"Origami" CNC Plasma Build - folding 1200 x 600mm cut area

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27 Jun 2021 04:50 - 27 Jun 2021 04:56 #213001 by Joco
It's Sunday and after much looking, thinking and planning I took the welding plunge on the table frame. The long sections are 1320mm and the ends are 900mm (well really 899mm but close enough). So I welded them out all out then took a 60grit sanding pad and cleaned it all up with this result. And what's more, much to my delight its FLAT and checked square to around 0.5mm from what I can read off the tape measure.


Here is a little video where I test it with the hinge design. I think this could work quite well. Especially as I dial in the centre of gravity.


All in all feeling pretty pleased with the outcome to date.

Cheers - J.
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Last edit: 27 Jun 2021 04:56 by Joco.
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27 Jun 2021 06:45 #213004 by rodw
Pretty cool so far!

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28 Jun 2021 03:34 #213086 by Joco
A little bit of tapping and we have a hinged table top in perfect balance with gravity.  Been like that for hours, just sitting there.
LOL - what we do when we need a break from work/computer-screen.

 
 
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28 Jun 2021 10:09 #213115 by RNJFAB
Love it Joco.

Super creative solution to suit your needs.

I'm excited to see how this all goes. Not long and you will be making sparks.

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02 Jul 2021 23:13 - 02 Jul 2021 23:14 #213514 by Joco
A little bit of advice sought:  While I realise that plasma is a lot more tolerant on the accuracy front than other machines, just because it is not that a precise process. At least not the version of  the process we tend to be building. So, I am pondering the best order of construction:   linear rails v's water table.

(a) Do I get the linear rails on and reference their alignment to the top of the flip-table frame then move on to #B or
(b) Do I work on the water table and the slats, get that all created and into a mounting system inside the flip-table frame, looking to get as level/flat as possible then move to #A?

My concern is that once I have the linear rails in I then have to worry about getting the table top wll referenced to their plan. Where as it might easier to do the referencing the other way around.

BUT I plan to have a THCAD so in theory so long as nothing is binding up in motion and variances in the linear motion plane  against the water table tops plane would be accomodated by the continual adjustment of the THCAD.

Views on the correct order? Am I over thinking it again? Or some other method/approach I have not considered?

Thanks - James.

 
Last edit: 02 Jul 2021 23:14 by Joco.

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03 Jul 2021 00:37 #213526 by rodw
not much point getting too stressed about it until your slats are in. But in any case, the accuracy is not affected enough to bother with.
eg. If your table was 10mm higher at one end than the other, the dimensional error is  about 0.04mm and you can't really expect better than 0.1mm from plasma!

I would just get it moving for now and align it when the slats are in
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03 Jul 2021 04:22 #213533 by Joco
Thanks Rod.  So if I am reading you correctly either way is fine so long as take some time to do some alignment against which ever is the fixed reference and to not get too hung up accuracy cose its not (as I noted) that accurate. i.e. if you get 0.1mm on plasma you are doing well.

Cheers.

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03 Jul 2021 09:18 #213543 by RNJFAB
I faced this same issue. So I went with adjustable slat holders meaning I could align to my gantry once it was all together. I think I saw this on someone else build and thought 'that is a sweet way to overcome a problem'.

I made adjustable holders for the slats, that way I'm able to adjust/level all the slats as required (so far this has been twice). I have replaced the slats 3 times now. Each slat has a few lives, right way up, upside down, moved from high cut area to low cut area, ground flat, until they are completely trashed. Slats are 50x3mm steel. 

On my table I think I have 5mm difference across 1200mm. However, with the new Mesa 7i96 and thcad10 it's irrelivant as this negats the difference. For perspective last night I cut some alluminium that had been creased for strength, it had a rise and fall of 15mm every 200mm. The thc meant that I could cut this and the torch followed maintaining perfect cut height (honestly it still amazes me).  

forum.linuxcnc.org/show-your-stuff/42411...a-cnc?start=0#207451
Pictures 3 & 4 show the adjustable holders.
 
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03 Jul 2021 22:12 #213602 by BigJohnT
If your going to have a THCAD card and a floating head with a touch off switch then bed level is not important. What is important is the X and Y axes are perpendicular to each other.

I put a slight curve in the sacrificial slats so they would not be fully under a straight cut and that also made the slats very rigid so small plates don't wiggle as the machine moves.

gnipsel.com/images/plasma/
gnipsel.com/shop/plasma/plasma.xhtml

JT
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04 Jul 2021 02:13 - 04 Jul 2021 02:15 #213635 by Joco
JT - re the axis being perpendicular to each other I guess other than being careful on construction that next part is getting the racking on the X under control.  Dual motors and independent homing with adjustable home reference points being key to that exercise?

After getting distracted by a new SLA 3D printer (never had an SLA one before) I got back to the getting the top frame proper mounted.  Success after a little drama trying to drill holes with a hand power drill.  Ended up having break out the TIG to fix a bung hole that was off position by just enough to be a problem.  Then big mill to the rescue!

 

After that it was easy and while it was on there power tapped the holes.  We now have finished hinges and top mounted!
 

Now there really is no more excuses time to tackle the Y axies linear rails and making the sides to support the X axis.  That will allow some motion testing as well.  I have the basics of the 7i76e all working on a test bed along with the drivers and motors.  I also have all the drive belts and reduction gears for the motors.

Cheers - J.
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Last edit: 04 Jul 2021 02:15 by Joco.
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