Using conductive paint to AutoLevel slate

Discussion about the arduino based g-code interpreter, grbl
jlauer
Posts: 115
Joined: Thu Jun 26, 2014 9:29 pm

Re: Using conductive paint to AutoLevel slate

Post by jlauer » Sun Dec 28, 2014 6:18 pm

Have you tried running your probes at a much higher feedrate? I bet you could get away with going really fast if you feel that your electrical connections are good on the aluminum foil. Anyone up for posting some video of the aluminum foil trick? This is cool stuff.

Xaracen
Posts: 122
Joined: Sat Apr 20, 2013 7:41 am

Re: Using conductive paint to AutoLevel slate

Post by Xaracen » Sun Dec 28, 2014 11:26 pm

I've been tempted to up the feed rate anyway, so I think I'll just do that, perhaps doubling it to 10mm/min to see how it goes.
Shapeoko v1 #????
500mm Y-slides with dual Y-steppers
375mm dual X-axis gantry
150W DC ER11 Sable2015 spindle
conductive probe via spindle shaft/toolbit (can probe while spinning!)
Arduino Uno running grbl v0.9i with grblShield v4.

Xaracen
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Joined: Sat Apr 20, 2013 7:41 am

Re: Using conductive paint to AutoLevel slate

Post by Xaracen » Mon Dec 29, 2014 10:19 am

Well, I just ran a short Autoleveller test on the foil covered slate pictured earlier. I set the feed rate to 10mm/min for a 3 x 9 matrix giving 27 probe points, just in the interests of saving time, with the following results:
Probing to aluminium foil on slate.jpg
Definitely not flat then!
Probing to aluminium foil on slate.jpg (30.01 KiB) Viewed 613 times
Ran the probe again at 20mm/min, then again at 50mm/min, without any problems, so I am much more confident about doing similar fast probes in the future.
Probing to aluminium foil on slate 50mm per min.jpg
Note the profile looks the same, but the figures are slightly different.
Probing to aluminium foil on slate 50mm per min.jpg (31.63 KiB) Viewed 613 times
The shapes of the profiles are the same, but the actual numbers for the Z-values differ between them. I wasn't expecting them to be identical, especially as three decimal places in mm is well beyond the accuracy of the shapeoko, and even two decimal places is not really meaningful, so I don't expect any significant issues to arise from these differences, unless someone knows better and can tell me.
Shapeoko v1 #????
500mm Y-slides with dual Y-steppers
375mm dual X-axis gantry
150W DC ER11 Sable2015 spindle
conductive probe via spindle shaft/toolbit (can probe while spinning!)
Arduino Uno running grbl v0.9i with grblShield v4.

WillAdams
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Re: Using conductive paint to AutoLevel slate

Post by WillAdams » Mon Dec 29, 2014 11:06 am

There's been at least one report of arcs failing in Grbl due to their being truncated to 2 (or 3?) digits, but working at 3 (or 4?).

Unless you're flipping the plane for arcs and placing them in the Z-axes it shouldn't matter.
Shapeoko 3XL #0006 w/Makita RT0701 Router w/0.125″ and ¼″ Elaire precision collets
Nomad 883 Pro #596 (bamboo)

Xaracen
Posts: 122
Joined: Sat Apr 20, 2013 7:41 am

Re: Using conductive paint to AutoLevel slate

Post by Xaracen » Mon Dec 29, 2014 11:53 am

I had a problem myself with truncating gcode millimetre parameters to two decimal places resulting in some failed arcs, where the same arcs were fine when I restored the default four decimal places. However, in the probing scenario above, in my "supposed-to-be-flat" 2.5D engravings, we are talking actual linear dimensions/co-ordinates, not parameters used in internal calculations by grbl, so I agree that these discrepancies are below shapeoko's "noise" level, and effectively insignificant. And F-Engrave's Gcode output doesn't generate any arcs anyway.

In other proper 3D milling operations, your worry about probe-modified arcs curving in the z-axis may well be relevant, and also where probing along the x or y axis is being done for whatever reason.
Shapeoko v1 #????
500mm Y-slides with dual Y-steppers
375mm dual X-axis gantry
150W DC ER11 Sable2015 spindle
conductive probe via spindle shaft/toolbit (can probe while spinning!)
Arduino Uno running grbl v0.9i with grblShield v4.

cvoinescu
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Location: Camberley, UK
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Re: Using conductive paint to AutoLevel slate

Post by cvoinescu » Mon Dec 29, 2014 4:00 pm

The G-code spec allows arc tolerances that require 4 decimals for inches and 3 decimals for mm (the tolerances are 0.0002" in inch mode, and 0.002 mm in millimeter mode).
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

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