First time build - Steel Frame CNC Router

[Davek0974]

Mig? Arc? Tig? What sort of welding?

Yes, always tack up first, when choosing where to weld, always think of contraction - the two sides of whatever you weld WILL be drawn together as the weld cools, no two ways about it, it will happen.

On a box frame I would tack up and check all square, then weld the inside 90 deg angle on opposing corners first. Next I would do the outside edges followed by the two faces. Welding the inner/outer sides first should help resist the tendency of the frame to buckle if the faces are welded first.

Test your settings well on scraps first.

[Davek0974]

Stitch welding is fine, in the right place - if you were welding a plate to the side of a box structure or maybe a corner fillet plate inside the legs, I would stitch, maybe 1" runs. For something like box section legs then seam welding is in.

Think of the stresses the part will encounter, it will help decide how to weld it.

[examorph]

Thanks Davek, I will be using a Mig welder for this. Should have the steel in this week and welding started this weekend.
Will tack up the entire frame and gantry assembly first and check if its all square, once OK I will fully weld/stitch where needed whilst baring in mind contraction.

Is epoxy leveling recommended for a build this size?

[Davek0974]

The chances of it being square when done are slim, treat it as sections and concentrate on getting each section as perfect as possible, whatever method you use there should be a method of tweaking the fit later - my plasma table is 1500 square, it is made up of two side frames bolted together with cross-tubes - i could shim the joints as needed which wasn't in the end but handy still.

The plasma was built in 2mm box section but carefully braced where needed to gain rigidity. I used about 21v / 140A and 0.8mm wire with a tri-mix gas (hobbyweld5) you need to get hot and fast, don't run the power low because it might warp.

Cant help with epoxy, never used it I'm afraid.

[examorph]

Hi guys, came home to find that the linear components had arrived today!! Woohoo

Attachment 17739Attachment 17740Attachment 17741Attachment 17742Attachment 17743

Seems to be great quality and Fred was a great help, excellent service and I understand now what you all mean by him being a great guy. Will keep these to a side until I get the epoxy and aluminium sorted. Blackburns offered 5754 as the nearest grade to MIC6 and quoted me £85 for 500 x 500 x 20 plate, is 5754 a suitable grade?

Also, steel arrived earlier this week so will be welding this weekend and hopefully have a frame/gantry setup soon.

[examorph]

Steel box section and plate had arrived earlier on in the week:
Attachment 17758Attachment 17757
Ended up buying a tungsten carbide blade for £80 to cut this as 5 of the 6 local suppliers I visited advised that the machine had a "non-standard" 25.4mm shaft.
Seemed to work fine the first day but when trying to cut the box section the next day, it seemed to require a lot more time/force, I think I may be cutting too fast and wearing out the blade.
Attachment 17759
Ended up with a bit extra 100x50 section and too little 50x50 section, I underestimated how much box section it would require and assumed I had more than enough at 7.5m of each. Guess its true what they say about assuming!! Requested price for 1m more of each and changed the design slightly to use the larger box section for the horizontal bracing:
Attachment 17760
Other than the two sections I am ordering, all box section has been cut, but unsure if some of it is still good as I think maybe 3 sections (bed supports and gantry box section) are 3-5mm shorter than what I needed, will this be OK filling up with weld?
Attachment 17761
Was hoping to have it all welded up this week but ended up being a slow start with the few hick ups pushing things back a week
All in all, it was a good experience and even though I had some problems, I enjoyed it and learnt a lot of new things

Some questions I hope you guys could help me with please:

• From what I understand 5754 aluminium is the grade but if specified as tooling plate, would this be OK for use on the Z-Axis without having to face it off?
• As this machine will be moved 3 times (welded in workshop, epoxy leveled in a smaller room for heating and installed in a shed) is it worth welding some adjustable feet to the legs?

[Davek0974]

Hi
I don't think you will be able to bridge 5mm with weld, if you had say five joints you could maybe bridge 1mm on each, better to make the frame fit what you have now, or maybe weld in a 5mm spacer plate somewhere. Done properly this could work.

Yes machined aluminium tooling plate is very good and ideal to use as-is.
Yes, fit heavy adjustable feet, always useful, but not the weedy ones with M8 threads ;)

[njhussey]

Other than the two sections I am ordering, all box section has been cut, but unsure if some of it is still good as I think maybe 3 sections (bed supports and gantry box section) are 3-5mm shorter than what I needed, will this be OK filling up with weld?

You'll be putting a tremendous amount of heat into the steel if you try to fill it. Why don't you do as Dave says and put a spacer, or cut a bit more off and weld a plate onto each end?

Some questions I hope you guys could help me with please:

• From what I understand 5754 aluminium is the grade but if specified as tooling plate, would this be OK for use on the Z-Axis without having to face it off?

• Yes tooling plate is the thing to go for, needs no surfacing.
  
  

• As this machine will be moved 3 times (welded in workshop, epoxy leveled in a smaller room for heating and installed in a shed) is it worth welding some adjustable feet to the legs?

[examorph]

Thanks guys, will get some adjustable feet sorted (>=M12) and also cut out some 50x50x10mm steel plate to weld to the frame legs for this. Will also make adjustments where I can to reduce the 5mm gap on the steel box section.

njhussey - Thanks for spotting that. The clearance behind the plate is 10mm, think I could get away with using hex heads and tightening them up with a spanner?
Attachment 17769Attachment 17768

[examorph]

Been a nightmare finding a local supplier that does box section without a 7.5mtr minimum order charge, but got one eventually who can do me some off cuts at a 3mm wall for a good deal.

Will the 3mm wall thickness box section be OK for the bed support beams and horizontal supports shown below in green? Will it also be OK to weld?
Attachment 17786