Prusaslicer 2.x

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Gwhite
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Re: Prusaslicer 2.x

Post by Gwhite » Sun Jan 03, 2021 2:58 pm

ednisley wrote:
Sun Jan 03, 2021 12:28 pm
Gwhite wrote:
Sun Jan 03, 2021 2:23 am
it tries to print with the build platform down near the bottom
If PrusaSlicer has different Z-axis speeds or accelerations than what you were using with S3D, this could be a symptom of having the poor overstressed motor lose its grip on reality and letting the platform drop while the leadscrew unwinds.

The numbers I've been using apply to my hardware and are not generally useful, of course.
I set PrusaSlicer up using the speed/acceleration limits M503 spits out about my M2E. It's possible I have a typo there. The homing process looks pretty normal.

airscapes
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Re: Prusaslicer 2.x

Post by airscapes » Sun Jan 03, 2021 3:03 pm

Gwhite wrote:
Sun Jan 03, 2021 2:56 pm
airscapes wrote:
Sun Jan 03, 2021 4:55 am
The Z offset on mine is adjusted by me with every layer height change, bed temp change (40C and 110C are not the same) and hot end change.. 10 - 12 is all good, it keeps the bed below the nozzle. when I put on the fiberglass plate it gets changed to 9.xxxx as that bed is a 1/4" thick. printing a square and measuring it, then adjusting M206 Z 12.xx is the way to go.. at least for me..

The files I posted should work as s3d does, not sure why you are having problems.. I have been using PS for the past several prints with no issues and better results than S3D
Can you check your post that had the 3MF & config file links? They appear to have been truncated and don't work.

In the meantime, I'm going to dig further into the gcode for the cal cube from the two slicers. The wipe operation is right after the homing process, and that should provide a clue.

Thanks!
Sorry about that
https://misc.airscapesart.com/prusaslic ... bundle.ini
https://misc.airscapesart.com/prusaslic ... leg_V1.3mf

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ednisley
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Re: Prusaslicer 2.x

Post by ednisley » Mon Jan 04, 2021 2:56 pm

Gwhite wrote:
Sun Jan 03, 2021 2:58 pm
the speed/acceleration limits M503 spits out about my M2E
Also verify that S3D used those same limits: this may be the first time the printer has tried to accelerate that hard.

You can also edit a failing G-Code file to remove everything except the prolog section to isolate the failure to a single command.

Long ago, a great manager taught me to debug problems by asking "What's new & different?", then never change anything until I could justify the before-and-after with hard evidence. [grin]

Gwhite
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Re: Prusaslicer 2.x

Post by Gwhite » Wed Jan 06, 2021 3:29 am

I finally had time to dig into this again. I compared the gcode generated by S3D for a cal cube to what is created by PrusaSlicer for the same model (not that it really matters because the problem occurs before it gets to the model...)

The one thing that I found that is markedly different is that the S3D code has a G90 command (absolute positioning mode) before it does anything. This is absent from the PS code.

So, I figured that must be it. Before I just popped that at the front of my PS starting code, I checked the gcode produced by both the config and the 3MF file that airscapes posted. Neither of them have the G90 code, and the code they produce looks very much like the code PS generated that makes my printer go nuts. All of his files are set up for PETG, and I'm using PLA, so I don't want to try just printing one.

I tried adding the G90 command to my starting gcode to see what happens. Given that airscapes has successfully printed with his config, I was longer convinced that was the answer. When it started to try to home the Z axis, it sort of surged a couple times. I think Ed's idea that it's being driven over speed may be the answer. I'll now go and cross check the limits from airscape's config & gcode against mine, paying particular attention to the Z axis.

Gwhite
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Re: Prusaslicer 2.x

Post by Gwhite » Wed Jan 06, 2021 3:57 am

I just compared the limits in my gcode to airscape's, and they only differ by an order of magnitude in places...

Here's the beginning of the gcode . I've interleaved them for easy comparison. My code is in black, airscape's is in red, and the results from running an M503 query are in blue:

M201 X900 Y1000 Z30 E2000 ; sets maximum accelerations, mm/sec^2
M201 X9000 Y9000 Z500 E10000 ; sets maximum accelerations, mm/sec^2
M201 X900 Y1000 Z30 E2000

M203 X200 Y200 Z75 E25 ; sets maximum feedrates, mm/sec
M203 X500 Y500 Z12 E120 ; sets maximum feedrates, mm/sec
M203 X200.00 Y200.00 Z25.00 E25.00

M204 P2000 R3000 T2000 ; sets acceleration (P, T) and retract acceleration (R), mm/sec^2
M204 P1500 R1500 T1500 ; sets acceleration (P, T) and retract acceleration (R), mm/sec^2
M204 S2000.00 T3000.00

M205 X4.00 Y4.00 Z0.40 E1.00 ; sets the jerk limits, mm/sec
M205 X10.00 Y10.00 Z0.20 E2.50 ; sets the jerk limits, mm/sec
M205 S0.00 T0.00 B20000 X4.00 Z0.40 E1.00

It appears that I have a typo in my maximum Z feed rate (aha!?). It's supposed to be 25, and I had 75.

What I don't understand is why airscape's printer hasn't exploded... He has a much lower Z max feed rate, but his X&Y feed rates are more than doubled, and accelerations are an order of magnitude (or more) higher.

I'll fix the Z feedrate & see what happens.

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ednisley
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Re: Prusaslicer 2.x

Post by ednisley » Wed Jan 06, 2021 2:47 pm

Gwhite wrote:
Wed Jan 06, 2021 3:29 am
G90 command (absolute positioning mode)
That's supposed to be the default reset condition for a 'normal' G-Code interpreter (which Marlin is, kinda), although it's good practice to include all the defaults your program assumes (*) will be true.
they only differ by an order of magnitude
Close enough for horseshoes, hand grenades, and 3D printing!

The G-Code path planner uses the acceleration value to ramp the motor up toward its maximum speed during a move from the current position to the next one, so there's an interaction between all three values for all three axes. Short moves never reach full speed in any direction, long diagonal moves don't use the full acceleration along the shortest axis motion, and downward Z-axis moves provide a gravity assist for the motor.

The Z-axis normally makes very short moves while the other axes remain stationary and never reaches full speed while printing. While homing, however, a too-high acceleration or speed value will require more torque than it can produce (generally while homing / moving upward), whereupon the motor stalls and the platform shudders downward while the motor turns in the wrong direction.

One might do a (likely half-assed) calculation, but running experiments will produce better values:

https://softsolder.com/2013/04/11/maker ... s-numbers/
https://softsolder.com/2013/07/02/maker ... culations/
https://softsolder.com/2013/05/09/m2-vs ... eleration/

Basically, for each axis you set a desired maximum speed and an absurdly high acceleration, make many long jogs in both directions while reducing the acceleration by factors-of-two until it runs smoothly, then reduce the acceleration by another factor of two. When you're done, you can be reasonably sure the printer runs as fast as it can in all directions.

Which is how I came up with the crackpot values for my M2 … [grin]

(*) Verily, it is written: Hell hath no fury like that of an unjustified assumption.

Gwhite
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Re: Prusaslicer 2.x

Post by Gwhite » Wed Jan 06, 2021 6:16 pm

I haven't had a chance to test the lower Z speed yet, but your description of its likely behavior is pretty much what I'm seeing.

I don't know how much you've hot rodded your hardware, but I'd be curious to see what values you came up with using your tuning process. (Strike that, I should have checked your links...)

I seem to recall that you replaced your Z motor at one point, but I'm guessing X & Y are stock? If they aren't that much more aggressive than the factory settings, I may not bother. Being retired, I generally don't need to push the speed on my prints and tend to go slow for a nice finish.

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ednisley
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Re: Prusaslicer 2.x

Post by ednisley » Thu Jan 07, 2021 1:08 am

Gwhite wrote:
Wed Jan 06, 2021 6:16 pm
don't need to push the speed
Nor I, as the plastic limits the printing speed to a small fraction of the maximum travel speed. Most of my motivation comes from curiosity, which, as we all know, can get ya into plenty of trouble.

The weight of the platform hardware means the Y axis generally requires lower acceleration and (maybe) speed than the X axis, particularly for motors slinging those heavy aluminum plates back and forth. The old-old Z axis motor was simply wrong (which is why I replaced it) and the newer ones are fine. The proper motor provides much better print reliability (because of its higher torque margin), but there's little to be gained by speeding up Z-axis motions unless the model requires Z hopping or similar weird behavior.

It's definitely not a plug-n-play process, no matter how hard everybody wishes …

Gwhite
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Re: Prusaslicer 2.x

Post by Gwhite » Thu Jan 07, 2021 2:23 am

Ed,

My first PrusaSlicer print is in the works as I type this. Your initial guess about over driving the Z-axis was spot on. Never having pushed it, I never would have recognized it, so all that experimenting you did was very valuable.

I want to double check a few things & clean up my configs, but I should be able to post my setup in a day or so.

Every one raves about how much better the prints are from PS, and I can hardly wait to try it on a couple things that S3D gave me fits over. Just having variable layer height & ironing should to be very helpful.

airscapes
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Re: Prusaslicer 2.x

Post by airscapes » Thu Jan 07, 2021 4:59 am

one thing to take note, which I have recently discovered when parts were not the proper size. If you use a set extrusion width you have to set that in all the places or it will use auto if set to 0
That is under print settings advanced.. 8 fields need to be set.. for example if you want to use .4 for the .35 nozzle as is the default in S3d.. all fields need to be set to .4 not just the first one.

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