SOMD – Lowrider Plasma CNC

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This topic contains 121 replies, has 16 voices, and was last updated by  Ryan 3 days, 18 hours ago.

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  • #98042

    Bryan
    Participant

    Another question about your machine: I followed your link above to your pictures and videos of your machine. I notice your 611 plate change colors. What material and thickness is that? Did the previous plate fail?

    My original build of the V1 LowRider was with 1/4″ lauan, which was really closer to 3/16″. It was really flimsy stuff that flexed way too much. When I rebuilt everything up to V2, I used 1/4″ MDF and painted it.

    On my to-do list is to redesign the torch mount. The way I have it cantilevered off the end puts too much bending on the center assembly and it is not very rigid. I have been thinking about implementing a torch mount inside of the DW611 base in the center. It would put any loading directly between the two X rails and prevent any twisting when the torch goes to touch off. Plus by using the DW611 base it makes it that much easier to tool change when I want to go back to routering. The big headache then becomes replacing the water pan with my MDF wasteboard.

    I’ve got a lot planned for the CNC upcoming. I’ve been spending a lot of my free time building a powdercoating oven for finishing parts (30″x34″x48″ inside dimensions)

    #98059

    kd2018
    Participant

    On my to-do list is to redesign the torch mount. The way I have it cantilevered off the end puts too much bending on the center assembly and it is not very rigid. I have been thinking about implementing a torch mount inside of the DW611 base in the center. It would put any loading directly between the two X rails and prevent any twisting when the torch goes to touch off. Plus by using the DW611 base it makes it that much easier to tool change when I want to go back to routering.

    Yea I figured I’d be rigging up a floating torch mount in the center too. Something that attaches to the standard router mount for quick change is an interesting idea.

    The big headache then becomes replacing the water pan with my MDF wasteboard.

    I had thought the waste board could just slide over the top of the (drained) water pan, no?

    I’ve got a lot planned for the CNC upcoming. I’ve been spending a lot of my free time building a powdercoating oven for finishing parts (30″x34″x48″ inside dimensions)

    Nice teaser, I’m looking forward to seeing it!

    #98061

    Bryan
    Participant

    I had thought the waste board could just slide over the top of the (drained) water pan, no?

    Although it would be nice, I’m afraid that I would lose too much rigidity while routing because then the Z axis is zeroed 4.5 inches higher at the top of the pan (3″ for the pan + 1.5″ of two MDF slabs).

    Nice teaser, I’m looking forward to seeing it!

    I just added some pics of the oven to the same shared album

     

    1 user thanked author for this post.
    #98101

    Badr ALHinai
    Participant

    Thank you for sharing your experience and keep it updated 🙏,  I was thinking alot about how i should done it and your topic helped me,

    One more thing, i like the way you designed the table, could you please share cad file that on the first photo on your google photo album? I think its fusion 360

    Best regards

    #98111

    kd2018
    Participant

    Anyway, Mesa 5i25 + 7i76 is ~$210, THCAD is $70. Total : $280 +tax (extra for a PC to run Linux if you don’t have one already. I use a $50 Dell Optiplex 960 off ebay)

    + the cost of separate TB6600 driver boards right? One for each stepper or one for each axis? I’m guessing it’s gotta be one for each stepper and you’re auto squaring in linuxcnc?

    What jitter are you getting with your computer?

    If you get an opportunity I’d love to see some pictures of your electronics.

    #99422

    Badr ALHinai
    Participant

     

    I did order exact parts as your

    – Mesa 5i25 with 7i76

    – Mesa THCad

    – TB6600 drivers

    I wired everything as attached photo, and change the 5i25 jumper to provide 5v power to 7i76,

    When i use pncconf wizard and hit axis test no motor will move

     

    I struggle alot and i read and searched alot i can’t found a solution, please if you can help or anyone i will appreciate it.

     

    #99424

    Bryan
    Participant

    Glad to hear this has been of some help. I can definitely share the table, but it’s not 100% completed. I don’t really like making assemblies in Fusion 360, much prefer SolidWorks so I kinda gave up on the design once I knew the general idea I was going for. A few pieces are missing, but hopefully it gets you started.

    One thing to note, the table was designed for the LR1 with wheels on top and bottom of the Y-axis rail. Because of this, my X-axis table supports lay on two Y-axis stringers. Those stringers have quite an unsupported span being only welded on the two ends, and adding all the weight of the water on top of this was not a great idea. At some point during this summer when I break everything down to throw some paint on and finish some welds, I may revisit this portion of the table.

     

    Anyway, Mesa 5i25 + 7i76 is ~$210, THCAD is $70. Total : $280 +tax (extra for a PC to run Linux if you don’t have one already. I use a $50 Dell Optiplex 960 off ebay)

    + the cost of separate TB6600 driver boards right? One for each stepper or one for each axis? I’m guessing it’s gotta be one for each stepper and you’re auto squaring in linuxcnc?

    What jitter are you getting with your computer?

    If you get an opportunity I’d love to see some pictures of your electronics.

    Yes, I think I paid about $10 each. Since the 7i76 allows for 5 independent step/dir signals I split all of the motors out to their own driver. You probably could just use DRV8825s and it would work the same, but I wanted some extra headroom in case I ever implement NEMA23s for extra speed without losing torque and skipping steps during 300 ipm jogs.

    I haven’t configured auto-squaring yet, but I have my limit switches already ran and its ready for it, just need to change the software side.

    I’ll have to get back to you on jitter. I’m running Linux Mint 18.3 Cinnamon, so not exactly a barebones build. Jitter wasn’t horrible (30,000-50,000 iirc), but it didn’t effect operation so I didn’t bother trying to lower it.

    I will upload some pictures of the electronic cabinet when I get a chance. It needs cleaned up, but its serviceable as it is now. I intend to mount the rack on the wall and possible make a DB37 connector to switch from control of the plasma to a separate MPCNC. Anytime I use GRBL on a raspberry pi it’s an unpleasant experience compared to LinuxCNC. :/

     

    Edit: Cabinet picture here: https://imgur.com/a/riWrbSj All stepper wires and sensors come into the back of the cabinet through 5 pin panel connectors. One or two wires are hardwired into the board (need to update with more quick connectors…) 5 TB6600 drivers, 24v Meanwell PSU, and a ground and 24v positive bus for easier connections. SSRs for router and plasma connections. The whole thing is currently turned on via the power strip, will need to update to an external switch with E-stop.

    1 user thanked author for this post.
    #99426

    Bryan
    Participant

    I did order exact parts as your

    – Mesa 5i25 with 7i76

    – Mesa THCad

    – TB6600 drivers

    I wired everything as attached photo, and change the 5i25 jumper to provide 5v power to 7i76,

    When i use pncconf wizard and hit axis test no motor will move

    I struggle alot and i read and searched alot i can’t found a solution, please if you can help or anyone i will appreciate it.

    I’m not sure if I ever used the test axis button; I briefly used the wizard to setup the general outline of the config files and edited them in a text editor. Once you have the basic lines, its easy to go in and adjust steps/unit and setting it negative if you need the direction reversed, etc.

    I’ll upload my configuration files to give you a baseline config that you can tweak to match your setup, but I would highly suggest to go through and comment out/delete lines that don’t deal with the initial movement setup. It can be very confusing trying to adapt configurations. Once you have the basic things working, you can reintroduce the other parts.

    My recommendation is to start one axis at a time and go from there. Steppers > Limit Switches > Relays > Rest of plasma stuff

    Also, you’d be better off starting a thread over at forum.linuxcnc.org for help getting everything initialized. I don’t know of many here that are using this setup so the help may be limited. I don’t mind helping, but you should start a separate thread and document what you’ve tried.

    One more thing, make sure you tie all of your grounds together. The grounds from the drivers and the PSU and the 7i76 should all be connected somewhere. Unconnected grounds have driven me wild chasing down a problem before…

    Edit: Upload isn’t working. Posted them to pastebin: https://pastebin.com/psz3q63S and https://pastebin.com/fzXqCJvJ These are the two basic files that should at least get the motors running. You may need to adjust how the axes are mapped, but it will at the very least move the motors. If not, you probably have a wiring issue.

    #99591

    kd2018
    Participant

    I don’t know if you’ve had to deal with this yet yourself. How would you handle tiling with a larger plasma cut part? It seems pretty straight forward with a router just dropping in some dowels for locating pins, but with a plasma torch I’m imagining it could be an issue with precision and repeatability. Maybe not. How have you/ or how would you handle tiling?

    I’ve tried googling but can’t seem to find any good examples of people tiling on their plasma table.

    On a side note, fedex just delivered to me a 7i76e. Time to start compounding the frustration 😉

    #99593

    kd2018
    Participant

    Edit: Cabinet picture here: https://imgur.com/a/riWrbSj … SSRs for router and plasma connections.

    Thank you for posting. While I’m new to cnc I have been playing with mircrocontrollers and ssr for a few years now. I wanted to caution you about the relays being attached to wood. I don’t know what relays you’re using but the chinesium cheapos are known to fail from time to time, when they fail they can go up in flames. Also, if any loosened connections were to arc it could ignite the wood. I’ve read stories of people setting their homes on fire. I know we’re already playing with torches and power tools and don’t leave these unattended, so we take on more risk and but also more precautions than those guys, but I just wanted to get that out there.

    #99605

    Bryan
    Participant

    I don’t know if you’ve had to deal with this yet yourself. How would you handle tiling with a larger plasma cut part? It seems pretty straight forward with a router just dropping in some dowels for locating pins, but with a plasma torch I’m imagining it could be an issue with precision and repeatability. Maybe not. How have you/ or how would you handle tiling?

    I’ve tried googling but can’t seem to find any good examples of people tiling on their plasma table.

    On a side note, fedex just delivered to me a 7i76e. Time to start compounding the frustration 😉

    That’s a tricky one. I haven’t seen anyone do anything like that with a plasma, either. Most people either have 4’x8′ (or larger) or 4’x4′. I wouldn’t recommend anything smaller than 4’x4′ just due to sheet stock sizes. If I ever had a request to do something 6′ long, I would probably just pass on it, or cut in two pieces and weld it back together? Yeah, nope, I’d pass. Since I probe the surface and adjust my Z-offset prior to every pierce, I’m not too concerned with how flat my water pan and slats are. The THC handles Z-movement very well, so I don’t have anything easy to index off of for things like pin indexing.

    Have fun with the 7i76e, I probably would have dropped the extra for ethernet if I did my research first.

    Edit: Cabinet picture here: https://imgur.com/a/riWrbSj … SSRs for router and plasma connections.

    Thank you for posting. While I’m new to cnc I have been playing with mircrocontrollers and ssr for a few years now. I wanted to caution you about the relays being attached to wood. I don’t know what relays you’re using but the chinesium cheapos are known to fail from time to time, when they fail they can go up in flames. Also, if any loosened connections were to arc it could ignite the wood. I’ve read stories of people setting their homes on fire. I know we’re already playing with torches and power tools and don’t leave these unattended, so we take on more risk and but also more precautions than those guys, but I just wanted to get that out there.

    That’s a good point, I did see the huge heat sinks that they come with but didn’t think much about putting them right on the wood. I’m sure they were the cheapest SSRs out there. My only comfort is that there is probably only a few mA running through the plasma SSR since its only purpose is to close an 18VDC circuit on the Hypertherm. Nonetheless, thank you for pointing that out, I do need to come up with a better system.

    #99614

    kd2018
    Participant

    My only comfort is that there is probably only a few mA running through the plasma SSR since its only purpose is to close an 18VDC circuit on the Hypertherm.

    Oh yeah, duh. I’m used to running 30+ amps through them. You’re probably fine. (*not an ee)

    #99700

    Bryan
    Participant

    Still a valid point for the 7 amps the DWP611 can pull, I just haven’t tried that one yet.

    #99743

    kd2018
    Participant

    I’ve tried to reverse engineer your wiring connections based on that photo. Assuming your tb6600 headers are in the same orientation as mine it looks like you simply wire Dir- from the mesa directly to Dir- on the driver, Dir+ to Dir+,  Pul- to Step-, and finally Pul+ to Step+?

    No need for limiting resisters or jumpers anywhere? The enable signal ports are meant to be left empty?

    I’ve seen conflicting information flipping through what docs I’ve found online… No need to worry about this common-anode active low active high business?

     

    https://www.amazon.com/gp/product/B07B9ZQF5D/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

    #99756

    Bryan
    Participant

    That’s correct, no need for anything extra on the 7i76.

    I left the enable pins empty and the steppers power up as soon as the rest of the electronics are turned on. In the future I’ll probably wire it to a separately controlled pin so I can turn the drivers off. The motors do get quite warm/hot after they’ve been on for some time. And my current setting was set appropriately for my steppers

    1 user thanked author for this post.
    #99769

    kd2018
    Participant

    Thanks again for all your help, Bryan. I’m jogging steppers now with linuxcnc!

    I hope you don’t feel like I’ve been hijacking your thread, I’ve tried to keep my questions relevant to your build.

    #99788

    Bryan
    Participant

    Awesome! Setting up the ini and hal files can be a daunting task, but you’re off to a good start.

    I don’t mind you posting here, it helps others who want to follow along with the same build.

    #100444

    kd2018
    Participant

    When I rebuilt everything up to V2, I used 1/4″ MDF and painted it.

    Just a coat of latex paint? Did you give it a sealing coat first? How has the MDF help up to splash back from the water pan?

    #100508

    Bryan
    Participant

    I actually used enamel spray paint. I wanted to use enamel on the steel so I just tested it out on the mdf first. Once it cures its fairly tough, probably acts as a sealant too.

    So far it’s held up fine. I’ve been thinking about replacing it with aluminum or skinning the bottom with 16ga powder coated steel. My wood storage shed gets wet during heavy rain, and I’ve had MDF get wet and mold before, so I’d like to avoid that.

    1 user thanked author for this post.
    #100698

    kd2018
    Participant

    Bryan,

    Can you tell me about the design of your floating torch?

    I don’t see that you’re using an ohmics sensor, or are you? I’ve read they can be a problem when used with a water pan.

     

    [edit]

    I think I found it: https://www.thingiverse.com/thing:2516238

    I’v made a mockup of this mount on top of a 611 plate to see how I can fit it in the center of the plate and miss the rails. It looks it could work without any changes to the float, it just needs some brackets. Looks like the brackets could use 2 of the existing mounting holes in the plate while drilling a few more. I’ll let you know what I come up with. Any suggestions? (the black rectangles represent space occupied by the x rails)

    #100723

    Bryan
    Participant

    kd2018,

    I do not recommend using that torch mount without heavy modification. I initially had my torch mount off the side of the plate and there was a ton of bending and twisting as a result. No amount of reinforcement would prevent it because it is cantilevered off the side. Just recently I designed a new torch mount for my machine torch using the center mounting location. Video of new torch mount: https://photos.app.goo.gl/ioZZzyQRcqQXKUMZ8

    It uses 8mm smooth rod with LM8UU bearings (8) pressed in. On one of the 8mm rods that sticks above, I have a spring to help return the torch back down. I may need to add a second spring, but 4 would have been too stiff I think.

    I’m still testing the design out and it seems to be working very well. Thingiverse (WIP) link: https://www.thingiverse.com/thing:3635521

    If you have a hand torch, you’d have to modify the center carriage, but 100% mount the torch from the center of the 611 plate, not the end.

    I’m only using a floating Z, but am interested in wiring up the ohmic sensing with a float switch backup. I mostly cut 16ga sheets, so there can be a lot of flex which messes up the initial height sensing (IHS). Yes, water can interfere with the ohmic sensing, but my air is usually always flowing after the first cut and displaces the water right below where it’s going to pierce next so I don’t think it will be a big problem.

    TorchMount

    Attachments:
    #100725

    kd2018
    Participant

    I was editing my previous post when you replied. Already ahead of you on moving that mount to the center of the plate 😉

    Your new torch mount looks good. I’ll look forward to the upload.

    [edit] interesting design! it’s got me thinking. Could you get away with 3 bearings/rods instead of 4? In an equilateral triangle pattern and oriented such that one side is open to allow mounting a hand torch..

    #100732

    Bryan
    Participant

    Could you get away with 3 bearings/rods instead of 4? In an equilateral triangle pattern and oriented such that one side is open to allow mounting a hand torch..

    Yes, probably. Two rods were good on the previous direction in the X direction, but provided no support in the Y direction. I initially tried 3 evenly spaced at  60 degrees, but it interfered with the 4 bolt pattern for the bottom of the baseplate. I’m sure you could make a new carriage for a hand torch. I only have the machine torch for my machine so I can’t try anything else.

    I mentioned it in the Thingiverse post but it is a work in progress. I printed it once and then sanded a few things to fit and drilled out the holes in the base plate a little bit to accept the 8mm rod. I’ll go back eventually and fix these and reupload, just be aware for now.

    1 user thanked author for this post.
    #100754

    Dui, ni shuo de dui
    Participant

    Very interesting thread, I somehow missed it.

    Someone was talking about straight cutters being expensive earlier. I don’t know if some of you kept digging, but in my case I ended up buying very cheap ones and they worked fine. something like that:

    https://www.aliexpress.com/item/P80-Straight-Head-Cutter-Machine-Arc-CNC-Cutting-Torch-Head-Body-Machine-For-Cutting-Torch-Cutting/32987236749.html?spm=2114.search0104.3.90.298039dbmUfT0r&ws_ab_test=searchweb0_0,searchweb201602_6_10065_10068_319_10059_10884_317_10548_10887_10696_10192_321_322_10084_453_10083_454_10103_10618_10307_10301_10821_537_536,searchweb201603_52,ppcSwitch_0&algo_expid=48f1bc9d-32c2-4fcb-b305-f7b089feda80-16&algo_pvid=48f1bc9d-32c2-4fcb-b305-f7b089feda80

    Or that:

    https://www.aliexpress.com/item/P-80-Plasma-Machine-Torch-Head-With-Black-Color/32998001770.html?spm=2114.search0104.3.226.298039dbmUfT0r&ws_ab_test=searchweb0_0,searchweb201602_6_10065_10068_319_10059_10884_317_10548_10887_10696_10192_321_322_10084_453_10083_454_10103_10618_10307_10301_10821_537_536,searchweb201603_52,ppcSwitch_0&algo_expid=48f1bc9d-32c2-4fcb-b305-f7b089feda80-36&algo_pvid=48f1bc9d-32c2-4fcb-b305-f7b089feda80

     

    Also, could some of you guys elaborate on that linux CNC DIY torch height controller? I’m especially interested in the electronics here, since I was discussing with the Marlin guys on a forum last year and they were interested in developping an option in their firmware to manage torch height directly with the Z axis, using some kind of modification of their bed leveling feature. This would mean that we could use the automatic torch height control very easily without any kind of hardware mods to our machines.

    #100759

    Jeffeb3
    Participant

    This would mean that we could use the automatic torch height control very easily without any kind of hardware mods to our machines.

    That would be awesome.

    #100762

    kd2018
    Participant

    I have not personally used this yet but I am building this system and have been doing some homework. Here is my understanding at the moment:

    For THC we’re using the Mesa THCAD. The THCAD takes input from the plasma machine, <200 volts, and converts that to pulses. The pulses are sent to the cnc controller to be read just like an encoder. The plasma machine is isolated from the rest of the electronics. The controller can read the pulse frequency and simply calculate the voltage. The controller itself then adjusts the z height.

    The manual says the output frequency is from 100 KHz to 1 MHz. So my first question would be can the arduino’s read that fast? The frequency output can be divided by 32, 64, or 128 at the expense of some resolution. I don’t have experience yet to know what kind of resolution is necessary for sufficient torch height control.

    Speaking of resolution, there are 3 versions of the THCAD, the -5, -10, and -300. That is they can read input from the plasma machine up to 5v, 10v, and 300v respectively. The voltage input from the plasma machine needs to be in the range of your THCAD card in order for us to be able to make useful calculations. And the more fully the machine uses that range the better resolution your readings will have. *Note the plasma input on these cards are very robust, you can input higher voltages than those without worrying about frying the card, you just won’t get useful frequency output.

    There is a a safety concern to consider. Ideally your plasma machine has voltage dividers onboard to reduce the input voltage into the THCAD appropriately for the -5 or -10 model. If your machine doesn’t then you’ll need to either use the -300 or provide your own high power voltage divider for the -5 or -10, and use appropriately gauged/rated wiring which exposes you or at least your electronics to “potentially deadly” high voltages.

    http://www.mesanet.com/pdf/analog/thcadman.pdf

    I would love to know if you guys could get this up and running with an atmega. Though I think developing the logic to control the torch height *intelligently* wont simply be a trivial task. As Bryan mentioned before, the logic will need to take other things into account like  when coming into a turn, speed changes, crossing kerf, etc. because all of this will effect the voltage reading. If you’re a code guy here is the open source effort to get this fine tuned in linuxcnc: https://github.com//phillc54/linuxcnc-plasmac

    [Edit #532134]

    Found this: https://www.cnczone.com/forums/general-cnc-plasma-oxy-fuel-cutting-machines/363498-teensy-torch-height-control.html

    #100809

    Bryan
    Participant

    Thanks for writing that up kd, saved me some effort. That is all my understanding as well.

    By far the best way to control a plasma cnc is with LinuxCNC; no debate there. There is a pretty steep learning curve but the guys over at the forum have been working for a while now (quite rapidly, at that) on developing a fully integrated control suite for plasma systems with any hardware combination, granted it runs LinuxCNC.

    Two links to follow would be: https://forum.linuxcnc.org/plasma-laser/36410-configuring-plasmac-a-complete-thc-plasma-config-for-any-hardware?start=70#133801 and https://forum.linuxcnc.org/plasma-laser/35449-another-plasma-component?start=770#133810

    There’s 80 pages of development on the second one and its getting better literally every day. The system that Phill has been working on outperforms commercially available systems according to those with experience.

    If you want to stay with Marlin, it is still possible, but you’ll have to use an external THC (or possibly follow the link that kd posted about the THCAD with a teensy board). The external THCs know nothing about the motion planner, and simply just respond to voltage. They certainly work as plenty of people use Proma THCs and Neurons, I just think there is a better way to control everything than having a “dumb” torch height controller.

    It only took me a few failed cuts due to warpage with my initial GRBL setup to switch to something with a THC.

    IMG_20190516_215636

    This is a file that I attempted to cut with my old system and it was too complex and warped too much on small areas that the torch would stop cutting through. I cut this the other night (16ga, cold rolled steel; roughly 24″ wide) and it was absolutely flawless. Virtually zero cut angularity  an no warpage (thanks to water table) and it was cut at 250 ipm! Dross on the backside was minimal and easily taken care of with a needle scaler.

    #100820

    kd2018
    Participant

    That looks awesome! Still using the nema 17’s @ 24v with TB6600?

    (trying to gauge what kind of speeds I’ll be able to get)

    #100822

    Bryan
    Participant

    Still using the nema 17’s @ 24v with TB6600?

    That’s correct. I can jog around at 300 ipm, too much more and it will skip steps. However that’s more than enough. I think they are 84 Oz-in nema 17s.

    #100856

    kd2018
    Participant

    That’s awesome! I’ve mentioned a few times over at the LinuxCNC forums that I’m building with nema 17s and someone usually questions the choice. Hopefully I’ll get as much milage out of them as you do.

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