Does anyone know if the current lowrider firmware can be used with this project on a minirambo board? It has an extruder connection but I am clueless when it comes to the firmware.
Thanks!
The usual Lowrider plus miniRambo runs with Marlin. That combo can run the GCode from Grblgru but not a 4th axis. So it will do XYZ projects you create and save the GCode from with Grblgru. Grblgru talks directly with Grbl not Marlin so generally that means using an Arduino Uno for 3 axes or a Arduino Mega 5X for more than 3 axes.
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Sorry-- I’m brand new to the forum and am just now trying to print out my parts for a Primo.
Fabric cutting is one of my eventual goals with my yet to be realized MPCNC and have been researching how cutter wheels and all of this sort of thing.
I am absolutely not an expert in motion controls, kinematics, CNC or any of this, but I do have a bit of experience with micro controllers.
I was trying to parse through this thread and was wondering if it were possible to decouple the direction of the cutter head from the the CNC and the tool pathsaltogether by using something like a cheap 9-DOF sensor to control a servo in the opposite direction of travel? I’d imagine it would only work on curves, as the cutter head couldn’t turn on the fly on a 90* turn. Was wondering if this had ever been explored anywhere
The 9dof wouldn’t really help. The only measurement that would be useful is acceleration and that would end up being super noisy.
But you don’t have to measure the direction of travel. It is right there in the gcode:
G1 X0 Y0
G1 X10 Y0 ; you are moving to the right.
G1 X10 Y10 ; you just took a hard turn up.
G1 X20 Y20; you just turned right and up.
Marlin will not tell you where you are in this file. So a separate system would be tricky. The gcode sender will send a few commands ahead of where Marlin is to keep a long buffer ready to run. So it won’t know.
But, if you were using the E motor for the move, you could edit the file before running it to be something like this:
G1 X0 Y0 E0
G1 X10 Y0 E0 ; In this example E0 is to the right
G1 X10 Y0 E90 ; turn up
G1 X10 Y10 E90; move up
G1 X10 Y10 E45 ; turn to right and up
G1 X20 Y20 E45
That requires a couple of things:
- E needs to be configured in Marlin to not be a complicated mess. Since it is designed for extruders, it tends to have a lot of features we don’t need. At a minimum it needs to have cold extrusion protection turned off and the steps/mm need to be something like steps/degree and the feedrates need to be adjusted appropriately.
- You need something that can read the gcode from CAM and set all the E commands. Something like Python could do this pretty well. I didn’t go read through this thread, but I thought that’s where we were heading. I think G2/G3 commands will be a second step, because they are a tad harder. But most CAM can use line segments instead.
Also, if you can find a lower tech way of doing it, like a drag knife or a laser then you’ll be saving a ton of headaches. I thought there were some threads on fabric cutting already.
There is an extension for inkscape that is supposed to get the info you need. If you parse through this thread you should find it.
Edit:
It’s post 100 or 101 in this thread
Yea, thanks for the reply. I guess I am reverting to the tech i feel comfortable with. The threads I’ve found on here have generally pointed to lasers or to this thread. Looking to industrial applications also leads to tangential cutters but their control systems are a black box to me. I was attracted to this project (MPCNC) because 1. the community docs and forum are super active, enthusiastic and positive and 2. it’s marlin based, which makes sense to me because I’ve been fooling around with 3d printers for bit. I guess I’ll need to dive deeper into the fundamentals of gcode and CAM. Thanks for the examples. They have given me a lot more direction than i had before
Grblgru has added an Active Tangential blade feature to his program now.
Combining a small stepper motor and a tangential blade mount and mounting them on the Z axis makes for even more fun with an MPCNC. Thingiverse has a couple of tangential blade designs for a MPCNC too.
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Awesome! We should add this to the docs.
Except, what firmware can support the A axis?
For firmware I’d suggest GRBL Mega 5X - runs on an Arduino 2560. An ESP32 with Barton Dring’s GRBL port will also do a great job. I’ve commented on those elsewhere in this forum.
Maybe I missed something, but does that support an A axis?
Yes. GRBL Mega 5X will support up to 6 axes. Last December I built a 3 rotary axis addition to my XYZ machine and had it running for a while. However, I found wrapping my head around that many axes was tough so I reverted to 4 axes and I’m at a point now I’m thinking about more 5th axis applications.
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Here’s a simple active tangential blade I built this evening. I’ll nail it to my machine later and try it with Grblgru. Since I had all the bits I just needed to print a blade holder. I used the version GeoDave designed for an 8mm shaft.
A small Nema17 stepper with a 5 to 8mm coupler and the usual 608 bearing to support the 8mm shaft, some bits of wood, a razor blade and voila.
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This looks really interesting. What do you think the maximum depth would be?
Thanks
Rob
has anyone considered using a rotary cutter, rather then a razer blade?
Hi Rob. The maximum blade stickout is 10mm but practically expecting to use a couple of mm less than that should work. The second notch in this type of blade can ‘sort of fit’ over the printed projection to give maybe 15mm max but I don’t think it was made to do that really. I will have to add a small stiff spring around the 8mm shaft to cushion the ‘touchdown’ of the blade tip on the work surface. I will likely allow the assembly to slide through the bearing just a little letting the weight of the motor bear against the spring. It would be a little too rigid/stiff as is although it would work. GeoDave has a discussion of his prototypes elsewhere in this forum.
Atom I have no idea about rotary cutters for this application.
I think the motivation against a rotary cutter is that the materials are too soft and the pulling and pushing of a rotary bit would just not make clean cuts. Even with a sharp blade, the tangential cutter is pushing down while cutting, not pulling or pushing to the side.
I would think a rotary cutter (think “pizza cutter”) wouldn’t be able to pivot smoothly for interior corners. A drag knife will still have a bit of a radius, but a big rotary cutter blade would never make that turn.
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im thinking this… should have close to the same cut angle as a raser but less drag force. It is far from a “big” blade at only a 1" diameter.
Ah, my mistake.
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