Low budget plasma setup, what do I need?

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29 Apr 2019 07:07 - 29 Apr 2019 07:07 #132247 by tecno
The stand with water-pan is going to be a totally separate unit, it will have some kind of registration for this CNC frame that will be stored inside my work shop when not in use to take minimal space. The Z assembly will be detachable also.

Mid ball-screw drive is no *low budget solution* and there will be no ball-screws on this at all. Too sensitive parts for the way this is going to carried around to/from storage.

SBR12 = I am going for the ball bearing solution = minimal friction and if needed in future it is easy to add another support rail witch I don´t think is necessary. This is not going to be a production plasma so to keep dirt from top of that part is easy.

I will have to make do with what I have at hand as regards material.
Last edit: 29 Apr 2019 07:07 by tecno. Reason: added text

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29 Apr 2019 08:36 #132252 by pl7i92
ok Nice so i will stop to give further advices as you got a real good plan for yourself

within the minute i got my 5Axis + ATC 7i92 Stepper 4Nm first time runnig oim pretty happy as it went so nice
without the pncconf and first time 7i92 user
BUT i got as same as you alot of help

i run lots of mashines but the men hou did this all desisted in 2018 and mow i got to do it by myself
as well as i did overtake his education work and confronted with near 100 mashines he build
with the students

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29 Apr 2019 09:39 #132261 by tecno
pl7i92
Please don´t take my answers/comments wrong here, I really appreciate advises and ideas from fellow LCNC users. So please share your knowledge as there are many reading what we do.

Yes I have a plan but who says this is the correct way to go?

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29 Apr 2019 10:01 #132262 by rodw
I would not go on opinion here.

I'd do some engineering calculations based on the maximum torque that could be applied based on the maximum gantry acceleration with the weight of the Z axis at the far end. If you check the specs of even a modest HGR-15 rail the maximum axial torque is amazingly high.

Whilst unconventional, there are plenty of much larger portable machines that run on a cantilever arm much longer than this one. I think you'd be surprised how the maths would stack up. Worst case, just go up a size in the rail if required.

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29 Apr 2019 11:45 #132267 by tecno
Looking at a rack solution, is Module 2 OK? 12 teeth pinion on stepper?

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29 Apr 2019 11:54 #132268 by andypugh
You would need a modified gear tooth profile at 12 teeth.

khkgears.net/new/gear_knowledge/gear_tec...te_gear_profile.html (Section 3..5)

You might not get very smooth movement with such a small pinion. 17 teeth or more would be better, but of course you are playing-off compromises against each other.

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29 Apr 2019 11:58 #132269 by tecno
Thanks Andy,

So 12 = unsmooth but more power
17 = smoother but less power

I wonder what I can get out of my Gecko 250 + these Longs steppers
www.ebay.co.uk/itm/Free-ship-LONGS-1PC-N...p2057872.m2749.l2649

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29 Apr 2019 12:00 #132270 by andypugh
Or you could use smaller teeth, but then they are more sensitive to contamination and engagement depth.

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29 Apr 2019 12:01 #132271 by rodw
Bengt, just add a 3:1 to 5:1 reduction drive. This thread has some good info about pinions and was the start of my journey.
forum.linuxcnc.org/30-cnc-machines/31509...pinion-drive?start=0

The sweet spot for plasma is about 25 mm of motion per motor revolution. My X axis seems to work nicely at around 30mm/rev.

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29 Apr 2019 12:17 #132273 by rodw
I use same sized motors with Longs Motors Stepper drivers. Allow about 700-750 rpm. I can get about 21 metres per minute with 3:1 timing belt reduction. They will be heaps for your small table.

I was cutting 1.6mm aluminiumn today at about 5500 m/min at 40 amps which is probably the fastest I have cut at. I found my specs on that axis
Rack: 1.5 Module,
Pinion: 20 tooth
Distance/Rev: 94.2477796mm
Timing Belt Gearing: 3:1 (31.4159265mm/rev)
Microstepping 5,000 steps per rev
159.15494327 steps per mm

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