Building a new table, any tips?...

[davek0974]

Got the steel cut today...

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Ends squared up and deburred, also cut,drilled and tapped the mount plates for the motion frame and the insert plates for the cross-beams. All ready for a welding session now.

I'm fitting castors and screw-down feet so I can move it about and level it up when assembled.

While I'm gathering info, extraction....

On my little table I built an air-box that sits along the front of the table between the now unused water tray and the slats...

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In the front i cut a slot with an area bigger than the pipe cross-section and also slightly tapered towards the middle in an effort to even out the air flow. It works well as long as the unused parts of the table are covered - i get no muck in the shop at all.

It's connected to this radial blower...

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I know I can get more out of it by dumping the corrugated pipe and fitting solid duct but it's not going to do a table with an area four times as big.

I don't have any spare power capacity so simply sticking a big-ass blower in there won't do it, need to get smart here. I could maybe run two of these blowers, they are pretty cheap to buy and with external motors they are immune to metallic hot muck.

I had thought about a zoned system - a four zone would work ok with the same blower. Question is, how would I do it???

Any smart ideas on extract??

Don't want water - its only half as effective and makes the machinery in the shop rust.

[davek0974]

Welded the end plates into the cross-beams...

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The leg joint plates onto the main beams...

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And the foot plates onto the legs...

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Fairly confident in the welds, did a quick destruction test on scrap first, nice and hot concentrating on the thicker parts and washing into the 2mm tube. Joints are ground flush now. Casters will be added soon, to the side of the feet, the feet can be screwed down to lift it off the wheels.

[SeanP]

Looking good Dave, nothing wrong with those welds, out of curiosity what mig welder do you have? Mine has packed in so its research time for me now.

[davek0974]

Its an R-Tech I-Mig 160, had it a few years now, nice machine, i have their Tig too but can't pick it up via self-teach, might need to do some evening classes on that one one day.

Ran out of gas of course got some C02 in the garage but prefer the hobby-weld mix.

[SeanP]

Thanks, same here with the Rtech tig I like that , will have a good look at there mig machines.
I like tacking up with the tig for a lot of jobs then mig welding.
You can learn a lot from Jody's welding tips and tricks videos he is a great teacher, it does take a fair bit more practice than mig I must admit, I have had a 30yr break from tig and it's taken a bit to get back into, it doesn't help when the eyes aren't what they used to be

[davek0974]

I only bought it for stitching stainless bits for the garden together, I try again every now and then but seem to struggle keeping a tight arc, usually end up either dipping it or just welding it to the work

I think what it needs is a second set of skilled eyes watching and saying 'stop, try this' or 'your'e going too slow/fast' etc. I was running a few beads then posting on the 'net and waiting for replies, gets frustrating really quick.

Have tried steel, ally and a bit of stainless, results vary from wow! did i do that? to WTF?

[davek0974]

Some scale drawings of a gantry end plate, I'm exploring ways of adding rigidity by adding strengthening ribs in strategic places. There would be two ribs for the beam, 50mm apart with boxing at two points as shown. The outer ribs would be inline with the two gusset plates on the inside.

GP1.jpg

The same idea but lighter and my guess is just as rigid.

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[SeanP]

Either of those look good Dave,,,you had better get some practice in with that tig welder

[davek0974]

Nah, I'm sticking with my trusty Mig on this one, I really need some tuition on the Tig I think, I tried self-teach but without some direct help I was just blowing gas and rods and getting frustrated.

[davek0974]

Started welding up the frame, the beam nearest the front is the motion support frame and is bolted to the legs, I'm using it for spacing and measuring here.

Plan is to weld the side legs into two frames then weld in the cross-beams to make it a box frame.

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Also got the castors on the legs.

[davek0974]

Got two welded side frames - standing side by side, there is no visible warp, I'm pretty chuffed with that as it was a concern. I levelled the frames between the bench and sawhorse using a spirit level wedged them up, shimmed the bolting points between frame and top beams then tacked the outer and inner faces, seam welded the lower and upper faces fully, then seam welded the outer face, inner face is left tacked as there is a cross-bream to go in.

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Its a bit bigger than my existing one Looks good though.

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Upon assembly i realised i could not weld in the lower cross-beams as planned, I'm not really up to vertical mig yet, cannot get it on the bench, and the underside welds could not be done at all. Answer - make some more bolt fitments out of 10x50mm bar, weld them on and bolt the lower cross-beams in, this will make disassembly easy too.

[davek0974]

Had a quick mess about with the Tig, i was semi impressed but seems a lot hotter, probably moving too slow?

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I'll stick with the Mig


Got the lower cross-beams fitted, then after a few tests it seems that a good way to fix my spacer/support strip was to use good ole pop-rivets, worked nicely. Also managed to get one of the racks fitted.

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[davek0974]

Ordered myself a new z-axis from Marchant-Dice, same as the existing one, also ordered a new motor and drive module for it plus a short length of wide HiWin rail and a carriage.

That lot should go together and form a new z-zxis with floating head, the existing one is ok but this means i can improve on it and also make the transition easier, all i need to remove from the old machine is the CandCNC MTA board, Axis control board and the THC controller.

I'll sell the old one off as either parts or complete assembly.

[davek0974]

Ok, linear rail came today

Using a taught line to check my beams, I have a slight bow in both sides, as you look at the table they would bow towards each other at the centre, the amount is about 1 to 1.5mm on each side so thats pretty bad and would give me a 3mm variation from centre of motion to either end.

Question is - how best to tackle this????

[acourtjester]

Well when I built my table I had a rectangle base that was welded up on a rotisserie. And when I was ready to weld on the rails I welded it at the 2 ends for each rails to the base and then check the rails. I was able to use a screw jack to push the rail out and then welded each center to the base now the rails are straight and parallel.

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[davek0974]

Nice, I can see how that would work.

Unfortunately, I could not weld up in one piece, not enough space etc. I have opted for a frame/chassis with the motion section bolted on at four points, the idea was that there was no risk of weld distortion, i could shim the mounts for level and it would make assembly/moving easier.

I'll continue as-is, then add a spreader bar or maybe use the middle slat support as a spreader, 3mm should be ok to remove.

I can mount a dial indicator on a long arm, one side mounted on a rail carriage and the other reading off the opposite rail, then adjust and stretch as needed.

[davek0974]

Got the Y axis motion fitted and the gantry supports tacked up.

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Even without the beam fitted the side supports are very rigid, most encouraging.

[SeanP]

That sounds good Dave.
Is it direct drive? will you get 1'' of movement to 1 turn of the motor? I think Tom says that's the right ratio.

[davek0974]

No, can't be done direct - pinion would be too small.

This is 47mm per turn, micro stepping should give the desired resolution.

If not then it is pretty simple to fit 3:1 reduction drives.

The idea was to see if it works, there are a few production machines that are direct drive.

[SeanP]

Ah ignore me Dave you sound like you have it well sussed out

[tcaudle]

Microstepping does not increase resolution. It increases smoothness. It actually decreases torque some. That is why most stepper drivers do step morphing that switches to full step above about 100 RPM. Those that quote the table resolution as that of microstepping should note that number and state that is at slow velocities. Your goal is acceleration not jaw dropping rapids.

[davek0974]

Ok thanks Tom,

So i have a resolution of 0.235mm/step.

As i said, fitting a reduction drive would be easy as the design leaves the rack and side plates fairly open in that area.

It will be interesting to see what really happens and if i can hit my speed of 9000mm/min and with decent acceleration, i have read that 1/10 of the speed should work so 900mm/s/s will be my first effort.

[davek0974]

Got the gantry supports welded up - very little distortion which was great, impressed myself with that one

One thing I can now say is, that gantry beam is damn rigid, i put a dial indicator between the gantry and side beam and it's practically a solid object

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Also got the X axis and THC mount welded up, came out nicely.

One question - I had to move the x motor rearwards, placing the rack on the back face of the beam - no biggy but, I had forgotten the rack bolts go across the rack face so are now screwing into nothing. Should i fit some short support angles like 10x20x4mm 100mm long and welded to the beam, and then mount the rack to them????

Or something better???

[SeanP]

Looking good Dave, I like the look of your rail on the gantry nice and deep,,,good choice.
Some use the double sided tape for the rack, might be a good way for yours?

[davek0974]

is that the ultra high bond stuff?
i wasn't sure if it really worked, might get some and try it.

yes the carriage rail is stupidly rigid, i could easily have used one Hiwin truck, oh well