I’m new to the forum and CNC Router interest. Looking very seriously at the Primo. Notice all controllers except the Rambo Mini are not available. Will the mini run all 5 motors on the Primo? Also does the mini support the xyz home limit switches and also a zero probe? I’ve looked all over the website and can’t find this info.
Thanks , in advance, for any help.
CarlG
The mini-Rambo can run the machine by setting up the x/y axes wired in serial but without the auto-squaring with the limit switches. If you want the auto squaring feature then it takes a board with at least five drivers – 2 for x axis, 2 for y axis and 1 for z.
Pretty much any board that supports 5 drivers (or more) and supports Xmin/max, Ymin/max & Zmin/max limit switches can run the firmware but depending on how far off piste you go it will rely on your knowledge of configuring and compiling the firmware.
Many folks who are unsure opt for something simple and cheap such as a RAMPs board with a Mega2560 (RAMPs is an add-on board that piggybacks onto the arduino). This has the advantage of being widely used, has all the features you need and ready-made firmware (plus as I said - it’s cheap so if you break it you aren’t losing a lot of cash!).
Have a read up on boards and ask in the forum for opinions on your choice. Lots of folks here willing to help.
For the record, the mini rambo is a great board and can run the primo just fine.
The full sized rambo or the skr pro can also allocate a specific driver for each motor in x and y. The only benefit is that while homing, it will move each motor independently until they each trigger their respective endstops. This is auto squaring.
Other than that one feature, they are essentially the same. For a long time, dual endstops weren’t an option, and we have made lots of very square projects by just pulling the gantry against the hard stops, and starting the machine in this position. After that, the motors move in lock step anyway.
If you do not have dual endstops, you can still do endstops. But honestly, this is a feature desired mostly by 3D printing aficionados and it’s not really that helpful. When doing CNC, the important thing is the work piece, not the machine limits. You want to set the 0,0,0 yourself anyway based on where you put the material, not based on the location of the endstops. It is really hard for us 3Ders to accept, but it is true.
When you connect two motors in series together, they will have the same amount of current going through them as if they were on separate drivers. As long as you’re not going super fast, the serial wiring will create the same amount of torque as separate drivers. Auto squaring really is the only benefit of having 5 drivers instead of 4 (except for some rare corner cases).
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Thanks Jeff … do you think the mini will support a zero probe? Not a deal breaker but a nice feature. The paper trick for Z Zero is pretty ez.
Again thanks,
CarlG
A Z touch probe? Yes, right out of the box. Not a corner probe for x, y, that is more work.
I use a mini rambo with z touch probe. It works great for everything I do. I ran it the longest time without a z touch probe too. I’m a full fledged member of the KISS principal and prefer less wires.
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Thanks Dave! Appreciate your answer. When you built your cnc, did it come with instructions on wiring up the arduino or did you need to research that all?
Also did you build the PRIMO?
I started with the old 525 version of the MPCNC a few years ago. I originally used a RAMPs style board. I upgraded to the mini-Rambo last year. I added the Z probe a few months after upgrading to the mini-Rambo.
Yes, I recently upgraded my machine to the PRIMO. If you look at my threads, you should find it.
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Wow! Just read your entire thread on building the Primo. You’re a better man than I 
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I know a thing or two cause I’ve seen a thing or two 