Do some filaments shrink? February 16, 2014 09:10AM |
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Re: Do some filaments shrink? February 16, 2014 11:47AM |
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Re: Do some filaments shrink? February 16, 2014 12:20PM |
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Re: Do some filaments shrink? February 18, 2014 10:22AM |
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Re: Do some filaments shrink? February 18, 2014 10:33AM |
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markbee and myself got around 75 as wellQuote
appjaws1
Over the weeks I have printed 3 of these sets and they all measured 74-76mm, 2-4mm short, this seems excessive and made me think that I was measuring it wrong but the instructions are clear.
Can you remember what your distance was?
Re: Do some filaments shrink? February 18, 2014 11:32AM |
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Re: Do some filaments shrink? February 18, 2014 11:32AM |
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Re: Do some filaments shrink? February 18, 2014 12:13PM |
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Re: Do some filaments shrink? February 18, 2014 12:34PM |
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Re: Do some filaments shrink? February 20, 2014 10:15AM |
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Re: Do some filaments shrink? February 20, 2014 10:40AM |
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Re: Do some filaments shrink? February 20, 2014 11:19AM |
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Re: Do some filaments shrink? February 20, 2014 01:18PM |
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Re: Do some filaments shrink? February 21, 2014 11:37AM |
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Re: Do some filaments shrink? February 21, 2014 01:26PM |
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Re: Do some filaments shrink? February 21, 2014 02:10PM |
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Re: Do some filaments shrink? February 21, 2014 02:23PM |
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Not necessarily, because Slic3r will compensate for the increased width by laying down a larger diameter circle. It may indicate that there is less percentage of error in a fatter width (which would make sense if any error is a fairly fixed amount - e.g. a 0.1mm error on a 0.4mm width is 25%, but the same 0.1mm error on a 0.5mm width is only 20%).Quote
Flyskyhy
You say that changing the extrusion width for perimeters to 0.62 (from, I assume, 0.5) improved the situation, that is, it actually made the inner diameter bigger? I don't really understand how that works, I would expect that enlarging the extrusion width would make the inner diameters smaller.
Re: Do some filaments shrink? February 21, 2014 03:38PM |
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Re: Do some filaments shrink? February 21, 2014 04:26PM |
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Quote
dmould
Not necessarily, because Slic3r will compensate for the increased width by laying down a larger diameter circle. It may indicate that there is less percentage of error in a fatter width (which would make sense if any error is a fairly fixed amount - e.g. a 0.1mm error on a 0.4mm width is 25%, but the same 0.1mm error on a 0.5mm width is only 20%).Quote
Flyskyhy
You say that changing the extrusion width for perimeters to 0.62 (from, I assume, 0.5) improved the situation, that is, it actually made the inner diameter bigger? I don't really understand how that works, I would expect that enlarging the extrusion width would make the inner diameters smaller.
Dave
(#106)
Re: Do some filaments shrink? February 21, 2014 05:00PM |
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Re: Do some filaments shrink? February 21, 2014 05:24PM |
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Quote
Marc van Beelen
Hi Arnoud,
thanks for your reply.
Could you explain how Slicr would produce an extrudor width of 0.85 at a layer height of 0.25mm?
I checked the G-files and saw that the extruder (set at 0.5mm) during circles was positioned exactly 0.25mm away from the perimeters.
Other question, with custom setting 160% for perimiters I would expect a higher flow of plastic in stead of less or?
Re: Do some filaments shrink? February 21, 2014 05:57PM |
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Re: Do some filaments shrink? February 22, 2014 08:55AM |
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Quote
Marc van Beelen
OK, I understand what you mean since you asume that Slicr adjusts the feed rate to create a bigger extruder hole.
In my test I mention it and I simply don't know what Slicr does with the feedrate when wider extrudor is defined.
What I do know that defining a wider extruder gives better results for the smaller holes
Also I know that with standard extruder width of 0.5, layer height 0.25mm, Slicr positions the head exactly 0.25 mm from the borders (of a round object) so I think that Slicr simply adjusts the extruder speed depending on layer height but positions the head, depending on extruder width (but no idea if it also sets a higher feedrate in case of wider extrudor head).
But to be sure I can do a simple test with the adjusted and tested 0.64 setting and see where Slicr positions it's head and compare the feedrates.
Anyhow, thanks for the info so far, I will keep you updated.
Re: Do some filaments shrink? February 23, 2014 10:40AM |
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Re: Do some filaments shrink? February 23, 2014 11:09AM |
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Quote
Flyskyhy
I looked into the Slic3r code to see what it actually does. If I understand it correctly, then it takes the width directly from the settings, specifically from the Print Settings->Advanced->Extrusion Width->Perimeter parameter. The line of plastic is deposited half that width from the edge. From the width, the extrusion speed is calculated, according to the following:
- if width > nozzle_diameter + layer_height, then the plastic is assumed to form a rectangle with two half-circles to the sides, squeezed sideway between the nozzle and the lower layer. It extrudes enough plastic to fill such a shape to the specified width.
- otherwise, the cross section is assumed to be a rectangle with the width of the nozzle and height of the layer, with extra material going into two half-ovals to the side. Enough is extruded to create a shape like that with the specified width.
Now, this has interesting consequences:
- The width cannot be smaller than the nozzle diameter, the logic does not account for that situation (I am not sure what would happen in practice anyway; is it possible to lay down lines thinner than the nozzle diameter?)
- If the width is exactly equal to the nozzle diameter, then the logic assumes an exactly rectangle line of plastic is deposited - not very realistic.
This becomes especially strange, because of the way the width is determined from the setting:
- if the setting is a percentage, it is a percentage of the layer height, NOT of the nozzle diameter.
- if the setting is 0 (the default), then it takes the nozzle diameter as width - again, not very realistic.
To give a concrete example: with a nozzle diameeter of 0.5mm, and a layer height of 0.25mm, if you set the perimeter width to 160%, it will actually be 0.4mm, smaller than the nozzle diameter! Therefor, you will not get accurate walls with those settings
In concrete, I would recommend to always set the perimeter extrusion width equal to the nozzle diameter + the layer height. That way, I think you should get a realistic computation and extrusion, and therefore more accurate walls. Slic3r should probably be updated to take that as default.
As soon as I get a chance, I will try to experiment with this a bit, too see what happens in practice with different parameters
Re: Do some filaments shrink? February 23, 2014 11:22AM |
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Re: Do some filaments shrink? February 23, 2014 11:25AM |
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Re: Do some filaments shrink? February 23, 2014 11:52AM |
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Quote
Marc van Beelen
@Arnaud31, I don't understand either why your perimiter width is set at 0.85. It will be a combination of various parameters. In my situation it took over the value as defined of in case of default the diameter of the nozzle.
Re: Do some filaments shrink? February 24, 2014 08:35AM |
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Re: Do some filaments shrink? February 26, 2014 09:12AM |
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