Is setting up Rotary Axis simpler on Masso than on Buildbotics?

Continuing the discussion from Elite Upgrade Kit Ordered (discussion):

Hey Andy,

how it is done on the buildbotics-derived ➪ Onefinity Original X-35/X-50/PRO Series Controller is described here. However in my opinion not in every case you need a 4th axis. Often it makes no sense to have Y functional and it is enough to connect the rotary axis as 3rd axis instead of Y. Think of the fact that you move with X carriage along the workpiece axis, go up and down with the spindle with Z, and rotate the workpiece. That are according to Adam Ries three axes. So if usually if you want to mill on a rotated workpiece, you only need X and Z, so you can disconnect (or switch) the left Y motor and connect (or switch) the rotary axis to this stepper output, and assign this MOTOR 1 from “Y” (=the left, master Y) to “A”, and deactivate MOTOR 2 (Y slave), so no hassle with running two Y motors on one axis output. Okay, you have a limitation if Y axis is disconnected, e.g. access to a location to probe on the machine bed, or to use a bitsetter to measure tool length after a tool change would have to be done in the line of X motion, assuming that your machine workarea width is longer than your rotary axis so leaves out a little room for that.

Yes, the ➪ Masso G3 CNC Controller internally has five genuine axis control outputs, so one more than the Buildbotics that is a Four-axis CNC controller. If you consider that you have X, two Y axes (one master, one slave) on your gantry-type machine, and Z, the fifth axis control output is freely available for an additional stepper motor, so connecting a rotary axis is done at this control output.

I don’t exactly know how to access it on the Onefinity Elite’s Masso G3 Touch version, as I don’t have (and will never have) an Elite machine nor a Masso G3 Touch, and in the Elite Manual, I don’t see a stepper output for the fifth stepper (A axis in this case) on the back of the Elite’s Masso G3 Touch case:

Image: Of the five stepper outputs, the Onefinity Elite’s version of Masso G3 Touch controller only makes four available on the back: X, Y, Z, and B.

However in the Masso Documentation, you see the five axes outputs that are present inside:

Axis Servo/Stepper examples

Wiring example

MASSO G3 side connector information

Images: Axis Servo/Stepper examples – Masso Documentation

Regarding powering the stepper motors, the Onefinity Elite power supply box has DC power supply for the fifth stepper driver and stepper on the last power port that is unlabeled:

Here you can get 24 V DC for five stepper drivers and motors, that are produced by a step-down converter from the 36 V version of the Meanwell LRS-350 switching power supply inside.
:warning: Be aware that the 24 V DC stepper driver and motor supply available on these five connectors will not be cut after Emergency Stop has been activated. On the Onefinity Elite Emergency Stop Button(s) wiring, disabling the steppers is done over the “Enable” lines of the stepper motor drivers, so the 24 V DC supply voltage will remain available here on the power supply box during Emergency stop.

:warning: Note that unlike the buildbotics-derived Onefinity Original Series Controller, the Masso G3 controller expects that you first connect a stepper driver for each axis, as it offers only the internal DIR{X,Y,Z,A,B} and STEP{X,Y,Z,A,B} control, and cannot control a stepper motor direcly. The Stepper motors that are used on the Elite Series are steppers with integrated stepper drivers (the little black box on each of the stepper motors). On the buildbotics controller, these stepper drivers are already present on the AVR mainboard, hidden inside the box and inaccessible (only the newest CNC controller version offers these DIR{X,Y,Z,A,B} and STEP{X,Y,Z,A,B} control lines on its new 15-pin auxiliary port to allow you the use of external stepper drivers).

So if your new rotary axis has just a bipolar stepper (four wires labeled A+, A-, B+, B-) without a stepper driver, you need to buy a stepper driver separately.


Excellent info, thanks, I did not know about the stepper driver!

Reason why I think the Masso is by far better for a rotary:

I have my rotary device permanently fixed to the far end of the wasteboard. I screwed oversized guide on my wasteboard and cut the guides to size with the 1F, so they should be parallel to the X rail.

Once I get my masso I will be able to move my spindle right over the rotary (remember the limit switches the Masso has, I just need the correct offset in VCarve), saving time on setup, no need to unplug any cables and change them back after use (switch Y to A and back). I also do not have to change the buildbotics controller configuration back and forth. I can have a tool setter permanently on the wasteboard and use that to determine the correct Z home. The time I savings will be significant.

Another advantage for me is that I will be able to make full 4 axis AXYZ cuts, meaning I can run my XYZ cut, rotate the workpiece by 90 degrees, do another XYZ cut, and so on which will give me the opportunity to create really complex objects (I can cut deeper than the Z zero position!!!) that cannot be created by just using AXZ axis. If I use the buildbotics to carve this way it would just be a nightmare. After carving the first side I would have to go through the whole process of switching cables, reconfiguring the buildbotics controller, etc. just to turn the A by 90 degrees, at which point even a manual jig that turns the workpiece a quarter turn would be more convenient.

That being said, if you don’t use the rotary often and plan to make very simple round objects like for example engraved pillars and don’t mind going through the configuration/cable swap the buildbotics might just work fine.

I used a Masso stepper from 1Finity for my rotary, it has the driver built in just like the other axis steppers, makes wiring up very easy, I had to replace the one that came with the rotary axis I purchased for this convenience.

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Do you mind sharing what rotary you purchased?

Amazon, It is commonly used here, the quality seems very good, I got the 80 MM chuck size, take note the thru hole in the spindle is good size but the hole thru the chuck is small.

CNC Rotary Axis 4th Axis with 3 Jaw Chuck,CNCTOPBAOS K11-80mm Hollow Shaft Dividing Head Rotational A Axis w/ 65mm Tailstock Reducing Ratio:6:1 for CNC Router Engraving Lathe Milling Machine

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What is the dia of the through hole in the Spindle? I have a different chuck I could install with a large through hole.

it is advertised at 22MM

Huge news for me. Have you gone further with the 4th axis since November? I want to be able to cut on four faces as if it were a flat, as you describe. I could start a new thread…

I was hoping to be running by now, but wiring is still not right, I hope tomorrow if I can sort it out.

What I believe is that you can run all your tool path on one side, manually rotate by typing an MDI command like
G0 A90
Then cut the next face.
Of course you could also manually stitch the g code together with the rotation commands in between.
Or run software like
Rhinocam Expert, which should do the rotation automatically.
Why not make a new thread.

Noted. First I’ll look deeper into the subject, and give you time to swim out in the shark infested waters ahead of me. Shout if you feel wet sandpaper against your leg.

By chance did you wire into the emergency stop using resistors as mentioned in the masso documentation?