Upgrading an MPCNC to PRIMO

I have an MPCNC that I built some time ago. I’m not sure if it is the original version or something more recent. I am using 3/4" conduit as my rails. The z carriage rocks on the horizontal rail as shown in the image titled Z Axis Pivots. The problem is that the bearings under the rail are not in contact with the tubing and I do not see any way of adjusting them. Other than that the machine operates well, but the wobble makes for poor quality projects.

Can I purchase a Primo middle and upgrade my machine? Are the centers on the x and y rails he same? Can I mount my existing Z axis and tool holder assembly to the Primo middle?

Also where do I find directions for assembling the primo?

Here is the link to the current version of the Primo Primo.

I can see from the pictures that yours is not the current version, but may be a Burly model as it uses a lead screw for the Z axis. I would look at the assembly instruction for the Burly and see what the procedure is to get the bearings in contact with the rails. Another frequent issue is that you may have a cracked or broken part, deep in the assembly, that needs to be replaced (reprinted).

The parts are all on Thingiverse. I have linked the 23.5 OD version, but there are links to all the others on the page.

Here is the link for the Burly instructions. Page down a bit to see the step by step assembly instructions.

It looks like the Z axis is very long, and I see the side supports for the X and Y rails. If you really need that height then so be it, but that is going to put a lot more strain on the Z axis, especially when it is extended fully down.

If you are not doing parts that are that deep, the LR3 might be a better choice. You can probably use most of the existing parts to make the LR.


Thanks for your input Mike.

I know I got a little carried away on the Z axis travel. I am trying to decide whether to try to rebuild what I have or basically start over. Other than the Z axis wobble in the one direction it performs pretty well. I guess one question I would have would be whether I could use my existing Z axis and tool mount with the new Primo middle (core). That looks like a nice upgrade.



I really don’t know if the Primo core can work with the Burly rails. @Ryan would need to field that one.


It depends on the size rails. Only one fit and I do not remember which one.

It would be best to update everything though. The Primo is better and as a whole package, significantly better.

I think I am going to order the Primo core and start from there. I’m using 3/4 conduit rails.


Also, the Primo looks pretty sweet!

What type of belting does the Primo use?


9-10 mm

Thanks Ryan.