that it will probably be better if you do.
Only issue with them is you have to buy 2000mm lengths. If there's something smaller you need let me know as I might have a bit...
What size did you buy out of interest, and who from so I don't make the same mistake?
So here's a video showing my router doing 1000mm/s (2362ipm) on the Y-axis:
All I did was change the pulley to 42T so the pitch of the screw is effectively 35mm. It's well above the critical speed of the screw, but interestingly it seems fine.
The video also shows the rotating ballnuts going happily at 15000mm/min.
Last edited by Jonathan; 15-09-2011 at 06:24 PM.
Jonathan what have you used on your Y axis, I can't quite make it out
The first of many upgrades to come:
I'll be fixing 20 meters of 2"x1/2" aluminium strip under the bed in a grid to make it a bit stronger, since it's only 20mm thick aluminium. I've got 6m of the aluminium angle to go round the perimeter to enclose flood coolant, which will be the next upgrade. I'll have the router drill an array of holes to tap M8 for clamping. I elected not to go for strips (to imitate T-slots) as the difference in price is not that great in the whole scheme of things and this should be stronger although either would have been sufficient. Need to get it at the right height too...
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