Enforce retraction before wipe

[SoftFever]

I received feedback that stringing has slightly worsened in some cases since version 1.9. After investigating and testing, it turns out that this issue occurs when retract amount before wipe is set to 0. This is because, after restricting the retraction speed during the wipe, Orca tends to perform a large amount of retraction after the wipe is completed in this scenario. This, to some degree, defeats the purpose of the wipe.

Before the fix:

After the fix:

@igiannakas

[igiannakas]

Interesting! I hadn't noticed anything different but let's merge it and I'll also test. It makes sense though!!

[Orel-A]

@SoftFever With this PR there is no way to disable retraction before wipe. But even if I compile the code without this change, the issue of retraction after wipe still remains.
In BambuStudio the gcode generated results in almost all retraction being performed inside the wiping procedure.

How BambuStudio does it:

How Orca did it before the PR:

How Orca does it after the PR:

The problem is that with eSun PLA+ that is slightly wet, this will cause spiderwebs due to the fast retract before wipe (Setting retract amount before wipe to 0% doesn't work), I guess it's causing the filament to be cut off from the nozzle instead of retracting it back to the nozzle.
With BambuStudio implementation there are no webbings.

[igiannakas]

The problem with the Bambu implementation is that it ignores the retraction speed. For example of you wipe over a very small distance your retraction speed can exceed what the extruder is capable off causing it to stall.

this results in blobs forming on the surface, which is particularly pronounced and occurring during tool swapping in multi material prints, and especially if the user has set a value for that retraction to be greater than the 0.4-0.8 default value.

Take a look here for some real failures with the Bambu logic: #3094

hence what this PR does is if the wipe distance available would result in a retraction speed higher than your configured value, it retracts then wipes the rest, respecting your set limit.

If you want all wipe to be done without any retraction, increase your retraction speed, but be careful not to exceed your extruder limits. Also increase the wipe distance, so it can at least in ideal scenarios wipe the full length using your retraction speed. Test this with a cube and observe in the gcode the wipe move.

retracting the excess before or after the wipe was debated and experimentally retracting before have better results as the wipe move cleans the nozzle and reduces stringing, vs retracting after the wipe which left some residue on the nozzle.

[Orel-A]

If you want all wipe to be done without any retraction, increase your retraction speed, but be careful not to exceed your extruder limits. Also increase the wipe distance, so it can at least in ideal scenarios wipe the full length using your retraction speed. Test this with a cube and observe in the gcode the wipe move.

I noticed that reducing the outer wall speed also affects this, resulting in more retraction being done inside the wiping procedure.
I don't want to increase my retraction speed. Sometimes there is nowhere to wipe into, this would leave residue if the retraction is too fast.
Do you have a better idea for this? For example limit the speed of the wipe itself to circumvent this?

retracting the excess before or after the wipe was debated and experimentally retracting before have better results as the wipe move cleans the nozzle and reduces stringing, vs retracting after the wipe which left some residue on the nozzle.

Indeed, I agree with you that retracting after wipe doesn't make sense. I think the 0.025mm retraction after wipe in BambuStudio is just a harmless bug. Unless something is happening in the microscopic level (maybe vacuuming via the air gap, may be fiction territory).

[igiannakas]

I think that by default wipe is done using the current feature speeds, hence why the amount of retraction varies depending on what you print.

You can override this and slow down the wiping process by disabling role based wipe speed and setting your wipe speed manually to something slow (30mm/sec or so).

[Orel-A]

Okay, I thought about this some more. I tried to play with some parameters, slowing down the wiping speed and changing the retraction speed.
However it doesn't make sense to me.
If you say the extruder motor stalled, then the limit should the speed of "Maximum Speed E" in the config instead. Seems more logical to me.
What do you think?
I've also looked into the PR you've presented the problem, but you use very high retraction lengths.
There is also the Maximum Jerk E to take into consideration.
Is that the correct "instantaneous movement" before the motor will be stalled? And we can use this instead?
If I slow down the wiping speed, that affects the Pressure Advance, maybe eliminates oozing before it travels.

[igiannakas]

Sort off. The max E speed values shouldn’t really be used for retraction operations. Why?

Because with wipe you’re retracting. If you retract too fast you’ll cause air to get sucked in the nozzle as the filament is a non Newtonian fluid. This will cause issues when starting printing your next feature with the deretraction move.

So you need to consider wipe as a normal retraction. Hence why the speed limit set in the retraction setting is respected. If you can retract faster, up the speed there.

prusa works around this by not allowing the user to specify a wipe distance. They calculate the distance based on the feature speed, retraction speed and retraction length. If there is not enough distance to wipe, they also retract then wipe.

Bambu slicer has this as a bug and hopes it’s not triggered.

Orca sets some safe limits and edge case handling with the above. It allows you to change the wipe speed (hence the amount of retraction that can safely be done over that distance), also it allows you to change the wipe distance itself (but too high wiping may result in surface marring), and you can also change the retraction speed.

My recommendation is to set your wipe distance to 1-2mm, your retraction amount to the least needed (I run 0.4mm), your wipe speed to be slow (30-50mm/sec). This should allow you to retract within the wipe for the majority of cases, while where it’s not possible the retract before wipe takes care of them.

my bug above was triggered due to a tool change. You want high retractions during tool changing to avoid filament blobs on the print ;)

[Orel-A]

I think the 0.025mm retraction after wipe in BambuStudio is just a harmless bug.

I was wrong. This isn't a bug. It actually eliminates spiderwebs, thin ones. I've done my tests.