Thanks! Got it on the frame. Makes absolute sense! :) I was already designing some jigs in my head to keep weld distortion under control. Now I can probably ditch those.
But with the Y. I basically just copied some designs I found here and there and I don't really have any more ideas. :(
Tips to help with stress relieving are Stitch weld and balance the welds IE: If you weld for half inch on outside face of steel box then immediately weld half inch on inside face opposite to keep balanced stress's. Don't weld all of one side up then turn over and do other, Also Don't weld in one spot for long but Move around and try to weld with minimum heat.
I noticed your Z axis plates look on the thin side what thickness did you have in mind.? For the front and rear Z axis plates I wouldn't go less than 15mm and 20mm is best balance of strength and cost.
Last edited by JAZZCNC; 17-09-2013 at 02:37 PM.
I make my living with welding and have big strong (200ton tested) jigs I could use and know how to hold weld distortion to minimum :)
But still I like your idea for the bed more. The massive amount of steel I designed there was in a hope that I could maybe use 15mm ali bed and stop excessive movements with the frame underneath.
So with the Y you basically suggest a structure shaped like a PFC?
Z axis plates? You mean the plate where the spindle and Z axis rails mount to? It is intended to be 20mm. At least in my head, have to check the drawing tho :)
Last edited by JAZZCNC; 17-09-2013 at 05:31 PM. Reason: Spell checker screwing me.!!
Ok, I updated the drawing a bit.
Did the "PFC mod", tho, now I have to fit the Y ballscrew somehow between the gantry and Z I suppose, so this is still going to change a bit.
Redesigned the bed a bit also. Didn't save any steel tho :)
Decided to have the extra steelwork under the bed just in case. Who knows, maybe I'll mill myself an engine block :)
Now the bits that could introduce side distortion are in one piece and there's a box everywhere under the edge of cutting area.
Left the green 30x30 bits in place. If I decide to have the bed only as big as the cutting area, these will help to mount "cutting fluid collection / mess containment solution"
I plan to cover the sides (and the edges then) with plywood or mdf or 1mm mild steel or something similar.
Now, couple other questions have risen as well.
First, on this picture below theres a 15x60mm riser plate under the gantry. I was wondering if it might be worth extending it and put the X ball screw mount straight to it instead of the gantry endplate?
Secondly. At the moment my Z rails are spaced 75mm apart, is this going to be enough or should I widen it?
I must thank anyone yet again for feedback. And for this forum in general! Amazing source of information!
Take some time to think about ballscrew alignment because little adjustments can make a big difference to performance and it doesn't take much to go from working fine to stalling motors, esp at higher speeds. So anything you do to make alignment easier you'll be thankful for when setting up.
Anyway here's my take and way of doing it. The Z axis width or space between rails and bearings doesn't matter so long has you can fit everything like ballscrew between them. So you can make it just the minimum width if you like.!! . . . . What far more important is the bearing spacing on the Y axis and the more(within reason) you have the better it will be, obviously this comes at the cost of cutting width so it's a balancing act and personally I won't go any less than 200mm with 300mm being better. I tend to make my Z axis width 180mm or minimum 160mm.
I only ever really use profiled rails/bearings if can help it and these are much stronger so can get away with 200mm but if using round type rail I'd be looking for more.
I've also noticed you have the X axis bearing spacing very close together.? Same applys here has well but not quite the same with you running twin drive but I'd still try and get the widest foot print you can afford, even if it means extending the top rails past the ends slightly.!
Ive tried to design most of the precision critical components with oval holes and left provisions for shims here and there.
Here's a picture of the new "PFC" to explain the "apart bit."
Tho I just realized that the number "75" should be actually 100. So many errors. Embarrassing....
So I gather that would be fine?
For bearing spacing on X and Y I do agree, tried to save some cash there but I'll increase it from 150 to 250.
Or would it be any good if I leave the bottom bearings on the gantry with 150 (or 200) spacing and do the top one say 300? (just to get the cutting area that little bit bigger?
Am I looking for the right things?
100% genuine original HIWIN BRAND Linear Guide1lot 2pcs HGR15 L=400mm rail with 4pcs HGH15CA carriage-in Linear Guides from Industry & Business on Aliexpress.com
If so, I'll redesign everything for profile rails!
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