CNC Plasma cutters, general idea and a lots of info for building them.

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23 Apr 2019 21:51 #131697 by andypugh

rodw wrote: [Anyway, it will be pretty trivial with mesa cards providing enough outputs. The beauty of LInuxcnc is its so extensible. Here is all the code you need for 2 zones utilising a 2 position flap so 4-6 zones would not need much more.

pin in float position "Motion signal for Axis position";
pin out bit trigger "True if downdraft segment should be triggered";
param rw float cutover "Absolute axis coordinate above which triggers zone change";
...


You could have just used the "comp" HAL component, or maybe "wcomp"
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25 Apr 2019 13:39 #131848 by docwelch
Just wondering if anyone had considered using coreXY for a plasma table. Since Tom is suggesting using GT2 belts for the smaller machines, a coreXY setup would eliminate some of the moving mass of the gantry and potentially help with acceleration. My concern would be the durability of the GT2 belts with respect to the sparks from the plasma torch. In a traditionally driven machine, you can place the belts so they would have minimal exposure but I'm not sure how you would do that with a coreXY machine. Am I too worried about the belt durability? Have I missed an easy way to protect the belts?

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25 Apr 2019 13:47 - 25 Apr 2019 14:01 #131850 by pl7i92
you can go with cheep ballscrew as of 12m/min up to 1m table 80cm cat area

then considder Rack pinion with 1:5 gear cheep and good for 8m/min cuts

the Timingbelt woudt be a AT5 the best to use no flex on 10m Width 750KG of tention

my 4 plasams and the 5th are on Rack pinion with 30:1 wormgear at 3Nm 72V
running 20m/min at 0,1mm/step
this is the setup tighten with a spring to the rack
it runs for a full shift with no steploss at 8m/min cut G64 P0.3
Double shielded ROBOT Cable 4x 0,75mm² in e-chain length 12meter at 72V 4,2A M880 7i76
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Last edit: 25 Apr 2019 14:01 by pl7i92. Reason: image
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25 Apr 2019 14:24 #131856 by islander261
Hi

If you read on some of the 3D printing forums you will find that corexy has it's own set of implementation challenges. Plasma cutting is dirty and does throw hot slag bits around so all belts need really good protection. Rack and pinion is cheap, easy to get and pretty forgiving of all the plasma debris that will be around your table. If you are going to be cutting 1.5mm or thicker you should have no problems with getting high enough speed with 3NM steppers and a power supply of 48V or greater. Your Z axis assembly with float switch and torch will be heavier than you first think. A rule of thumb I once heard for stepper driven plasma is to have your total reduction so 1 revolution of the stepper yields about 25mm of travel on your X and Y axis. Mine is a little less than that but within an order of magnitude.

John
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25 Apr 2019 21:00 #131889 by tommylight
That is quite easy to avoid when building a new machine, just hide the belts behind rails or frame. Not easy on an existing machine.
Although they can work without a hitch even without cleaning for over 3 years and not covered at all! I had such a customer!
Having them near the torch is a no no.
I do not know what Xcarve uses as linear slides, but those chinese rollers on aluminium extrusion will be done with inside of a week of heavy usage on a plasma machine.
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28 Jul 2019 13:59 #140803 by tommylight
Been long enough !
Sorry for the delay but the friend that was providing parts for me from Germany is back in Kosovo so i am having difficulties sourcing parts, but at least now i order a lot more so i gathered a nice pile of Mesa boards, Lam Technologies and other types of drives, lots of power supplies, and finaly yesterday got a delivery of 6 meter long round supported rails at 16, 20 and 30mm with respective carriages. Took 2 months to have them here! Next shipment will be here a week after i order, so that is one less problem.
Now i have to do some calculations and some drawings to first check how much i can squeeze with what i already got then order a lot of metal profiles ( IF i can manage to gather some money as i am almost broke! :) ) .
I have :
Linear round supported rails:
16mm 6 meters plus 12 carriages with holders and 16 without holders.
20mm 6 meters plus 12 carriages with holders.
30mm 15 meters plus 15 carriages with holders.
Linear rails square
Hiwin HGR25
1 piece 118cm long
1 piece 78cm long
1 piece ~55cm long
1 single carriage.

I need to build:
1 small machine at 2X1 meter cut area.
1 medium machine at 3X2 or 3X1.5 meters cut area.
1 big machine at 6X2 meters cut area.

The big machine will use the above mentioned 30mm supported rails for the Y axis, meaning having to cut the 3 meter piece and but join it to the 6 meter ones to get 7.5 meters of rails on both sides, planing on making the gantry very wide at 60 to 100cm, so that will end up with 6.5 to 6.9 meters of cut area.
Now comes the tricky part, i would like to use the HiWin for the X axis, but, but joining square linear rails in a "hand tools" work shop is a no go, so any ideas are very welcomed. This would leave the 20mm and 16mm ones for the other 2 machines to play with, but no matter how i look at it, i will need some more rails. Luckily i have a local source for unsupported round rails ( local hydraulic equipment service ) and a local bearings shop that has a stock of carriages for round rails and rack and pinion module 2 just for me ! :)
Since this is a joint venture, can someone please do a drawing or a render or a scrible of how a plasma machine should look like as a finished product. Not the standard ones. It has to look as a piece of art, not a square box. Even some nice decals will do, if it contains the words: Linuxcnc and Mesa, and maybe, just maybe a company name ( i do own localy " Kosova Hardware" and " PC Kosova ", the first is usable but to long ).
As i have access to a lot of local busineses, printing on anything, plastic sheets, and some other stuff is easy, good paint job is very hard so i have to use car repair shops that costs a lot, but i have to go that route.
More to come.
Regards,
Tom.
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28 Jul 2019 16:01 #140809 by pl7i92
there are nice sets for 1500mm mashines on the market
also very good working 1300mm square rails cheep ballscrew sets


BUT what i think there is a individuell need
as here we got sheeds at 2500x1500
and also low standard at 2000x1250
so a need to fit tables

you can order sheets as you like in main mesurmands as standard
you woudt also like to go cheep standards to fit your table on mass use

hobbyists or education may prefer small mashines that can be moved as 500x500mm is a real comen one

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28 Jul 2019 17:19 #140816 by tommylight

pl7i92 wrote: there are nice sets for 1500mm mashines on the market
also very good working 1300mm square rails cheep ballscrew sets

Looked at them, they do look ( and are ) cheap untill you try to order them, then you get the 935$ shipping so they are not cheap anymore. And the quality is really terible for the ballscrews. They are usable, but not anywhere near some NSK's i got.

pl7i92 wrote: BUT what i think there is a individuell need
as here we got sheeds at 2500x1500
and also low standard at 2000x1250
so a need to fit tables

Here the standard sheet is 2000X1000mm, then 2500X1250, 3000X1250 and 6000X2000. Rarely there are 3000X1500mm.

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27 Aug 2019 11:57 #143317 by tommylight
No ideas ? Drawings ? Scribles ? Nothing ???
Oh well, been thinking about how to mount the rails so that they are covered completely to protect from fine dust and debree while working around the table, came up with an idea and have some chicken scratches i made on the phone ( the Galaxy Note pen is such a nice thing ), so i will try to upload that now.


Not much to look at buy a rough idea.
Regards,
Tom
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06 Oct 2019 17:47 - 06 Oct 2019 17:49 #147278 by machinedude
i have plans to add bellows from ballistic nylon that are sewn together. i started putting some pieces together and it seems like the idea will work well so far. the section i am working on is the section across the gantry so those will be very long to cover everything. the nice part about bellows is they don't take up very much space when closed up. very expensive to buy but making them is pretty cheap but just takes a lot of time making them.

every machine is different so i would think things would change to some degree between machine designs but bellows seem like the best solution to me at this point.

one thing that caught my attention from the start was how long machine torches are so mounting those up high to keep as much distance from the rails as possible seems like good practice in general. since water tables are a popular choice. i seen people taking silicone check valves from Fram oil filters to use as splash guards on the torches too to keep the mess down from splashing.
Last edit: 06 Oct 2019 17:49 by machinedude.

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