PETG - lot's of crashes  

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alasdair
(@alasdair)
Eminent Member

Hi all.

I'm struggling with lots of crashes during my prints. I use PETG (exclusively). What seems to happen is I get a 'ball' or 'knot' of PETG that gets bigger and bigger until it forms a lump that is sufficient to impede the printer head (i.e. it catches on the underside of the fan guard or somesuch), which triggers a crash.

My first layer seems to adhere ok to base plate. My crashes are more often within the first 3 or 4 layers, but also sometimes happen further up.

I am wondering if the underside of the print head is the problem? It is quite dirty from molten PETG filament.

I'm not sure if I have provided enough of a description here? but would be grateful for any advice.

Cheers

Posted : 23/07/2020 10:04 am
Clemens M.
(@clemens-m)
Reputable Member

Are you sure, that your nozzle ist tight screwed against the heater block? Maybe you changed the nozzle not too far in the future?

Best regards, Clemens

Posted : 23/07/2020 10:10 am
alasdair
(@alasdair)
Eminent Member

Hi Clemens, thank you for your response. I will check the nozzle, but it is the original nozzle & I haven't changed it, so I imagine it's probably ok.

Posted : 23/07/2020 10:26 am
Clemens M.
(@clemens-m)
Reputable Member

Was that a problem from the very beginning? Who´s the manufacturer of the PETG filament?

Best regards

Posted : 23/07/2020 10:31 am
alasdair
(@alasdair)
Eminent Member

It's hard to say if a problem from the beginning, as it's only recently that I've been doing these larger footprint prints. Seems not a problem on smaller prints. Prusa filament, exclusively.

Posted : 23/07/2020 10:57 am
alasdair
(@alasdair)
Eminent Member

Here's a (not very good) of a problem area starting to build up. This print is 100% infill (rectilinear)

Posted : 23/07/2020 11:02 am
Peter M
(@peter-m-3)
Prominent Member

Petg stick more to the nozzle, at least a little.

Petg on pei bed, clean with dish soap, the use window cleaner on bed, this leaves a bit on the bed so it does not stick to much and damages your bed.

Clean bed with dish soap, and adjust the first layer, this is very important, make a picture for us to see(the first layer only). This is very important for all the printing in the future.

Try different speeds, temps.

And more pictures wen it fails could help.

 

general how I work:

A new sheet will stick less then a used one.

PLA sticks more difficult on a powder coated sheet. Is still possible settings need to be more preciese.

This how I work on a pei sheet(there are always exceptions):
Most important to 3d printing is:

1. 3d print will never be like start and i have the print, there will always be problems!!!!!!

2. A clean sheet, use dish soap, then you can print on it. A few prints you can use alcohol, then again dish soap,
big flat models and models with small footprint on sheet- use glue stick(and not every glue stick is the same,
use one that makes a thin layer), and big flat models and small footprint, use a big brim attach to model so footprint is bigger.

Petg sticks to much on the pei sheet, use window cleaner, this leaves a layer on the bed, so it does not stick to much.

3. To get it stick very good, a 100% first layer is very important, see youtube for movie on this.
Every new print watch the first layer, and look if it is 100%, this will also prevent a big ball of filament on your nozzle wen model let loose during printing.

Extra: (normally not needed).

First layer, print hotter.
First layer slower.
Bed more heat.

Most problems are first layer to get this 100%, and bed not clean.

Bad filament is possible, or filament with water inside.

Move extruder to the top and extrude filament, it should go straight down(if not, nozzle possible blocked),
it should be thick enough(if not, nozzle possible blocked, or partial blocked), (do a cold pull),
if Bubbling during extrusion then it has to much water inside.
Check after the first layer is ready, then you see if it sticking enough, and not releasing and sticking to the nozzle.
If you see white spots like a bubble on the bed, then filament is releasing from bed.
Also no gabs between lines should be visible.

Use 7x7 calibration for first layer, see settings in the printer.
Search for " 3D printer first layer problem Calibration process" on youtube, movie on first layer calibration, with a good zoom in.

Posted : 23/07/2020 11:03 am
alasdair
(@alasdair)
Eminent Member

Thanks Peter. I will look at a 'deep clean' of nozzle and underside of print head, and will share photo of first layer in due course.

Posted : 23/07/2020 11:05 am
alasdair
(@alasdair)
Eminent Member

Am guessing this the root of my problems..

Best tips on getting this cleaned properly please.

Thanks all.

Posted : 23/07/2020 11:56 am
alasdair
(@alasdair)
Eminent Member

Assume I need to heat the head up? What's the best way to do this? Is it in the SETTINGS, TEMPERATURE, NOZZLE menu option?

Posted : 23/07/2020 11:59 am
Peter M
(@peter-m-3)
Prominent Member

Check if it is not coming from higher up on the nozzle, it could leak.

Nozzle temp high(filament temp), then try to clean, after that i go a little higher, then more comes of the nozzle.

Clean nozzle before printing, otherwise it will stick more to the nozzle.

Petg you also could try printing with a little lower temp.

Posted : 23/07/2020 12:06 pm
alasdair
(@alasdair)
Eminent Member

Thanks Peter, will try all this now.

Posted : 23/07/2020 12:17 pm
alasdair
(@alasdair)
Eminent Member

In the process of cleaning the head I have noticed what appears to be a 'slick' of molten PETG that seems to originate higher up (see photo). Does this look like a leak? If so - I guess this would explain a lot of my trouble?

 

Posted : 23/07/2020 12:35 pm
Peter M
(@peter-m-3)
Prominent Member

Look for  manual how to tighten(replace ) nozzle, you could try tightening it after cleaning, do as in a manual is written down.

on prusa website or on e3d website you can find this.

in the future you also need this to change the nozzle.

 

Posted : 23/07/2020 12:57 pm
alasdair
(@alasdair)
Eminent Member

Thanks Peter, will do. It doesn't look like the leak is from the nozzle-to-block connection though, more higher up?

Posted : 23/07/2020 1:30 pm
Peter M
(@peter-m-3)
Prominent Member

This post was modified 4 months ago by Peter M
Posted : 23/07/2020 1:59 pm
vortical
(@vortical)
Active Member
Posted by: @alasdair

Hi all.

I'm struggling with lots of crashes during my prints. I use PETG (exclusively). What seems to happen is I get a 'ball' or 'knot' of PETG that gets bigger and bigger until it forms a lump that is sufficient to impede the printer head (i.e. it catches on the underside of the fan guard or somesuch), which triggers a crash.

My first layer seems to adhere ok to base plate. My crashes are more often within the first 3 or 4 layers, but also sometimes happen further up.

I am wondering if the underside of the print head is the problem? It is quite dirty from molten PETG filament.

I'm not sure if I have provided enough of a description here? but would be grateful for any advice.

Cheers

Are you keeping your filament dry?

I'm getting the same problem.  It seems to get better the longer I keep my PETG in drying bags (sealed bags with a dessicator meant to keep a whole house dry.)   (I live in Fog City.)  

Other than that, babysitting the print and removing those evil nubs as they develop has gotten me through some prints.

Posted : 29/07/2020 8:23 pm
vortical
(@vortical)
Active Member

PETG absorbs ambient moisture and gets waterlogged..  That seems to make steam bubbles in the filament that can distort the bead as it comes out the nozzle. It also seems to increase stringing that develops into those nubs -for reasons I don't understand.

Posted : 29/07/2020 8:31 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: @alasdair

Here's a (not very good) of a problem area starting to build up. This print is 100% infill (rectilinear)

Looking at your pics, it DEFINITELY looks like you have a leak out the of the heater block. The nozzle is not tight enough against the heatbreak and filament is oozing out the top. Note that is it critical that the nozzle it tight against the heatbreak, not the heat block.

When tightened at 285C, there should be a small < 1mm gap between the nozzle hex and heater block. Some of the instructions focus too much on that gap, and not on the fact that it should be impossible to fully tighten the nozzle if the heatbreak has been inserted far enough. Done correctly, the block acts as a nut holding the nozzle and heatbreak together. If anything, the heatbreak should be inserted a bit extra into the block to ensure a good seal.

Also be aware that 100% infill is going to be tricky with PETG. PETG likes to stick to whatever's hottest, and if it hasn't fully adhered to the underlying layer, it will stick to the nozzle and create those nasty top layers. Try using less infill. If you need part strength, increase perimeter count and use thicker perimeter extrusion widths.

@voritcal's point about PETG and moisture absorption is also relevant. If too much moisture is absorbed, printed filament will swell and bubble, causing over-extrusion. Over-extrusion on top surfaces bulges upwards and catches on the nozzle on subsequent passes.

Fix that leak first. That's your biggest problem and a disaster waiting to happen.

This post was modified 4 months ago 2 times by bobstro
My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 29/07/2020 9:08 pm
alasdair
(@alasdair)
Eminent Member

Thanks Bobstro, Vorticle. The hotend is as built and supplied in the Prusa kit, I've not played around with it, nor replaced the nozzle. The nozzle seemed tight.

I managed to remove it from the hot end housing, and sure enough the heatsink was loose. Is now tightened. I cleaned up the block as best I could so I can be sure to notice any further, fresh, leaks. Nothing so far.

After this, the first prints were encouraging, definitely better, but then last night it crashed again for same reasons. And again, this is 100% PETG (Prusament) infill. I acknowledge your words re 100% infill. I will try a reduced infill but these parts are application items, not models or home play stuff, so it will need to be 70 - 80% infill I think (i.e. 20% infill was nowhere near strong enough).

I don't keep my PETG in a special climate container thing, but do try and keep the dehumidifier sachet in the bags with them when not printing.

I have a suspicion that the dirty nozzle is inclined to 'collect' the molten PETG up the outsides of it (sometimes), perhaps a fresh nozzle will help.

I appreciate that 100% infill is, perhaps, a bit 'extreme' but would be nice if it can work when it is called upon.

Posted : 30/07/2020 5:43 pm
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