First Plasma CNC build with a cutting space of approximately 500*500

04 Oct 2021 20:37 - 04 Oct 2021 20:39 #222216 by besi99
Hello to all members of the forum,

I want to share my journey of building my first plasma CNC table with you. Maybe you guys also see some improvements I can do or some kind of mistake i made. A couple days ago I started to draw a 3d Model of my plasma table.

Components I chose are:
-Nema 23 step motor for X/Y-Axis
-Maybe Nema17 for Z-Axis (or Nema 23 depends on how heavy the torch holder gets)
-DM556T as stepper driver
-Frame out of 40*40*3mm box material
-Some Aluminium C-Beam 40*80 extrusion
-MGN15 linearrails
-Balls screws for X/Z-Axis and a belt system for Y-Axis

I willl attach some pictures of the current state of the CNC 3d Model. So you guys can see what iam planing to build. Its my first completly self CNC build. One year ago i succssesfully build a MostlyPrintedCNC which worked fine. I still need to think of a Brain for the CNC i have read something about Mesa boards which seemed quite often used here. I will have to do more research about them or other Boards.

I would love to know what you guys think of my build.

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Last edit: 04 Oct 2021 20:39 by besi99.

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04 Oct 2021 21:45 #222223 by tommylight
To much rails, for such a small machine a single rail per axis is enough. X axis out of aluminium - belt with reduction - 2 carriages since they are MGN, Z axis as lite as possible - ballscrew/leadscrew/allthread works perfectly - floating head is nice to have, Y axis belts with reduction - 2 carriages per rail/side.
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05 Oct 2021 18:31 #222301 by besi99
So I could remove the the C Beams and go straight on the box steel with the X linear rails. That would also bring the hight of the Y-Axis down. I will do the changes in solidworks an do an update on how far I got. I will ask a local company tomorrow if they have some 6 meter steel bars on hand so I can start with the Frame build.

Thanks for the nice reply. I will have to get a closer look on your builds to maybe I can steal some ideas :D because your machines just look amazing.

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06 Oct 2021 09:53 #222343 by Joco
You could go on the steel for the linear rails which is what others have done.  You just need to be prepared to do all the drilling/tapping.  If you use some 40x40 or 60x60 extrusion you can use the T mounting you planned and just have single rails.

If you want speed a light gantry is key.  A plan rectangular aluminium gantry beam will be lighter than the 6060 style extrusion.  But the extrusion is very convenient from a mounting point of view.  Just a choice.

Have a think about how much clearance you want under the gantry and how you want to achieve that, particularly as to the creation of the gantry side plates to support that.  This will inform some of your design choices as well.  You might decide you still want the raised Y axis sides as it means you can have smaller/shorter gantry side plates.

Cheers - J.
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11 Oct 2021 21:53 #222872 by besi99
Thanks for your reply Joco. I didnt directly go on steel with the linear rails that would have been to much drilling/tapping. I will stick with the aluminium extrusions but I will use some 40*40 with a single T-Slot. I think it will also be a bit easier to get the alingment of the rail perfect. If i do some kind of mistake while drilling it will be much harder for me to get the rails straight.

The Y-Axis C-Beam also got deleted. I went with a 60*60*4 aluminium profile. I designed it like your recent built (hopefully its okay that I kinda stole your design :D ). I will either do the drilling/tapping by myselfe or I will ask a local company I have worked for if they can do it with their big CNC they use to cut profiles for aluminium windows.

Also I have started designing the pully system for the X-Axis. I will add a picture of that its still kinda rough and still needs work. Also i will have to do some belt tensinors. For the reduction I am still not sure if 2to1 or 3to1 definetly need to do more research on that.

Tomorrow I will start with the Z-Axis i will try to build a floating Z-Axis like Tommy mentioned.

My box steel for the frame should also arrive this week so i can start building.

New Gantry with less rails and half of the X-Axis Belt I will try to get the stepp motor under the frame so nobody will be able to hit it or something else.

Belt X-Axis drive currently without belt and tensioner.

I just realized how bad my english got :D hopfully you guys understand at least half of ot :D
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11 Oct 2021 22:57 #222881 by tommylight
I thought that nickname sounds familiar so i just checked the profile and sure enough Besi99 is from my neck of the woods, so here we go off topic and totally not understandable by most here:
Po ku je mor shype ?
Loosely translated from Albanian :
Where are you, Albanian?
Looses something in translation, but it is probably the most used expression when people meet after a while.
Back on topic:
I like the Y rail and motor/reduction/belt positioning as it is easy to cover everything with some thin plate if it becomes necessary due to water splashing ... we are talking about a water table, right?
Also the idlers are missing on the reductions, 2 on each side required.
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12 Oct 2021 08:12 #222906 by Joco
I debated 2:1 and 3:1 reduction ratios.  I settled on 3:1 and it seems to be working out pretty well.  You get a significant increase in torque on the smaller motors, and the resolution per step works out pretty good.  I'm running 3Amp Nema 23 with 1.26Nm holding torque.

Running 48v on the motors gives some good pep to them without  risking too much heat generation. 
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12 Oct 2021 23:24 #222988 by tommylight
I mostly use 1:3 reductions (more precisely 1:2.8 to 1:3.3 depending on the motor pulley as i have 16, 20, 21, 22 and 23 teeth ones) and even when the motors are under driven (2.4A motors at 1.8 to 2A) the have enough power to bend something out of shape if, god forbid, someone jogs the machine at full speed while the sensors are being installed (that someone is usually me :) ).
Power supply and drives are important speed wise, cutting speed is limited by the material/torch/current so no gain there really, but the parts in between can be sped up immensely, so instead of 5 cut plates a day you get say 6 or 7 depending on how complicated the cuts are.
My big machine (3X2M) can barely and unreliably do 9M/M with 24V powering the drives, while it does not skip a beat at 55M/M with 72V, that reminds me, i still have it at 24M/M since i moved and leveled the table (the ground is sloped) so i can set it back at 36M/M where it usually is set. Thinking of it, it does make one hell of a fast 3D printer if i get some time to build a very fast extruder/hot end and mount it on ... getting off topic here ... i did build a hot end "volcano" style last night a tested it today = works perfectly... i'll kick myself out
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23 Oct 2021 22:56 #224040 by besi99
Uhh I completly forgot that youre from Kosovo Tommy if i am right. My dad comes from there too. Nuk di bashk mire me shkrujt shqip. Te pershendes prej Gjermanis. (In translation for the other users. I am not that good in writing albanian. Greetings from Germany).

It took a while to improve the design of my plasma table because my Pc to be more specific my 8Gb RAM did not like the big SolidWorks file and kept crashing which was very frustrating. Iam waiting for my two bigger ram sticks to arrive which should solve the problem. I did a couple of changes to the belt drive. I moved it a bit closer to the steel frame. The GT2 belt is now as high as possiple against the frame. I also switched the idlers with the reduction so the belts should follow nicely.

Also my floating head is almost finished. Its still a bit bulky and i will try to remove more weight. I just need to add the Z/Y-Axis stepper motor and the Solidworks desing should be finished. So i can start ordering more parts. The steel which i ordered didnt not arrive till now hopefully its there next week so i can start cutting and welding. If also bought some linearrails and carriges.

Thats the enclosed reduction. Iam not quite sure if I am going to close the other side up to. Maybe it will get to hot for the Nema23 if i do that? And yes it will be a water table. Thats why the frame legs are a little bit in so the water tub has something to sit on.

Thats a picture of the finale version. I caculatet the belt sice for the reduction online its 176mm in lenght. Do i need an idler bearing on the reduction belt too? Or can i tighten the belt up by moving the nema if i add some bigger holes?

Thats my floating head design as I said still pretty bulky and heavy I think i can make it a bit lighter. Maybe i will 3d Print the floating head out of ABS or something like that. It should be plenty strong for a plasma torch. How much movement do you guys add to the floating head before the switch triggers is 20mm to much? The red part is where the torch will be. Green part are some bearings.

As always thanks for the help and the nice replys.
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24 Oct 2021 00:06 #224048 by tommylight
Dang it, i wrote a lot and accidentally hit the "back" button on the mouse .... me angry ...

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