Sort of DIY Plasma Table Build

[aggierailroad]

Hey folks, I used to be pretty active here and kind of tapered off as I started my business and the projects were more "commercial" driven rather than done as a hobbyist. Anyways, things have gone well and now I hope to have the time to post more and show folks how we do things at our growing but still small manufacturing shop - Raum Furniture.

As it would so happen, our shop needed a plasma table due to a growing volume of cut parts and a general lack of reliability by local suppliers. Along with supply chain problems, we were seeing and predicting massive increases in COGS (Cost Of Goods Sold) by outsourcing our cutting. Political, pandemic, or paltry differences aside - we needed a table.

Well, I wasn't too thrilled with what I saw on the market. Mind you this was the end of 2019 and the beginning of 2020. Financing was cheap, but table performance was just "meh". Everyone used the same controller and you were just competing on table specs and service. As an avid DIY, tinkerer and has-been engineer I decided to use this as a learning opportunity to expand our company's services into automation. I know our formal name indicates that we build furniture, but a lot (most) of our work comes from industrial and commercial projects in the prototyping and heavy fab world. Automation is a good fit for us as we've expanded our plasma knowledge into the creation of custom 4 axis cutters and some (weirdly) spinach and lettuce picking machines.

I digress. I decided to start this thread as a platform to discuss plasma, my designs, your frustrations with plasma, and to unashamedly promote a few of the kit pieces we've created in the design of our tables. No, I won't share CAD files. Not even if you ask nicely. I will share my thoughts, my tips and tricks and of course, try to provide fairly priced and high-performing products to help you if you decide to DIY a plasma table.

Check back for more updates!

 

[bri_man57]

Subscribed, looking forward to what you post!

Sent from my SM-N920T using Tapatalk

 

[aggierailroad]

Sort of DIY Plasma Table Build Update 1

I've been designing the Z then X and lastly Y axes for almost a year now. I'll get into that later - but suffice it to say I have a few hundred hours into CAD and maybe a few hundred more into the design of the motors and drivers. MOST of this time has been in keeping track of revisions, adding parts to the master BOM and creating systems that will allow this machine to be reproduced in the future as easily as possible. I've been designing and building professionally for quite a few years now and I've never had to do this before. Everything until now has been a one-off, or a short production run never to be repeated.

Like most folks I'd just order parts from McMaster, keep sloppy drawing files and revisions and my CAD would slowly lose its ability to be parametric and adapt to changes as I got lazy. Fortunately for this project I've been as disciplined as I can and have kept records and note and parts lists and all the above in the hopes to help folks out down the road. Finally, we're building that road!

With all that said, the table design is only 75% complete. I'll jump around as I talk about the build, but I'd like to start with the Z axis and the electronics I designed to integrate the sensors required. My main motion controlled is handled via LinuxCNC with an add in known as PlasMAC. More to come on that.

My struggle bus started with understanding the mechanical parts of a plasma system but not all the inputs needed to keep it running, safely to boot. I was vaguely aware of limit sensors, home switches, etc. but didn't understand how they talked to the controller and where they needed to be placed on the table. There are some great DIY gantry and table designs out there but I was worried about buying them and still not knowing where/how to hook everything up as that's never discussed ANYWHERE!

So, I began to design a new Z axis after some advice from a mentor that said, "Start at the torch, it's the only thing that you know at this point." That made a lot of sense after a few failed attempts at a table design where I started around the plate. The fallacy with that approach is that you don't know how wide to make your gantry, and thus your table, because you don't know how wide your Z axis head is. Maybe this is intuitive to you all, but it wasn't to me.

Here's what I came up with:

Basic overview is that we worked with a Chinese manufacturer to build the extrusion profile and motion components to our spec. To be frank, our expectations were exceeded. They really did do a great job and this unit is almost completely sealed against dust and smoke. It uses a ball screw and a NEMA 24 motor to drive the cutting head for ohmic touch off and Torch Height Control. We've got about six inches of Z travel so you can cut shapes from big box section if you need to. Rotary is handled off table so we don't have the extreme 8" clearance of some tables.

Some features include a simple to use magnetic breakaway in case of torch crashes (part tip-ups being the most common). We also have a cross hair laser that is used to align the plates. You no longer need to get out a measuring tape and fight a 3/8" plate on slag filled bed strips to align with the rails. We have a fix in software! Just move the head until the cross hair is in line with the top edge in two places and a long edge in two places. We automatically spin the plate in software (dynamic coordinate systems) so you don't have to fight moving heavy stuff- great for guys like me that don't have a crane or forklift.

The laser also lets you spot your start point so you can reuse your scraps and drops for more efficient material management. No more guessing if the torch is close enough!

On the other side is a set of magnetic limit switches to keep the Z head from crashing. We've also got a pretty trick touch-off sensor for guys using submerged water bed cutting when ohmic won't work.

That's enough for today - I've got parts to build! Next up I'll discuss more features and talk about sensor integration.

 

[Dissident]

Looking forward to following this as well. Exciting build!

Sent from my LIO-AN00 using Tapatalk

 

[MP&C]

Subscribed!!

 

[koditten]

Since I'm building my own table as we speak, color me subscribed.

Table is done, just need to learn the software.

 

[aggierailroad]

Subscribed!!

Do you even count?

 

[MP&C]

Heck yeah! I don’t have one of those toys.

 

[aggierailroad]

Heck yeah! I don’t have one of those toys.

OK OK OK - fair enough. Slow weekend for progress around here. Hopefully some good updates around the bend!

 

[kazlx]

Having built a DIY table, I don't think I'd do it again. Not that there's anything wrong with it, but it's just a lot of time wasted if you plan on using it to make money. There are a few good tables on the market basically complete, for what I would consider very reasonable costs. I purchased my gantry from Precision Plasma and the last time I looked I don't think they even had anything reasonable. I think their small hobby DIY kits got eaten up by affordable complete machines. When I built mine, they were basically the only ones doing a gantry.

In the long run, plasma wasn't a good fit for me, but that's very situational. They are good at a lot of things.

 

[aggierailroad]

Having built a DIY table, I don't think I'd do it again. Not that there's anything wrong with it, but it's just a lot of time wasted if you plan on using it to make money. There are a few good tables on the market basically complete, for what I would consider very reasonable costs. I purchased my gantry from Precision Plasma and the last time I looked I don't think they even had anything reasonable. I think their small hobby DIY kits got eaten up by affordable complete machines. When I built mine, they were basically the only ones doing a gantry.

In the long run, plasma wasn't a good fit for me, but that's very situational. They are good at a lot of things.

Well you called me out - I will admit it's a bad choice for a business to do a DIY table when you can get something pretty decent for $20k financed at $300/month! I took this on as a way to learn more about automation and motion control as our customers are asking for that in our prototyping shop. Secondly, as this evolved, we realized there is a huge market for guys that want to build, and are looking for something better than a Crossfire table. So we plan to offer "kits" for the pro hobbyist, or small fab shop that doesn't see what they want or is after the learning experience like we are. All this is taken with a grain of salt as we also have a 5x10 import fiber laser with dual beds and all the goodies - something that can be had for $65k on the used market.

That being said, your pain is why I'm trying to make all this accessible and easy. Precision plasma is a great gantry and when I first read about your build all those years ago, I've just about kept one in my shopping cart for the same amount of time. What I couldn't get around was the electronics, motors and packaging. The fab is the easy part. So, I'm using the good fortune I had in 2020 to allow me the time to do this the right way and offer up components that can be used for a scratch built plasma or as parts of another kit, such as the stuff from Precision Plasma or even Langmuir/Crossfire.

All that to say I agree, it's not worth it as a business but to some guys it still is - at home and in a small fab shop. We have mostly been using our stuff for custom tables - one a pure rotary setup to automate the cutting of steel barrels for a chair manufacturer.

Enough chat, here's some Z axis pics for the meat and potatoes:

We ended up printing the torch mount using a FormLabs Rigid4k material. It's glass reinforced and feels almost like ceramic. Printed 0.004" undersized on the bore so time to clean it up for a running free fit of the linear bearing that holds the torch.

Just about to tease in there.

Done!

After this, despite how well it takes a tapped hole, we added some M5 (sorry) heat-set threaded inserts. All it takes is a tip adapter for a soldering iron and you press in the inserts into a 9.5mm hole. Pretty easy and allows for some durability when taking on and off a prototype part like this. I did not use inserts for the stainless set screws that lock the linear bearing in place. The bearing is a 35mm ID for most Hypertherm and Thermal Dynamics machine torches.

The reason for all this is to streamline the mechanical touch off in the event of a problem using "ohmic" touch off from the machine tip. This error happens a lot with water beds or if there is some weird spot and the circuit can't be completed. If it's not clear - the plasma needs to "zero" the top of steel so that it knows from what distance to start piercing from. Proper pierce height makes for a better hole and increases consumable life. After the pierce, Z height is controlled using the Torch Height Controller which monitors voltages and does some fancy calculations. More on that to come.

Cheaper tables don't use a THC (or even move in Z at all) and you can get some bad or no pierces and other problems. Sure, they cut, but we are trying to achieve the best possible cut we can here.

 

[slodat]

There’s a lot of good documentation out there on what is needed for the controls, though it may not be plasma specific. Three axis motion stuff is well documented in my experience. I learned the most when I moved to a controller that had a strong user base and manufacturer that listened to its customers. What control system are you going to use?

You’ve done some really nice work here. I’m in for the ride. My next machine will probably be a cnc plasma.. unless I find a turret lathe I can’t pass on.

 

[steel 35]

Furniture shop? Where's the router

 

[aggierailroad]

Furniture shop? Where's the router

Already have one 4x8, water cooled spindle and auto tool changer.

 

[aggierailroad]

There’s a lot of good documentation out there on what is needed for the controls, though it may not be plasma specific. Three axis motion stuff is well documented in my experience. I learned the most when I moved to a controller that had a strong user base and manufacturer that listened to its customers. What control system are you going to use?

You’ve done some really nice work here. I’m in for the ride. My next machine will probably be a cnc plasma.. unless I find a turret lathe I can’t pass on.

I'd have to agree, but in my research a LOT of the info out there for controls was built on logic for plasma. What I really mean by this is the motion trajectory planner stuff in software. So some folks said, hey, here's a computer that controls xyz, let's just stick a torch on there and cut parts. Unfortunately, what we've found is that plasma doesn't behave the same way (as have Hypertherm and their awesome cutting software) and we have nearly completely rewritten the motion planner and HMI ourselves.

To answer your question about control system - we have chosen to go with LinuxCNC's PlasmaC control and a custom HMI. There's a lot to argue here about pros and cons of "open-source" versus proprietary and I've likely heard all the points before from both sides. Happy to hear anyone's thoughts here. What we ultimately decided is that keeping the software open-source allows for a better product that one focused team can develop on their own versus the lag in updates that folks (mainly our group) has been developing for free. Lastly, it's free. Anyone can get it, slap it on any table and make good cuts. We have been approached by a few major manufacturers (Tormach..) about 6 months before their tables were released. If you follow Tormach's history, you know they have a long affair with LinuxCNC and built a company on it. I've considered paying for this kind of in-house motion control development, but then I'd be just another guy trying to sell a mid-priced plasma table - the difference being I'd be one of the few with my own control software.

All this rambling just means that I think plasma should be affordable, easy and fast. This, to me, means a combination of DIY, open-source and reliability. This is especially true to the small hobbyist and job-shop types that need parts cut and could feasibly afford a small fiber laser.

Thanks for the compliments. There is a Hardinge small turret lathe for sale locally here that is semi-automated with what looks like relay logic. Pretty cool machine. What do you make where you want a turret?

 

[latebreak]

Have you checked out the Langmuir Systems Crossfire Pro? Great plasma table for DIY for the price point. Probably not suited for semi-pro or full time fab shop.

I have one I am currently assembling and starting up. I struggled with making the jump to the next step up (like STV CNC), which was about 2-3x the cost of the Crossfire Pro.

I think there is a niche market somewhere between the two...especially if you could deliver a 5'x5' table for a reasonable cost.

My other 2 cents - design around a Hypertherm power supply and make integration with their CPC implementation and machine torches. Nobody ever regretted a Hypertherm purchase and their fine cut consumables are supposed to be fantastic.

 

[latebreak]

Maybe some other comments based on my Crossfire Pro so far...

Offer a 1 piece water pan of reasonable thickness and depth so folks can safely use 65 amp + power supplies. I am having a local fab shop make me a 16 gauge pan for my Crossfire Pro.

Think about water management. A lot of Crossfire Pro users have systems to pump water in and out of their table to minimize corrosion and ease cleanup of slag and dross.

Come up with some protection for for the lead screws (if you go the path of screws vs belts) as on the Crossfire Pro they are rather exposed and fragile.

Perhaps offer some design flexibility in terms of the stand/base. Some want mobile and leveling and some want stationary.

 

[steel 35]

Already have one 4x8, water cooled spindle and auto tool changer.

Nice:
I am looking at 1200. and change to upgrade to Linux;
and the thought of trying to learn something again

 

[aggierailroad]

Nice:
I am looking at 1200. and change to upgrade to Linux;
and the thought of trying to learn something again

Lot easier to do this stuff to the router. Build it strong and heavy and the rest follows suit. We are down to shaving ounces off the gantry here to have 5G rapids.

I've seen the 1200s come all over the place in terms of their linear rails and ball screws. Not saying Hiwin is the best, but most of the importers will let you spec your suppliers for some of this critical stuff for not much more money. Give it a shot when you go to order!

 

[aggierailroad]

Maybe some other comments based on my Crossfire Pro so far...

Offer a 1 piece water pan of reasonable thickness and depth so folks can safely use 65 amp + power supplies. I am having a local fab shop make me a 16 gauge pan for my Crossfire Pro.

Think about water management. A lot of Crossfire Pro users have systems to pump water in and out of their table to minimize corrosion and ease cleanup of slag and dross.

Come up with some protection for for the lead screws (if you go the path of screws vs belts) as on the Crossfire Pro they are rather exposed and fragile.

Perhaps offer some design flexibility in terms of the stand/base. Some want mobile and leveling and some want stationary.

Thank you for your thoughts. Unfortunately, we're not in the same ball park compared to a Langmuir. No Z, no THC, and all the other problems you've mentioned. I am curious, based upon your purchase history and recommendations for improvements - you're almost at a "name-brand" table in terms of specs by the time you finish your upgrades. Why did you not choose to just get, say, a JD2 or Maverick table for about $15k, financed at around $300/month? Money is about even and the headache is less with a well-tuned machine that has all the extras you are not happy about with your Crossfire.

Regarding leadscrews - we will not be using them. It is really hard to turn a leadscrew fast enough to get the kind of acceleration and cut velocity needed for the thin gauge stuff without suffering through screw whip and excessive wear. Also, it takes quite a motor to turn the screw due to inherent drag losses from the design. For my table I have chosen to use hardened vee rails and vee bearings - ultra fast, low friction and they have a sort of self-cleaning feature. The verdict is split on plasma on H rails versus vee rails, but we figure it'll be better in the long run. A lot of this is based upon our history with laser and recirculating ball bearings causing premature failures at high speeds (due to the ball change in direction when recirculating). This is a lot of nerdy talk to say - we're using a helical rack and pinion and vee-rails for motion.

 

[Kenny1448]

What software are you going with to run the table? Ive used grbl, Mach 3 and now use uccnc. uccnc for the with. What THC are you going with? Ive built quite a few tables in my time. Willing to help you anyway I can.

Im getting things ordered right now for 5x10 as we speak

 

[aggierailroad]

What software are you going with to run the table? Ive used grbl, Mach 3 and now use uccnc. uccnc for the with. What THC are you going with? Ive built quite a few tables in my time. Willing to help you anyway I can.

Im getting things ordered right now for 5x10 as we speak

Kenny, I am using a subset of LinuxCNC called Plasmac. We have our own THC that we reckon is pretty stinking good as we use a PID controller to smooth the typical "bang bang" response most torches have. I'm definitely interested in hearing about what features you like and dislike about all the tables you've used. I've got a pretty long list myself but love other inputs. There's a lot of improvement that can be made out there and I aim to do what I can.

Progress has been slow as business is picking up. I got the electronics in and have tested the boards. I'll try to post soon.

 

[Kenny1448]

Kenny, I am using a subset of LinuxCNC called Plasmac. We have our own THC that we reckon is pretty stinking good as we use a PID controller to smooth the typical "bang bang" response most torches have. I'm definitely interested in hearing about what features you like and dislike about all the tables you've used. I've got a pretty long list myself but love other inputs. There's a lot of improvement that can be made out there and I aim to do what I can.

Progress has been slow as business is picking up. I got the electronics in and have tested the boards. I'll try to post soon.

Linux is probably going to be your best bet as it is filled with options to better tune your cutter. Ive used Proma SD, Proma 150 and now going with a Minithc. My first 2 tables were rack and pinion, not very clean cuts but then I went with a 3:1 belt reduction and am able to run HP book settings with very clean cuts. Used stepper motors in the past with good clean cuts, will probably go with DMM servos with 10:1 planetary gear reduction on my next build. Thinking this will be my last build. Gear reduction in my opinion is best. It's been probably 5 months on this current build, still deciding on motors although I bought some Nema 34 900oz 8 wire motors for it but starting to lean more toward servos. I build them then use for awhile then sell. Not a business for me, just a hobby

 

[latebreak]

Thank you for your thoughts. Unfortunately, we're not in the same ball park compared to a Langmuir. No Z, no THC, and all the other problems you've mentioned. I am curious, based upon your purchase history and recommendations for improvements - you're almost at a "name-brand" table in terms of specs by the time you finish your upgrades. Why did you not choose to just get, say, a JD2 or Maverick table for about $15k, financed at around $300/month? Money is about even and the headache is less with a well-tuned machine that has all the extras you are not happy about with your Crossfire.

Regarding leadscrews - we will not be using them. It is really hard to turn a leadscrew fast enough to get the kind of acceleration and cut velocity needed for the thin gauge stuff without suffering through screw whip and excessive wear. Also, it takes quite a motor to turn the screw due to inherent drag losses from the design. For my table I have chosen to use hardened vee rails and vee bearings - ultra fast, low friction and they have a sort of self-cleaning feature. The verdict is split on plasma on H rails versus vee rails, but we figure it'll be better in the long run. A lot of this is based upon our history with laser and recirculating ball bearings causing premature failures at high speeds (due to the ball change in direction when recirculating). This is a lot of nerdy talk to say - we're using a helical rack and pinion and vee-rails for motion.

$3000ish shipped for a 48x33 table with Z axis THC is why I went the Langmuir Crossfire Pro route. Sounds like you may be thinking of the Original Crossfire.

I am a hobbyist, so anything larger that 4x4 or 5x5 just is not practical or necessary for my shop. The Crossfire Pro fit into my needs. If an option existed for $5000-6000 that was a notable upgrade from the Pro, I would have gone that direction. I was not looking to spend $15K, nor would I finance a tool not used for revenue generation.

Local fab shop was $450 for a gorgeous 16 gauge 304 water pan. That solved my issue with the thin, 2 piece pan from Langmuir. I’m making a couple formed guards to protect the Y-axis lead screws so maybe $50 in material there. The one piece water pan also makes water management easy as I have a center drain with a 1” NPT bung and a stainless ball balance to drain.

My comments were observations. My crossfire pro has met my needs and overall I am happy.

V rails sound interesting. Will continue watch your progress.


Sent from my iPhone using Garage Journal

 

[aggierailroad]

$3000ish shipped for a 48x33 table with Z axis THC is why I went the Langmuir Crossfire Pro route. Sounds like you may be thinking of the Original Crossfire.

I am a hobbyist, so anything larger that 4x4 or 5x5 just is not practical or necessary for my shop. The Crossfire Pro fit into my needs. If an option existed for $5000-6000 that was a notable upgrade from the Pro, I would have gone that direction. I was not looking to spend $15K, nor would I finance a tool not used for revenue generation.

Local fab shop was $450 for a gorgeous 16 gauge 304 water pan. That solved my issue with the thin, 2 piece pan from Langmuir. I’m making a couple formed guards to protect the Y-axis lead screws so maybe $50 in material there. The one piece water pan also makes water management easy as I have a center drain with a 1” NPT bung and a stainless ball balance to drain.

My comments were observations. My crossfire pro has met my needs and overall I am happy.

V rails sound interesting. Will continue watch your progress.


Sent from my iPhone using Garage Journal

Just for grins now as we've both made our beds and will lie in them - but did you see the Brian Oltrogge Platform CNC? I've seen one converted to plasma. Worked great and fits the right size for garage shops. He's a pretty smart dude.

 

[midwestracer2003@yaho]

this post died or was it carried on elsewhere

 

[tarbellb]

Bump!