I’ve been lurking for a while now and have some ideas for my build, but I have a few questions/considerations I could use help with. I want to have a 4’x8’ work area with 1/2 of that area designated for routing/milling/laser operations and the other half for plasma.
- What BoB and drivers, or combo (like the RAMBo) would be optimal to handle all processes? I will add THC (probably a Proma) in the future.
- I'm considering 2"x2" steel square tube for the frame with uni-strut under the full bed. The plasma would have a water box that would sit on top of the strut to allow me to remove it and accommodate a full sheet of ply/? if needed when routing/milling/laser large jobs. Thoughts?
- Dust Collection...... Obviously, there are considerations with wood dust and a plasma cutter in close proximity. Hopefully the water box will minimize the danger, but safety is paramount as I have no desire to file insurance claims on my garage. What has been working well for you guys?
TYIA for your help/advice.
Since you are going to be reconfiguring for different cutters anyway, I’d look seriously at the differences you need in the bed between the different usages. For the plasma you really want a flat bed with open latticework and made from something that doesn’t melt or burn easily. For router milling you want a material that’s flat but soft enough to not harm your cutter when you go a little deep. For laser either would work. What I’d suggest is build the whole table for plasma then mount a spoil board when you’re going to be milling. You can swap surfaces relatively easily, just unclamp and slide the spoil out when you’re going to be doing plasma and slide it back in and reclamp when cutting wood or lasing.
That sounds like a great idea and totally doable. Do you have ideas/experiences with the BoBs that will work with the Proma for THC? I don’t want to relearn the software when I add the THC, i.e. I want to use the board, firmware and software from the beginning that will allow me to add the Pronto at a later date.
A little background on this project:
I currently have a PlasmaCam 4x4 with some of the software upgrades, including THC, and I have adapted it for doing MINOR routing. The table and software are great for plasma, but the table lacks the rigidity for accurate routing and repeatability. Also, the software is extremely proprietary (not even a distant cousin of open source) and with software upgrades costing $1k each (for enabling a checkbox), not even close to worth the trouble to try to get it to perform multiple processes.
As much as I wish things were different, I don’t have space in my workshop for a 4x4 (~5x5 footprint) plasma table and a 4x8 (~5x9 footprint) router/laser/milling table. I have contemplated a build like this for a couple years now and was impressed when I saw Ryan’s design since it allows for almost unlimited scalability in size and process, unlike any other design I saw or came up with.
On that note, Thank you, Ryan, for making this awesome idea open source and allowing the maker community to run with it. I watched your interview with Thomas and schools are a great idea and opportunity for this type of design, IMHO. Kids need things like this to inspire them and get them to turn off the phone for a while (I grew up in the Atari era so gaming time was limited to when Dad wasn’t watching the news and bikes were the best things to have). Oh, how things have changed.
I look forward to hearing everyone’s input on control hardware/firmware/software and posting pics of the table build. In the meantime, if anyone needs metal parts plasma cut, send me a message. The 4x4 is still up and running for now. I plan to sell it when the big table is finished.
Software-wise the plasma side of things should be easy. Use a CAD or drawing package to generate a DXF, import that into ESTLCAM and export your gcode. Import the gcode into Repetier-Host and run it on your Low Rider. Wood works the same for 2D. For 2.5D and 3D milling use 3D CAD to generate an STL and then the same process to get it to your Low Rider.
Needless to say it’s not quite as easy as that, the trick is getting your CAM settings to match your machine, with bit selection, speeds and depth of cut dialed in for the best work.
Thanks for tolerating the noob questions
"Use a CAD or drawing package to generate a DXF, import that into ESTLCAM and export your gcode."
I'm currently using F360 for modeling and rendering. I will probably continue to use that software for modeling and g-code generation since I'm familiar with it already.
What I’m not clear on is what type of BoB works well with the Proma, or does it matter? Are there better (but comparably priced) THC products for the DIY community? I feel I missed out a bit by jumping straight to PlasmaCam and DesignEdge instead of good 'ol trial and error. The routing/milling processes seem to have a lot in common with 3DP (routing especially, although both are essentially the inverse of 3DP), but laser and plasma have variables unique to those processes, IMO. I think the torch height control is what really seems to add to list of unknowns for me because actual torch height-to-z zero is a constantly changing, material specific variable which can’t accurately be accounted for in the CAM. I understand how the THC works, i.e. how it “knows” what to do, but not how some BoBs can handle it and some can’t (or maybe they all can). I guess I just need to do some more research
I’ve been working on a similar setup to the one that you are thinking about. My LR was designed as a plasma cutter first, router/laser second. I built my frame from 2.5" square, 2x3" and 1x2" 14ga steel tubing. The table is decently rigid, but I am (someday) going to go back and finish welds and figure out where it needs more support. Here’s a link to my build: https://www.v1engineering.com/forum/topic/somd-lowrider-plasma-cnc/
One thing to keep in mind, and really depends on what your plans are, is how important flatness is for routing. Ideally, you would want to surface your MDF spoilboard so that it is parallel to your cutter. This may be problematic if you plan on taking the spoilboard on and off without indexing exactly where it goes. Even then, you may run into problems or require another surfacing pass. For through cuts, this is not as big of a deal as you can just set it to cut an extra 0.010" deeper, or however out of parallel the bed is. For a plasma table design you’ll want 14ga or so 1.5-2" slats, on edge. Parallelism is not as important because it will be dealt with the THC.
I started out with the Mega/RAMPS 1.4 stack with GRBL on it because I liked using that for cnc as opposed to Marlin. However, like you already know, a THC is pretty much guaranteed on a plasma cnc, especially for thin sheets. Due to the fact that Marlin/GRBL doesn’t really have any support for THCs (it has been done, but there’s not much information out there when I was building), I decided to go with LinuxCNC. For hardware I’m using Mesa Electronics 5i25 FPGA card with a 7i76 breakout board. This gives me 5 independent axis stepper control with 32 inputs/ 16 outputs. THC is THCAD-300, which is a voltage to frequency converter card, and is integrated in with the motion planner to allow for complete control over movement and adjustment. This is definitely not the easiest way to setup a plasma cnc as the learning curve can be quite steep if you’ve never edited configuration files but it is not impossible. The LinuxCNC forums are incredibly helpful (like here). All in cost for these three boards was about $270ish.
As far as the Proma, a lot of people use it with success. It’s a standalone THC so it can be used with any motion control system. It handles the Z axis movement independently of Marlin/GRBL/etc. I’m not exactly sure how you would wire it up if you wanted intermittent control of the Z axis, like for routing, but I’m sure it can be done. I’m not sure if standalone systems can account for corner lock or not, which happens when the machine slows down to traverse a corner and heat build up causes voltage to spike, which in turn tells the THC that it needs to drop the Z (torch dive). Having a THC integrated with the motion planner can account for this.
Lastly you’ll want to investigate a floating-z torch mount. This is used to reposition the Z zero for each pierce. I’m working on one now that is a remix of https://www.thingiverse.com/thing:2516238
Thank you so much for the information.
"I decided to go with LinuxCNC"
Maybe a dumb question, but does LinuxCNC only work on a Linux system (whether virtual machine or primary OS)?
"LinuxCNC forums are incredibly helpful (like here)"
No Link. I will browse for some though. Any that you prefer?
"Lastly you’ll want to investigate a floating-z torch mount."
Will the software not allow for ohmic touch-off before each pierce?
I looked at your build and I’m impressed I hope I can continue to pick your brain on this topic.
Yes, LinuxCNC only works on Linux operating systems. It utilizes a realtime kernel (RTPREEMPT) to execute all motion planning events in conjunction with the Mesa hardware and for that reason it can’t be run on a VM. I currently run it on Linux Mint, but you could use a different flavor. Getting the correct kernel installed is most important.
Sorry, https://forum.linuxcnc.org/ are the official forums.
You definitely can utilize ohmic sensing instead of a typical touch-off. I just chose the floating z + limit switch because it seemed to be easier and I haven’t researched ohmic sensing enough. You may have problems with ohmic sensing and a water table if water is splashed underneath where you will be probing, but plenty of people have done this exact thing before.