I just finished building and testing an ABC rotary axes platform for my Lowrider. I have been using a 4th (A) axis for sometime and decided to build 2 more for fun. Admittedly only 5 axes are useful at a time but what the heck… I am running the unit with Grblgru under one of his 5 axis models (#3) for now. I can access the 6th axis via Macros within the program.
Thanks to Gauthier Griere’s GRBL-Mega-5X port of Grbl 1.1l I can easily run these with a Arduino Mega 2560. The one on my Lowrider is wired to external stepper drivers and I also have a Mega 2560 + Ramps 1.4 running on my MPCNC so it will easily drive 5 axes. I have the Pinout so I can wire an external stepper to the Ramps for a 6th axis later if necessary. I have already altered this Grbl version so I can run my Laser properly off the Ramps (12v with a 5v TTL lead). That modification is posted elsewhere in the forum.
This was an inexpensive build using Nema23 steppers, 20 and 60 tooth pulleys and a cheap ‘lazy Susan’ bearing for the C axis. I used 18mm birch plywood since I had a bunch of scraps. I use the same bearings as for a Lowrider with 8mm rods. I tried to balance it so the B axis is level when there is some wood in my scroll chuck. The AB intersection is located directly over the C axis. It normally sits in the hole at the centre of my worktop but doesn’t photograph well down there.
A = 360 degrees of motion - as many turns as I want
B= 180 useful degrees+
C= 360 degrees x 2 since the wires will wrap around the B
It is for Playing With to Learn about using these 3 axes Not for pinpoint accuracy. I plan to machine or burn wood or plastic Not metals.
That looks amazing and raises so many questions:
-How does the electronics work? You have two Arduino communicating with each other? One for XYZ and the other one for the three other letters we need to invent after Z?
-Do you have pictures of the electronics, and even better, schematics?
-Would you be willing to do some kind of tutorial for noobs so we could try building something like that ourselves?
-Did you mill things using that contraption yet? any pics to share?
-How does the CAM work for that kind of stuff? is it easy to work with for the homegamer?
I sooo with this thread to become a long one, that’s something I wanted to try doing for a really long time on the MPCNC but I always wondered about the electronics/firmware/CAM side of things. Please, please share as much as you can with us and keep posting!
This is 6 axes total. The reading I’ve done suggests that generally only 4 or 5 are used at a time for a lot of things. The really fancy $$$$$$ CNC machines can even have more axes but the software is really expensive. It is often enough to have a rotary axis - a 4th axis - often designated A. The convention is for A to rotate around X, B rotates around Y and C rotates around Z. Combinations of C and B or A and B are common and often dictated by what the purpose of the machine is.
As far as electronics goes, it is as simple as described above. Thanks to Gauthier Briere’s great port of GRBL to Arduino Mega 2560 this is a straightforward job.
The pinouts for a RAMPS card are on Github here:
I took the pinouts for the plain Mega 2560 from the cpu_map.h file here:
I have both a plain Mega wired to external stepper drivers for my Lowrider, and a Mega plus Ramps wired to my MPCNC. Other than the extra pins and steppers this is as straightforward as wiring a regular version of these CNC machines. I don’t bother with endstops but do use the Probe and Laser.
Another way to wire this for lower power Nema17 steppers like Ryan uses is to wire the Step and Dir connectors to two Arduino Uno CNC shields. That way the motors can be run on 24 volts through the shields, and the Mega 2560 on USB. There is a complete set of stepper pins just below the Reset button on those little shields that the Mega can be connected to, then place the DVR8825 stepper drivers in their places after setting the jumpers for micro steps, and connect the stepper motors to the usual 4 pin places on the shield. Make sure there is a common ground between boards. Since the Uno shields are not connected to an Uno there is room for 3 axes per shield to keep things simple.
The Mega 2560 is programmed with GRBL-Mega-5X using Arduino IDE the usual way described on Arduinos site.
As far as CAM goes I am using Grblgru for that. It can handle 5 axes for now. I have other postings on this forum about that and 4th axis use. It is Not easy to use this many axes which is why I built this to experiment with. The CAD programs seem to be key to sorting out many of the problems and I am Not experienced with them yet. Using a 4th rotary axis is a good place to start and it is easy to build with a stepper, shaft and Chuck mount of some kind. For those who want to do metals that is Not for these light CNC machines. The software can do it but it takes a lot of money to achieve the necessary rigidity for metal work I believe, a basic fact lost on many who should know better. As I indicated above I plan to play and learn on wood and plastic with routers and lasers.
Well thanks, it is now clear for me about the electronics!
Still need to dig around the CAM software a little.
So that’s cool, I can now seriously put a 5 axis CNC on my list of next projects!
Just need to design the machine, but I have a few ideas for that already.
Grblgru is soon to post an English manual for Grblgru and having edited it, I can say it is quite helpful to learn this program. It is a combination of workbook and manual for many of the features. If you can read German it is already available on his site.
There are also several videos available on YouTube but they stretch back 5 years so some are for much simpler versions. There are more up to date videos on Grblgru.com. Best of all, the program is Free. You don’t even need a CNC machine to use it. Grblgru initially developed this as a learning and GCode try out program. This is great for schools and other learning environments. He added a GCode sender and other features as he went along.
Grbl-Mega-5X manages 5 axes ‘as is’ which is probably enough for practical purposes. If you really want 6 axes you have to go into the Config.h file in the grbl folder. Near the top of the file is # define N_axis which you change from 5 to 6. Recompile it all in Arduino IDE and upload to your Mega 2560. If it doesn’t work, make sure the config.h file you altered is the one in the Arduino Library folder. Otherwise sometimes you need to reset the EEPROM of the Mega board with $RST=* command. Gauthier Briere has also written CN5X which is a basic control panel for up to 6 axes. I used it to quickly check the status of my Mega + Mega Grbl 5X. Find it here:
