hello,
I am looking into building the MPCNC. Is there a design modification already completed that allows for single motor operation of the y axis?
I have been looking around but have come up empty handed thus far.
Thanks
RR
Not that I know of, why is that of interest to you?
In my opinion that is one of the main design strengths, two smaller steppers give you lots of power and the ability to auto-square.
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I’ve had an Aliexpress Nema 23 4 axis kit kicking around for a couple year and figured I should finally do something with it.
Figured it would be easier to use the slave port for homing/auto squaring X and a single motor Y design to prevent misalignment.
Suggestions?
NEMA23 motors are a pretty large change to the printed pieces
If those are 4 wire though, you can run 2 motors in series off of the same driver. This prevents an entire re-design. Still, there are more appropriate designs out there for the larger motors. People have done refits for the Primo and LowRider designs, but they’re outliers, and support on the forums for that kind of redesign is going to be limited.
I would probably suggest that (if your kit supports 4 wire motors) you can use it with NEMA17 motors, with appropriate current settings, and use the kit with the X/Y motors in series. This uses only 3 of the 4 axes, and gives you the possibility of adding a 4th axis spindle later.
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Yeah I’ve noticed the consensus of the forum is nema17 is a better fit for the design.
Currently I have two motors wired to x output, (bench testing) and achieved opposite rotation.
If I am being completely honest, the MPCNC isn’t my final design/goal. My objective is to build a budget machine to help fabrication pieces for a more stout design. No insults intended.
The MPCNC seems to be one of the best budget builds I’ve run across.
Returning to the original topic of post.
How problematic is the MPCNC design (assuming wiring x & y in series) for squaring (missed steps)
Appreciate the responses!
RR
Historically, series wiring was in the majority for MPCNC builds, but it seems that dual endstops (individual wires to each stepper) is now in the majority. So, machines of both wiring configurations have been used extensively. As for lost steps, this is my understanding: for normal cutting, there is no difference between the two types of wiring. Both motors are getting the same power no matter what the wiring. The one difference is that if you want to push the speed for some reason (say fast rapids, or pen drawing, or lasers), series wiring will begin to lose steps sooner than dual endstop wiring. This can be mitigated by running the control board at a higher voltage (if your control board supports it).
Squaring can be accomplished in series-wired machines by providing a physical endstop to push against before the first electronic movement of the steppers.
Dual endstops is more accurate and consistent. Most of us ran for 5+ years without dual endstops though so it isn’t an issue, just a different way of doing things.
100+mm/s Is where this starts to come into play if I remember right and you will not be cutting at these speeds, if you do, just switch to 20mm pulleys instead.
To perform as well as it does all aspects have been refined over the years. Changing anything is really non-optimal. What machine are you planning on moving to and why not start there? (Market research for me)
This is what is pretty obtainable if you are detail oriented. I am fairly certain most machines can not beat this by very much until you add a handful of zero’s to the price. We did actually have another company try this and did not hit this mark.
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Thank you for all this feed back.
I don’t have a specific machine in mind, however a couples year ago did model my own variation of a machine in fusion based on Avid’s and Joes’s machines.
Market research answers: (not necessarily in order)
-I am frugal
-I enjoy the challenge of building not buying.
-I don’t want to buy a kit from someone.
-I like the expandability of the MPCNC (as i am not 100% on the size on want)
-Given I am not 100% on the size of machine I want, jumping the cost to aluminum extrusions only to find I am dissatisfied with size is a deterrent to build it first.
-Your engagement/support on this thread alone is reinforcing that my choice to attempt a MPCNC build first
Best answer!
If that is the case, the autosquaring is really a nice feature. If you build a machine, nothing is perfect, autosquaring can really really dial in the accuracy. Steppers and drivers are relatively inexpensive.
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I think ill have to consider a board upgrade then. I believe auto squaring will eliminate a few head aches.
I think I’m the only one, but I prefer series-wired with (single) endstop per axis and manual squaring by cogging the machine. I think this is just as good as dual endstops in terms of absolute positioning and repeatable squaring, but with less wiring. Holding against hard stops alone does not provide absolute positioning (not better than one cog) and there is a chance that squareness could differ by one “cog”, so it’s not fully repeatable.
This is an older video from a previous incarnation that I have already torn apart and rebuilt, but I use the same approach to this day.
The MPCNC is perfect for the hardware hacker in that it is very modification-friendly. Part of that is the design, part is the low cost, which puts a limit on risk, and part is the community that is very receptive to modifications.
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Did you just turn energized stepper motors???
Yes.
It’s hard without the knobs, but if you can get a good grip it’s not that hard to cog them by hand. Pliers should also work if you don’t mind scuffing the pulleys.
By the way, each “cog” as I call it is four whole steps of the stepper motor, or 1/50th of a revolution, which is 0.64 mm if youre using a 16-tooth pulley. So it’s not hard to visually see if it is lining up to the same place.
So I just found out my steppes do not energize on start. Do you run a script to energize them?
Oh never mind I see now you home with single and then it is energized. I do not have limit switches. May need to get some.
He seems to start by homing the machine, which will energize the steppers.
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Roger that light turned on after I rethought the process. So if I use squaring brackets how would I energize steppers without moving or homing?
Awesome thank you