calibration of a cnc

[mat_au]

ok now i need some more help, im just about ready to smash this bloody thing. so all the axis are working but now trying to get the voltages right so they run. i dont know what im doing wrong but its getting very frustrating. im getting loud noises, clicking. and when i kinda had it right i decided to run some g code just to see how it went. and well lets just say it was nothing like a square. ive calculated the step via an online calculator.

im using the cnc shield - http://blog.protoneer.co.nz/arduino-cnc-shield/

and the cnc - http://www.makerstore.com.au/product/ox-cnc-mechanical-kit-large/

steppers - x and y - Nema 23 Stepper Motor 1.26N.m (6.35mm shaft)
and z Nema 17 Stepper Motor 560mN.m

any help would be greatful

[Master Splinter]

Clicking/loud noises sound like you're accelerating too quickly and missing steps/power insufficient to overcome inertia. A NEMA 23 should be happy with 24-48 volts, NEMA 17 about 24 volts...so a good 24 volt, 5+ amp power supply would be my first guess, as would dialling the acceleration right down to a snail-like pace for initial setup. My second guess would involve punting the arduino controller into a nearby sturdy metal receptacle that is emptied weekly by sanitation engineers and using a Geckodrive instead.

[mat_au]

thanks ill dial down the acceleration and as for the arduino im starting to think the same thing ive had nothing but problems with it

[snowyskiesau]

WHat stepper drivers do you have installed on your cnc shield? A4988 drivers might be pushing it to drive NEMA 23 motors but if the drivers are DRV8825, they should handle it OK.
As MS said, try slowing down until you can get reliable movement, then play around with speed/acceleration.
The Gecko G540 is an excellent if expensive step up. It's what I'm using on my 6040 router and will be using on my nearly completed XYZ-Carve.

[mat_au]

yes they are the A4988 drivers.

tell me more about the gecko g540? how do you connect it if you dont have a parallel port?

and would it work on my steppers i have now?

[snowyskiesau]

If you're running LinuxCNC or Mach 3 then you will need a parallel port (although Mach 3 can be used with an external USB connected interface such as a Smoothstepper). The existing stepper motors will be OK as the G540 can drive motors up to 3.5A.
Assuming you want to keep using grbl and the arduino then it is possible to interface a cnc shield to the G540, which is what I'll be doing, but it's not a straight forward exercise - I'm still in the planning stage.

Sticking with the arduino/cnc shield, then as long as your steppers can run on the current that an A4988 can supply (1A without a heatsink, 2A MAX with a heatsink and fan), then your existing set up will work although not quickly and the torque of the motors may be lower due to the current limitation.

[mat_au]

yes i have heat sinks and 2 large fan - enough to keep it very cool. i guess ill keep going at it. would just be nice to have something go right and smoothly for a change

[foobillious]

I'd go through the set up process for each axis one by one to make sure you have everything working right. You'll end up chasing your tail otherwise.

I'm not sure about the shield your using, but its common with those types of drivers that you have to adjust the current for each motor to ensure you arn't loosing any steps. The process is normally set the trimpot to about 1/2 way and then do a rapid move on that axis (i.e G0 X200), although go larger if you can. If the motor looses steps then turn the pot up a little bit and try again. If its fine, turn it down until you start loosing steps, and then go a little bit above that point. If you arn't sure if you are loosing steps just move back to the 0 point (G0 X0) after the first move - if you don't end up in the same place each time you've lost steps (overly simplified).

You normally also need to configure the grbl software so it knows how many steps / revolution your motors are, and how far the carriage will travel per revolution (or step, I forget which way round it is). There are probably a bunch of other parameters to configure, like acceleration rates, power off idle etc.

The software your using to transfer commands to the arduino can also have some bad effects. I get unreliable results communicating with my tinyg using a number of standard windows terminal packages, but tgFX works fine, and I believe there are a number of web based programs to transfer g-code to the arduino (I don't recommend that though - internet connecting industrial control machines is just stupid).

It'll help people make suggestions if you provide more info about your setup - i.e what power supply voltage and amperage your using, what amperage your steppers are rated for etc