SOMD - Lowrider Plasma CNC

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Here’s the build log for my Lowrider CNC Plasma/Router combo.

Specs

Update: There is now a 48"x48"x3" water pan installed while plasma cutting to keep the smoke down. After a few tries of sealing leaks, it is now operational and much much better than cutting on open slats. The garage no longer hazes up with conductive metal dust which can damage other electronics, and I am no longer inhaling all of it! I would highly suggest adding a water table if you are doing any significant amount of cutting.

Working area is 4’x5’ with a footprint of about 5’x6’. The 4’ (about 50" actually) was the critical dimension because I did not want to have to rip stock down to get it to fit on the table. I settled with 5’ on the length because I value the garage space more than the few times I imagine I will be cutting an entire sheet. Since the table supports 6’ of length, I can easily cut a full sheet by splitting the jobs and shifting the stock in between.

Hardware

Update: I am now using Mesa electronics hardware (5i25 & 7i76 combo, with the THCAD-300 THC) with a Dell Optiplex 960 PC running LinuxCNC. I learned early on that you just can’t get reliable cuts without a torch height controller, which GRBL does not support. I switched over to LinuxCNC so I could use a proper plasma setup, and I couldn’t be happier. There are plenty of inputs and outputs on the breakout board (32 in, 16 out) which can interface all of my limit switches, torch/router on relays and future user MDI buttons. The board also has 5 dedicated stepgens, so I can run each stepper motor off of its own driver. The drivers that I am using are TB6600. This allows me to move up to NEMA 23s if I find I want a little more speed for rapids.

I purchased the Hypertherm 45XP unit with the machine torch because I was losing my patience with the Lotos machine. While capable of cutting the 14 ga, I would still run into issues because the arc voltage coming off the unit (which is measured by the THC) was quite dirty. This led to crashes and material wasted. After switching to the 45XP I am able to cut almost twice as fast (250ipm vs 140ipm in 16ga) and the cut quality is miles ahead. No more edge angularity on parts, and much less dross on the back side. This wasn’t a necessary upgrade, but I am glad that I did it. Another thing, the Hypertherm doesn’t cause my WiFi to black out whenever it is turned on. This is convienient because I routinely ftp files between my home PC and the garage over the network, as well as listen to music via an Echo Dot.

OLD
I am using the standard RAMPS 1.4 stack with DRV8825 drivers and NEMA 17 steppers (84 oz-in I believe)

The plasma cutter I am using is the Lotos LTP5000D, 50A, pilot arc start with the standard torch and running off of 220V. For such a low cost cutter, it has surprised me with its cut quality, but I have much to learn yet about reducing dross and minimizing part cleanup. I have ran 22/4 shielded alarm wire for all of the steppers and grounded the shielding inside a metal junction box. So far, I have not seen any problems due to noise from the plasma cutter. However, I use a Netgear powerline adapter to get internet to the garage and rebroadcast it with a secondary router for wifi, and the plasma totally messes the signal up when the machine is turned on.

The focus of the machine is for plasma cutting thin (14 GA) sheets of steel, but easily switchable for routing with replacement of the slats for 2 sheets of 0.75" MDF. (Yes, I understand the potential hazards of mixing sawdust and hot bits of metal). I already have a 28"x28" MPCNC for most of that work, but always had been itching for something larger. The MPCNC will probably get resized in half for a better focus on rigidity.

Software/Firmware

Update: As stated earlier, I am running LinuxCNC on the Mesa electronics. LinuxCNC runs on a realtime kernel which means that there is no command buffer like Marlin and GRBL firmwares. This is convienient when jogging around as I can just use the arrow keys and whenever I’m at the position I’d like I stop pressing the button. No more worrying if the key was pressed too many times and its going to jog further than I wanted. This small feature is one of my favorite parts about the switch. LinuxCNC is used by a lot of industrial CNC companies. Tormach’s PathPilot interface is running LinuxCNC. Customizability is through the roof, as is the support of the userbase. The only drawback is that it does require more hardware (a full PC running Linux).

OLD
Flashed onto the Mega is GRBL 1.1f. I wanted something more geared towards CNC with better user interfaces than the LCD screen or other 3d printer oriented solutions. I have tried CNC.js via the Raspberry Pi 0W, and it worked until I turned the plasma cutter on and it takes out my wifi. I needed a solution that would not require networking, and I could control from the CNC. I am currently running bCNC on a Raspberry Pi 3 with a 7in touch LCD and it seems to satisfy all of my needs. It is fast and responsive (doesn’t require network connection to send commands which results in double jog movements or otherwise no response), and the GUI works well on the Pi3, whereas cnc.js would not. It also has a lot of great gcode editing tools and some limited CAM functionality which is welcomed.

To-Do
Tear it all down and paint everything

This has been a work in progress where I’ve been learning a lot about welding and metal working in general. Thanks to you Ryan for making this platform that we can take and create things with at such a reasonable cost, and most of all supporting it to a high level. I went all in on the MPCNC two years ago and have a MP3DP as well because I knew this community has a strong base and it’s a great place to hang out (or in my case, lurk).

Google album with more details, videos as I progress… https://photos.app.goo.gl/WywV1Q9XHMPcCAEk7

4 Likes

This thing is just epic. I love it.

w.r.t. cnc.js (and if you like bCNC, then that’s fine too):
You can install a “shopfloor tablet” UI, and then use the pi3 to connect to itself (no networking required):

Or, since you have a pi3 now, you could also do wired Ethernet.

As I said in your google photo album, a machine like this can make a lot of money. Cutting signs out of metal and painting them can be big bucks (I think, never tried). I can’t wait to see what you end up doing with it.

Yeah, I tried the “shop floor tablet” layout and it was lacking pizzazz. I could re-write the template, but bCNC was there plus it has autoleveling functionality built in, which is awesome. Ethernet is a no-go as well bc the signal all passes through over the electrical connection via the powerline adapter, which becomes useless with all of the noise generated by the plasma cutter on the garage subpanel. Thankfully the controller is ok.

Plan on doing lots of signs. Going to scour etsy to steal ideas from. Only problem is that the steel sheet prices keep going up ?

Dude…dude. HOlywhoa. Yup you now have the entire lineup of V1 tools (zenXY dinner table?) and officially the absolute baddest ass LowRider ever.

I need a plasma cutter, need as in no projects for it but I wanna play with it!

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I do not have a zenXY yet, but a large table one does sound really cool.

No no, the projects come afterwards. If nothing else, then use it to cut stiffener plates for its own machine. My torch holder is (currently) 3d printed pla, which has started to warp due to the intense heat source right below it, imagine that… So I cut a heat shield for it and problem solved. Next will probably be the XZ plates because why not?

Yes. I didn’t know I needed that until right now.

Oops… I meant YZ plates.

You mean the little ones? Why not all of them?

First piece went pretty well, 1/4" mdf + 14 ga steel is way better than the 0.190" plywood I had before. Gotta love a machine that can improve itself!

Awesome - I love that you’re doing this project. This is something that I want to do later on down the road. Langmuir systems is building a very similar product (much smaller size) and selling it for around $1000 without plasma cutter. Link below:

What I found really interesting though was their recommended plasma cutters - you can find them under the LEARN tab with the following statement up front.

the CrossFire™ CNC plasma table was designed as a hobby-level machine to accept a wide variety of available plasma cutters on the market today. The only hard requirement is that the plasma cutter does not use a High Frequency start mechanism in order to initiate the plasma arc. These style of plasma cutters are strictly forbidden for use on the CrossFire™ machine because the High Frequency arc can cause permanent damage to the machine’s electronics components.

Keep us posted on how this goes - you’ve got me fired up!

I did look into the Langmuir system however the size and lack of rigidity were an issue because I wanted to cut wood with this as well. Most plasma cnc designs are not entirely robust. There are no cutting forces seen by the gantry, so they can get away with much smaller carriages.

I’ve got less than $1200 in this build, plasma included.

This is excellent! I’ve the same make/model of plasma cutter that you used on your project. Did you know they make a straight cutter head intended for CNC? They run about $100. It’s basically a straight head instead of the curved one that comes with it.

It won’t be much longer before I start my build. Thanks for the nudge. :wink:

 

g.

1 Like

Thanks. Do you have a link for the machine torch? Only one I could find was about $180. It would be much easier to use the straight torch.

 

[quote="geneb,post:12,topic:7650"]

It won’t be much longer before I start my build. Thanks for the nudge. ?

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Go for it! Can’t wait to see yours

Whoops - it looks like I mis-remembered the price, or they jacked it up by $80 since I last looked a couple of years ago. I went to the Lotos Technology website and yep, it’s $180. :frowning:

 

g.

 

Agree, way better option to build your own. Less expensive and a much more capable machine. The other site was only interesting because they’d consolidated a list of plasma cutters which weren’t high frequency starts.

Do you have pics of how you shielded the electronics package? I’d like to get a closer look at that.

Really fired up about what you’ve done, I think its awesome.

I ran 5 pin aviation panel connectors for all everything. The fifth pin allows me to ground the shielding to the connector, and then inside the box I can connect them all together. Inside the box is kind of messy, I really don’t have enough space to lay everything out neatly and the tape I was using to hold the RAMPS board is having a hard time sticking…

All of the green wires are the shielding ground leads, as well as a ground from the power supply. Everything is ground to the junction box, but I didn’t follow through with grounding the table or driving a ground rod in the floor yet because I haven’t had any issues (that I can tell, at least). If I notice a problem, that is what I’ll end up doing.

Behind the power supply in the box is a buck converter to power the Raspberry Pi 0w in the bottom. As stated above, I’m no longer using the Pi 0, but a Pi 3 now directly. The buck converter module allows me to power the Pi via the sole power supply, because the Mega can’t supply enough current for everything.

Thank you! I appreciate it.

2 Likes

Thanks Bryan, appreciate the photos and the detailed explanation!

One more question, how are you physically connected to the plasma cutter to send it commands? I read back thru the post but must have missed it if it was in there. Thanks

 

Right now the only connection is via the 3 pin connector on the front of the plasma to trigger the torch via spindle on/off commands M3/M5. When the cnc is controlling it, I disconnect the connector that comes from the torch (button) and plug in the connector I made that is connected to a 5v relay.

Current setup lacks a torch height controller (THC) which would monitor arc voltage and vary Z height to compensate for warping and unlevel cut surfaces. Those modules cost $250+ so I’m trying to figure out if I can make one and use it with GRBL.

1 Like

That would be a fun add on. You’ll have to solve measuring high voltages, not shorting through a microcontroller and then injecting height commands into grbl. All great puzzles.