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flashp0int

Retraction settings

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Looking for some expert insight on that one.

 

On the left, with retraction, on the right without retraction.

 

 

  1. I checked if I get missed steps or if filament slips, it does not seem to. The feeder pressure on the filament seems to be fine.
  2. If printing something that requires fewer retraction (here it is quite intense), this never appears. The brim and the first 5mm do not feature under-extrusion.
  3. I tested back and forth extrusion of 100 and 300mm with Pronterface and the feeder seems to be spot on. E-Step value has been adjusted as I use a MK8.

Without retraction, the print is fine. I need to clean more, but I do not have under-extrusion.

Is there another setting I should adjust? I am wondering if the retraction back and forth values are potentially slightly different because of the MK8 change. The difference is only 6,3% which could explain why I just slight underextrusion over time.

Retraction setting 4.50mm

Speed 30 mm/sec

0.2 mm layers

Thoughts ? Advises ?

Thanks in advance!

 

gallery_35056_1189_19531.jpg

 

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Could be that the steppers and/or the drivers get hot and start loosing steps and/or get locked? Though I could not expect this to happen after 10 layers or so, as in the picture, but could happen if the current is also high.

 

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Thanks @3Dmaker4U

The temperature is 16-19°C, that should not be too hot. and the bottom of the UM2 is quite well ventilated.

I guess I am going to take the head appart and check the teflon to be sure.

Enabling retractions on prints with way fewer retractions does not cause under-extrusion. This really starts happening over time. So retractions every 2-3 seconds seem to cause problems over time.

What you cannot see here is that the first 5mm the tube walls are thick. I saw under-extrusion at 6-7mm and paused the printer in order to make sure material was properly inserted. As you can see, the tube get better for a couple of centimeters (thin walls), then it starts again. But it does not deteriorate completely to the point of not printing anymore (like under-extrusion I had with the stock feeder).

Btw: Temperature is at 210°C

 

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I dismantled the head in order to check the Teflon.

 

Turns out the Teflon has some sort of dent on one side and not on the other. Could this be the reason that prevents proper retraction and flow? It seems to be on the side where bowden tube might pressure the material into the teflon piece. (check picture below).

 

Another surprise was that the heat cartride and sensor seem to be clued or stick to the heat piece. I did not dare to pull with anything else than my fingers. Is this normal ? Unless there was a clog I never pushed over 230°C.

 

Capture Teflon

 

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I dismantled the head in order to check the Teflon.

 

Turns out the Teflon has some sort of dent on one side and not on the other. Could this be the reason that prevents proper retraction and flow? It seems to be on the side where bowden tube might pressure the material into the teflon piece. (check picture below).

 

Another surprise was that the heat cartride and sensor seem to be clued or stick to the heat piece. I did not dare to pull with anything else than my fingers. Is this normal ? Unless there was a clog I never pushed over 230°C.

 

 

 

Hi Flashp0int,

Retraction is a tricky thing. especially when it happens a lot like you said.

This is because (the way cura works now), is that it retracts and primes the same amount.

But because there is still a little oozing, it takes a little bit more material to get the material flow back up to the same amount it was before the retraction happened. as well as the material that is 'lost/extruded' as the nozzle pressure gets primed again.

So if there are a lot of retractions in a row you keep missing that little bit that oozed out of the nozzle together with the bit that is lost while priming.

In a normal print, the time it takes to print a layer gives the nozzle time to compensate and you won't really notice it.

but when stress testing like this it can definitely occur.

Slowing down the printing time and the retraction distance/speed (30mm/s seems a bit high) might provide a solution here. so play around with these settings.

We are trying to come up with a clever way to incorporate it into Cura in the future, but it will take a while to come up with a proper algorithm for it.

so, no real solution, but hopefully a little more understanding about the problem :)

 

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Thanks @MartijnvG :)

Retraction speed is 25 mm/s (default I guess), the 30mm/s are the print speed (sorry for the confusion). I'll definitely look into playing with that setting. I have to print slower, as the tubes move and vibrate if I print at 50mm/s.

Any thoughts on the Teflon piece and the hot-end ?

Btw, would be great if we could tell Cura to

 

  1. Densify infill close to the shell (somewhat possible on Slic3r)
  2. Change layer thinness and speed at given height (even better if automatic)

Best regards

 

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I was/am having the same problems as above. My prints looked like garbage. The filament wasn't sticking to the bed plate and warping real bad. I cleaned the nozzle multiple times, adjusted my bed plate temp and filament temp to no avail. So finally after reading many post and landing on this one I followed what Flashp0int did:

I dismantled the head in order to check the Teflon.

 

Turns out the Teflon has some sort of dent on one side and not on the other. Could this be the reason that prevents proper retraction and flow? It seems to be on the side where bowden tube might pressure the material into the teflon piece.

Since I do not have a new Teflon piece and need to be able to print I filed the lip off of the Teflon to smooth it out. I also disabled retraction in CURA. I also adjusted some more settings:

Retraction settings on the machine 2.0mm

Bed Temp. 70C

Flow rate 115%

Nozzle temp 214

speed 85%

I also added a raft to my part, really sucks getting it apart, but it worked. So with this temporary work around I am able to print now. I will order a new PTFE coupler and change my settings back to see how it works.

 

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When I changed the PTFE orientation (180°), it delayed retraction problems and soon after the retraction problems I started to have serial-cloggs.

The new PTFE solved that and it printed better than on day 1. But after just a month, I had to get a new PTFE, as 30 hours printing Colorfabb XT already ruined the new one ( a very expensive print ).

My intend is to talk about this with Ultimaker in Paris. If this is something you need to change monthly, it should be much much cheaper.

 

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If the PTFE piece does need to be changed out often then it is a major design flaw, Ultimaker needs to be responsible for changing the design of this part ASAP or they are going to loose customers. I can't afford to and don't have the time to keep replacing parts to keep the machine running. I understand that parts wear out, but this soon?

 

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