Linear Advance, is it coming back?  

Re: Linear Advance, is it coming back?

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.

Re: Linear Advance, is it coming back?

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.

Re: Linear Advance, is it coming back?

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

Re: Linear Advance, is it coming back?

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


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.

Re: Linear Advance, is it coming back?

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... 😛

Re: Linear Advance, is it coming back?

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... 😛

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!

Re: Linear Advance, is it coming back?

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.

Re: Linear Advance, is it coming back?

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...

Re: Linear Advance, is it coming back?

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.

Re: Linear Advance, is it coming back?

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.

I was sorely tempted to try it, but after looking through the edits that PR made I was spooked off. I don't doubt that it's good code, it's just A LOT of changes. Will let Prusa vet that out.

Got this going last night before bed. 7hr~ print with no issues other than some stringing from me getting used to this new filament.

Re: Linear Advance, is it coming back?

If LA is activated in the firmware, gcode M900 K0 will turn it off.

I wanted to disable Linear Advance on my MK2 for a test, and found that K0 didn't do anything compared to K15 or K30

Talked to the support chat, and they said that LA cannot be disabled with K0 in Prusa's Marlin fork.
It has to be deactivated in the firmware, like it is now.

This still true?

Re: Linear Advance, is it coming back?

XPila's latest pull request ( https://github.com/prusa3d/Prusa-Firmware/pull/475 ) has been merged into MK3 branch. This adds an "Experimental" menu with several cool things (see link). Here's the latest version of the firmware with LA enabled:

Re: Linear Advance, is it coming back?

Just pulled this little beaut off the bed. Prusa Silver PLA, 15mm/s external perimeters with 600mm/s accel, no post cleanup yet so the feet/trunk still look rough. Posting to point out how smooth and uniform the layer lines are now compared to our previous attempts. This is with 3.1.1+LA+Recent XPila merge in firmware above. 🙂

Full zoom recommended. .2 layer height lookin pretty damn smooth.

Re: Linear Advance, is it coming back?

MK3 really should of had a 32 bit board.... sure the enisy V2 will have that.

Re: Linear Advance, is it coming back?

I prefer a optimized software over a more power full processor

Re: Linear Advance, is it coming back?

I prefer a optimized software over a more power full processor

This is kind of the same thing. A more powerful processor can allow a person to write more readable and maintainable code. I consider this to be optimal.

On the other hand, if one has a processor that is limited in performance compared to the task then you will have to 'optimize' in all kinds of places to try to save instructions (time) to make sure the tasks can be complete. One also has to work extra hard to protect code from being interrupted at the wrong time - though one can argue that is always the case no matter the power : )

The math inside the printer is at least 32 bit integer math and in some places floating point. With just an 8-bit processor a lot of instructions have to be strung together (by the compiler) to do just simple rudimentary tasks. With an upgrade to a 32 bit processor with floating point included this math would be completely trivial and this can simplify the code a great deal.

btw, I am using Linear Advance in my printer - I think I have always had it because I skipped the software versions that did not have it.

Re: Linear Advance, is it coming back?

You are right, of course

There is a balance to achieve.

More powerful hardware makes programmers lazy. At least there is potential for this 😉

How is the einsy compared to Apollo flight computers? Could you land on the moon with einsy?

lol

Re: Linear Advance, is it coming back?

MK3 really should of had a 32 bit board.... sure the enisy V2 will have that.

Apologies for somewhat hijacking the thread...

While I have been convinced that the MK3 will suffer from not having a 32bit processor, I believe that it will be a long time before we see a Prusa i3 with such a chip. Marlin currently does not support 32bit chips at all. I am not even sure it supports 16bit chips. That means that, first, someone would have to build a 32bit board with Marlin in mind, and then the entire Marlin firmware would have to be ported to that chip.

Since Prusa is highly invested in the Marlin firmware, I don't see them switch to another firmware that already has support for existing 32bit boards. So, basically, Prusa will either have to do the work or be at the "mercy" of other board manufacturers to do the work for them.

No matter what, the main point is that it will be more and more work with exponentially higher difficulty to squeeze more performance from the aging 8bit chips. This is made even harder by the unknown (to me) level of optimizations performed by the compiler. I don't see Prusa writing Assembly to optimize for instruction count, instruction pipelining, etc.

Re: Linear Advance, is it coming back?

I know this is only semi related to this thread but.....

I'm pretty used to configuring Marlin so can you almost use that current version or do you have to use the files provided on Github?