1.7*0.74*0.4m Mill / Router building...

[Jonathan]

nice cnc you have there Jonathan are you going to paint it at some point ??

Thanks... it's not going to rust where it is so I don't think I'll paint it. It's there to make things not look at Paint would also get annoying if I need to add bits to it.

[luke11cnc]

Jonathan
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

[Jonathan]

I really thought 20 mm rails for the bed would be more than ample to carry the weight of the whole cnc machine

They will be ample to carry the weight since each of the 20mm bearings is rated for about 880N. That's not as excessive as it might seems though, see what I posted here:
http://www.mycncuk.com/forums/showth...near-bearings-...

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.

where on earth do you all get your aluminium from as I have ordered off ebay, it arrived today so bent it is unusable

I now use http://www.aluminiumwarehouse.co.uk/
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?

[Jonathan]

1000th post

So here's a video showing my router doing 1000mm/s (2362ipm) on the Y-axis:

http://www.youtube.com/watch?v=k3MG7...=youtube_gdata

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.

[Jonathan]

I had a request for some more photos, so here they are in no particular order:

[deannos]

Hi,
Jonathan what have you used on your Y axis, I can't quite make it out

[Jonathan]

Jonathan what have you used on your Y axis, I can't quite make it out

Which part in particular?
It uses an RM1610 ballcrew, 3Nm stepper motor...nothing unusual.

[deannos]

Which part in particular?
It uses an RM1610 ballcrew, 3Nm stepper motor...nothing unusual.

Your gantry in particular, is it ali box section

[Jonathan]

Your gantry in particular, is it ali box section

Yep:

I went to a small local metals supplier and picked up a meter of 80x3mm aluminium box section for the Y rails to mount on

It's mounted with 20mm aluminium plate milled to fit in both ends. It's adequate, but I would advise using something a bit stronger. Since the rails are on both sides of the box section it had to be aluminium since the width of steel box section is not accurate enough. Extrusion is a good option, but quite expensive.

[Jonathan]

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...