LowRider 3 CNC Plasma Torch Mount with floating Z and magnetic breakaway, prints without supports (v1.2)

Printable files for the torch mount (for LR3-based plasma cutting table) are now available on Printables. Click here!

Note: this is designed for a machine torch (aka pencil torch, or straight torch), but could no doubt be modified to hold a hand torch.

The following is copied and pasted from the Printables listing description:

On my Design8Studio YouTube Channel I have a 6-part series of mini-installments on the process of designing and assembling this plasma torch mount with floating Z and magnetic breakaway. Below is the 6th and final video from that series. Consider watching them all (individual links below). All are shorter in running time than the final one, which takes time to explain why floating Z is desirable for plasma cutting .

Playlist links (with running times) of the mini-installments:
Links of interest:
Products used as shown in video:
Other Amazon links:
  • Magnetic breakaway — allows the torch to “bend” away instead of damaging the tip whenever an immovable blockage is encountered unintentionally. Can save your plasma torch tip in a pinch.
  • Floating Z with end-stop — for a full explanation of why a floating Z is desirable in plasma cutting, watch the sixth video in the series (linked above).
Print and Assembly:
  • Print the parts as oriented. No supports needed, assuming your printer is capable of a decent amount of bridging.
  • Attach your wiring to your end-stop. See link above for the crimp-on spades I used (avoids soldering and easy to remove if need arises). Leave the excess wiring plenty long enough to go through the LR3 core, all through your drag chain*, and onwards to your CNC control box, wherever you plan to locate it. *(Consider my printable drag chain if you’re short of cash, otherwise opt for store-bought, injection-molded, as that’s better for drag chains than printed.)
  • Use two (2) M3 x 16mm screws and two (2) matching M3 nylock nuts to attach your end-stop (product link above) to the printed part labeled “1.magnetic-torch-FLOATING-Z-mount."
    Note: Remember to now run your excess wiring through the hole in the center of the LR3 core.
  • Use at least four (4), and up to six (6) M5 x 25mm screws, along with matching M5 nylock nuts, to mount the printed part labeled “1.magnetic-torch-FLOATING-Z-mount” to your LowRider 3 core. The LR3 core has nut capture slots in the back for this purpose. As shown in the videos, it’s advisable to pre-thread the nylon parts of the nylock nuts before attempting the mounting in this step. While mounting, it’s helpful to carefully hold the nylock nuts straight (and deep) in their capture slots (with something like needle nose pliers) while you run the screws in from the front, at least until the screws get threads into the nuts.
    Note: For the upper sets of screw holes on the LR3 core, which normally on a LowRider 3 are for mounting a router, you can get away with using M5 x 30mm screws (instead of 25mm). However, if attaching to the lowest screw holes (normally used for dust collection ring on LowRider 3) avoid 30mm, and use 25mm instead, or else the screws will collide with the 608 bearings in the core.
  • Use two (2) M3 x 8mm screws to mount the linear rod (product link above) to the printed part labeled “1.magnetic-torch-FLOATING-Z-mount”
    Note: these two shorter screws are for the two middle holes in the linear rod, not the upper most hole or the lower most hole—see below for why. This step is shown in video #1 in the playlist above.
  • Use either two (2) M3 x 12mm screws or two (2) M3 x 16mm screws, together with knurled threaded inserts, either M3x4x5mm inserts (on 12mm screws) or M3x6x5mm inserts (on 16mm screws) (with the inserts acting somewhat like super thick washers) to mount the linear rod to the printed part labeled “1.magnetic-torch-FLOATING-Z-mount”
    Note: these two longer screws are for the upper most hole and the lower most hole, to have the screw heads “proud” to act as stop blocks, to prevent the slide bearing from sliding off the linear rod. This step is shown in video #1 in the playlist above.
  • Using a metal file, slightly scuff the bottoms of eight (8) of the round, neodymium magnets (product link above), and then using two-part epoxy, mixed well, evenly applied to the eight slots in the printed part, glue the magnets (with scuffed bottoms downward) inside their slots in the printed part labeled “2.magnetic-torch-tool-mount-BASE.”
    Note: In the scuffing, the goal is scratches, not simply to remove material. The more scratches, the more the glue has something to grab onto. This step is shown in video #5 in the playlist above.
  • Use either four (4) M3 x 4mm screws, or four (4) M3 x 6mm screws, to mount the printed part labeled “2.magnetic-torch-tool-mount-BASE” to the sliding bearing on the linear rod. This is the same part you glued the magnets into in the step above. This step is shown in video #5 in the playlist above.
  • Using a soldering iron, insert four (4) of the knurled threaded inserts (aka “heatserts”), size M5x10x7mm, into the four larger holes on top of the printed part labeled “3.magnetic-torch-tool-mount-BACK-v1.2.stl.” This step is shown in a couple of the videos, but certainly in video #6 in the playlist above.
  • Repeat the scuffing and gluing of eight (8) more magnets, this time into the printed part labeled “3.magnetic-torch-tool-mount-BACK-v1.2.stl.” This is same part you just put heatserts into. This step is shown in video #6 in the playlist above.
  • Use four (4) M5 x 12mm screws to mount the torch between the two printed clamping parts labeled “3.magnetic-torch-tool-mount-BACK” and “4.magnetic-torch-tool-mount-FRONT.”
  • After waiting a day or two for the epoxy to fully cure, magnetically attach the torch (with clamping parts) to the LR3 core, and test out both the magnetic breakaway feature and the floating Z feature. As Ryan of V1 Engineering would likely say, “make plasma cutting sounds with your mouth and you amaze your friends with your powerful creation skills.”
  • If all is well, you are now ready to mount the modified LR3 core to your LR3 bridge (X gantry).

Change log:

  • September 10, 2022 at 3:00 pm — initial upload of v1.2 (previous iterations were privately printed and tested, never uploaded here).

My PayPal tip jar: https://paypal.me/dougjoseph

View all my LowRider 3 CNC remixes:

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*Product links are Amazon affiliate links.

The above torch mount with magnetic breakaway can be seen in action, with full illustration and explanation of the floating Z operation, in the video below.

LowRider 3 CNC DIY Plasma - LinuxCNC: Probing, Framing, & Cut Recovery!


A floating z should be really interesting for ACP (ACM) panels vgrooving…


Hello again! Please explain more of what you meant. ??

The floating Z only comes into play when probing to get the height of the material for plasma cutting.

I cannot imagine a use for this floating Z feature outside plasma cutting, and in particular would not think it would be used when using any kind of bit to carve Aluminum Composite Panels.


To clarify further: I now have two LowRider v3 machines. One is dedicated solely to plasma work on metal. The other one is for carrying a router, and pen, etc. The one for plasma is the one with the floating Z.

I’m struggling to understand what you meant. ??

A floating z can be used to make the v goove for folding the acm panel, you ensure the same height all across the panel. You need to use another piece wich will give you the correct height across the cuts. Later im going to take a picture or vetter yet a video of one machine using it and it makes perfect cuts all day long

I’ve not ever heard of that before. I am curious to know more.

This should be achievable with a lr.

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@DougJoseph yesterday i bought a 5’x10’ cnc used (really lighlty used) but im keepeing both lr2 (and slowly transform then to lr3 with time… The lr are going to keep doing what they do well (plastics and mdf/ply)

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Yes, its a vwheel with cbeams xyz . Going to use some linear rails i have laying around and reuse the 3mts cbeams in another project later on. I got it for the cost of a single 10ft cbeam shipped to my country :cowboy_hat_face: thats a bargain. Im not a fan of the electronics but thats cheap

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This is really interesting. I’m not aware of firmware support in Marlin but I can definitely see the value potential. Maybe a hack that borrows from babystepping can get something similar. Or maybe an external device that literally uses babystepping. (The external device would need an enable/disable signal so it doesn’t fight the controller at the wrong time.)

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I dont think that. Your z will be whatever you set it to. You release the spindle and with the stopper at a fixed height it press and you run the tool and carve what you need at always the same height (0.5-0.2 mm can make a complete acm/acp panel unusable (tell me how i know)

Now imagine 2 small motors like this one on the x axis ( Brushless mini ) one fixed to work with the Z axis as usual, the other one free floating in a rail with some added weight when in use and locked up out of the way when not in use.

This small motors i have used one and it makes the machine to go really slow cutting mdf but it chews the acm panels like butter