SOMD – Lowrider Plasma CNC

New Home Forum LowRider Your Builds – LowRider SOMD – Lowrider Plasma CNC

This topic contains 124 replies, has 16 voices, and was last updated by  Ryan 2 months, 2 weeks ago.

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  • #63060

    Robert
    Participant

    Just Funished my Mini Low rider and ran a program it works fine but, when I turn off the the steppers or the Lcd controler everything drops all the way to the table. and every time I set Z zero then reset the lcd, same thing happens is there a way I can fix this problem? appreciate any help.

    #63061

    Jeffeb3
    Participant

    There is a flag to keep the motors on when it powers up. If that isn’t it, make a post in low rider troubleshooting and we’ll figure it out.

    1 user thanked author for this post.
    #73066

    SuperJoe
    Participant

    This is a great build.   Thank you for the specifics.  Did you make any progress on LinuxCnC?  THC for the win if it can be compatible.  I like the idea of  Rpi3 as well.   Any updates?

    #73116

    Bryan
    Participant

    I took a long break while it was too hot to sit out in the garage and learn LinuxCNC and troubleshoot code at the same time.

    A few weeks ago I dove back in and focused on getting the router side of the machine working well. I was able to achieve 0.005″ accuracy on holes for locating pins. I have upgraded the power supply to 24v so I can achieve a good signal-to-noise ratio on my inductive sensors and gain more top speed on the steppers for G0 rapids. Right now the max rapid jog speed is about 400 ipm! Plasma cutting prefers to have high rapid speeds as to not build up too much localized heat which leads to deformation.

    This week I have been focused on getting the THC working and tonight I think I have my first results. I am testing a 5″ horizontal line on an incline and letting the THC do its thing. In short, a voltage is set in gcode and the THC takes over to handle adjusting the z-axis. I’ve labeled the spots on the voltage and z-commanded vs time graph. All that is left is to tune the settings and prevent runaway crashes.

    More photos and a video of that cut here: https://photos.app.goo.gl/WywV1Q9XHMPcCAEk7

    I also purchased a small (large) server cabinet to house all of my electronics. I’ll post some photos of that next time I’m in the garage.

    1 user thanked author for this post.
    #73122

    JDGreen
    Participant

    That is excellent progress.
    I ordered and received THC parts and can’t wait to free up a couple of days to get it going.
    What is the arc voltage value you use for the THC setpoint?
    I have a Lotos machine too.
    Thank you for sharing.

    #73124

    Bryan
    Participant

    Which thc did you go with?

    I found 66 volts on 14ga steel to work best so far. However I did not really test the card with a known voltage to make sure its accurate. Only calibration I’ve done so far is setting the frequency at 0 volts (118.2 kHz) and the scale, both of which are derived from the little sticker on the back of the thcad-300.

    Also that is around 20-25A set on the cutter  I’ll be bumping that up to gain some speed once it’s reliable.

     

    #73125

    JDGreen
    Participant

    Thanks for the voltage info.
    I bought a proma-elektronica THC-SD from Poland
    http://proma-elektronika.com/index.php/en/products/thc-torch-height-control/compact-thc-sd

    #76229

    Bryan
    Participant

    I’m getting to the point of fine tuning a new THC component that is actively being developed on the linuxcnc forums to compete with professional offerings. I’m able to make consistent cuts with multiple probe touchoffs for the first time. My confidence is building as I try larger cuts.

    New video cutting a V-22 at 85 ipm: https://photos.app.goo.gl/JyMRxWiTHNsnk8TT6

    3 users thanked author for this post.
    #76947

    Chris
    Participant

    This is great, I’ve been trying to gather info on this topic in recent weeks. I’d really like to put my small plasma cutter in the hands of a CNC controller. In addition to a table, I’d like to make a tubing cutter and marker for making roll cages. Something like this but capable of handling tube up to 3″ (exhaust work as well):

    https://www.youtube.com/watch?v=6cXeHAkBaY8

    I think the the mechanical structure of the MPCNC & LowRider are great for plasma due to the low cutting load. As you know much better than me, finding the right solution for control is the not so straight forward part. Is there a place where this is all better documented? Within the LinuxCNC forums? Are you and others planning to make the solution available?

    I know that Centroid is working on enhancing their Acorn product to work with a THC, so it could be a several months before that’s available.

    #77020

    Bryan
    Participant

    I think the the mechanical structure of the MPCNC & LowRider are great for plasma due to the low cutting load. As you know much better than me, finding the right solution for control is the not so straight forward part. Is there a place where this is all better documented? Within the LinuxCNC forums? Are you and others planning to make the solution available?

    That’s the main reason why I think the LowRider is a good fit for plasma, no cutting forces involved. The dual Z axis does make things a little less desirable vs a singular z axis that moves up and down quickly in response to THC movements, but its been working well for me so far.

    All of the info I’ve gathered for the controls side has been via the linuxcnc forums. There is a lot of variability with respect to hardware setup, most of us use Mesa FPGA cards with breakout boards to handle all of the step/dir commands instead of via PC parallel port. For development of the actual THC I’ve been following along here: https://forum.linuxcnc.org/plasma-laser/35449-another-plasma-component.

    I took a look at the Centroid Acorn. It could work with an external THC (Proma, Neuron) but doesn’t look like it would work easily with the Mesa THCAD that I’m using atm. It has an encoder input which is how I sample the arc voltage, but it’s only available via the RS-232 connector, and not broken out as screw terminals. If you like the ethernet capability, check out the Mesa 5i25 and 7i76E bundle. You’d gain an additional step/dir output (5 which is required for individual drives on the LowRider, Acorn only has 4), and 32/16 outputs/inputs vs 8/8 on the Acorn. I need to update my original post because I’ve changed all of the hardware from when I first started out on this journey.

     

    1 user thanked author for this post.
    #77100

    Chris
    Participant

    I appreciate your sharing, thanks Bryan.
    As I love to metal work, this is a big deal to me given the affordability.

    I’ll study your recommendations in order to gain better perspective.
    DIY is awesome, but the electronics get overwhelming for me quickly, which become really limits the rate of progress….

    As a result, I’m willing to spend a bit of money for the commercial solution.
    I’m 90% done with an Acorn implementation on a small mill, it’s gotten cold here, so I’ve diverted attention to a garage heating solution 🙂

    I’m a novice, but I like Acorn, it’s been trouble free and the primary forum support folks are good.
    From what I can tell in the instructions, hardware pairing is not an issue with Acorn, similar to what we are doing with Marlin:
    http://www.centroidcnc.com/centroid_diy/downloads/acorn_documentation/paired_axes_acorn_user_guide.pdf

    It’s not necessary to use up the 4th axis, they call it software pairing.

    Acorn plasma change control discussion:
    http://centroidcncforum.com/viewtopic.php?f=60&t=2071

    Looking forward to seeing this through, thanks again for sharing.

    #77107

    Bryan
    Participant

    This machine is definitely capable. The bottleneck really comes down to the quality of your plasma cutter. I rapid jog at 300 ipm, but can only really cut at 100 ipm. I’m working to fine tune the cut settings to get it cutting faster, but I may have reached my limit with the Lotos LTP5000D. Of course, at higher speeds you fight a losing battle with inertia and rigidity; trying to turn sharp corners and maintain cut quality.

    From my short time in this domain, I’ve seen that DIY solutions for plasma cncs are somewhat primitive. Having a tightly coupled THC and motion controller like the $$$$ professional machines can make all of the difference in cut quality. Plasma cutting steel on a cnc is much closer to milling metal vs wood. The settings are more sensitive when you’re trying to maintain 0.060″ cut height at 100+ ipm to prevent overheating and warping the material. An external THC solves half of the problem, but it doesn’t know what to do with an upcoming corner, or when the torch has passed a kerf that was created by something it already cut and the voltage spikes.

    I’m glad to see that Acorn is working on coupling the THC into the motion controller. It’s not trivial.

    As far as the hardware pairing, yes this is what we have done with Marlin/RAMPS 1.4 since the beginning; first wired in parallel and now series. You could run the LowRider with 3 axis inputs, hardware pairing the extra Y and Z motors. You would lose individual control such as auto-squaring both the Y and the Z axes. The Z axis is probably not as critical to square since you will be maintaining the cut height with the THC, but at some point you may like to have automatic Y squaring. You could do this with the 4 axis setup (XYYZ) where Y is software paired and Z is hardware paired.

    #77168

    Bryan
    Participant

    First real project: 14ga steel and burned wood flag, roughly 22″x14″

    Learned a lot about piercing (59 pierces on the main piece) and poor quality consumables that don’t last long at all. Bending the steel took quite a while. My FIL helped me bend the wide portion with a hydraulic press and bending die, but I bent the lower strips by myself (my own press is on the way!)

    I also am working on a shinier version where I stripped the mill scale in muriatic acid (HCl) and grinded it with a flap disc. Should be finished with that one this week.

    I started this build over the summer with intentions of making a few things in support of a craft fair which is this Saturday, so I’d say my planning is quite superb.

    Source for the flag dxf, and lots of other plasma projects: http://www.langmuirsystems.com/fireshare/rustic-usa-flag

    3 users thanked author for this post.
    #77180

    Ryan
    Keymaster

    Looks nice. I bet with a little weather outside the colors will be completely different. Grey wood and red rusty steel. Awesome project, I am sure the craft fair will go well.

    2 users thanked author for this post.
    #77218

    Chris
    Participant

    First real project: 14ga steel and burned wood flag, roughly 22″x14″
    I started this build over the summer with intentions of making a few things in support of a craft fair which is this Saturday, so I’d say my planning is quite superb.

    LOL, I couldn’t agree more, EXCELLENT project management !!!

    Thanks again for share your learning and insight. It’s very helpful to me in finding direction for my effort. It’s surprising to me how much effort chasing this topic on the LinuxCNC forum, 11 pages in less than a month. I’ll cut wood for a while, that will be good experience. I have some ideas around making mold for fiberglass parts that need some vetting. Hopefully that will keep me busy long enough for Centroid to complete their plasma revision.

    I don’t quite follow what you’re describing with axis motor pairing, but I need to read more. This is actually where I am in my MPCNC build. I traced out the kit wiring harness yesterday, but still don’t have my head wrapped around why the circuits work yet …  but it’s cool !!

    #77232

    Bryan
    Participant

    Thanks again for share your learning and insight. It’s very helpful to me in finding direction for my effort. It’s surprising to me how much effort chasing this topic on the LinuxCNC forum, 11 pages in less than a month.

    I haven’t been in tune with DIY plasma cncs for a long time, but I’ve seen a lot of development within the last month even. It’s a good time to be getting into it.

    I don’t quite follow what you’re describing with axis motor pairing, but I need to read more. This is actually where I am in my MPCNC build. I traced out the kit wiring harness yesterday, but still don’t have my head wrapped around why the circuits work yet …  but it’s cool !!

    Depending on the controller board you select, it may not have enough stepper driver inputs for each motor to have its own independent control. Independent control is nice when you want to square up an axis with two motors. Ex: Move Y1 and Y2 to home switches, when Y1 switch is triggered then keep moving Y2 independently until it triggers it’s own home switch. You couldn’t do that with a hardware pairing mode because both motors see the same step/dir signals.

    You can combine several motors together, such as both Y motors, by wiring them in series (Ryan has instructions on this). That Acorn board only has 4 axis inputs, so you could do independent control over XYZ and for the 4th do a software pair of the other Y motor. You’ll be forced to do a hardware pair (series wiring) of the two Z motors since you don’t have the 5th input available. Does that make any more sense?

     

    #77396

    Chris
    Participant

    Conceptually, yes, I can see where the logic and drivers would search and adjust to trigger both home switches simultaneously, which would then result in a square machine.

    I guess where I’m confused is the MPCNC set up, I’m working on this item currently, haven’t tested the auto-square, doing the series wiring of the first axis motors…..  🙂
    The motors are wired in series and there are 2 home switches, 1 for each motor of the axis, each is wired back to the Rambo.
    Is the firmware still able to square the axis, even though there is only 1 driver for both motors, but 2 switches?

    Admittedly, I may be blind to something fundamental / foundational to understanding the solution….
    That’s where I’m struggling, you’re being clear.

    It’s not having seen this work yet, first hand, is where my brain is getting in a knot …
    And thanks for continuing to entertain my remedial questions.

    #77400

    Jeffeb3
    Participant

    The motors are wired in series and there are 2 home switches, 1 for each motor of the axis, each is wired back to the Rambo.
    Is the firmware still able to square the axis, even though there is only 1 driver for both motors, but 2 switches?

    No, dual endstops requires dual motor drivers. For the mpcnc, you need 5 drivers. I always point out, there were thousands of machines that worked well before dual endstops. It’s an improvement, but it is a bit more expensive and complicated.

    1 user thanked author for this post.
    #77658

    Chris
    Participant

    In this case, it payed to ask the dumb question. Not sure how I missed it in the instructions, but it’s all right here:
    https://www.v1engineering.com/wp-content/uploads/2017/11/Rambo14-DUAL-help-fixed.jpg

    I actually went to the trouble of figuring out the series wiring and made a custom cable, from CAT5, for my long axis. Even though it’s a waste, it was kind of fun to drive both motors and house both endstop switch wiring in a single cable ….

    Back to crimping those tiny wires…..  At least I found my correct crimping tool, no more needle nose pliers !!!

     

    #97557

    kd2018
    Participant

    I was wondering if you could elaborate on how you put the water pan together? Use a brake to bend it into shape or weld for miles? Use any kind of sealents other than relying on the weld?

    #97566

    Bryan
    Participant

    The water pan is made out of 14 ga steel. I had a shop make two bends for a 3″ tall wall in a U-shape. They did not have a box brake, so making 4 bends was out of the question unfortunately. They gave me two strips of steel, 3″x48″ for me to weld on to make the other two sides.

    A few things I learned from doing this: if possible, find someone with a box brake that can bend all four sides from one sheet. If you want a 4’x4′ pan, then this means you need to start with a 5’x10′ sheet in order to have the wall height included. By welding on the two side pieces, I probably should not have welded the entire length. I did it in 2-3″ sections at a time but I believe it warped the pan too much. After welding I laid on a lot of 100% silicone sealant and filled it with water. It did leak in a few places so I added some more. Again, if I had all four sides bent it would have saved all the trouble.

    After a second round of silicone it has stopped leaking and held water for a few months no problem. The weld beads got in the way of a proper seal due to my lack of experience welding. Perhaps brazing would have been a better way? Or fewer welds and more sealant.

    For the first two months I left the water untreated and it was rusting a good bit. Nothing more than surface rust, but it will definitely not last. There are ways to go about preventing it from rusting. I decided to add sodium nitrite and it’s kept the water clear.

    Oh… And instead of a 48″x48″ pan I should have done about a 50″ square. The sheets of steel get caught on the edges because it’s not perfect and I have to bend back the walls to get the sheet to sit flat.

    Edit: I also got some flex seal liquid that I was going to try out but haven’t needed to yet. Was wondering if it could prevent the pan from rusting

    1 user thanked author for this post.
    #97569

    kd2018
    Participant

    Great info, thank you. What does a Fab shop charge for those bends?

    #97570

    Bryan
    Participant

    I paid roughly $100 for the steel and to have it bent around 5 months ago. I probably could have gotten it cheaper but I didn’t take the time to shop around. Cutting on open slats produced too much smoke and metal powder that I wasn’t enjoying using it. Now it stays clean. I would probably pay double that if it was bent on all four sides and I wouldn’t have to worry about leakage…

    1 user thanked author for this post.
    #97932

    kd2018
    Participant

    If you had to guess about how many linear feet of shielded wire did it take to wire up your table?

    What CAM software are you using? In an email with the estlcam developer they told me it’s not suitable for plasma, they didn’t elaborate as to why. I know it doesn’t have curved lead-in/lead-out or peirce. If that’s the only reason I can make a post processor to fix that.

    Finally, do you pay special attention on keeping your electronics distanced from your plasma? If so how far?

    #98029

    Bryan
    Participant

    I would guess around 70-80 feet. I tried to be a little conservative in case the controller location changed.

    I bought this roll from Amazon (500′) and I still have a lot left over: https://www.amazon.com/Shielded-Conductor-Security-Burglar-Station/dp/B0783QFGZG/ref=pd_lpo_vtph_23_tr_t_2?_encoding=UTF8&psc=1&refRID=476N4EVC7Y9DK49YHFH7

    SheetCAM has been the easiest thing to use, by far. It’s based on DXF/SVG files so it saves a few steps from fusion 360. Since I use LinuxCNC, I don’t even use a complicated post processor. There’s a script that runs inside Axis (my LinuxCNC control GUI) that has a control panel on the side of the screen where I can real-time adjust cut voltages and speeds. No need to bake that into the post processor since it can be changed so easily.

    Post processing for plasma is pretty straight forward. You need to modify your torch on commands to include any piercing routine (go to Z -100 and wait for limit switch trigger, go to pierce height, dwell at pierce height, go to cut height, resume path). Lead in and outs are helpful to keep cut paths clean and prevent overblown holes from when you pierce.

    What control board/firmware are you using?

    I think I’ve been extremely lucky on EMI. I haven’t noticed any ill effects since the beginning (save for my wifi going out), but when I switched to the Hypertherm even that works fine. I did not drive a copper ground rod into the ground and tie all the grounds to that, but I would have if I had problems. At a minimum I would run shielded cable and ground the shielding at one end (control box) as a precaution. There’s lot of horror stories on this subject, and a lot come from HF start machines (cheap Chinese plasmas). When in doubt, ground everything.

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    #98030

    kd2018
    Participant

    What control board/firmware are you using?

    I haven’t settled on that yet. I was hoping RAMBo with Ryan’s firmware + Proma THC SD would suffice just for simplicity. If I really do need to just go the Mesa + linuxCNC route I can do that. I’m a long time linux tinkerer so that won’t be an issue. I don’t understand at the moment exactly how the THCAD-300 THC is used. And to muddy the waters a little more I get the impression that grbl would at least be better for this than marlin?

    …I did not drive a copper ground rod into the ground and tie all the grounds to that, but I would have if I had problems…

    Answered before I could even ask!

     

    BTW the link to the wire you gave says solid core wire but the picture shows stranded. The shielding is a plastic sleeve + bare wire  instead of a foil?

    #98034

    Bryan
    Participant

    In my opinion, an integrated THC like THCAD-300 or (-10) is better than the “external” THCs like the Proma. The THCAD is integrated into the motion planner, so it can be conscious of current speeds. The external THC reacts to the instantaneous voltage reading and nothing more. It doesn’t realize that you are slowing down to go into a corner. With the Mesa/THCAD setup you can account for %feedrate and adjust the logic corresponding to your THC. Proma is more of an open loop control and the THCAD is closed loop.

    The THCAD converts the arc voltage (or divided arc voltage if using the -10) to a frequency. This frequency is then sent to the Mesa hardware which reads it and is converted back into the voltage level. That way you aren’t sending raw arc voltage from your plasma to your control board, just a low voltage, variable frequency signal. Another benefit is that it is much cheaper than the external THCs. You could get Mesa boards + THCAD for less than a Proma.

    LinuxCNC (on any hardware) > Mach3/4 > GRBL > Marlin. I would switch the first two if you didn’t have any Linux experience because it can be daunting to set everything up with the correct real time kernel and such whereas Mach3 is more turnkey. The customizability is endless with LinuxCNC if you are all about fine tuning and min/maxing your setup. As far as the last two, I never really liked Marlin for CNC router applications, I always thought GRBL was a much better solution because that’s what it was made for with multiple coordinate systems and special gcodes and Marlin is a 3D printing firmware first and foremost. I know that Marlin has expanded a little recently to include CNC support, but it has nothing for plasma machines.

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    #98035

    Bryan
    Participant

    BTW the link to the wire you gave says solid core wire but the picture shows stranded. The shielding is a plastic sleeve + bare wire  instead of a foil?

    I’m not sure if that was the exact product listing I bought, but it had the same packaging. Mine is definitely stranded wire, not solid. It should have 4 insulated conductors + bare conductor + foil + plastic outer sheathing. The foil is what is providing the shielding.

     

    Sorry if I linked the incorrect one, I’ll edit once I find the exact one I bought.

    1 user thanked author for this post.
    #98036

    kd2018
    Participant

    You could get Mesa boards + THCAD for less than a Proma.

    Well sir, you’ve about got me talked into it! Thanks again for all of your help, you’re thread has been extremely informative.

     

    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?

    #98040

    Bryan
    Participant

    You could get Mesa boards + THCAD for less than a Proma.

    Well sir, you’ve about got me talked into it!

    Sorry, I mis-remembered the price of the Proma (I thought it was closer to $300???)

     

    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)

    Proma + Rambo ~= $350

    The linuxcnc forums were super helpful for me when I was getting everything started, I would check them out before you buy your boards

    Thanks again for all of your help, you’re thread has been extremely informative.

    No problem, that’s what I was hoping for. If it helps someone else get up and running faster than I did, it is all worth it.

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