I’m building a Lowrider 3 for cutting cardboard and I’d like to explore using a tangential cutter driven by a 6th stepper motor. I’ve seen this great thread on the gcode
What do I need to add a 6th stepper to my V1-supplied Jackpot which is currently enroute? Just a TMC2209 Stepper motor driver, cable and stepper?
Something like:
It looks like the FluidNC config already has a ‘c’ axis defined which is a starting point. Is that correct?
Anything I’m missing here?
Yes, FluidNC supports defining a C axis.
I’ve installed a TMC2209 in a jackpot and twiddled a config.yaml to use it. The jackpot seemed fine with the 6th TMC.
You’ll also need to have CAM software that can generate appropriate gcode so that FluidNC can then operate that additional axis.
I’d love to see you document your build as you go, this is a topic that will interest many others.
I believe the stepper driver ports are named x, y, z, a, b, c, but the axis from the gcode is “A” like normal.
The “c” refers to how it’s wired and the physical position, and not the name of the axis.
I think I messed with it a little and it worked out of the box, but it has been a minute.
Looke like I had it backwards, and it is “C”.
But at the time I was sure it could be called axis A in the config.
I didn’t play with this part as I only have a bench test setup with steppers and endstops. I don’t actually have a 4+ axis machine to play with.
So may i ask how you will do the gcode??
Weirdly the gcode is the easy bit for this. I’m making a scalable shipping box so it’s all straight lines and no curves.
I can quickly build a csv of (x,y) dimensions to start and stop each cut.
I’ve written a python script to work with my current drag knife which then looks at each cut, figures out what angle it is, moves the knife ‘back’ from the start of the cut, brings it down and moves it towards the start of the cut to drag it in-line, then plunges to full depth at the start of the cut. At the end of the cut it over-shoots by the drag amount. It goes through each line in the spreadsheet and creates a gcode file for those cuts. I’ve been testing this on my mpcnc and it works really well, but it leaves me with curved entry cuts and isn’t nearly as elegant as a tangential knife.
I figure that the hardware side of the tangential knife looks pretty easy, and the gcode is easy for me to generate. I just don’t have much experience with the electronics element and no experience with FluidNC
Well than the community can help you.
We have plenty of experience with the electronics and config file modifications.
I expect after a few iterations we’ll get you running as you continue your build.
Thanks Jim
Am i right that all I need is “any old” TMC2209 driver, a generic 4-wire stepper, and a cable?
I’ve only tested with BTT family TMC2209 v1.2 drivers, and those will work.
There are 2209 stepsticks in the wild that have funky UART configs and if you had the misfortune of buying one of those you may need to play with jumpers or do pin shorts.
Any stepper rated for the torque your axis needs should work.
A suitable extension cable to hook that stepper up to the jackpot.
Steppers have varying pinouts, so the cable may need attention to get right.
Rather than a stepper could I use a servo? This would negate the need for homing.
It looks like FluidNc supports servos. I’ve got a couple of MG 996R continuous servos and if I’m understanding correctly since these are 4.8-6 volt I’d connect one directly to a GPIO pin rather than the motor drivers. The servo is 3-wire so the ground would go to the boards ground, and the other two wires to the GPIO. Have I understood that correctly?
Here’s what I found in the FluidNC wiki: Axes | Wiki.js
I’ve never tried it myself, but there are many people who have.
Good luck
Wouldn’t that negate the need for homing, but then introduce the need for an encoder so you know position?
FluidNC supports servos but since they aren’t used on V1 machines the expertise here is limited.
We’d still provide what support we can if you’re using a jackpot.
There are also expansion boards that use the header that is on the jackpot.
Ryan designed in a compatible connector to the ones Bart uses on his own native designs.
We have users running spindle controls with these parts (as an example.).
You’ll need to do relatively more of your own design and implementation the further away from a typical machine configuration that you go.
It will be interesting to see what you come up with.
I use a servo on my CoreXY vinyl cutter to control Z. As I am using it, it does kind of need to be homed, because it knows that its range is 5mm (It is actually closer to 8mm, but I don’t actually care, since I want it either “lifted” or “cutting” and engaged with the base, so everything has Z at.either 4mm or -1mm. Since FluidNC doesn’t know where the servo is at power on, the home sequence move it to “full up” and I tell the machine that is +4mm. There are probably other ways to do that, which do not involve a home sequence at all, but I haven’t found them.
I have a plugin for CorelDRAW and it does gcode for tangential knife. The plugin is not mine, I asked the guy and he made it for me.
I have a video where you can see a little work on the prototype of the machine. and cutting 36.20 minutes. there you can see a plugin for CorelDRAW . if you need it I will give you a plugin .
