fat PLA tips

[Daniel Rosen]

Hi Group: I am having problems with the PLA tips. Since I installed the 3D chameleon every PLA tip comes out of the extruder with a weird shape and bloated (2.1 to 2.2mm). This causes blockage primarily at the bondtech inlet during retraction. I tried many things that Bill indicated with little success. He has being amazing in giving me advice but would like to hear if others are experiencing the same problem and possible solutions. 

Things I did: 

1) upgraded to original Bondtech BMG extruder

2) replace PTFE tube between the hot end and BMG for one with 1.8mm ID

3) various ways of retraction to shape the tip. for example retracting and inserting quickly from 2 to 10 times to see if the tip will shape and stay at less that 2.1mm

I will really appreciate any feedback

Dan

[William Steele]

Hi Dan,

Your tip indicates that your printer is retracting the filament prior to the tip shaping causing it not to be able to push the filament all the way to the tip.  The easiest way to fix this is to add the distance of the retraction back to the start of the tip shaping routine.

So, if for example, you have a retraction of 8mm, just add a G0 E8 F10000 (or whatever your deretraction speed is) followed by a G92 E0.

Bill

[Daniel Rosen]

Thanks Bill. So this is my retraction routine. I am not sure I understand what you mean about add retraction distance. But the tip besides the funny shape is also bloated at 2.1 or 2.2 mm. Not sure what else to try to keep it within tolerance.

; Auto generated 3D Chameleon Tool Change GCode for Cura
; --- Extruder #1 End G-Code ---

M117 Unloading Tool T0
G92 E0

G90 ; move to absolute mode
M82 ; turn absolute distances for the extruder

G0 X314 Y139.5 F2000

G1 E10 F300 ; Extrude 10mm to warm the heatbreak filament

G0 E-50 F2000 ; quickly retract the filament to shape it
G0 E-80 F600; slowly allow it to cool
G0 E1 F2000 ; blob elimination
G0 E-50 F2000 ; quickly retract the filament to shape it
G0 E-80 F600; slowly allow it to cool

G0 E1 F2000 ; blob elimination
G0 E-10 F2000 ; quickly retract the filament to shape it
G0 E1 F2000 ; quickly ram the filament to shape it
G0 E-10 F2000 ; quickly retract the filament to shape it
G0 E1 F2000 ; quickly ram the filament to shape it
G0 E-10 F2000 ; quickly retract the filament to shape it
G0 E1 F2000 ; quickly ram the filament to shape it
G0 E-10 F2000 ; quickly retract the filament to shape it
G0 E1 F2000 ; quickly ram the filament to shape it
G0 E-10 F2000 ; quickly retract the filament to shape it
G0 E1 F2000 ; quickly ram the filament to shape it

G0 E-50 F2000 ; quickly retract the filament to shape it
G0 E-80 F100; slowly allow it to cool

M107 ; this printer has the fan in the way, so turn it off

G92 E0
G0 E-100 F2000
G92 E0
G0 E-100 F2000
G92 E0
G0 E-100 F2000
G92 E0
G0 E-100 F2000
G92 E0
G0 E-100 F2000
G92 E0
G0 E-55 F2000
G92 E0
G0 E-30 ;
G92 E0

G91 ; move to relative mode

G0 X3 Y3 F2000 ; press the button
G4 P400 ; dwell for .3 seconds
G0 X-3 Y-3 ; back off the button
G4 S2; wait for it to happen
G0 X3 Y3 F2000 ; press the button

G4 P400 ; dwell for .3 seconds
G0 X-3 Y-3 ; back off the button
G4 S2; wait for it to happen

G0 X3 Y3 F2000 ; press the button
G4 P400 ; dwell for .3 seconds
G0 X-3 Y-3 ; back off the button
G4 S2 ; wait for it to happen

G0 X3 Y3 F2000 ; press the button
G4 P3500 ; dwell for 3 seconds

G0 X-3 Y-3 ; back off the button
G0 X3 Y3 F2000 ; press the button

G4 S10 ; <<---- INCREASE VALUE (S = Seconds) TIME IF IT DOESN'T UNLOAD FROM THE Y ADAPTER, DEFAULT IS 10 SECONDS WHICH SHOULD BE ENOUGH

G0 X-3 Y-3 ; back off the button

[William Steele]

In Cura, there is a setting called "Nozzle Switch Retraction Distance" that needs to be compensated for.  So, take that value and add it back to the current position right after the G92 E0 command at the start.  So, if your distance is 10mm, then you'd need to add a G1 E10 F10000 to add that distance back so the filament is actually in the tip... then adding a second G92 E0 will reset it to E0.  Basically, you undoing their retraction.  You can optionally set their retraction distance to 0... however, there other scenarios where they use it and it's helpful, like to and from the prime tower.

As or the diameter, I'm not sure what hot end you have, but we provide a 1.8mm diameter 85mm length of PTFE tube that is used to constrict that down to a manageable size.  Here is a simple way to install it: https://www.thingiverse.com/thing:4806296

Bill

[Daniel Rosen]

My Nozzle switch retraction distance default was 16mm. I set the Nozzle switch retraction distance to 0 and did not see any improvement. Neither helped adding the G1 E16 F2000 line. Now, the filament has a string with a blob at the end with a tip of 2.2mm that gets stuck at the extruder.

I tried the 85mm PTFE tube with the coupling and did not help. I replaced the entire PTFE tube with a new PTFE 1.8 ID for the entire length between the hot end and the extruder but the tip is still >2.1mm…Frustrating.

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[William Steele]

So, in looking at your tips, there are three things going on.

1) The long whispy strings indicate that the temperature is a little low.

2) The 2.2mm diameter also tells me that it's not inside the 1.8 while it's cooling... there's no way it could be larger than the diameter of the tube if that was the case, even with the above stringing.

3) The blob indicates that the ramming routine is not going all the way to the tip... in fact, it looks like it's pretty far away.

So, to tackle each one, try these:

1) Raise your temperatures until those strings go away.  But this is the lowest priority... tackle the others first.

2) Make sure the 1.8 goes all the way to the tip.  Do you have some form of custom hot end or all metal hot end that doesn't have a PTFE liner?  If you do, then this is the root of the issue... you need to separate the blob elimination from the tip size cooling routine and cycle between the two.  So, don't spend too much time at the tip (right now, you've got a lot of cycles there) and allow all the cooling to happen in the 1.8mm tube.  Perhaps the distance between needs to be greater.  Pull the filament out of the all metal hotend and allow it to cool diameter wise in the 1.8mm tube, then push it back into the hot end to remove the blob.  You can cycle between the two without issue.

3) This is tied to 2, but let's make sure we know exactly where it is starting... because that tip with that string between the filament and blob clearly indicates it's nowhere near the nozzle when it's ramming.  There must be something else going on in the gcode or firmware telling it to retract and we're actually not at E0 when we think we are.  Just judging by your picture, I'd say you're at least 10mm farther our than that... maybe more.  So, increase the G1 E10 command until you start forcing filament out of the tip... once you do that, you know that you're there and can then set it to E0.  (You can dial it back down a bit to stop over extrusion if needed... but first we want it so we can visibly see it.)  One other thought I had here is that the this has a very large heat zone (or heat creep) and the filament is actually melting up high.  If that's the case, we need to break the filament off there and do the diameter shaping and then the string elimination from there.

As always, pics and videos will help.

Bill

[Daniel Rosen]

1) I am printing at 210C already using PLA. I think this is almost the upper limit temp

2) I have the stock extruder with the PTFE liner. I disassembled it and pushed the 1.8mm all the way into the extruder. I am sure there are no gaps now.

3) It has to be the gcode

still getting blob with string and blockage.

THIS IS MY CODE AS OF RIGHT NOW. I NEED TO POST A VIDEO TO SHOW WHETHER THE PRINTER DOES THE FOLLOWING SEQUENCE CORRECTLY.

; Auto generated 3D Chameleon Tool Change GCode for Cura
; --- Extruder #1 End G-Code ---

M117 Unloading Tool T0
G92 E0

G1 E10 F2000 IF I INCREASE THIS TO VALUE I  GET A BLOB ON TOP OF THE PRINT

[William J. Steele]

Ok... let's break this down.  After looking at this code, I'd say that the blob elimination might be too excessive here... let's break it down and see where the tips are at each point.

The idea is that the routine is doing things in stages, so its easy to stop those stages and actually look at the filament to determine what effects the previous steps have had.

The first one is here:

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From: 3d-printing-...@googlegroups.com <3d-printing-...@googlegroups.com> on behalf of Daniel Rosen <dgros...@gmail.com>
Sent: Monday, May 17, 2021 9:55 PM
To: 3D Printing Tips and Tricks <3d-printing-...@googlegroups.com>
Subject: Re: fat PLA tips

 

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[William J. Steele]

Dang it... it send before I found finish type it in.

The first one is here:

G1 E10 F300 ; Extrude 10mm to warm the heatbreak filament
G0 E-50 F2000 ; quickly retract the filament to shape it
G0 E-80 F600; slowly allow it to cool

Let's get a look at the filament here.

(You can remove or comment out all the rest of it down to the M107... which you might not need either... that's turning off the fan... but that's only for those printers that have the switch in a location where the fan might hit it.)

Bill

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From: William J. Steele on behalf of William J. Steele <wjst...@wjsteele.com>
Sent: Tuesday, May 18, 2021 9:11 AM
To: Daniel Rosen <dgros...@gmail.com>; 3D Printing Tips and Tricks <3d-printing-...@googlegroups.com>

[Daniel Rosen]

thanks for not abandoning me! I posted this video showing the retraction sequence. This is before the changes you mention above. I will try with those modifications now. I could not take a pic of the filament because the tip breaks inside the extruder when I try to take it. I zoomed in to show the string and blob I get.

https://youtu.be/kTvXKNtOFE8

[Daniel Rosen]

This is the tip I get doing

M117 Unloading Tool T0

G92 E0

G90 ; move to absolute mode
M82 ; turn absolute distances for the extruder

G0 X314 Y139.5 F2000

G1 E10 F300 ; Extrude 10mm to warm the heatbreak filament
G0 E-50 F2000 ; quickly retract the filament to shape it
G0 E-80 F600; slowly allow it to cool

 

[William J. Steele]

The video is marked private, but you can wait until after you make the changes... seeing what you already have won't really help... we need break down the steps and watch its progress to determine where the issue is being introduced.

Bill

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From: 3d-printing-...@googlegroups.com <3d-printing-...@googlegroups.com> on behalf of Daniel Rosen <dgros...@gmail.com>

Sent: Tuesday, May 18, 2021 8:03 PM

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[Randy Zimmer]

I'm missing the start of this discussion. I see reference to 1.8 and 2.2mm and the title, "Fat Tips". Are you trying to print 2.2mm with a 1.7 spool?

[William J. Steele]

No... the filament being pulled out of the hot end by the 3D Chameleon can sometimes swell beyond the diameter of the normal 1.75mm, causing it to jam in the PTFE tubes or extruder.  This is due to the nature of the filament itself, which will continue to swell as it is cooled.  The 3D Chameleon combats that by constricting the swelling during the cooling process to a confined 1.8mm PTFE tube in the hot end.

This thread is trying to understand and solve the issues that Dan is having with his setup, which is swelling as well as "blobbing", where a knob of filament is semi-detached from the filament, further causing issues.

Bill

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Sent: Wednesday, May 19, 2021 6:40 PM

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[Daniel Rosen]

Hi Randy. thanks for jumping in. Below Bill explained my problem with the retraction settings. I did some homework and this is what I get after sequentially introducing the gcode

I came to the conclusion that my printer defies all the rules of physics! how can the filament diameter be greater than the PTFE internal diameter?