pac.m
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Is geometry correction really happening on all axis?

Wed Jan 11, 2017 6:38 pm

Hello,

I am completely new to 3D printing and I am currently in the process of trying to learn as much as I can about the subject. That said, I was browsing the web looking for information when I stumbled across a document titled "THE FIRST PRINTER TO AUTOMATICALLY CORRECT ITS GEOMETRY IN ALL AXES" http://www.prusaprinters.org/first-prin ... -all-axes/.

After watching the video link on the document and reading some of the documentation, it seems to me that the corrections the printer does are only limited to the printer bed X, Y and Z axis but its ignoring the actual printer Z axis itself. In other words, as far as i can see, the printer accounts for the bed not being aligned to the printer X and Y liner rods, it even account for the bed being tilted or warped (pretty cool stuff). What I don't think it accounts for is for the bed to be aligned to the Z axis (Z linear rod).

I have attached a picture describing the idea I am trying to convey in case it helps. The picture show how even though the X and Y axis are consider to be perfectly straight by the printer, the Z axis could still be miss aligned causing potential problems.

Is my assumption about the Z axis not being corrected a correct assumption or am I just not getting something?

EDIT: Just t be clear (or hope to be clear), in the attached picture, imagine that the X, Y and Z axis represent the printer X, Y and Z linear rods, also, assume that the printer bed is perfectly flat and perfectly aligned to the X and Y linear rods. Given those conditions, would the printer do anything about the misaligned Z linear rod?

Thank you.
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patrizio.b
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Re: Is geometry correction really happening on all axis?

Wed Jan 11, 2017 7:16 pm

Do you mean the kind of geometry error that would cause the print of a leaning tower of Pisa?

pac.m
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Re: Is geometry correction really happening on all axis?

Wed Jan 11, 2017 7:53 pm

patrizio.b wrote:Do you mean the kind of geometry error that would cause the print of a leaning tower of Pisa?
Yes, exactly. But taking into consideration that the leaning is only due to the Z axis linear rod misalignment, the rest of the printer is assumed to be perfectly aligned including a perfectly flat bed.

patrizio.b
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Re: Is geometry correction really happening on all axis?

Wed Jan 11, 2017 9:49 pm

I don't think there's any correction for that. But, by design, it would be more difficult to have such a misalignment: X/Y are assembled with screws and nuts, the bed can bend, but Z rods are hard steel firmly held between two fixed mounts (..almost).

Btw, your assembly goal is to have no X/Y corrections at all, so you'll not be going to use that feature for more than 2-3 days. The correction is just a gimmick (if you have squareness OCD... and if you're on this forum... :mrgreen: ), the added value is the response of the calibration!

bubnikv
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Re: Is geometry correction really happening on all axis?

Thu Jan 12, 2017 5:18 pm

The printer corrects the skew of the X/Y axes. It has no way to measure the angle of the Z axis towards the XY plane, so this skew cannot not corrected for. The "Z" axis correction relates to the bed unevenness only.

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