Scaling in Slic3r

I can't figure out how to scale an item in Slic3r by a decimal amount like, say, 0.7%. The scale box only seems to allow increments of one. And yes, I know i can scale the model in the CAD software but want to know if its possible to do in Slic3r.

Cheers.

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Sebastian

Flash Creator X
Creality CR-X
Anycubic Photon

0.7% is very little.
(Stating the obvious)

The only workaround I can think of is to scale it to 1%, Export the .STL from Slic3r. Re-import the new .STL and scale that to 70%.

-a

Thanks Alan. I think I wasn't clear enough in my post. I don't want to scale to 0.7% but rather increased by 0.7% (the shrinkage for ABS is 0.7% btw) so I want to enter 100.7 into the scale window...

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Sebastian

Flash Creator X
Creality CR-X
Anycubic Photon

It would seem the same approach could still be used. 95% scale of 106% scale is 100.7% scale.

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sfinke
Thanks Alan. I think I wasn't clear enough in my post. I don't want to scale to 0.7% but rather increased by 0.7% (the shrinkage for ABS is 0.7% btw) so I want to enter 100.7 into the scale window...

Shrinkage does not work the same in FFF printing as it does for a moulded part. This is because all the shrinking occurs on "live" extrusions, so instead of affecting the overall dimensions of the object, it acts only to reduce the effective extrusion width slightly and the printed dimension remains accurate. Easiest visualised on the Z axis (but a similar mechanism takes place in the X and Y axis). After depositing (say) a 1mm layer, that layer will cool and shrink down leaving a gap of (say) 0.007mm under the nozzle. When the nozzle rises 1mm to print the next layer, there will therefore be a gap of 1.007mm. But the extruded plastic will completely fill that gap - the layer height will become 1.007mm instead of 1mm and so progressively compensate for the shrinkage on every layer (the extrusion width will be very slightly thinner).

If you think about it, normal shrinkage cannot occur in Z, otherwise by the time the build height reaches 100mm, the part will have shrunk down to 99.3mm (most of it will be cool and have shrunk as much as it's going to shrink) leaving a huge gap between the part and the nozzle. If you increase the height of the object to "compensate" in Slic3r, you will end up with an object that is too high.

XY works similarly, with the corners of a cube remaining in the same XY positions as the nozzle printed them, though dimensional changes can take place due to warping (which is caused by shrinkage but is a different mechanism dependant on part geometry). So unlike conventional injection moulding, you should not increase the part size to compensate for shrinkage.

Dave

Edited 1 time(s). Last edit at 07/01/2015 09:15AM by dmould.

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IMBoring25
It would seem the same approach could still be used. 95% scale of 106% scale is 100.7% scale.

Awesome. Thanks.

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Sebastian

Flash Creator X
Creality CR-X
Anycubic Photon

Quote
dmould
XY works similarly, with the corners of a cube remaining in the same XY positions as the nozzle printed them, though dimensional changes can take place due to warping (which is caused by shrinkage but is a different mechanism dependant on part geometry). So unlike conventional injection moulding, you should not increase the part size to compensate for shrinkage.

This is only half the truth. If you have a heated bed, shrinkage is the sum of what you described plus the shrinkage due to the delta temperature of the bed. So in fact, the real shrinkage in size for object 10cm width printed in PLA on a heated bed with t=60°C is indeed around 0,4mm and not 0,007 as you assume. Quite more complex is the shrinkage in Z direction, since with every layer printing gets far away from the heated bed, so shrinkage is larger when printing a flat object (high influence of the heated bed to the layers) as when you print a tall object (influence of the heated bed gets smaller, as greater the distance of the printed layer gets).

And this is not a dumb theory, this is a reporduceable and measurable fact. For this reason it is absolutely not understandable why slic3r (different from all other slicers I know) does not allow decimal digits for scaling.

Edited 1 time(s). Last edit at 11/14/2015 06:01AM by Zaldoran.

If you need to bump the size in the XY plane a bit go to print settings>advanced and look for XY size compensation. You can enter whatever value you need there and X and Y will be grown/shrunk by that amount.

I found it useful when printing a pulley for a gear belt. The XY size compenstion allowed the pulley's pitch to match the belt perfectly.

XY size compensation can be useful for tricky parts like that, but if you have to use it for every part you should probably recalibrate your printer.

Edited 1 time(s). Last edit at 11/14/2015 06:54AM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

A very interesting discussion. Thanks to all!

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Sebastian

Flash Creator X
Creality CR-X
Anycubic Photon