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

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04 Sep 2021 23:37 - 04 Sep 2021 23:38 #219638 by Joco
Yeah horrible black dust.  Hopefully the water table would keep that to a minimum.  I'm thinking about options to cover the ends.  I can 3d print some plastic plugs for the mounting holes that I made for the CNC work.  Then either a plastic or sheet metal/aluminium to keep the motors and pulleys more clean.

Oh and soved the stuck beaing alignment issue. A little bit of 3-in-one oil and some leverage.  Some of these were not too bad others were so solid I thought I was going to bend the bar before they clicked loose.


 
Last edit: 04 Sep 2021 23:38 by Joco.

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04 Sep 2021 23:55 #219641 by rodw

Very nice, indeed ! :)
Soon all that will be covered in black dust ! :(

Yes, you quickly forget how clean they are at the start of their life!
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12 Sep 2021 07:40 #220280 by Joco
This is a bit hacky but heck if don't care, its first real world movement.  Seriously ...  FIRST MOVEMENT.  Yeah I know, nothing new for many here but I'm stocked.  It's always so cool with a bunch of design and thinking and advise taking and machining actually has a good result.  :-)

First up some photos of the setup to get things working, just to prove what I have made isn't going to be an epic fail.

 
 
 
 
 

Video time:

 
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12 Sep 2021 08:38 #220282 by Joco
Just a short clip of rapids at 30m/min and acceleration of 3m/s/s.  Obviously "real" plasma tables can do higher speeds but I'm impressed what these relatively small nema23's can do with this 3:1 gearing.

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12 Sep 2021 11:17 #220291 by tommylight
Very nice and very glad you are happy ! :)
Now back to work and stop jogging the poor thing all day long ! :)
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12 Sep 2021 19:32 #220361 by Joco
tommylight - ok, back to it!  So, belt tensioning. I’m starting to think through how best to do this.  As a result a couple of questions …

(1) how tight do you need to get the belts? Mine are steel reinforced, i couldn’t find fibreglass at the time I ordered.  Plus how do you tell if you have the belt at the correct tension?

(2) what sort of belt locking and tensioning mechanism did you use? If your build logs contain a pic just say and I will go looking again. I just can’t recall seeing any on this aspect of things. 

cheers - J. 

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12 Sep 2021 21:36 #220370 by tommylight
1- if they spring back like guitar wire = they are to tight! :)
Have the machine running back and forth some 50mm and watch the straight parts of the belt, if the line they are moving at moves, tighten some more.
Not easy to explain, it is something requiring practice. Seen people braking them or bending the motor shaft ....
2- usually an M8 screw+ 2x 608 bearings+ 2 wide washers+ 2 nuts = all this mounted in a short slot between the motor and the big pulley. On long runs i do not use tighteners as the flex on the belt is enough to keep them in check.

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12 Sep 2021 22:59 #220378 by Joco
Thanks.   Think I understand the guitar part.   Re the "watch the straight parts of the belt" what I am taking from this is if that flat part of the belt is shift and/or the teeth on it are moving back and forth from a witness mark then you probably have excessive slack such that there is too much backlash in the system.

Re the tensioner I had a look at one of your builds again as I was trying to visualise what you are getting at. Pic below from your 2+2 thread.
File Attachment:

Do you mean that one of the idler is in a slot and that after getting the base tension in place when clamping the ends you shift that to tune it in?

Thanks - J.

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12 Sep 2021 23:57 #220380 by tommylight
Yes and yes, both idlers have a small slot as the space for them is very limited.

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13 Sep 2021 22:31 #220520 by Joco
Working on belt tensioner system.  I looked into following tommyligts pattern and while possibly doable its going to be very tight and if I get it wrong it will be a little destructive on the gantry side plates.   So for now I am going to try something along these lines.

Tensioner assembly drawing.  This will be mounted under the end of the table frame.


Shown in context of the overall assembly at the end/edge of the table top with the gantry side shown in a homed position.  I might end up using this end as a fixed mounting point and put the adjustable end (the one shown) at the other end where this is a bit more room .
 

Not perfect but workable I think.
 
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