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curly ooze from nozzle and poor line start with ASA  

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hawai
(@hawai)
Reputable Member
curly ooze from nozzle and poor line start with ASA

just when I thought I had understood a few things a new problem arises, isn't life entertaining? 😉

Firstly when heating up athe filament oozes out of the nozzle, curls up and sticks to the side. Instead of a straight line this generates the seed of a future blob. Worst with ASA but also noticeable with other material.

Then when the first line gets laid down on the bed it doesn't start directly but takes about 1mm to begin laying down a line and the line often starts with a little blob.

I don't have an image at hand, because I was too frustrated and stopped the print and binned the offender.

I have fiddled with the temperature of both extruder and bed, maybe too much. Could that be a temp issue?

Printing ASA at 260/105 for the first layer and then 260/110. Default numbers for ASA and slightly higher than recommendations from filament manufacturer (Kiwi3D).

Thanks again for any good idea!

Napsal : 30/01/2020 7:49 am
RH_Dreambox
(@rh_dreambox)
Prominent Member
RE: curly ooze from nozzle and poor line start with ASA

From your description, it seems that you need to lower the nozzle a little bit so that the filament is pressed firmly against the bed.
Another reason may be that the bed needs to be cleaned from fingerprints. You do this best with detergent and warm water, wipe with paper.

Bear MK3 with Bondtech extruder

Napsal : 30/01/2020 8:36 am
hawai
(@hawai)
Reputable Member
Topic starter answered:
RE: curly ooze from nozzle and poor line start with ASA

I already get comments from my partner that I should do the dishes as often as the print bed and I do have quite an impressive stack of jeff jordan squares from first layer calibration sitting next to the printer.

I thought I had that sorted with a nice first layer calibration and a squeaky clean sheet and bang this happened. I will retire to square one and give the sheet another thorough clean and print another couple of squares.

Napsal : 30/01/2020 10:24 am
GKMAKEIT
(@gkmakeit)
Estimable Member
RE: curly ooze from nozzle and poor line start with ASA

I do this with my printers to avoid the "oozing" at the warm up stage. This won't help after the print starts, but makes the beginning much better. What build plate are you using?

 

Napsal : 31/01/2020 3:37 am
Steve se líbí
hawai
(@hawai)
Reputable Member
Topic starter answered:
RE: curly ooze from nozzle and poor line start with ASA

@gkmakeit

Thanks for that, that seems the more logical startup sequence to me anyway, I have incorporated it and will see if it makes a difference, have increased the length of the intro line at the same time. I didn't have any issues with the Jeff Jordan Squares and noticed the longer intro line.

Napsal : 01/02/2020 12:54 am
GKMAKEIT
(@gkmakeit)
Estimable Member
RE: curly ooze from nozzle and poor line start with ASA

Are you using a smooth PEI sheet or the textured powdercoat!

Napsal : 01/02/2020 1:15 am
hawai
(@hawai)
Reputable Member
Topic starter answered:
RE: curly ooze from nozzle and poor line start with ASA

ooops, sorry, forgot to answer that question:

smooth for ASA, textured for PETG at the moment

Napsal : 01/02/2020 1:17 am
GKMAKEIT
(@gkmakeit)
Estimable Member
RE: curly ooze from nozzle and poor line start with ASA

I've never used ASA or the textured plate, what other filament is ASA most similar to?

If you use the textured plate with the exact same filament as the smooth plate do you have to lower the first layer a little? I'm think because of the texture it has to "push" (lower first layer) more filament out to get into the lower potions of the plate for adhesion. 

Napsal : 01/02/2020 5:01 pm
Sembazuru
(@sembazuru)
Prominent Member
RE: curly ooze from nozzle and poor line start with ASA
Posted by: @gkmakeit

I've never used ASA or the textured plate, what other filament is ASA most similar to?

If you use the textured plate with the exact same filament as the smooth plate do you have to lower the first layer a little? I'm think because of the texture it has to "push" (lower first layer) more filament out to get into the lower potions of the plate for adhesion. 

The primary reason for lowering the Z-height when switching from the smooth sheet to the textured sheet is because of the coating thickness. When detecting the actual height of the bed surface the only thing that the printer can "see" is the spring steel sheet in the core of our removable printing surfaces. The Z-height is a correction to some internal "stand-off" distance that is hard coded into the firmware (or is a result of the analog value from the PINDA that is used as the trigger) which is intentionally higher than necessary. The smooth sheet has a thicker coating between the spring steel sheet core and the top surface than the textured surface does. That thicker coating results in a higher Z-height than the thinner coating does.

My analogy for why the Z-height adjustment is used is to look at cutting from sheet stock to a finished shape. First you rough cut with a fast (but not precision) tool to get rid of most of the excess material. This is what homing the Z does. Then one uses more precision tools to make the finishing cuts to get to the desired shape. This is what adjusting the Z-height does. This analogy might not be perfect (no analogy ever is), but it makes sense in my twisted little mind. 😉

See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs

Napsal : 01/02/2020 6:52 pm
GKMAKEIT
(@gkmakeit)
Estimable Member
RE: curly ooze from nozzle and poor line start with ASA

I worked over 12 years as a mechanical engineer and watched over CNC machining, sheet metal fabrication and design, I understand completely. 🙂 

I was only asking about the first layer  because I was curious. I’ve never had my hands on the textured plate or ASA filament.

 

Napsal : 01/02/2020 7:03 pm
hawai
(@hawai)
Reputable Member
Topic starter answered:
RE: curly ooze from nozzle and poor line start with ASA

firstly ASA is a bit of a pain in regards to warping, I chose it for the option of vapour smoothing, but for the sake of the overall project I'm currently giving PLA a try.

My z-adjustments for the textured sheets are roughly around -1.1.-1.08 and for the smooth sheet around -0.75. This is consistent with what others have said as well. The explanation I got is that the textured sheets has peaks and troughs and the probe only measures the peaks. The material has to reach the bottom of the troughs as well so a slightly lower nozzle position seems to be needed to achieve this.

My very limited experience so far seems to confirm this. Also the different oozieness properties of different materials seem to come into play here. Changing from a PET-G based material to PLA right now, I had to adjust the z by 30 micm upwards to get a good calibration square.

My learning point from this, new material means new jeff jordan squares...

Napsal : 01/02/2020 11:13 pm
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