weird z axis sound with G1 lines

Discussion about the arduino based g-code interpreter, grbl
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dointhangs
Posts: 179
Joined: Tue Jun 05, 2012 7:31 pm

weird z axis sound with G1 lines

Post by dointhangs » Tue Sep 18, 2012 5:51 am

I have been having a funny problem with a grating sound on my z-axis for awhile that I havent been able to figure out.
If I enter a G0 (seek) code like G0 z2 or G0 z-2 I have motion in a normal manner. But if I enter the same sort of movement as a G1 code I get the sound, even if its at the exact same speed setting. I guess the good news is that the motor still goes to the same spot, the position is coming out ok. Have tried multiple $4 and $5 (feed and seek) grbl settings.
Another thing is if I enter any F value at the end of a G1 line like "F100" it comes back in the console (universal gcode sender) as F60.0. Is that weird??
I have checked my pot settings, not tonight, but it checks out right around the recommended 0.6V...
I've got the nema17 steppers from sparkfun. 400 steps per rev I believe with no microstepping. I have the rev3 buildlog shield. All jumper pins are in place for x and y which I believe corresponds to 16x microstepping. I have no jumpers for the three z-axis jumpers for no microstepping, just 400 steps per rev.
I have definitely run a M8 tap through that z-axis delrin nut a few times. Havent added lube to it though.
below is a 12s vid of the sound. In this one it seems like the machine is going down for a second normally then the sound kicks in but I also see it immediately without delay after a command line entry.
Below that are my grbl settings.
http://www.youtube.com/watch?v=Ej8s5p-E ... e=youtu.be
$0= 174.98
$1 = 174.98
$2 = 320
$3 = 30
$4 = 500
$5 = 500
$6 = 0.1
$7 = 0
$8 = 9.8
$9 = 0.05
Shapeoko #298, dual drive upgrade, acme z axis, open bed endplates and a slightly larger ("expanded desktop") work area!

jsbannis
Posts: 80
Joined: Tue Apr 10, 2012 11:09 pm
Location: Chicago, IL

Re: weird z axis sound with G1 lines

Post by jsbannis » Tue Sep 18, 2012 1:04 pm

Sounds like an old dot matrix or floppy drive :shock: possibly some resonance between it and the machine?
shapeoko #0057

edwardrford
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Location: Dixon, IL
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Re: weird z axis sound with G1 lines

Post by edwardrford » Tue Sep 18, 2012 3:50 pm

Can you post the version of grbl you're using? is it 0.8a?

It sounds and looks to me like it's binding from the speed. Try this. We're going to send your machine in a box pattern, raising and lowering the z-axis at various speeds.

Code: Select all

(xy plane selection, absolute coordinate mode, mm mode)
G17 G90 G21
(send z-axis to +10mm at 100mm/min)
G1 F100 Z10
(Send X axis over to 100mm at 1200mm/min)
G1 F1200 X100
(send z-axis down to 0 at 200mm/min)
G1 F200 Z0
(send Y axis up to 100mm at 1200mm/min)
G1 F1200 Y100
(send X axis to 0mm at 1200mm/min)
G1 F1200 X0
(send z-axis up to 10mm at 300mm/min)
G1 F300 Z10
(send y-axis to 0mm at 1200mm/min)
M02
Shapeoko 1 #0 - a couple of upgrades.
Shapeoko 2 #0 - a couple of upgrades.
Shapeoko 3 #2 - Stock

dointhangs
Posts: 179
Joined: Tue Jun 05, 2012 7:31 pm

Re: weird z axis sound with G1 lines

Post by dointhangs » Tue Sep 18, 2012 5:30 pm

Yes it is in fact 0.8a. Thanks Edward I will run tonight and report back.
Shapeoko #298, dual drive upgrade, acme z axis, open bed endplates and a slightly larger ("expanded desktop") work area!

dointhangs
Posts: 179
Joined: Tue Jun 05, 2012 7:31 pm

Re: weird z axis sound with G1 lines

Post by dointhangs » Wed Sep 19, 2012 2:46 am

Alright then I have played with this now using edwards box as a starting point.
F100 is just bad news for my setup. At F140 things are a bit grating but much less so and then at 150 we are golden in terms of noise.
On the lower end, below F80 its just bad with the motor seizing up.
I put a new M8 threaded rod in last week. I am looking behind my z-axis makerslide and its just badly badly wobbling on any motion. It was straight on the install a week ago. I took more care with properly tightening the coupler onto the threaded rod but maybe it is still off. Maybe the delrin nut is off. I swore I loosened the delrin nut and ran the new threaded rod through it to straighten it in case it was crooked. Or did I blow that?
the heeks cnc default z feed rate is 100. I will just watch that on those and all other jobs - my salvation may lie in an ebay order for a M5 to M6.35 coupler. Hopefully it will show up, it was coming from taiwan and cost about $4 including shipping. I will score a new M8 threaded rod and I will have a buddy at a shop turn the M8 rod down until it fits cleanly in that coupler. I will then be super careful with the delrin nut and check that out really well.
Following any posts titled z-axis with keen interest :-) keep em coming
Shapeoko #298, dual drive upgrade, acme z axis, open bed endplates and a slightly larger ("expanded desktop") work area!

cvoinescu
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Re: weird z axis sound with G1 lines

Post by cvoinescu » Wed Sep 19, 2012 7:51 am

Hey doingthangs, I just wanted to point you to my buildlog, where I describe what I hope is a useful Z axis modification. No additional parts required.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

dointhangs
Posts: 179
Joined: Tue Jun 05, 2012 7:31 pm

Re: weird z axis sound with G1 lines

Post by dointhangs » Wed Sep 19, 2012 3:54 pm

Cat i had seen that post at a moment I didnt have time to appreciate it - I just read it in better detail - yes this is great THANKS.
Shapeoko #298, dual drive upgrade, acme z axis, open bed endplates and a slightly larger ("expanded desktop") work area!

cvoinescu
Posts: 4442
Joined: Thu Jul 19, 2012 6:50 pm
Location: Camberley, UK
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Re: weird z axis sound with G1 lines

Post by cvoinescu » Wed Sep 19, 2012 4:18 pm

You're welcome. :)
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

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