Grbl with Synthetos Grblshield

Discussion about the arduino based g-code interpreter, grbl
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alpha
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Grbl with Synthetos Grblshield

Post by alpha » Sat May 19, 2012 2:55 pm

The info from our wiki:
Notes on using Grbl with Synthetos Grblshield

There are no changes required to the github distributed versions of grbl operate a Synthetos grblshield.
Grblshield is compatible with grbl version 0.7x and later releases. Synthetos Grblshield
Grblshield is compatible with grbl version 0.6 using a special, patched release.
Grblshield is not compatible with grbl version 0.5
I did install grbl_v0_8a_edge_328p_16mhz_9600_build20120310, that was maybe not so smart - however I guess it should work and the steppers on my table are rotating...

Now I want to modify the Grbl settings, the wiki tells me to change the Z to 1x stepping - but as far as I can tell this is not an option on the Synthetos Grblshield. I did see DrRob's online calculator http://noblesque.org.uk/ShapeOko/grblcalc/ but if I change the Z to 8x stepping it gives me this warning: Greater than 30kHz! Less than 2x step pulse width! - from the sound and the looks I don't think I can ignore this (if I use the calculated settings)?

Does anybody has a Synthetos grblshield with a ShapeOko, if so please post your working settings; thank you!

DrRob
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Re: Grbl with Synthetos Grblshield

Post by DrRob » Sat May 19, 2012 4:57 pm

alpha wrote:Now I want to modify the Grbl settings, the wiki tells me to change the Z to 1x stepping
I found the z-axis to be quite noisy at low speeds with 1x stepping, so I've switched to 4x microstepping for Z, and 8x for X and Y. I changed the step pulse width to 20us to avoid the warning, although I'm sure it would still work with 30us - making it 20us just evens out the mark/space ratio when running at max speed. Maybe I should change the calculator so the warning only shows if the mark or space get really small (but how small?).

Enraged cut a trace on his Grblshield to achieve a different microstepping setting for the Z-axis - see: http://shapeoko.com/forum/viewtopic.php ... race#p1665

Rob.

alpha
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Re: Grbl with Synthetos Grblshield

Post by alpha » Sun May 20, 2012 4:01 pm

Here is my guess:
http://old.alpharesearch.de/pics/IMG_20 ... 092747.jpg
http://old.alpharesearch.de/pics/IMG_20 ... 092627.jpg
I did send a PM to user Wilafau to verify if all this is right... so I will wait until I cut and solder.

Now the big question is should I select 1/2 step like Wilafau or 1/4 step like DrRob??? With 1/2 speed I could theoretically do a higher seek rate, but I don't know if this is true?

aldenhart
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Re: Grbl with Synthetos Grblshield

Post by aldenhart » Mon May 21, 2012 1:35 pm

I submitted a length response to Wilafau's over in Electronics discussing these issues. Rather than reposting, here it is:
http://www.shapeoko.com/forum/viewtopic.php?f=4&t=221

-- Alden

DrRob
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Re: Grbl with Synthetos Grblshield

Post by DrRob » Mon May 21, 2012 2:42 pm

alpha wrote:Now the big question is should I select 1/2 step like Wilafau or 1/4 step like DrRob??? With 1/2 speed I could theoretically do a higher seek rate, but I don't know if this is true?
I don't know if this will help, but I uploaded some video of my Z-axis running in full-step, 1/2 step and 1/4 step modes, in an attempt to show the difference in noise:
Not sure how clear it is. In reality, the noise of the Z-axis motor is nothing compared to the noise of the cutting tool, and there's no problem at all with resolution on the Z-axis, so any step mode is ok.

I've haven't done any experiments to determine the max seek speed possible on the Z-axis.

Rob.

alpha
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Re: Grbl with Synthetos Grblshield

Post by alpha » Mon May 21, 2012 5:46 pm

Rob,

I guess you are still using the stepper motors you posted on the wiki page http://www.shapeoko.com/wiki/index.php/User:DrRob with 400 rev?
DrRob wrote:... I don't know if this will help, but I uploaded some video of my Z-axis running in full-step, 1/2 step and 1/4 step modes, in an attempt to show the difference in noise...
Thanks for the Videos! Yes, it was interesting to hear the difference... I guess everything lower than 8x stepping will work...

DrRob
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Re: Grbl with Synthetos Grblshield

Post by DrRob » Mon May 21, 2012 7:52 pm

alpha wrote:I guess you are still using the stepper motors you posted on the wiki page http://www.shapeoko.com/wiki/index.php/User:DrRob with 400 rev?
I am, yes.
alpha wrote:I guess everything lower than 8x stepping will work...
I think so, yes.

Rob.

AtomSoft
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Re: Grbl with Synthetos Grblshield

Post by AtomSoft » Wed Jun 27, 2012 7:10 pm

DrRob wrote:
alpha wrote:Now I want to modify the Grbl settings, the wiki tells me to change the Z to 1x stepping
I found the z-axis to be quite noisy at low speeds with 1x stepping, so I've switched to 4x microstepping for Z, and 8x for X and Y. I changed the step pulse width to 20us to avoid the warning, although I'm sure it would still work with 30us - making it 20us just evens out the mark/space ratio when running at max speed. Maybe I should change the calculator so the warning only shows if the mark or space get really small (but how small?).

Enraged cut a trace on his Grblshield to achieve a different microstepping setting for the Z-axis - see: http://shapeoko.com/forum/viewtopic.php ... race#p1665

Rob.
Hey Rob if you change the warning would you please update us... Also i can update the grbl calc i made using your original code.
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aldenhart
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Re: Grbl with Synthetos Grblshield

Post by aldenhart » Wed Jun 27, 2012 10:24 pm

Here are the details on the Synthetos grblshield Z axis mod.
http://www.synthetos.com/wiki/index.php ... r_Shapeoko

You can do this yourself or ask us to do it if you are ordering a board.

- Alden

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