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Brigandier
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Linear Advance, is it coming back?

Fri Feb 09, 2018 11:11 pm

Has anyone heard any updates on when Linear Advance is making a comeback? I see the flag for it in the firmware, but was hesitant to re-enable it. What was the problem with it originally? It's a bit more important to the PETG printers... :)

EDIT to include my post below. Again, use at your own risk! This was disabled by Prusa to fix USB issues, I don't see why us sdcard users should suffer for it until they figure out a fix.
Brigandier wrote:
Sat Feb 10, 2018 1:28 am
Took the plunge, uncommented the LIN_ADVANCE line in the latest (3.1.1) release. Already seeing massive improvements on my PETG.

Now, I don't know what Prusa's opinion is of people posting customized firmware so if this is violating anything please let me know, but if you guys are interested please find it attached. This is the firmware from the MK3 branch on Github, with the only adjustment being line 321 in Configuration_adv.h to uncomment #define LIN_ADVANCE. Best I can tell, all LIN_ADVANCE references elsewhere do an "ifdef" to check if this is defined or not.

DISCLAIMER: I am NOT a Prusa employee or necessarily even that great of a programmer. You are using this at your own risk and on the premise that it is working okay for just me on a couple prints thus far. If the details in this thread are accurate, you do not want to use this if you do any type of printing over USB. This is for sdcard users only!
Last edited by Brigandier on Sat Feb 10, 2018 1:42 am, edited 4 times in total.
Waiting for MK3 to be worth using... still waiting...
My MK3 Parts: [New Shoes] [TPU Micro Springs]
My MK3 Software: [G81 Heatmaps] [OctoPrint Heatmaps]

waldemar.g
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Re: Linear Advance, is it coming back?

Fri Feb 09, 2018 11:20 pm

Brigandier wrote:
Fri Feb 09, 2018 11:11 pm
Has anyone heard any updates on when Linear Advance is making a comeback? I see the flag for it in the firmware, but was hesitant to re-enable it. What was the problem with it originally? It's a bit more important to the PETG printers... :)
There is an alpha version for the MK3 on their github, but you must compile it yourself.

fulcrum
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Re: Linear Advance, is it coming back?

Fri Feb 09, 2018 11:42 pm

Brigandier wrote:
Fri Feb 09, 2018 11:11 pm
What was the problem with it originally? It's a bit more important to the PETG printers... :)
If I remember correctly, they disabled linear advance in order to get printing from USB working. Apparently, linear advance was so computationally intensive that cause the code that reads commands from the serial USB to skip commands.

alex.g9
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Re: Linear Advance, is it coming back?

Sat Feb 10, 2018 12:44 am

i hope they bring it back, and just allow a toggle of LA vs USB id take LA over usb anyday tbh

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Brigandier
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Re: Linear Advance, is it coming back?

Sat Feb 10, 2018 12:47 am

alex.g9 wrote: i hope they bring it back, and just allow a toggle of LA vs USB id take LA over usb anyday tbh
fulcrum wrote:
Fri Feb 09, 2018 11:42 pm
Brigandier wrote:
Fri Feb 09, 2018 11:11 pm
What was the problem with it originally? It's a bit more important to the PETG printers... :)
If I remember correctly, they disabled linear advance in order to get printing from USB working. Apparently, linear advance was so computationally intensive that cause the code that reads commands from the serial USB to skip commands.
If this is the case, I will definitely turn it back on. To get acceptable quality on my PETG prints I have to turn speeds down quite a bit, and it's causing filament buildup in accel/decel areas of solid infill due to no LA I suspect, as well as crappy corners on everything. I do all my prints from sdcard.
Waiting for MK3 to be worth using... still waiting...
My MK3 Parts: [New Shoes] [TPU Micro Springs]
My MK3 Software: [G81 Heatmaps] [OctoPrint Heatmaps]

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Area51
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Re: Linear Advance, is it coming back?

Sat Feb 10, 2018 1:17 am

Brigandier wrote:
Sat Feb 10, 2018 12:47 am
fulcrum wrote:
Fri Feb 09, 2018 11:42 pm
If I remember correctly, they disabled linear advance in order to get printing from USB working. Apparently, linear advance was so computationally intensive that cause the code that reads commands from the serial USB to skip commands.
If this is the case, I will definitely turn it back on. To get acceptable quality on my PETG prints I have to turn speeds down quite a bit, and it's causing filament buildup in accel/decel areas of solid infill due to no LA I suspect, as well as crappy corners on everything. I do all my prints from sdcard.
That is my experience too - PETG prints faster and nicer with LA active. On my MK3 I have firmware 143 (RC4) and will keep that until LA gets active again. At the moment my MK2S with LA prints faster and nicer than my MK3 with RC4... but that will hopefully change... :P
Take a look at my MK2/MK2S/MK3 printer parts on Thingiverse ;)

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Brigandier
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Re: Linear Advance, is it coming back?

Sat Feb 10, 2018 1:28 am

Area51 wrote:
Sat Feb 10, 2018 1:17 am
That is my experience too - PETG prints faster and nicer with LA active. On my MK3 I have firmware 143 (RC4) and will keep that until LA gets active again. At the moment my MK2S with LA prints faster and nicer than my MK3 with RC4... but that will hopefully change... :P
Took the plunge, uncommented the LIN_ADVANCE line in the latest (3.1.1) release. Already seeing massive improvements on my PETG.

Now, I don't know what Prusa's opinion is of people posting customized firmware so if this is violating anything please let me know, but if you guys are interested please find it attached. This is the firmware from the MK3 branch on Github, with the only adjustment being line 321 in Configuration_adv.h to uncomment #define LIN_ADVANCE. Best I can tell, all LIN_ADVANCE references elsewhere do an "ifdef" to check if this is defined or not.

DISCLAIMER: I am NOT a Prusa employee or necessarily even that great of a programmer. You are using this at your own risk and on the premise that it is working okay for just me on a couple prints thus far. If the details in this thread are accurate, you do not want to use this if you do any type of printing over USB. This is for sdcard users only!
Waiting for MK3 to be worth using... still waiting...
My MK3 Parts: [New Shoes] [TPU Micro Springs]
My MK3 Software: [G81 Heatmaps] [OctoPrint Heatmaps]

RotaryDane
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Re: Linear Advance, is it coming back?

Sat Feb 10, 2018 6:58 am

alex.g9 wrote:
Sat Feb 10, 2018 12:44 am
i hope they bring it back, and just allow a toggle of LA vs USB id take LA over usb anyday tbh
I've been thinking the same thing - add a toggle in settings somewhere which might display a warning when you try to enable it:

"Warning! Linear Advance is an experimental feature, which seeks to relieve pressure buildup in the nozzle during print moves for improved print quality, but might cause stability issues for Octoprint and USB tethering.
Enable at your own risk and ideally only if printing exclusively from SD card.
>
Continue and enable Linear Advance?
>Yes
>No"

This would give people the option to use it regardless and knowing the risk.

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Area51
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Re: Linear Advance, is it coming back?

Sat Feb 10, 2018 1:32 pm

RotaryDane wrote:
Sat Feb 10, 2018 6:58 am
alex.g9 wrote:
Sat Feb 10, 2018 12:44 am
i hope they bring it back, and just allow a toggle of LA vs USB id take LA over usb anyday tbh
I've been thinking the same thing - add a toggle in settings somewhere which might display a warning when you try to enable it:

"Warning! Linear Advance is an experimental feature, which seeks to relieve pressure buildup in the nozzle during print moves for improved print quality, but might cause stability issues for Octoprint and USB tethering.
Enable at your own risk and ideally only if printing exclusively from SD card.
>
Continue and enable Linear Advance?
>Yes
>No"

This would give people the option to use it regardless and knowing the risk.
If LA is activated in the firmware, gcode M900 K0 will turn it off. This is an easy way to disable and see the effect of LA in a print.
As the code is still in the firmware, I assume, it still uses resources and gives problems with serial/USB/Octoprint.

There is a good description of LA on Marlin firmware docs: http://marlinfw.org/docs/features/lin_advance.html

Prusa should release an official firmware version with LA enabled to all of us not using USB/serial/Octoprint - we are missing out all of the other updates to filament sensor, motor stepping updates, PSU noise, etc...
Take a look at my MK2/MK2S/MK3 printer parts on Thingiverse ;)

koen.k
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Re: Linear Advance, is it coming back?

Sat Feb 10, 2018 3:55 pm

Area51 wrote:
Sat Feb 10, 2018 1:32 pm
Prusa should release an official firmware version with LA enabled to all of us not using USB/serial/Octoprint - we are missing out all of the other updates to filament sensor, motor stepping updates, PSU noise, etc...
The explanation in https://github.com/prusa3d/Prusa-Firmware/pull/457 implies that even with printing from SD various parts take too long to compute, using serial just makes it worse.
I'd recommend applying that PR locally and give it a try if you want LA.

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