Humble Beginnings - For Alu

[D.C.]

Yup that is the one.

If you are mounting a metal frame on top of two bits of what looks like wood... Don't.

Wood swells and expands depending on moisture content, the arrangement you have will warp the frame and throw your rails out of alignment. You also have your linear rails going over a joint. Don't do that either, unless you are going to take your frame to a big engineering shop and have the whole thing surface ground you will have zero chance of fitting the rails properly with that arrangement.

[Husky]

Ok, wood is out

Ah ok, good point about the rails! I'll shorten them back down.

[Husky]

Shortened the rails.
Changed the bed from being welded to bolted, not quite finished yet.
Changed the angles from box section to plate.
Added bolted gantry cross beams
Added bolts to attach gantry to rails. Had to enlarge box section on top of sliders to 60mm, 5mm wall.







I need to get round to sorting the materials. I have the box section all set to mild steel, but all the fixings and rails are just set to a generic high strength steel.

Current weight of what's on the screen ~55kg

[JAZZCNC]

Will there be more frame work to that base frame.? If not then then you'll need to be sure what ever it sits on is 100% flat and true other wise that frame will easily twist and put the rails on different planes.
Profiled linear rails don't tolerate twist (Or bend) very well and will bind to some degree. Doesn't take much to lock them up solid.!!

One other thing I see thru experience of mostly cutting Aluminium is that chips get fired every where and with this design the profiled rails are in direct firing line. They will act has stops and chips will collect building up in the profile of the rail. While the bearings will mostly push these out the way some of them will get thru and into the bearings, which over time will considerably reduce the bearings life. Over time It will also have an affect on finish quality because it will reduce the bearings smooth running causing notchyness that passes thru to the cutter.!

You could get away from this very easily with a slight design change to how gantry mounts to bearings.? Instead of using the short piece of Box section has riser then make that piece full length of the machine and mount directly onto the frame. Put the linear rails on this then mount the gantry to the bearings directly using a plate to replace the short box section.
The plate could be 20mm Ali or 10mm steel either would work ok. Personally I'd use Ali plate has welding thick to thin steel creates heat distortion and make the Triangle brackets out of Box section along with larger Triangle plates for strength. (see pic)

This one change will give several advantages other than moving the rails out of direct firing line.?
#1 Increase travel 100mm because rails can now go right to end of machine.
#2 Make aligning rails parallel and planner to each other easier by simply shimming or adjusting the Long piece of box section.
#3 Make gantry mounting and bolt access easier.
#4 Will be stronger and looks neater.
#5 Easy future height clearance upgrade if required by simply inserting another piece of box section or spacer between bed frame and linear rail box section.

Hope that helps.

[Husky]

Will there be more frame work to that base frame.?

Yeah, Originally I planned to lay it atop some massive ass bits of wood. But it seems that this is a bad idea... So I need to draw up some legs and cross braces etc for it now.

You could get away from this very easily with a slight design change to how gantry mounts to bearings.? Instead of using the short piece of Box section has riser then make that piece full length of the machine and mount directly onto the frame. Put the linear rails on this then mount the gantry to the bearings directly using a plate to replace the short box section.
The plate could be 20mm Ali or 10mm steel either would work ok. Personally I'd use Ali plate has welding thick to thin steel creates heat distortion and make the Triangle brackets out of Box section along with larger Triangle plates for strength. (see pic)

I had to read it a few times to get what you meant but figured it out in the end haha.



Thanks for the info, I'll get drawing! :)

[Husky]

Ok, drawings changed.

Added bolts etc
Changed gantry runners
Changed gantry sides

[Husky]

Well hello there people (yes oh dear it's actually been more than a year wow). So I got caught up in renovating my house (still doing) and lots of life things. I've been wanting to get back to this for so long now and I can't resist staying away any longer. I've just got to figure out where I was!

So I loaded up my old CAD files and gave this thread a re-read to try and get back in the swing of it. I prodded CAD for a bit and had a nosey round my design.

What I can see is a heck of a lot of bolts... What do you guys think about them? My thoughts are that they are a prime point for the frame to slip out of alignment, perhaps I should really just put them all down as welds? I think my initial idea was that bolting them would give me the ability to fine tune the angles and alignments when built to get them spot on, but a fresh look is making me think twice about it.

Secondly, chopping up and tapping all those aluminium blocks is going to be such a big task i may as well take it somewhere to get it precisely welded anyway.

Here's a picture (because we all love pictures) of the design as it stands, I made it all rusty to represent the year of neglect