grblshield and Z axis

aldenhart
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Re: grblshield and Z axis

Post by aldenhart » Mon May 21, 2012 9:28 am

I'll wait for your pics and then we can combine them with the post and put it on the wiki.

One small point: I'm unsure if the X and Y steps/mm are accurate or not as I derived these numbers from the wiki and have not tested them myself.

-- Alden

DrRob
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Re: grblshield and Z axis

Post by DrRob » Mon May 21, 2012 2:22 pm

aldenhart wrote:There has been some discussion that grbl cannot support the Z step rate - I don't think this is the case. The published $5 of 1100 mm/min is 18.3333 mm/sec. 8x microstepping makes 1280 steps per mm for Z - and that's 23,433 steps per sec - assuming 1.8 degree motors - well under grbl's max rate of about 30,000. (at 1200 mm/min it's asking for a pulse rate of 25,600 pulses per second)
Just a note to explain the discussions about grbl and Z step rate - the recommended stepper motors (http://www.sparkfun.com/products/10846 from the parts list on the wiki) are 0.9 degree 400 steps/rev, so at the recommended 1100mm/min and 8x microstepping that's a pulse rate of ~46933 pulse/sec, which is well above grbl's max rate of about 30,000...

Rob.

aldenhart
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Joined: Tue Apr 10, 2012 2:17 pm

Re: grblshield and Z axis

Post by aldenhart » Mon May 21, 2012 2:59 pm

You are correct. I was looking at the 200 step motors. I do not have 400 step motors to test. Perhaps we can run the same set of tests on the 0.9 degree motors - What's the Z limit on 8x, 4x and 2x - given a reasonably clean mechanical system?

aldenhart
Posts: 132
Joined: Tue Apr 10, 2012 2:17 pm

Re: grblshield and Z axis

Post by aldenhart » Mon Jun 04, 2012 11:37 am

I have written up a simple Z axis mod that can be made in a couple of minutes. It's posted here:
http://www.synthetos.com/wiki/index.php ... r_Shapeoko

Note that all the Inventables full kits (i.e. those with grblshield) are going out with the mod.
Also, grblshield can now be ordered with the mod and we'll do it for you (give us a day or so to get it on the store - in the meantime, send us an email.)

-- Alden
Last edited by aldenhart on Mon Jun 04, 2012 6:57 pm, edited 1 time in total.

vios
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Joined: Sun Apr 22, 2012 12:00 pm

Re: grblshield and Z axis

Post by vios » Mon Jun 04, 2012 3:26 pm

aldenhart thanks for the write up.
That's what I need ;)

Tom Smith
Posts: 297
Joined: Mon Apr 09, 2012 9:55 pm
Location: North Vancouver, British Columbia

Re: grblshield and Z axis

Post by Tom Smith » Mon Jun 04, 2012 7:03 pm

vios wrote:aldenhart thanks for the write up.
That's what I need ;)
Thanks for the photos, very helpful...now how about a younger pair of eyes so I can perform this surgery?! ;)

Tom
_______________
ShapeOko1 191

nio
Posts: 115
Joined: Mon Apr 09, 2012 7:31 pm

Re: grblshield and Z axis

Post by nio » Tue Jun 05, 2012 12:54 pm

So i've 200 steps motor on X and Y axis, and 400 steps in Z axis (kickstarter kit), do i have to set $2 to 320?? or 640??

edwardrford
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Re: grblshield and Z axis

Post by edwardrford » Tue Jun 05, 2012 1:06 pm

Depending on what your microstep is set to on the z-axis will determine your $2 value

If your Z-axis is 400steps/rev, then:

1 revolution = 1.25mm
1mm/1.25mm = .80 revolutions = 1mm

1x = 400 steps * .80 = 320
2x = 800 steps * . 80 = 640
4x = 1600 steps * .80 = 1280
8x = 3200 steps * . 80 = 2560


Clear as mud?
Shapeoko 1 #0 - a couple of upgrades.
Shapeoko 2 #0 - a couple of upgrades.
Shapeoko 3 #2 - Stock

nio
Posts: 115
Joined: Mon Apr 09, 2012 7:31 pm

Re: grblshield and Z axis

Post by nio » Tue Jun 05, 2012 1:29 pm

not too much jajaja!!! i'm totally newbie in the CNC world, but don't worry the problem is me , not your explanation :)
But where do i set the microstep??

Thanks

edwardrford
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Re: grblshield and Z axis

Post by edwardrford » Tue Jun 05, 2012 1:34 pm

The good news is that we were all new to CNC once :-)

Some people forget that, but the amount of time and frustration I experienced when I was new to CNC has stuck with me, and part of the project is to get people past that feeling as quickly as possible! It looks like you're close to getting something going, so let's focus on your controller.

What stepper controller are you using? (Buildlog.net stepper shield or grblShield or DrRob's Board or something else?)

It might be easier if you attach a picture of your controller for us.

-Edward
Shapeoko 1 #0 - a couple of upgrades.
Shapeoko 2 #0 - a couple of upgrades.
Shapeoko 3 #2 - Stock

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