Small plasma table design

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yngndrw
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Small plasma table design

Post by yngndrw »

I was hoping for some feedback on a plasma table design which I'm working on.

Being in the UK, we don't have the same range of plasma tables available over here. I could import, but then I'd be hit by some rather expensive shipping and import duty costs.

I started working on my design, inspired by the Langmuir designs as well as the JD design - Although my design has drifted somewhat.

One constraint that I have is the water table, I don't particularly want to make my own water table tray and there aren't many available to purchase over here. My plan was to use this 32"x28"x2.8" tray to build an initial small plasma table to start with, then I may upgrade in the future if I need to.

Here's my design so far, it's still a work in progress (Gussets to add to the motor mounts and the torch holder/floating head have not been designed):
https://cad.onshape.com/documents/1f2ca ... 106bc50726

For the Z axis, I'm planning on using a Chinese ready-made axis - Probably the 200mm version but possible the 100mm version will work, I need to check once I've designed the slat setup:
https://www.ebay.co.uk/itm/285137191178 ... 7005672112

I have a small THK HRW21CA linear rail (28mm travel) to use for the floating head. For the main axes, I'm planning on using 20mm supported round rail as it's robust (I'd be concerned about dust and splashed water on proper profile rails) and dirt cheap. It's also a little more forgiving for alignment, while profile rails constrain more degrees of freedom and tend to conform to whatever you bolt it to.

For X / Y motion, I'm planning on using closed-loop steppers (Or cheap AC servos, depending on my mood when I go to order them!) and either a belt drive or a rack and pinion setup. The belt drive is very cheap and easy as they are very forgiving for alignment. A rack and pinion setup would require me to design something to manage the tooth engagement.

The frame is 50x100mm (2x4") box section for the gantry and Y rails, 50x50mm (2") box section for the legs and cross members, and 50mm (2") angle to support the water tray and the bottom shelf. I'm planning on isolating the water tray from the frame with a thin sheet of HDPE for grounding purposes.

I've not managed to come up with a break-away design that I can easily fabricate yet, I may start without and then plasma cut something once it's up and running. I haven't included belt mounts as I'll likely just tack something on without a proper design. But the main issue I'm having is that I don't know if I've completely overdone it. I could just build it out of 20x20mm or 20x40mm aluminium extrusion and V wheels, but I'm concerned about dust on the bearing surfaces, the gantry strength in terms of sag and I'm not sure it would be any cheaper than a welded frame.

I do also plan on building an enclosure around it, if I can be bothered / the dust annoys me enough. There are also cable chains to add to the design.

So I'd like some advice and feedback about my design please: Have I gone over the top on rigidity? Is it not rigid enough? Will a belt drive be okay for this sort of machine or should I bite the bullet and go with a rack and pinion design? Do I really need a breakaway torch? Will the supported round rails be robust enough for the dirty environment of a plasma cutter?
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Re: Small plasma table design

Post by Joe Jones »

That is all Greek to me. Sorry. Someone will be able to help you with this project though.

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Re: Small plasma table design

Post by adbuch »

yngndrw wrote: Fri Jun 21, 2024 9:32 pm I was hoping for some feedback on a plasma table design which I'm working on.

Being in the UK, we don't have the same range of plasma tables available over here. I could import, but then I'd be hit by some rather expensive shipping and import duty costs.

I started working on my design, inspired by the Langmuir designs as well as the JD design - Although my design has drifted somewhat. ...............

Your design sort of reminds me of my first (and only) attempt at designing and building a small diy cnc plasma/engraving table.

http://deserthybridscom.ipage.com/deser ... index.html

Mine uses stepper motors running open loop direct drive, fully supported round linear rails very similar to yours, water tray/grate assembly with a removable top for converting to cnc routing/engraving. Runs on Arduino/GRBL using Candle control program. I had fun designing/building it, but now it pretty much sits in the corner as I already had a Plasmacam 4x4 table and subsequently acquired several of the AvidCNC router tables.

I think you will have lots of fun with your build, and other here will have more useful input as some of them (Tom in particular) have build a number of diy cnc plasma/router tables with great success. Good luck with your build.

David
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Re: Small plasma table design

Post by acourtjester »

Welcome aboard the site, there are many DIY types here and show their tables, You are doing the correct thing in doing research before building your table. There are many designs and many will work just fine, many boil down to what you may have available to you. I have built many tables with the mechanical design remaining the same with changes in the electronics and software used, the last change from stepper to servos. Some of the reasons are cost and tools I have to assist in the construction. If your send me your email address in a private message from here I will send you (free) info about construction and suppliers that I used from the Google drive to your computer. I know this has help others due to the number of plans I sold and parts I have supplied to builders. By no means do I claim this is a prefect design but I have used my tables to cut parts used by others for their table and many very nice projects for myself and others, using it for plasma, routing, metal scribe and diode laser etching.
Lots of fun to have after you build one :Yay
DSCN2135.JPG
2 tables 4x4 and new 4x8.JPG
DSCN2032.JPG
DSCN1991.JPG
DSCN0285.JPG
DSCN4366.JPG

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yngndrw
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Re: Small plasma table design

Post by yngndrw »

Thank you for the responses, help and advice.
adbuch wrote: Sat Jun 22, 2024 1:47 am
yngndrw wrote: Fri Jun 21, 2024 9:32 pm I was hoping for some feedback on a plasma table design which I'm working on.

Being in the UK, we don't have the same range of plasma tables available over here. I could import, but then I'd be hit by some rather expensive shipping and import duty costs.

I started working on my design, inspired by the Langmuir designs as well as the JD design - Although my design has drifted somewhat. ...............

Your design sort of reminds me of my first (and only) attempt at designing and building a small diy cnc plasma/engraving table.

http://deserthybridscom.ipage.com/deser ... index.html

Mine uses stepper motors running open loop direct drive, fully supported round linear rails very similar to yours, water tray/grate assembly with a removable top for converting to cnc routing/engraving. Runs on Arduino/GRBL using Candle control program. I had fun designing/building it, but now it pretty much sits in the corner as I already had a Plasmacam 4x4 table and subsequently acquired several of the AvidCNC router tables.

I think you will have lots of fun with your build, and other here will have more useful input as some of them (Tom in particular) have build a number of diy cnc plasma/router tables with great success. Good luck with your build.

David
How reliable were the supported round rails? My main concerns are rust and dirt from the dirty water being splashed up and slag being sprayed up from piercing operations.

It looks like your design is using 2" square tubing based on how well-matched they are to the supported round rails. I can't fully tell from the pictures, but it looks like the gantry is slightly sagging from the weight of the z-axis? If so, that suggests that going with a 2x4" gantry might be the right call. Not that sagging really matters with round rails and THC, but it's best to get a good handle on how strong it needs to be at the design stage if I can.

I also noticed that your design doesn't have any diagonal bracing - Has it been okay without? I was hoping to avoid it if possible because it impacts the usability of the bottom shelf, but I wasn't sure if I could get away without it.


acourtjester wrote: Sat Jun 22, 2024 9:54 am Welcome aboard the site, there are many DIY types here and show their tables, You are doing the correct thing in doing research before building your table. There are many designs and many will work just fine, many boil down to what you may have available to you. I have built many tables with the mechanical design remaining the same with changes in the electronics and software used, the last change from stepper to servos. Some of the reasons are cost and tools I have to assist in the construction. If your send me your email address in a private message from here I will send you (free) info about construction and suppliers that I used from the Google drive to your computer. I know this has help others due to the number of plans I sold and parts I have supplied to builders. By no means do I claim this is a prefect design but I have used my tables to cut parts used by others for their table and many very nice projects for myself and others, using it for plasma, routing, metal scribe and diode laser etching.
Lots of fun to have after you build one :Yay

DSCN2135.JPG
2 tables 4x4 and new 4x8.JPG
DSCN2032.JPG
DSCN1991.JPG
DSCN0285.JPG
DSCN4366.JPG
Yes availability of parts has been a major issue. I'd have ideally liked a deeper water tray, but 2.8" seems to be the deepest I can find. Not having a milling machine and the lack of local breakaway mounts is also a bit of a pain, but just something to work around. It would have been a lot easier if I had a plasma cutter to use in order to build this plasma cutter! But that's okay, at least I'd have this one in case I do decide to build a larger one in the future.

Thank you for the offer, I'll send you my email now.

It's interesting that you've gone for a single-motor Y-axis design - I think that might work quite nicely on my design, I'll have to play in CAD and see how it fits.

I love the computer consoles and signs by the way!
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Re: Small plasma table design

Post by yngndrw »

This is the curve ball that I keep seeing, the reason I'm questioning my design so much - I keep seeing some really simplistic designs such as this:
https://www.runstenracing.se/?cat=61

Essentially it's just tiny steppers (Nema24 & Nema17), tiny aluminium extrusion (20x40mm, 40x40mm) with V-wheels and a belt drive setup (6mm GT2). Contrast that with other setups which are so rigid they put some CNC Routers to shame, it leaves me wondering how far I should go with the design given that this will be a stepping stone design due to the limited water tray size.

I could take that entire design, place it on top of my base frame (Replacing the supported round rails) and possibly end up with something that's much lighter (In terms of the moving parts) and simpler. I would have to make all of the parts by hand, but considering there are 56 drilled and tapped holes in my design for the supported round rails alone it may still be easier to build.
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Re: Small plasma table design

Post by adbuch »


How reliable were the supported round rails? My main concerns are rust and dirt from the dirty water being splashed up and slag being sprayed up from piercing operations.

It looks like your design is using 2" square tubing based on how well-matched they are to the supported round rails. I can't fully tell from the pictures, but it looks like the gantry is slightly sagging from the weight of the z-axis? If so, that suggests that going with a 2x4" gantry might be the right call. Not that sagging really matters with round rails and THC, but it's best to get a good handle on how strong it needs to be at the design stage if I can.

I also noticed that your design doesn't have any diagonal bracing - Has it been okay without? I was hoping to avoid it if possible because it impacts the usability of the bottom shelf, but I wasn't sure if I could get away without it.
For my purposes, the round fully supported linear rails are reliable and work quite well. This particular table has a combination of water table/draft system so there is not much in the way of water or slag contaminating the rails. Plasma dust from piercing is really not a problem, and the rails can be wiped off from time to time as needed.

There is absolutely no sagging of the gantry from the weight of the z-axis. I designed this to be stout enough to support a router motor for routing/engraving - and testing indicated that this table holds extreme accuracy for machining out pockets, etc. There is some added diagonal bracing, but it doesn't impact the usefulness of the lower shelf for storage, etc.

I am not necessarily recommending my design or construction techniques, and have simply offered this as an example of a particular diy design project. My particular design did involve the use of welders and machine tools (mill, lathe, etc.) which I happen to have on hand here at my shop. Many will not have access to these tools, and as such would need to come up with a more "bolt together" design perhaps using aluminum extrusions, etc.



David
Last edited by adbuch on Sun Jun 23, 2024 5:12 am, edited 1 time in total.
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Re: Small plasma table design

Post by adbuch »

yngndrw wrote: Sat Jun 22, 2024 6:57 pm This is the curve ball that I keep seeing, the reason I'm questioning my design so much - I keep seeing some really simplistic designs such as this:
https://www.runstenracing.se/?cat=61

Essentially it's just tiny steppers (Nema24 & Nema17), tiny aluminium extrusion (20x40mm, 40x40mm) with V-wheels and a belt drive setup (6mm GT2). Contrast that with other setups which are so rigid they put some CNC Routers to shame, it leaves me wondering how far I should go with the design given that this will be a stepping stone design due to the limited water tray size.

I could take that entire design, place it on top of my base frame (Replacing the supported round rails) and possibly end up with something that's much lighter (In terms of the moving parts) and simpler. I would have to make all of the parts by hand, but considering there are 56 drilled and tapped holes in my design for the supported round rails alone it may still be easier to build.
There are lots of documented designs out there for you to study. If you can find one that is proven and works - than perhaps that may be a good path to follow. I would check Youtube for videos of small diy plasma tables that actually work and perhaps replicate one of those existing designs.

Good Luck!!

David
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Re: Small plasma table design

Post by adbuch »

acourtjester wrote: Sat Jun 22, 2024 9:54 am Welcome aboard the site, there are many DIY types here and show their tables, You are doing the correct thing in doing research before building your table. There are many designs and many will work just fine, many boil down to what you may have available to you. I have built many tables with the mechanical design remaining the same with changes in the electronics and software used, the last change from stepper to servos. Some of the reasons are cost and tools I have to assist in the construction. If your send me your email address in a private message from here I will send you (free) info about construction and suppliers that I used from the Google drive to your computer. I know this has help others due to the number of plans I sold and parts I have supplied to builders. By no means do I claim this is a prefect design but I have used my tables to cut parts used by others for their table and many very nice projects for myself and others, using it for plasma, routing, metal scribe and diode laser etching.
Lots of fun to have after you build one :Yay

DSCN2135.JPG
2 tables 4x4 and new 4x8.JPG
DSCN2032.JPG
DSCN1991.JPG
DSCN0285.JPG
DSCN4366.JPG
Tom - thanks for showing us your finished diy tables and some of the great parts you have created using these. That combination of plasma, routing, metal scribe and laser etching is one that is hard to beat. It's always fun to see some of the work you have done and offers quite an inspiration to others hoping to follow in your footsteps.

David
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Re: Small plasma table design

Post by yngndrw »

Thank you David, apologies it must have been a trick of the eyes - In that case if there's no sagging and you're happy with the milling performance with that size of tubing then it suggests that I've overdesigned my version and I can likely simplify it somewhat. I had been apprehensive that aluminium extrusion and plastic V-wheels may not be strong enough but with the capabilities and sizes of yours and Tom's machines, I think I could get away with a much lighter design (With parts which are easier to source) for my initial build. That will then give me some experience with this kind of machine and I'll also be able to use it to either improve this machine or to build a larger one in the future.
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Re: Small plasma table design

Post by acourtjester »

There is not a problem starting small, the electronics and software can be used for a larger table, you will need to increase the motor sizes with larger tables due to the increase in weight. You are correct about using Aluminum extrusion and plastic V-wheels those are really for very light table construction. There are table with Aluminum extrusions but a larger and more expensive type with roller bearings. On a plasma setup, the torch and cable weight with added Z axis size need larger components. Where are you in the UK there may be members there close enough for a look see to help with some of your decisions.
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Re: Small plasma table design

Post by yngndrw »

Yes I'm doubting the plastic wheels, especially in a dusty environment.

I think I have a plan now, I was originally going to use 20mm supported round rail, but if I use 12mm supported round rail instead that has a mounting hole spacing of 22mm for the rail which is close enough to the 20mm slot spacing for 20mm aluminium extrusion. I can then use 20x40mm extrusion for the Y axis which will allow me to use the standard 20mm belt drive setup and I won't need to drill 28 holes in steel to mount those rails. It will also give me some nice adjustable slots for limit switches etc.

For the X axis/gantry, if I use 40x80mm C-beam I can mount two 12mm rails side by side and again as it's using standard 20mm extrusion I can use the same off-the-shelf belt drive setup.

For the Z axis, I can drop this down to a much smaller and lighter axis:
https://www.ebay.co.uk/itm/284542467049

The torch will be the miniature robotic torch as the full machine torch is far too long. The bend radius of the torch is 76mm so I think I can just about get away with that in cable chain, as long as I'm careful where I start and end the chain.

This plan still relies on the supported round rail which doesn't need a super flat surface and I avoid drilling/threading 56 holes in steel which is nice. I think that the 12mm rail will be strong enough but there's only one (easy) way to find out.

I'll have to get it drawn up in CAD and see how it all fits together.
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