Problems with PET  

Re: Problems with PET

I had a lot of issues trying to print PET with Slic3r PE. Had to lower the speed settings way down because the default speed setting tore infill and was too fast to apply the first layer.

After that I discovered that for what ever reason Slic3r PE has a 1 second delay when the extruder should be extruding filament on the first layer. Meaning, the tool head is moving in motion of the printed part but the extruder was not extruding filament on time leaving some parts of my first layer incomplete.

After taking a lot of time to debug Slic3r PE I decided to print PET using my Simpify 3d profile after I modified the temp settings. That worked beautifully.

Re: Problems with PET

I am using 3D Jake clear PET filament. I used Prusa Control to create gcode file. I used Prusa PET and Generic PET settings and both fail.

I have following problems:
1. Filament transport is skipping. It makes strange noises and material is not nicely applied. Even first line is broken in pieces.
2. The printed part is a mess. Layers are not nicely applied.
3. Sometimes there will be small parts of material left over during print.

According to 3D Jake this should be the settings:
Recommended processing temperature: 210 - 230 °C
Recommended heating temperature: 60 - 80 °C

Prusa settings for PET are higher than this. I was successful printing with Prusa PLA material.

What should I do?

Did you re-adjust your live-Z setting? When I move from PLA to PetG I need to lower the Z in order to get a good first layer. Otherwise I get a bowl of spaghetti 🙂 Before you do this, write down the current Live-Z number so when you switch back to PLA you know where to set it. There are other adjustments that can/should be made but they require a more robust slicer interface.

The 210-230 does seem on the low end for PetG, but each manufacturer should know what's best. I print PetG exclusively and I print at 240-255.

RE: Problems with PET

My biggest problem is that I hear strange cracking sounds from the extruder. I already see that when I load the filament. At 230C I get nice line out of the nozzle. But it is slowly coming out of the nozzle.

But when I increase the temperature, then this line is not nice (I get small bubbles every few millimeters). At 250C the line out looks bad.
I slowed down the speed as recommended (also to keep up with slow extrusion). But this does not help.

Main questions:
1. How do you determine that the temperature is right?
2. How do you fix cracking noises from the extruder?

Here is the picture:

[attachment=0]20180715_075444[1].jpg[/attachment]

Re: Problems with PET

Look carefully at the nozzle as it extrudes. Are you seeing steam or froth coming out? Your filament may be saturated with moisture. You can dry it off at low temp in an oven if so.

Re: Problems with PET

Filament is brand new.

Re: Problems with PET

There are instances of receiving brand new filament and it needs to be dried.
If you are hearing cracking, and in that picture there are definite bubbles- I would dry it out and see if it helps, it doesn't cost anything and it won't hurt the filament.

Re: Problems with PET

What is the most common problem when you load up the filament and the transport cogs would start jumping (and not pushing the filament) through the extruder? How do you fix that?

How would wet filament cause that?

Re: Problems with PET

My biggest problem is that I hear strange cracking sounds from the extruder. I already see that when I load the filament. At 230C I get nice line out of the nozzle. But it is slowly coming out of the nozzle.

But when I increase the temperature, then this line is not nice (I get small bubbles every few millimeters). At 250C the line out looks bad.
I slowed down the speed as recommended (also to keep up with slow extrusion). But this does not help.

Main questions:
1. How do you determine that the temperature is right?
2. How do you fix cracking noises from the extruder?

Here is the picture:

20180715_075444[1].jpg

Looks like your live z needs to be more negative.

Re: Problems with PET

My biggest problem is that I hear strange cracking sounds from the extruder. I already see that when I load the filament. At 230C I get nice line out of the nozzle. But it is slowly coming out of the nozzle.

But when I increase the temperature, then this line is not nice (I get small bubbles every few millimeters). At 250C the line out looks bad.
I slowed down the speed as recommended (also to keep up with slow extrusion). But this does not help.

Main questions:
2. How do you fix cracking noises from the extruder?

This crackling is moisture. you need to dry the filament. This type of filament can absorb right out of the air and in only a few hours it can go from being useable to not. It is not as bad as nylon or PC but it still will absorb water which leads to poor printing results.

Re: Problems with PET

This crackling is moisture. you need to dry the filament. This type of filament can absorb right out of the air and in only a few hours it can go from being useable to not. It is not as bad as nylon or PC but it still will absorb water which leads to poor printing results.

What is an acceptable humidity range for the printing environment for these hydroscopic filaments such as PETG? I routinely manage the humidity levels where I print, and keeping at between 40-50% and between 20-25 celcius is standard. Is that acceptable?

Re: Problems with PET

It's hard to find an answer more precise than "as low as possible". I've run across a few references targeting 20% or so. Definitely below 50%.

Re: Problems with PET

20% wow that's low. IT would be impossible for me to bring the humidity down to even below 30%. It makes me wonder if the hydroscopic filaments needs to be stored inside a heated container at all times. I definitely won't be trying to dry them out inside my propane stove!

Re: Problems with PET

20% wow that's low. IT would be impossible for me to bring the humidity down to even below 30%. It makes me wonder if the hydroscopic filaments needs to be stored inside a heated container at all times. I definitely won't be trying to dry them out inside my propane stove!
The general process seems to be:

With some materials, drying the night before a print seems to be common, though I've not seen PETG described as needing such prep.

The big issue seems to be how long it's exposed to moisture. With PETG, I've been OK (so far!) having it out for 1-2 days while printing, but placing in a sealed bag with desiccant for any longer periods. YMMV and environmental specifics surely come into play.

Re: Problems with PET

This crackling is moisture. you need to dry the filament. This type of filament can absorb right out of the air and in only a few hours it can go from being useable to not. It is not as bad as nylon or PC but it still will absorb water which leads to poor printing results.

What is an acceptable humidity range for the printing environment for these hydroscopic filaments such as PETG? I routinely manage the humidity levels where I print, and keeping at between 40-50% and between 20-25 celcius is standard. Is that acceptable?

i try to keep mine @ 10% on the humidity cards i have in each ziplock back i keep filament in. I also keep 4 or more color changing dessicant bags in it so i know at a glance when the desiccants need to go in the microwave to get the moisture out.

for you, i would suggest checking with eh mfgr but pet g normally takes 160-180 for 4 hours or so to get the moisture out.

a dedicated dryer costs $60-120
https://www.matterhackers.com/news/filament-and-water
https://www.intservo.com/products/esun-ebox-for-3d-printing

or you can print parts and make one for $20
https://www.thingiverse.com/thing:2778707

Re: Problems with PET

The plot thickens (pun intended)...

Thanks for the education!

RE: Problems with PET

He is talking about PET filament not PETG. They have different properties and different results.

RE: Problems with PET

The topic concerns PET filament, not PETG

RE:

Your filament is showing classic signs of being damp. 
(a) you can rescue damp filament by drying it in a dryer such as offered by Sunlu or Eibos

(b) look at how you are storing your filament. It needs to be kept at less than 30%RH. I suggest this needs to be measured rather than using a home made box with Silica Gel thrown in

you will find that Silica Gel performance as a drying agent is substandard. It can take 12-24 hours or more to get the RH down.

superior dry cabinet solutions use a desiccant called Zeolite which is an engineered compound designed to adsorb moisture. It’s commonly called a “Molecular Sieve” for this reason. Such cabinets generally have an automated mechanism to recycle the desiccant when it becomes saturated.

My own  example of such a cabinet reduces RH inside to <10% within 30 minutes of opening and closing the door to fetch out or replace filament. The doors have magnetic seals. The cabinet can store 38 rolls of filament.

RE: Problems with PET

1. Print a temp tower model, e.g. https://www.printables.com/de/model/4667-all-in-one-temperature-bridging-tower-pla-petg-gco
2. Dry your filament. The small bubbles are from moisture in your filament that is boiled and turned into steam.