I just try to keep the overall weight balanced on the X bearings. Mostly It's just balancing act between losing or gaining cutting area.
Last edited by JAZZCNC; 07-08-2013 at 08:29 PM.
I'm looking for more local sources for materials. I have a good local steel yard 5 miles up the road that i've used several times before - so am happy to use them for the framework, but their aluminium stock is low, a bit battered & unreliable.
I've found that there's a branch of Blackburns Metals not too far from where I work - does anyone have any experience with them as a supplier for aluminium?...quality & prices ok?
No experience with Blackburns but if you haven't got a milling machine to surface standard plate then who ever you use I recommend you buy ground flat plate for key areas like Z axis and bearing plates. . . . It's more money but worth the expense because standard plate is never flat, it may look flat but it's not.!! So for critical areas like Z axis and bearing plates where surfaces must be flat and parallel to each other they must be surfaced flat.
I have the capability to surface plate and still I buy ground plate for these areas has it saves me hassle and time and even careful milling can't match ground surface quality.
Even Round rail which is very tolerant of bearing/rail miss alignment will bind and stick if plate is slightly cupped, less than 1mm cup, bow or twist over 300mm bearing plate length will be enough to totally lock the bearings when fastened to plate. Normal rolled plate can have that much error and I've seen plenty folks fall foul of this and corrected several bearing plates for people because of this.
If you can't get it from Blackburns then I suggest aluminium ware house because they cut to size and you can order just slightly larger than you need for those areas. Your Looking for ECOCAST at AW it's here. Aluminium Plate - Cut to Order - Aluminium Supplier | Aluminium Stock | Aluminium Warehouse
PS: For rest of plates like motor mounts and even gantry sides etc then normal plate is fine, if you have decent metal scrap yard near by it's worth checking them out has often they have offcuts etc from industry and some can be large and quality, most just charge scrap value.
Last edited by JAZZCNC; 10-08-2013 at 09:11 AM.
At the moment I was thinking more for the less important parts - motor mounts etc as it will make life a lot easier having a reliable local source that I can nip into to get the occasional piece without any postage costs.
I've seen AW mentioned in several build logs & have them bookmarked already when it comes to the important parts. It seems the narrowest width for the Ecocast is 100mm which may well make a design decision or 2 for me as well...although this could be an issue when it comes to mounting the Y rails on top/bottom of the gantry?
I assume that 5mm Ecocast will be ok for the rails to mount to?
I think steel is an excellent idea, so is a stick welder, but I would still like to take this opportunity to screw up your whole design at the last moment because that is what I do best
When a weld cools it solidifies then shrinks. The shrinking bends everything out of shape with no possibility of correcting it. If you are a novice welder your welds are unlikely to be drop dead gorgeous and the effect is amplified.
Meaning you end up with a framework that is wildly out of square, it fills half the workshop, is tricky to get it out the door and take it up the dump.
If you are fiendishly clever you can try to pull everything square by welding in cross braces after the event and hold the thing in tension.
If however you plan ahead and weld plates bearing bolt holes to your bars you have a chance to straighten things up after everything has cooled down. A round file can move a bolt hole, an angle grinder can square up a face, packing can be tack welded in place.
Easy to find out for yourself. Saw a piece of box section in half, weld it back together, see how straight it is.
He's partly correct about heat and cooling, shrinking but if done correctly like I said short welds spread around it can be minimised enough to be fine. The wildly out of square comment just means he's been doing it wrong. .
The squareness of the frame isn't critical, yes it's got to be close but 1-3mm or so out won't hurt.! And if welded has mentioned it won't warp or twist anywhere near that amount.
It's the rails that matter and these MUST be square and parallel to each other and on the same plane.
To help your self with this on the Long axis, which I call X it pays not to weld the top rail but bolt it to flat plates. If there's any error then you can shim into plane and move parallel and square to each other very easily.
Then there are other little tricks for dealing with things like the top plates rails sit on arn't flat etc. Putting Epoxy putty between rail and plate creates a lovely surface and give enough time shim square etc and then when dry you have perfect surface and it's also helps dampen resonance.!!. . . . There I've give one of my tricks away. . Dam.
I do this all the time so believe me it's not difficult so don't let comments like "Victor" Robin "Meldrew" put you off welding because it's by far the Cheapest and strongest way to build a machine.
Edit: Better elaborate on the Epoxy comment.!! . . . You must put piece of cling film or thin plastic between top rail and putty other wise you'll stick the buggers together and never get them off. . . . . .Oh and it's not expensive. 125g packs for £2 and it goes fair way has your only spreading thin, 2-3 tubes will do full machine.
Last edited by JAZZCNC; 10-08-2013 at 11:13 AM.
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