Bowden compensation
Posted by nikbjo
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Bowden compensation February 06, 2013 08:58AM |
Registered: 11 years ago Posts: 29 |
Would it be possible to make slic3r compensate for the "springiness" in bowden extruders so that it extrudes a little extra material at the beginning of a move (since some of the extrution will build upp pressure in the bowden tube) and a little less during the last part (where the pressure in the bowden tube "help" with the extrution) so that the preassure in the bowden tube is close to zero at the end of the line.
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Re: Bowden compensation February 06, 2013 01:59PM |
Registered: 13 years ago Posts: 228 |
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Re: Bowden compensation February 06, 2013 06:28PM |
Registered: 13 years ago Posts: 2,947 |
nikbjo Wrote:
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> Would it be possible to make slic3r compensate for
> the "springiness" in bowden extruders so that it
> extrudes a little extra material at the beginning
> of a move (since some of the extrution will build
> upp pressure in the bowden tube) and a little less
> during the last part (where the pressure in the
> bowden tube "help" with the extrution) so that the
> preassure in the bowden tube is close to zero at
> the end of the line.
That should not be possible since it is your firmware that syncs the axis together so the slicer can not make the filament start coming out sooner. If you increase your acceleration the hysteresis will be greatly reduced. Also the only thing a Bowden extruder needs from the slicer to get better results is during retraction to make sure the head does not sit still while retracting.
-------------------------------------------------------
> Would it be possible to make slic3r compensate for
> the "springiness" in bowden extruders so that it
> extrudes a little extra material at the beginning
> of a move (since some of the extrution will build
> upp pressure in the bowden tube) and a little less
> during the last part (where the pressure in the
> bowden tube "help" with the extrution) so that the
> preassure in the bowden tube is close to zero at
> the end of the line.
That should not be possible since it is your firmware that syncs the axis together so the slicer can not make the filament start coming out sooner. If you increase your acceleration the hysteresis will be greatly reduced. Also the only thing a Bowden extruder needs from the slicer to get better results is during retraction to make sure the head does not sit still while retracting.
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Re: Bowden compensation February 13, 2013 04:34PM |
Registered: 11 years ago Posts: 29 |
It's a loot easier to do in the slicer than in firmware since you have to analyse the extrution and its even if it could possible be done with look ahead functions in firmware you have alot of more time for computations during slicing.
After looking a little on skeinforge the Oozebane script seems have that finction.
After looking a little on skeinforge the Oozebane script seems have that finction.
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Re: Bowden compensation February 13, 2013 04:43PM |
Registered: 13 years ago Posts: 2,947 |
nikbjo Wrote:
-------------------------------------------------------
> It's a loot easier to do in the slicer than in
> firmware since you have to analyse the extrution
> and its even if it could possible be done with
> look ahead functions in firmware you have alot of
> more time for computations during slicing.
>
> After looking a little on skeinforge the Oozebane
> script seems have that finction.
NO. Because the firmware synchronizes the axis together so you can not have the extruder start before the x or y unless it is done in the firmware or is just a blob before the axis starts. Oozebane is for DC extruders, oozestep was for stepper extruders and bowdens but was never actually part of SF. The only thing SF officially had to try and deal with bowden cables is called dwindle and it results in under extrusion.
Marlin has a function called "advance" that is supposed to de-synchronize the axis but does not work properly, but is the only way to deal with hysteresis if it was actually an issue that could not be overcome with other settings like acceleration and jerk.
-------------------------------------------------------
> It's a loot easier to do in the slicer than in
> firmware since you have to analyse the extrution
> and its even if it could possible be done with
> look ahead functions in firmware you have alot of
> more time for computations during slicing.
>
> After looking a little on skeinforge the Oozebane
> script seems have that finction.
NO. Because the firmware synchronizes the axis together so you can not have the extruder start before the x or y unless it is done in the firmware or is just a blob before the axis starts. Oozebane is for DC extruders, oozestep was for stepper extruders and bowdens but was never actually part of SF. The only thing SF officially had to try and deal with bowden cables is called dwindle and it results in under extrusion.
Marlin has a function called "advance" that is supposed to de-synchronize the axis but does not work properly, but is the only way to deal with hysteresis if it was actually an issue that could not be overcome with other settings like acceleration and jerk.
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Re: Bowden compensation February 13, 2013 08:39PM |
Admin Registered: 17 years ago Posts: 7,879 |
I think advance was created to compensate for the normal lagging response of the hot end, not for Bowden hysteresis. Are you saying it is totally broken, or just doesn't work for Bowden?
[www.hydraraptor.blogspot.com]
[www.hydraraptor.blogspot.com]
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Re: Bowden compensation February 13, 2013 09:06PM |
Registered: 13 years ago Posts: 2,947 |
nophead Wrote:
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> I think advance was created to compensate for the
> normal lagging response of the hot end, not for
> Bowden hysteresis. Are you saying it is totally
> broken, or just doesn't work for Bowden?
Not sure but from my testing it did not work with a Bowden. Also other people that have tested it say it does not help, but I do not know the official state of it. It looks to have been implemented and never changed or updated as far as documentation is concerned.
From my findings all it did was move the bump around a little. I tried values from 0.001 to -0.001 where it did move the bump as stated but did not reduce it in anyway.
-------------------------------------------------------
> I think advance was created to compensate for the
> normal lagging response of the hot end, not for
> Bowden hysteresis. Are you saying it is totally
> broken, or just doesn't work for Bowden?
Not sure but from my testing it did not work with a Bowden. Also other people that have tested it say it does not help, but I do not know the official state of it. It looks to have been implemented and never changed or updated as far as documentation is concerned.
From my findings all it did was move the bump around a little. I tried values from 0.001 to -0.001 where it did move the bump as stated but did not reduce it in anyway.
| FFF Settings Calculator | Gcode post processors | Geometric Object Deposition Tool Blog |
| Tantillus.org | Mini Printable Lathe | How NOT to install a Pololu driver |
|
Re: Bowden compensation February 14, 2013 04:19AM |
Registered: 11 years ago Posts: 29 |
Sublime Wrote:
-------------------------------------------------------
> nikbjo Wrote:
> --------------------------------------------------
> -----
> > It's a loot easier to do in the slicer than in
> > firmware since you have to analyse the
> extrution
> > and its even if it could possible be done with
> > look ahead functions in firmware you have alot
> of
> > more time for computations during slicing.
> >
> > After looking a little on skeinforge the
> Oozebane
> > script seems have that finction.
>
> NO. Because the firmware synchronizes the axis
> together so you can not have the extruder start
> before the x or y unless it is done in the
> firmware or is just a blob before the axis starts.
>
It doesnt have anything to do with syncronization of axis, the slicer specifies how much to extrude during each move. The slicer increase the extrution during the first part of a "line" for example during a 1 mm long move, and extrudes a little less during the last 1 mm of the line.
-------------------------------------------------------
> nikbjo Wrote:
> --------------------------------------------------
> -----
> > It's a loot easier to do in the slicer than in
> > firmware since you have to analyse the
> extrution
> > and its even if it could possible be done with
> > look ahead functions in firmware you have alot
> of
> > more time for computations during slicing.
> >
> > After looking a little on skeinforge the
> Oozebane
> > script seems have that finction.
>
> NO. Because the firmware synchronizes the axis
> together so you can not have the extruder start
> before the x or y unless it is done in the
> firmware or is just a blob before the axis starts.
>
It doesnt have anything to do with syncronization of axis, the slicer specifies how much to extrude during each move. The slicer increase the extrution during the first part of a "line" for example during a 1 mm long move, and extrudes a little less during the last 1 mm of the line.
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