Build initiated: 2’x3’ Primo in TX

Hi all! Excited to get this project underway. I am starting a build of the MPCNC Primo with a 24” by 36” work area. I’m using the 23.5” C parts, printed on a Prusa i3 MK3S clone I built about a year ago.

I’m using @Ryan ’s hardware kit and the SKR1.2 board and have a Makita RT0701C on order.

I’ve built a 48” square table since the table size requirements are about 48”x36”, leaving some room in the front for tools, controls, or a computer.

I’ll primarily be cutting wood, but will certainly dabble with the pen plotter/ drag knife. I may try some aluminum and carbon fiber (in a water bath) at some point. Lastly, I’m interested in building a needle cutter for foam board - I’m a long time fan of FliteTest and have previously build several foam board airplanes, including ones I laser cut at a local Makerspace.

I’m nearly done with printing parts, with a bunch of the smaller parts arranged on the build plate going as my final print. I still need to print the tool holders and possibly an electronics box.

Stuff to figure out still:

  • CAM software, I use Fusion360 for CAD
  • Control software, I’ve used Mach3 years ago, and my
    local makerspace uses VCarve
  • Computer, touchscreen housing, pendant or game controller

That is going to be a monster. Only seen a few ever built that size. Take is slow, have fun!

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Mine is that size… but I’m using 1" tubing, “J” size, not the conduit. It’ll be fun!

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Yeah, mine was 2x4, but 1 inch tubes as well. I would anticipate the long rails sagging, but you can support the outer rails. Having a 2ft rail for one of the gantry tubes should help the longer one, though, since they’ll have to sag the same amount. I think it will be fine, but you’ll have to be careful with your CAM. Can’t wait to see it!

Here’s my progress after the first day of assembly:

I had a pretty difficult time squaring up the feet, extrapolating out the right angle from a 6" triangle. After much frustration and a lot of re-drilled screw holes, I finally googled for help, where a YouTube video lead me to the 3-4-5 method which I’ve somehow lived this long without learning. Using a tape measure and my chalkline lead to much better results, and I’ve got my diagonals with only about 1mm of deviation.

Next step, to assemble some trucks!


Day 2 assembly went pretty smooth. Trucks, rails, and core are assembled:

The tension on the trucks feels very good, and I tuned with all trucks on a single tube, tilting to ensure they slide at same rate.

I am noticing some play in the core clamps for both axes, similar to what is described here: New Primo core clamps loose fir - #16 by NickM


I’ll try the suggestion in that thread of seeing if the core bearings can seat closer to the tube. Has anyone else reading this experiences similar issues?

Edit: looks like @vicious1 has some guidance on this here: Loose Core - #7 by vicious1

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Okay, I removed the gantry, loosened all three bolts on the core clamp, and first tightened the tension bolts before the two core bolts. When inserted, the tubes were much tighter, and I then adjusted the tension bolt to proper tension. The result is smooth travel of the tubes with no play - Looking good!


Day 3:

After getting the core clamps tensioned appropriately, I moved my attention to the Z Axis. For the Z rails, I quickly modeled my own jig for the screw holes, and then drilled them out using a drill press. The bit I used really struggled with the steel, but cut after some patience and oil. The holes looked acceptable after some deburring and chamfering.

For the lead screw, I cut it about 3/4" longer than the minimum length, using a dremel.

The rest of the Z Axis went together pretty smoothly, and I installed the Makita tool mount as a placeholder. My black filament ran out when printing these toolholders, so I switched to red about halfway through. The result looks pretty cool.

Next up is squaring, belts, wiring, and electronics.


I’ve returned from some traveling and continued my build, adding the belts and setting up the SKR 1.2 Pro. Thanks to @vicious1 for pre-loading dual end stop firmware, all I had to do was reverse stepper wires a few times until I had proper movement.

I followed the basic software guide and was able to successfully plot the crown a few times while remembering my G92 command to set the origin.

I have not hooked up the end stops yet, but plan to do so and perform calibration and adjustments with them. I then need to sort out the cable management, mount electronics, and get familiar with software while plotting and testing the drag knife all before I fire up the Makita router.

One question I have for those reading - has anyone had issues with PLA printed parts warping from high temperatures? I’m setup in a garage in Texas and just noticed significant warping on another project that was stored in the garage (3dsets rancher). From what I’ve seen in the past, parts under tension are more at risk for this.


For me my garage gets in the upper 90’s, no issues yet. Most my builds are up for a couple years.

Out here south of Phoenix we see 120 in the summer routinely. On the first heat, my parts relaxed a little and needed to be retightened. Two garage walls and the ceiling were covered by the house. Second summer, no issues. I’ve measured as high as 110 out there.

A friend out here has a standalone shop, and maybe the temp got a little higher. His primo relaxed a lot and his modified lowrider (aka HEAVY lowrider) warped the xz pieces so badly that there wasn’t even a thought of “well, maybe…”

Do you have any windows in there? If the sun shines on it for anytime throughout the day it’ll melt… Ask me how I know :rofl:

What part of Texas?

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I’ve also just built a primo with 2’x3’ working area. The only difference is I’m using the dewalt660 instead. Take your time setting it up and enjoy.

How has your 2X3 build been holding up? I want to build this size, if not I will build something smaller but with a table that allows me to put bigger pieces under it.

I want a simple build.

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Mine is doing very well with 3/4 conduit in a hot garage in Florida, no issues. Very accurate. The only thing I’d suggest if you’re going to use 3/4 conduit is making sure your conduit is straight as possible. I had some bowing in mine at first.

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Still happy with this 2x3? I’m getting ready to build and am strongly leaning on this size, also with 3/4 conduit (but in a cool basement) Are you just cutting wood or have you done any aluminum?

My build is this size. I heavily recommend using 1" steel tube for this size, the more rigid, the better. I only cut wood, but sometimes near the center of the long axis, I get jitter from the steel flexing.

I’m happy with it, but i have to agree with Supraguy. Rigidity in the mid spans are becoming an issue as i push it harder than i should. I used to do coasters and light stuff, but lately started making cabinet doors and starting to see some issues. So, as long as you keep passes light, you should have no issues.

Thank you both for the feedback. Perhaps I will keep my table the same size but do the build for 2x2, giving me flexibility (pun intended) to reassemble for larger builds if/when needed.

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