MakerGear Forum

I'm using eSun transparent PETg to make a fairly large quantity of these box things.

I'm dependent on the clarity of the result. I was making prints with good clarity, then
I loaded a new spool of filament and noticed the transparent quality decreased, its more milky
now, and I get a fair number of these small charred chunks distributed throughout my prints.

I noticed the eSun batch number on the spools is different.

It is possible that somewhere along the way I have messed up my slicer settings, but I don't think so.

In the attached photo, the right box was printed with the first spool of PETg is the result is quite
good. The left box is with the new spool and you can see the print has various discontinuities and
two brown chunks embedded in the result.

Anybody clues or advice about how I can get back to a result like the right box?

bignordique

The charred chunks look like some carbonized junk coming out of your nozzle, (or falling off the outside of it if you had something clinging to the back of the nozzle that maybe you didn't see?) Did you run cleaner filament through before you switched over from printing PLA? Do you have a dust wiper on the filament?

As far as the transparency goes, are you printing at the same temp for both spools? I've noticed that sometimes different temperatures can change the way a filament prints.

Jules wrote:Did you run cleaner filament through before you switched over from printing PLA?

I've run filament cleaner through the nozzle and still get blobs of stuff (including the cleaner filament) coming out for some time after starting a PETg print (after running some filament other than PETg, which for me usually means PLA). I've come to the conclusion that the only way to prevent it is to have a nozzle dedicated to PETg, especially if quality is critical on the print surface.

I've noticed that sometimes different temperatures can change the way a filament prints.

PETg is very sensitive to temperature, but also to speed (which possibly amounts to the same thing). I try to avoid the setting in S3D that slows the print down for small-area layers, because the difference in surface finish between the fast- and the slow-printed parts of the piece will be very noticeable. As far as I've noticed while experimenting with it, the slower you run the print, the glossier the PETg surface ends up; so if you're going for better transparency, keep the print speed down.

Although that said, the differences between the two prints in the photo look like they go way beyond just adjusting the speed and temperature. Since it's a new spool, it's always possible that something is a bit different about it. Have you checked the filament diameter to make sure it's both on target and not varying? If the filament diameter looks good and consistent, then try adjusting the temperature by 10 degrees (upward or downward, but probably upward).

both tim and jules hit on some good stuff. the black certainly could be coming out of the hot end for sure but from the looks of the print i see 1 of 2 scenarios going here. this is just a guess for one possibility. #1 the spool has a little moisture in it which is making it cloudy. the surface of the print is rough so it seems there are some air bubbles there probably from moisture. the air bubbles are popping and making the surface rough causing the pet to collect on the nozzle and cook until its black and it falling into the print. now i have never had a moisture issue with any of the 40+ spools of this stuff i have printed BUT i have never printed the clear stuff and i have heard someone else on another forum say that the natural is prone to sucking moisture. #2 another scenario is that the filament is actually dry but the dia is slightly larger and your over extruding just a touch which is causing it to collect on the nozzle and drop the charred stuff in the print and the cloudiness is just from a difference in temp on your machine or the spool needs a slightly higher temp than the previous spool. i vote for #1 but could even be a combo of both.

Lets see...

I've heard there can be problems running different materials through an extruder. This particular extruder has only ever extruded PETg.

I literally cut the bag open and immediately installed the new spool of PETg on the machine. I live in Colorado and its generally very dry here. If its a moisture problem, then that moisture must have been installed at the PETg factory.

I know I'm using the same temperature (250). Speeds might be different. As mentioned, PETg likes to run slow. When I first noticed this problem I started turning the speed down. That helped some.

I just measured some filament from both spools. The newer spool that's giving poor results appears to be slightly thinner??

I haven't run "cleaning filament" through the extruder yet. Its on order.

Its possible the outside of my nozzle is dirty. The nozzles seem to acquire a burned look after a while.

Next steps are to clean everything up as well as I can and try again. I ran myself out of PETg so it'll have to wait until more arrives.

I literally cut the bag open and immediately installed the new spool of PETg on the machine. I live in Colorado and its generally very dry here. If its a moisture problem, then that moisture must have been installed at the PETg factory.

If that is the eSun brand, it can happen. i cut open a spool of PLA that had just arrived and put in on the machine and had it start breaking while printing because of all the moisture that it had absorbed during manufacture. Could be part of the problem. Might be a bad batch.

(i dried it out by sealing it in a bucket with an open bag of rice for a couple of weeks - the rice sucked enough of the moisture out of the PLA that it lost a lot of that brittleness and i could print with it.)

bignordique wrote:I literally cut the bag open and immediately installed the new spool of PETg on the machine. I live in Colorado and its generally very dry here. If its a moisture problem, then that moisture must have been installed at the PETg factory.

PETg is hydrophobic. I keep mine out in the open all the time, because I don't have enough dry-box containers for all of my filament spools. Moisture is not a problem with PETg.

in many cases i think it is but it must have something to do with the formula. if you look up pet is says its hydroscopic but then again many of the filament companies producing say the opposite or dont comment about it at all. i leave all mine sitting out as well and never an issue. like i said i never used the clear though and i know of other people that have has moisture issues with the clear. who knows really.

You can have moisture issues with petg. I have seen it on more than one of my rolls of esun. For those of you that don't I imagine you have central air and keep your print area at a very steady temp and humidity level. Or I just am the odd man out. I keep everything in dry boxes now.

I keep everything in dry boxes too and the bottoms are filled with hundreds of those little descant packages. Even when I have a roll on the printer its in a dry box.