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Three parameters

Posted: Sun Nov 23, 2014 8:25 am
by brumbaer
I know there will be documentation at some point, but I started on my 1.7 compatible iPad-controller version in ernest and would like it to be as compatible as possible.

So far it looks good, printer management, calibrations and material editing incl. factor tool are up and running.
But there are four values I can only guess what they really do.
It would be nice if somebody could spare the time to tell me about

Shrinkage Multiplier in Material Definition
Is it just informational or is it really used and yes what for.
Does it define the size after print i.e. .98 or the factor to compensate for it i.e. 1.02

MDM in the factor tool.
Where does it come from ? It’s not the Machine Specific Multiplier that’s MSM. Is it the Projector Multiplier from the Configuration File ?

X/Y Axis calibration Multiplier
Is it used and if so where ? I.e. it be used to multiply the stl data before slicing, but then the job file would no longer be printer independent

Unsupported Pixel Multiplier in Print Dialog
When is a pixel considered unsupported ? What is multiplied by the factor ?

Any help appreciated

Three parameters

Posted: Sun Nov 23, 2014 8:54 am
by mikej
Shrinkage multiplier is really used. If you create a material with .98 (2% post cure shrinkage), it will increase the image and the z steps such that it's printed larger. (and hopefully shrinks to correct size after post cure).

MDM, This is a factor that comes from the configuration file, yes it's the projector multiplier. The line in the config file should be changed to "Machine Dependent Multiplier" (and will be at some point). It's meant to adjust for more than just the projector.

XY is for scaling the image to compensate for errors made in the Projector Calibration (done using the grid). The only way to use it effectively is to do the best possible Projector Calibration, print a test object, and then measure the actual print before post curing. The multiplier would be the object's designed dimension divided by the object's actual measured dimension.

On any given layer, when we expose a pixel, there is either a pixel "above" it already formed and we need to cure long enough that we ensure we adhere to it (ie, supported) or there is no pixel above it and so we want to cure long enough to form the layer at the desired, sliced, thickness. The normal calculated exposure times ensure we "stick" to the above pixels. As a standard, for unsupported pixels, we expose only 80% of that time, to reduce the z-bleed issue.

Three parameters

Posted: Sun Nov 23, 2014 9:46 am
by brumbaer
Thank you very much for the answer, Mike.

What's not clear to me is when Shrinkage Multiplier and XY Calibration are applied.

Shrinkage can't really be applied when slicing, as the material is not known.
So I assume the pixelmap for the current layer is scaled before the exposure-map-time is computed. Modifiying the number of z-steps is straight forward.

IS XY calibration what i measure or what the software shall do. I.e. A print 10% too large would call for a value of 1.1 or .9
Is the XY calibration applied at the same time as the shrinkage ? I.e. scalex = X-Calibration / Shrinkage;


Three parameters

Posted: Sun Nov 23, 2014 1:14 pm
by mikej
Both XY and Shrinkage are used at the same time to scale the image that's about to be exposed (at print time, not during slicing).

It's desired/measured. So if a print was supposed to be 1.0 and measured 1.1, the value would be 1.0/1.1 = .9091 (so it's a corrective multiplier)

Three parameters

Posted: Sun Nov 23, 2014 2:34 pm
by behold3d
I think this would be a great addition. Thanks for working on this!

Three parameters

Posted: Sun Nov 23, 2014 3:29 pm
by mikej
It's been in effect since v1.7.0

Three parameters

Posted: Sun Nov 23, 2014 9:35 pm
by brumbaer
Thanks Mike