New 36" x 36" Primo Build and some questions

Finished my build a few weeks ago and have played around with it some. About 3 feet by 3 feet, 4.5 inches in workable z height. Steel 1" OD x .045" wall mechanical tubes. SKR v1.3, dual endstops (not configured), and 84oz in Nema 17 motors. Modified the skr and tft case to mount to the side of my table, and added modifed cable chain mounts to fit my chains.

Here are some pics of the build / some coasters I cut out. Just drew a box w/ circles in solidworks and overlaid the skiers on it in estlcam. I also used the CNC to route out the slots for T-Tracks to be inlaid into the wasteboard, but it looks like I’ll have to lower some of them as I ran the bit into one when trying to cut out a coaster.

Some questions I have:

  1. How do I enable the dual endstops / what benefits does it provide? When I try to home my machine in the menu it doesn’t move. So far I have just been using the endstops to square the router between jobs if I think I knocked something. My workflow has in general been
    a) Create .dxf with a virtual copy of my work material, with origin in the bottom left
    b) Manually jog the machine until the bit is centered on the bottom left corner of the material, and just barely touching the surface
    c) Restart the cnc to make that the new origin, and cut
    Then, if I want to do a bit change, I turn off the router, raise Z, change the bit, manually jog the machine back to x,y = 0, get the bit so it’s just barely touching the surface of the material again, restart the machine, and cut. Is there a better way to do this?

  2. I am interested in cutting out guitars. I have a slab of ~17" x 17" x 1.75" Ash that I want to cut into a telecaster shape, mostly because it should be 2D cutting and that seems simpler. What are my options for cutting out the entire body contour around the edges (1.75" thick)? Is there a bit that can do it or should I be looking into a router upgrade?

  3. How should I get started trying to mill aluminum? Just buy a sheet of alu or a block? I bought these bit sets Genmitsu RR20A, 0.118”(3mm) Shank, Rotary Burrs, 20Pcs Bit Set | SainSmart –, Genmitsu 1/8" Shank 10-PCS Titanium Coat HSS Rotary Burr Router Bit Se –, Genmitsu MC40A, 1/8" Shank, CNC Cutter Milling Carving Bit Set, 40-PCS | SainSmart – (and already broke the 0.8mm titanium bit), but the product pages aren’t very clear on what each bit is for or how deep they can cut.

  4. Has anybody had success running a laser on the machine? I’d be interested in something that can engrave slate / wood / metal and can cut out ~.5" or more of plywood or similar material.

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  1. b) I usually manually drive to my 0, though I have a touchplate, I rarely use it. If you want to even be closer to the wood, you can stick a piece of paper below the endmill and move it around. As soon as you can’t move it anymore and it rips a bit you have found 0.
    c) You do not have to reset after the tool-change, at least when using Estlcam. I think Marlin should (?) be the same and remember the last position if you don’t turn off the machine. You only have to 0 Z.

  2. I cut 3cm (1.2’’) with my Primo with a normal endmill. Just buy one that is long enough and you should not have any problem, seeing that you can go quite deep. Otherwise try two-sided 3D milling (I want to to a guitar as well, didn’t continue yet. Since mine hasn’t got as much clearance I thought about doing two boards and glueing them together).

  3. I bought 10kg of aluminium from ebay. You have to be careful to buy the “right” kind. Here is a page that you might be able to translate with a list which you can easily machine and which one you can’t (Aluminium Fräsen leicht gemacht – CNC Blog). Mine is rated “good” and works well.
    I recommend trochoidal milling for aluminium, you can go as deep as your endmill lets you and as fast as your MPCNC goes without beginning to swing. It’s the idiot-safe way to mill aluminium. If you have to do a pocket, use peel from the inside.

  4. You can find some laser-cut things in “Things you have made”. If you search for “laser” you can find the topics and the users respectively.

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If you have the dual endstop firmware installed, they don’t need enabling, but if the switches are not connected, it won’t move. The switches need to be connected in “normally closed” mode, which means that when nothing is triggered, they short the (S) pin to Ground. If the connection is open then the pin reads as triggered, and the machine stops.

As to benefits, mostly it’s that you can set the stop switches so that they are triggered when the machine is square, so you don’t need to worry about how it is when you first power it up. Just hit the home menu item and the machine will square itself.

To reset the origin, I used a small gcode file, or you can use a terminal. Send the command G92 X0 Y0 and the machine will take wherever it is as the 0, 0 point. This way you don’t have to worry if anything moved after you set the machine to square. You can send G92 X0 Y0 0 and it will reset all 3 axes. Using a touchplate automates finding Z=0

For the guitar body, I would probably just use a deep bit to cut and then follow up with a roundover bit myself. It seems easier than trying to do anything too fancy with a double sided cut, but you can do a double sided job where you cut the “top” then flip the work over to cut the bottom. It usually requires some sort of registration pin, which you use to fix the work in place relative to the machine.

Milling aluminum on a 36" by 36" machine will be difficult. I have a 25" by 37" work area, and I don’t think that it’s stiff enough to do a good job on aluminum for myself. The bigger the work area of the machine is, the less rigid it is.

Laser, on the other hand is easy enough. A diode laser isn’t difficult at all, and I think the stock V1 formware currently supports it. A CO2 laser is a bit less safe, but it has been done. Personally, this is NOT the machine architecture that I’d run a gas tube laser from. The NEJE A40640 laser (40W = ~10W optical output) is supposed to be able to cut 1/2" plywood, with air assist.

Do you have recommendations for a deep bit? I am still very new to this and don’t know what all the bits are. The sainsmart ones don’t even list a cutting depth as far as I can tell.

What did you use for the tubes on your MPCNC?

Do you know if I would need to make an enclosure to run a laser on it? Thank you for the tips and advice!

The laser won’t care if there’s an enclosure or not. It comes down to your level of risk tolerance with regards to your eyesight and your lungs. I won’t run a cutting laser that’s not in an enclosure, but there are other ways to mitigate the risks.


I have one of these as a deep cutting bit. It has a little over an inch of cutting depth available. I’ve also used long 1/4" router bits. Probably nothing in 1/8" shank will be suitable. At least nothing that I’ve seen.

My Primo uses 1" DOM steel. I got .065" wall, so there is thicker available, but larger area geometrically degreases rigidity. The longer the tubes you use, the more flex you will get in the machine, and that translates into trouble cutting. Once my LowRider build has stabilized I do plan to reduce the size of my Primo so that I can give aluminum cutting a serious go, but I feel that it’s not feasable at the 25" by 37" size.

You do not need an enclosure to run a laser. My LowRider will have a laser, and I made a CoreXY based laser cutter that has no enclosure. There are limits, however. Eye protection is needed for anyone in the room, including pets. Certain materials cannot be cut without full ventilation. Vinyl and some other plastics produce cyanide gas when burnt, as well as acidic condensates which will attack your steel and bearings, so I limit the things that I cut with the laser to things I know are safely combustible. You do have to be aware that a laser can hurt you faster than you can possibly react. It can do so at a distance much greater than a tool like a saw or a spindle, and the injury that it can do can be life changing and permanent. I will always advocate care and attention with any power tool, but lasers are another category higher.

It turns out that vinyl produces hydrochloric acid when lasered from the carbon-chlorine bonded to make the vinyl. It does not make cyanide, however laser cutting ABS, a common 3D printed substance will make cyanide, so yes, do be careful what you laser. It may not be in your best interest to check out “will it lase” much like “will it blend” type of experimentation.

If you are going to laser anything with your CNC, do have ventilation for it and an air assist is also a good idea. There is a reason that nice laser cutters come in a vented and fully enclosed box.

I thought it was vinyl too, but I stand corrected. My friends in the sign industry won’t cut vinyl in their lasers even with full ventilation, nor will they cut many other things with the laser.

Leather and bone are on my no cut in the house list even with a fan the oily smoke lingers in an enclosure for a long time and is hard to get rid of

IMO, enclosure for laser is usefull and nice to have :

  • It will help for ventilation as it will canalised/reduced the volume of air/fumes to extract.
  • Also possible to make a filter panel to filter some bad lights; disclamer : Always use good laser goggles.
  • You can add a webcam on top and configure it in LightBurn for visual positionning.
  • You will already have your enclosure when you will decide to work with a router

If interressed have a look on mine:

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