Retract "While" moving?

[changedsoul 2]

I need  a bit of help. I have enabled retraction which seems to help very well for stringing and blobs. The problem I am having is "it seems" while watching it print, that it pauses over the last printed area while its retracting, leaving a scar / melted spot on the surface. While this seems to not be an issue if you have a direct drive as the retract time is so small its hardly noticeable, but with a bowden tube, that extra second and half or so makes all the difference.

 

I have tried upping my retract speeds to upwards of 100mm/s, but to be honest I dont see much change in time between 30mm/s and 100mm/s. I am using Marlin firmware, and this speed issue may just be a limitation of the arduino. What I am hoping may solve my problem, or perhaps someone else can offer a other solution, is if its possible to issue the retract during a rapid movement to the next location. That way it wont pause over the printed area you just got done with.

Is there a setting that enables this? Currently  the code output always has a retract on its own line and thus the pause while the extruder retracts. It seems to me that even if I could retract faster, it might be even better to just retract while its going to the next location.

 

Is this possible?

 

[burtoogle 514]

Hello @changedsoul, please attach a gcode file that has this problem. Thanks.

[changedsoul 2]

Here is the boat. You can see every time there is a retract, its all alone on its own line. and the longer the bowden tube, the longer it needs retracting, and the longer it sits over the part while its retracting.

Is there a solution to this, maybe a setting for a work around?

And I know the code says I am retracting at 65mm/s, but I can visually see the printer stop while retracting for a good 1-1.5 seconds.

This very well by my firmware and arduino brains causing it as a 2.5mm retraction at 65mm/s should be virtually instant, but its not. Thats why I am hoping there is a solution.

 

CFFFP_3DBenchy.gcode

Edited June 8, 2019 by changedsoul

[obewan 37]

Unless you have changed it in config.h,  marlin sets the max extruder feedrate to 25mm/s

 

#define DEFAULT_MAX_FEEDRATE          { 300, 300, 5, 25 }
 

[burtoogle 514]

Hello @changedsoul. Thanks for the file. I can't see anything obviously wrong with the retractions but you appear to have enabled the new nozzle wipe feature which is intended to keep the nozzle clean.

 

[changedsoul 2]

1 hour ago, obewan said:

Unless you have changed it in config.h,  marlin sets the max extruder feedrate to 25mm/s

 

#define DEFAULT_MAX_FEEDRATE          { 300, 300, 5, 25 }
 

I don’t have my config in front of me, but I believe I changed my extruder to 300 also. 

1 hour ago, burtoogle said:

Hello @changedsoul. Thanks for the file. I can't see anything obviously wrong with the retractions but you appear to have enabled the new nozzle wipe feature which is intended to keep the nozzle clean.

 

Yes, I was playing with settings trying to see if I can get it to keep moving while it was retracting. 

 

So so is there a way to do what I am asking?

i have to retract 3mm to stop oozing. That 3mm kills my top surface when it pauses on the surface to retract. A nice linear move while it’s retracting I suspect would solve it, but I am just speculating. 

[burtoogle 514]

I don't know what the problem is here because with my bowden extruder I am retracting 4mm at 30 mm/s and it does it with no really noticeable delay (well, 133 mS, I guess). So there must be something in your firmware that is limiting the extruder speed. Perhaps your extruder accel/jerk is out of whack?

[changedsoul 2]

Perhaps. I believe my extruder acceleration is set at 4000. 

I guess I need to experiment more. 

Maybe I can set my retract for like 65mm and then play with some settings and see if I can get it to do it in a second at 65mm/s give it take the ramp up and down speeds.   

I guess I can just crank the tops speeds and acceleration for the extruder up up and away and see what comes of it.  

Its a geared Bondtech extruder. 

Anyone by chance know it’s max speed before it looses steps?

[burtoogle 514]

I am also using a Bondtech (BMG) and it is configured with acceleration 3000 mm/s^2, jerk 20 mm/s and 830 steps/mm. I am using firmware retraction at 50 mm/s and prime at 30 mm/s.

[changedsoul 2]

22 hours ago, burtoogle said:

I am also using a Bondtech (BMG) and it is configured with acceleration 3000 mm/s^2, jerk 20 mm/s and 830 steps/mm. I am using firmware retraction at 50 mm/s and prime at 30 mm/s.

I was using firmware retraction as well. The code I posted was using non firmware because I was going back and forth seeing if it would output retract moves during a move line. It appears both methods produce the exact same output. I tested a firmware and non firmware retract program and it seems the firmware (G10/G11) is actually slower than specifying the actual movement. I read that firmware retracts are supposed to be faster, but what I am observing is the opposite. While I like the idea of being able to adjust retract settings without re-slicing, I think I have to abandon that.

I also noticed my extruder doesnt have a smooth movement at high speeds. It sounded like binding gears and such, so I removed the planetary reduction add on and it was still present. Trying to feed it 100mm in length and a speed of 65mm/s causes it to stall. Dropping it to around 60 will keep moving, but its probably close to stalling so I dropped it down to 50mm/s to be safe. While its moving though, I can hear a very uneven sound coming from the motor. So I can only speculate its a crummy driver (which is possible), or my arduino cant keep the pulses going to it steady while doing other tasks (which is probably also possible).

Maybe its time I drop the arduino all together.

So I am thinking the G10 may be slower because instead of just executing a line telling the extruder to move so much, its got to go into another subroutine possibly causing more overhead than a standard move? I dont know, I just guessing here.

[enderender1 0]

I have the same issue.

 

Just like changedsoul describes, if Cura adds retraction G-Codes, during these retractions, the head stands still. It's not very long (100-200ms, depending on retraction length and speed configured), but during that time, obviously, the nozzle is already oozing.

 

What happens now is:

1. head is moving, normal extrusion, i.e. printing

2. head goes to a standstill

3. retract

4. head moves somewhere else

 

IMHO, what needs to happen is something like this:

1 head is moving, normal extrusion, i.e. printing

2. retract, but at the same time, head keeps moving

3. head moves some more without extrusion until retract is done (i.e. "wipe")

4. head moves somewhere else

 

 

 

 

[GregValiant 1,324]

There is a post-processing plugin called "Retract Continue" that may be what you are looking for.  A snippet looks like this:

G1 F2100 E1171.74913  <-- The real retraction
G1 F9000 X148.838 Y101.798 Z4.54 E1170.892546087006  <--more retraction during combing
G1 X152.237 Y104.958 Z4.54 E1168.572050396426  <--more retraction during combing
G1 X153.335 Y104.793 Z4.54 E1168.016886231516  <--more retraction during combing
G1 F2100 E1176.74913 <-- Prime for the next extrusion

I think that Z-hops in the gcode confuse the plugin (they short-stop the "continue" part), but this isn't something I use very often.

[enderender1 0]

Ahh, that is nice, thanks, I'll try that out.