My new CNC machine. Arduino controlled:

[schoeftinger]

Originally Posted by aggrav8d I don't know if it helps but I wrote an instructable about combining Sparkfun stepper breakout controllers and Arduino to run the electronics for a CNC machine. I'm still working to put my frame together (sourcing parts is awful). Once I have that complete I'll be working on hacking together some control software.

Very impressive!
I've done a very similar thing recently, but with only 2 steppers.
An Arduino Uno controls 2 EasyDriver boards with a SparkFun stepper attached to each.
I'm using this setup for an automated guitar pickup winder...

Anyway, I'm wondering how you manage to controll the steppers live from the PC???
When I tried running Firmata on the Arduino to control the steppers live from the PC (via USB), I noticed that the transfer rate was too low...
I guess without some dedicated caching and execution logic on the Arduino, the USB connection won't suffice, right?

-Tom

[dkirtley]

I keep reading people explaining that you can't control motion over USB well enough for it to be usable. Of course I really can't figure out why the people doing it seem to not understand that it's not possible. Kind of like the arguments that aerodynamically, bumblebees can't fly. Reprap, Makerbot, Dank, Planet-CNC all have them running off usb without too much difficulty. All these except the PlanetCNC board are running arduinos (or something real similar -- Sanguino). The Planet-CNC is using a PIC processor. Printers seem to be able to handle it pretty well too.

They have interpreters running and just issue commands for the movement and not trying to control individual steps. The processor on the board handles the stepping and other controls. There is a big difference between just sending a move command rather than 15000 steps.

The only real problem with it is the small memory on the arduinos, although they are going to spooling stuff onto flash cards. Pop in a 2GB flash card and the memory problems seem to be much less constraining.

Make: Online » Arduino GRBL Has an article about a 3 axis arduino shield. Just for fun I ordered one but am waiting on shipment that is due pretty soon. Anxious to get one to play with.

[schoeftinger]

Well, I'm not saying that live control via USB is not possible.
It should be definitely possible if you use some smart command encoding and caching instead of transferring a dedicated command for every single stepper step to the board.

From my experience, however, there is a sh*tload of use cases where I WANT TO transfer dedicated commands for each stepper movement.
From my personal experience, this unfortunately limits you to approx 20% of the max. performance (with 1 stepper) when issuing the commands from the Arduino locally.

BTW, when using some smarter command mechanism the Arduino memory contstraints should not be a problem at all.
I guess I'm just too lazy to write myself an Arduino library for G-Code (or whatever proprietory command language)..

Thanks for the link to the 3 axis Arduino shield! - That's going to save some effort compared to wiring and soldering stuff to the EasyDrivers...

cheers,
-Tom

Originally Posted by dkirtley I keep reading people explaining that you can't control motion over USB well enough for it to be usable. Of course I really can't figure out why the people doing it seem to not understand that it's not possible. Kind of like the arguments that aerodynamically, bumblebees can't fly. Reprap, Makerbot, Dank, Planet-CNC all have them running off usb without too much difficulty. All these except the PlanetCNC board are running arduinos (or something real similar -- Sanguino). The Planet-CNC is using a PIC processor. Printers seem to be able to handle it pretty well too. They have interpreters running and just issue commands for the movement and not trying to control individual steps. The processor on the board handles the stepping and other controls. There is a big difference between just sending a move command rather than 15000 steps. The only real problem with it is the small memory on the arduinos, although they are going to spooling stuff onto flash cards. Pop in a 2GB flash card and the memory problems seem to be much less constraining. Make: Online » Arduino GRBL Has an article about a 3 axis arduino shield. Just for fun I ordered one but am waiting on shipment that is due pretty soon. Anxious to get one to play with.

[dkirtley]

What you might consider if you want something a "bit off schedule " is to take one of the basic g-code interpreters and add in a couple "extra commands" that you can put it into some immediate mode or customize some extra commands.

I started with playing with the easy drivers too. I am still relative beginner again. It has been 20 years since I have played with any electronics. In many ways, I am starting from scratch.

I am just surprised that they don't have more integrated shields like this. My opinion is that they are thinking too small. I could see having an integrated shield with extra flash and volatile memory, maybe 6 or 8 stepper controllers or I2C addressable array of them, a couple high power PWM motor controllers and/or brushless ESC, a couple high voltage ac relays, and a few servos to play with. It would make things like the RepRap a thousand times simpler. I guess they just like making up cables and stringing things together.

Originally Posted by schoeftinger BTW, when using some smarter command mechanism the Arduino memory contstraints should not be a problem at all. I guess I'm just too lazy to write myself an Arduino library for G-Code (or whatever proprietory command language).. Thanks for the link to the 3 axis Arduino shield! - That's going to save some effort compared to wiring and soldering stuff to the EasyDrivers... cheers, -Tom

[schoeftinger]

Fwiw, I've never seen any greater re-usability in "higher-level" open source hardware.
Most people just use basic, good-quality boards and start hacking their proprietary code and design a simple hardware just about fit enough to support their use cases.

The better & more re-usable components are mostly quite expensive (& too complicated to build them from scratch yourself)...

However, looking at that triple-stepper control in your link, I guess Arduino could be a pretty darn good choice for a home-brewed CNC control.

just my 2 cents!
-Tom

[AndyL]

Honestly the grblshield interested me, but ... By outward appearance it's just 3 of the reprap driver boards mounted on a nice shield format... That A3892 is the only headache, SMD components don't make for easy DIY'ing...

Part of my CNC use is to cut and drill PCBs, usually arduino shields... The one nice thing about that A3892 is the microstepping, but there's also the L293, good for a similar output in a simple 16pin DIP package...

Experimentelle Interfaces WS 06 » Blog Archive » Motortreiber L293D

L293Ds are a whopping 8$ each at my local electronics supply... Add a protoshield Freeduino SB-Protoshield (SKU: 16090) - HVW Technologies and you've got the same functionality... If you don't want to cnc a shield for yourself...

To be a true grblshield, they should have added the SD card; Arduino Forum - SD card read/write with Arduino - again a nice simple circuit... relatively easy to put it all on one shield - for way less than that commercial product....

[dkirtley]

I also like the new Makerbot 2.4 motherboard. SD card, outputs for 5 steppers, limit switches broken out, AT power supply connector, plus 20 digital pins brought out to a connector. Pricey at $85 without any stepper controllers.

I think it is potentially a better implementation but still falls short in my opinion.

[rinthesun]

Few comments
1) Grbl directly interprets GCode and CNC USB Controller by Planet CNC does not. You need both the PC program and the 18F4550 controller, since the PC code converts the GCode to an optimized form.

2) Grbl can handle limit switch with three arduino pins. PlanetCNC does also but uses 6 pins.

3) PlanetCNC has input for 8 switches for jogging step motors. Grbl does not.

4) PlanetCNC has some additional outputs. So far Grbl does not.

I assume can jog motors with small GCode program. I do not see why jogging can't be added to Grbl. Could use two arduino pins to a shift register like a game keyboard.

A PC program to work with Grbl would be handy.

[hippy]

They have some major advances using the propeller chip by Parallax Home having eight gogs (cpu cores) with plenty of memory with expansion.
Each axis can be controlled by an individual gog (core) which all the gogs can communicate with each other.
And the Propeller chip itself is roughly $8.00.
Theres downloadable code on file for controlling stepper motors and servo's.

[re3e]

Originally Posted by aventgps The arduino board is programed with a modified reprap gcode interpreter. 3 axis motion and 6 limit switch...

hey , basically following the same steps , going with arduino mega 2560 , got my 3 h-bridge going and i am able to control steps/usteps, direction and speed , my original plan was to use CNCLinux for toolpath / gcode , but the LPT limitation is having me look at what else (+i'd like to use the arduino for more then jist the sensor loop back) .... considering a gcode interpreter on arduino but haven't found anything workable yet .... could consider coding one but it looks much larger then i see as a n00b