Problems printing pure PET after switching from PLA  

Re: Problems printing pure PET after switching from PLA

For most brands of PETG those temperatures are too high. PETG typically prints between 225 and 245 depending on brand. It flows well enough to load and unload at the top end of PLA temperatures. So changing too and from can be managed at 220. Print the first layer at the lowest temperature possible then raise the temperature if needed when the speed goes up for the other layers. The first layer should be printed slowly and as cold as possible as PETG likes to stick to hot things.

Regards,
Martin

Re: Problems printing pure PET after switching from PLA

I will do it this way :

First, I will go back to PLA to check if something got wrong with PTFE tubing you mentioned. After suucesful print, still with PLA loaded, check if your extruder is extruding what is supposed to do. From Pronterface console extrude 100 mm. Make 100 mm and 110 mark on the filament and issue commands on the console :
G91
G1 E100 F300
G90

Mesure how much filament was extruded, it could 100 mm, it could be more, it could be less, does not matter if you are printing fine.

Now load PET, use temperature recommanded by manufactuer and measure again, you should get the same value (+/- 2mm). If not, that means that something is preventing the filament.

Remove 2 screws on extruder to check gear, is filment well aligned ? Check id gear is fixed well with motor.

Close, start the print, watch the extruder gear from the maintenace window on the left, gear should turn left when motors turn left.

if good so far but you still have problems, try cleaning filament. I use it every 10 h hours of printing, it works fine.

I will also contact filament manufacturer. They have nice site and they recommand Prusa printers 😉

Re: Problems printing pure PET after switching from PLA

For most brands of PETG those temperatures are too high. PETG typically prints between 225 and 245 depending on brand. It flows well enough to load and unload at the top end of PLA temperatures. So changing too and from can be managed at 220. Print the first layer at the lowest temperature possible then raise the temperature if needed when the speed goes up for the other layers. The first layer should be printed slowly and as cold as possible as PETG likes to stick to hot things.

Regards,
Martin

Thanks for the suggestion Martin, but I am not printing with PETG, I am using PET. This is different, and requires a hotter temperature. Typically 250 Deg C.

Best,
Mike

Re: Problems printing pure PET after switching from PLA

I will do it this way :

First, I will go back to PLA to check if something got wrong with PTFE tubing you mentioned. After suucesful print, still with PLA loaded, check if your extruder is extruding what is supposed to do. From Pronterface console extrude 100 mm. Make 100 mm and 110 mark on the filament and issue commands on the console :
G91
G1 E100 F300
G90

Mesure how much filament was extruded, it could 100 mm, it could be more, it could be less, does not matter if you are printing fine.

Now load PET, use temperature recommanded by manufactuer and measure again, you should get the same value (+/- 2mm). If not, that means that something is preventing the filament.

Remove 2 screws on extruder to check gear, is filment well aligned ? Check id gear is fixed well with motor.

Close, start the print, watch the extruder gear from the maintenace window on the left, gear should turn left when motors turn left.

if good so far but you still have problems, try cleaning filament. I use it every 10 h hours of printing, it works fine.

I will also contact filament manufacturer. They have nice site and they recommand Prusa printers 😉

Thanks so much for the help mate! I will try all of this, and contact the manufacturer if that doesn't work.

I will come back here with either a solution or further cries for help ;).

Best,
Mike

Re: Problems printing pure PET after switching from PLA

Hi guys,

I have tried the various checks and solutions posted here, to no avail, everything checks outs.

Would be very grateful for more suggestions.

Re: Problems printing pure PET after switching from PLA

If you haven't tried using the latest Slic3r, I recommend giving it a shot. I haven't tried PET yet, but I've been working with PETG, NGEN and XT. I've jumped around trying out various slicers since getting my Mk3 in late March, but recently decided to stick with Slic3r since that's where Prusa's development is focused. On a lark, I ordered some Colorfabb XT-CF20 (carbon fiber infused XT). Based on previous experiences, I expected all sorts of problems figuring it out. Much to my surprise, the 1st print prepared using Slic3r 1.40.0 printed beautifully, albeit slowly. Looking through the various Slic3r settings, all the speeds were identical to the much faster PLA prints. I then noticed the Filament Settings->Max. Volumetric Speed setting was set to 1, versus 8 for PETG and 15 for PLA. Rather than focusing on speed, this setting controls the amount of filament that can be pushed through the hot end.

You might look to see if any of the other Prusa filament presets come close to PET. I looked through the B-PET website and didn't spot any printing guidelines.

Re: Problems printing pure PET after switching from PLA

Yeah I use Slic3r too, although I don't know if I am using version 1.40.0, I will check tonight. I will check the volumetric speed too and come back with an update. I will try setting it super low, to see if that makes a difference.

Re: Problems printing pure PET after switching from PLA

Yeah I use Slic3r too, although I don't know if I am using version 1.40.0, I will check tonight. I will check the volumetric speed too and come back with an update. I will try setting it super low, to see if that makes a difference.
Slic3r 1.40.1-beta+ is now available!

I've set Print Settings->Speed->Max volumetric speed to 11.5 per a post from E3D on the max. capabilities of the V6 extruder. My (imperfect) understanding is that this is the target "ideal" rate not to be exceeded for the extruder. This provides a printer (extruder)-specific upper limit for the Filament Settings->Advanced->Max volumetric speed setting per filament. These 2 settings ensure that none of the factors set for speed, acceleration, nozzle size, line width and/or layer height exceed the extruder capabilities. Rather than trying to tweak a dozen settings for each print and nozzle combination, I set these settings once for each printer (well, my only printer for now) and for each filament type.

This is by far the best overall per-filament adjustment I've found. Nothing in Cura, Simplify 3D or other slicers I've tried is as flexible. I was getting really tired of using a spreadsheet to do calculations for Simplify 3D. After figuring this out, I've switched between NGEN, NGEN Flex, PETG, woodfill, carbon fiber fill, coffee fill and PLA without issue. I just run eSun cleaning filament through and do a cold pull whenever I switch filament types.

Re: Problems printing pure PET after switching from PLA

So I have updated Slic3r to the latest version. I changed the Max volumetric speed to as low as 0.8 mm^3/s, no/default retraction, no/default fan, hotter than required. I check other speeds: 8 mm^3/s, 6 mm^3/s, and 2 mm^3/s.

Still no luck. I get motor skipping about 10% into printing the Benchy model. I have not tried a different model because obviously I should be able to print a simple boat.

I get no skipping when printing with the Prusa silver PLA. I use a cleaning filament between filament swaps.

I am reluctant to dismantle the extruder to have a look at the PTFE tube. Mainly because this would take time and I may damage something, and also because i would have thought a problem with the extruder would present itself when printing with PLA, not just from using the B-PET filament.

Is my assumption perhaps not correct?

Re: Problems printing pure PET after switching from PLA

So I have updated Slic3r to the latest version. I changed the Max volumetric speed to as low as 0.8 mm^3/s, no/default retraction, no/default fan, hotter than required. I check other speeds: 8 mm^3/s, 6 mm^3/s, and 2 mm^3/s.What are those other speeds? Under Print Settings->Speed->Autospeed, I have Max volumetric speed set to 11.5 (limit of the E3D hotend) and the slope settings both set to 0.

Still no luck. I get motor skipping about 10% into printing the Benchy model. I have not tried a different model because obviously I should be able to print a simple boat. I get no skipping when printing with the Prusa silver PLA. I use a cleaning filament between filament swaps. It sounds like you've cleaned it out well. As you note, it's printing PLA after PETG just fine, which is usually where problems with old filament show up. At 10%, you've moved past the slow 1st layer and may be getting to the infills where things usually speed up.

You could just try dialing back speeds using the front knob (I'd try 80%) to see if that helps. Wait for it to skip, then rotate the knob. If it doesn't, you've likely got something mechanical going on. If it does, you know it's something you can tweak in the slicer.

Just to confirm: You did select one of the PET profiles in Slic3r, correct?

Have you adjusted the tensioner screws on the left side of the extruder housing as viewed from the front? Mine are set to a hair's width below flush with the housing. PETG can be a bit slippery compared to PLA, so being too lose might cause problems. Over-tightening can also case the filament to be damaged, which you'll see when you unload it.

Make sure you've trimmed the filament off cleanly and that it's not damaged from prior attempts. It is possible to get bum filament.

I am reluctant to dismantle the extruder to have a look at the PTFE tube. Mainly because this would take time and I may damage something, and also because i would have thought a problem with the extruder would present itself when printing with PLA, not just from using the B-PET filament.
Quick tip: Don't be scared of opening things up. Opening up the extruder and removing a jam is a necessary maintenance step you need to know how to do, and only takes a minute. There are no precise tolerances at the feeder mechanism to worry about when just opening and closing it.

I nearly panicked when I had my 1st major jam and associated filament snarl. It was only after opening it up and looking with a flashlight that I discovered a stray bit of filament. (Not that this sounds like your problem.)

Just go slow, put the screws in a safe place, and read the assembly manual for the kit which you can find online. After my 2nd jam, I got familiar with opening up the extruder and checking things. I also jumped in and figured out nozzle removal and replacement. Go slow with the nozzle, don't use too much pressure, and fully support the heat block as you work.

Fixes go very quickly now, and I'm not hesitant do swap something when I want to try 2-3 new filaments out in an afternoon.

Re: Problems printing pure PET after switching from PLA

What are those other speeds? Under Print Settings->Speed->Autospeed, I have Max volumetric speed set to 11.5 (limit of the E3D hotend) and the slope settings both set to 0.

Bad spelling may have caused the confusion. These are other Max volumetric speeds I tried under the Filament Settings -> Advanced -> Max volumetric speed.

I have Max volumetric speed set to 11.5 (limit of the E3D hotend) and the slope settings both set to 0.

I copied these settings, as well as setting Filament Settings -> Advanced -> Max volumetric speed to 4 mm^3/s (this surely must be slow enough?) and tried printing a Benchy again. Skipping started at around 6% into the print (this is several layers after the first layer and onto infills). As you suggested, I used the speed tune during the print and reduced this. Although motor skipping persisted, I used gentle force pushing down on the filament to help the motor. This worked, and it continued to print, but only for approx 5 minutes. I had to keep reducing the print speed and helping the filament with physical force when skipping started until 20% print speed (reducing speed in steps of 10%). At this point I also increased the hotend temperature to 265 deg C.

Motor skipping still continued. I cancelled the print at 20%, because I couldn't be bothered to keep pushing the filament down to stop motor skipping every 5 minutes.

Just to confirm: You did select one of the PET profiles in Slic3r, correct?
Correct.

Have you adjusted the tensioner screws on the left side of the extruder housing as viewed from the front? Mine are set to a hair's width below flush with the housing. PETG can be a bit slippery compared to PLA, so being too lose might cause problems. Over-tightening can also case the filament to be damaged, which you'll see when you unload it.

I have tried too tight and too soft, and everywhere inbetween. If the tension isn't good enough the motor doesnt skip, instead the filament just grinds against the gears.

Make sure you've trimmed the filament off cleanly and that it's not damaged from prior attempts. It is possible to get bum filament.
I make sure to do this every time I reload the filament, which I have to do this before every print, since it jams on every print prior (using PET of course).

Thanks for the heads up re stripping down. Good to know that dismantling the extruder isn't too difficult.

There is something I have noticed while spending hours tonight trying to fix this issue:

The stepping motor is running very hot. From digging online, it looks like it can safely run up to 80 deg C. I would say the motor reaches 80 deg C (perhaps a bit hotter), from making touch comparisons between an 80 deg C bed and the stepping motor. I can only place my finger on each object for around 5 seconds before it's too hot to touch. Anyways, the main point about this is that obviously, when printing the first layers, the stepping motor is cold. No problems occur here. When skipping happens, the stepping motor is very hot. Perhaps it's warping the PET somehow?

The other thing I was worried about was heat creep, where perhaps heat is climbing up the extruder. This P-BET filament is a lot flimsier than the PLA strangely enough. It definitley marks easier from the stepper motor gears.

To sum up:

I have no skipping problems with PLA, no skipping problems when feeding PET into the extruder, and no skipping problems during the first couple of layers of a Benchy print with PET.

Skipping problems occur around 6% into a print. Reducing print speed, stopping the cooling fan, and stopping retraction all help to extend the time before motor skipping occurs, but do not resolve the problem such that a complete print can be made.

I have ordered in another PET filament from a different brand. This time PETG actually. I suppose I should at least eliminate the possibility that it's this type of filament.

Re: Problems printing pure PET after switching from PLA

setting Filament Settings -> Advanced -> Max volumetric speed to 4 mm^3/s (this surely must be slow enough?Just as a last resort, you could try 1. That worked with a thick carbon fiber filament I used.

[...] When skipping happens, the stepping motor is very hot. Perhaps it's warping the PET somehow?You've tried all of the normal troubleshooting steps. Can you tell if you're experiencing skipping (the bondtech gears slipping) or extruder reversing from back-pressure? I've got an extruder visualizer on mine, and when I'm simply feeding too fast, I can see the visualizer move back. Yours sounds like the gears are simply slipping. Is the filament frayed when you remove it? (Try resetting then immediately ejecting it when it skips.) I'm doing a large vase-mode print with PETG and while the extruder motor is warm, it's not hot. I can leave my hand on it comfortably. A hot day in Phoenix was certainly warmer!

The other thing I was worried about was heat creep, where perhaps heat is climbing up the extruder. This P-BET filament is a lot flimsier than the PLA strangely enough. It definitley marks easier from the stepper motor gears.It sounds like a challenging flexible, which is not what I'd expect having read up on it. The fact that it flows easily with manually-applied pressure indicates you don't have a clog or other mechanical obstruction. It may simply be inconsistent, although that doesn't explain why it's OK when doing non-infill layers. It really sounds like the extruder can't get a good grip. It sounds like an interesting material, but I can't get it affordably here in the US.

[...] I have ordered in another PET filament from a different brand. This time PETG actually. I suppose I should at least eliminate the possibility that it's this type of filament.That's what I'd try next. Good luck with it, and let us know if it works with "normal" PETG.

Re: Problems printing pure PET after switching from PLA

Thanks for the help on this bobstro. I really appreciate it.

Just as a last resort, you could try 1. That worked with a thick carbon fiber filament I used.

Tried that tonight. Still skips at around 10% into the print.

Can you tell if you're experiencing skipping (the bondtech gears slipping) or extruder reversing from back-pressure?

The extruder motor is reversing, it is clearly visible.

I'm doing a large vase-mode print with PETG and while the extruder motor is warm, it's not hot. I can leave my hand on it comfortably. A hot day in Phoenix was certainly warmer!

For me it is definitely too hot to leave my fingers on it for anything longer than 5 seconds after around 20 mins of printing. I was concerned that this was something that had changed since printing with PLA, so I also tried printing a Benchy with PLA tonight, and it went absolutely fine, no skipping.

Yeah I will come back with an update once I receive the new filament. Thanks again for the help. I am determined to find a solution to this. I have seen previous people report that Prusa said the problem was the stepping motor running too hot. This could perhaps be it, but I am not certain. The B-PET filament is much more flexible than the PLA. Perhaps the motor is melting it slightly. I examine the filament carefully after having to remove the jam each time. It is always the same: it doesn't look like it has melted where the gears are, but the end of the filament is always melted a fair way up (approx 6 mm up the filament) in comparison to the PLA filament when pulling it out from a heated hotend (approx 3 mm up the filament). The width of the melted PET end is the same as the melted PLA end (approx 2.25 mm).

Re: Problems printing pure PET after switching from PLA

I have attached an image of 3 black PET filament ends after jam, vs 1 silver PLA filament end after pulling out.

Re: Problems printing pure PET after switching from PLA

Ok so I bought some PETg filament, and this printed absolutely fine. I also bought some recycled PLA and this was also fine.

I am at a loss as to why this particular PET filament causes motor skipping. Perhaps it is a bad batch? The width of the filament is ok.

Re: Problems printing pure PET after switching from PLA

I just want to share my bit about my issues and how I resolved them. For a while, I would either have to leave my enclosure open with the AC running, or I would have to make sure prints didn't run for a long time. Consistently I would have jams at near similar layer heights. For reference, this only occured with PLA. PETG and other materials that heated at a higher melting point did not experience this issues nearly as frequent (but it did happen once or twice). This might not fix your issue, but it might be worth looking into.

What did I do to fix this? Well I did a few things. To preface this, I read through a lot of forums and tried a lot of work arounds without modding the printer. Then I started by replacing the PFTE tubing, insuring to have the end rounder off as described in the manual. Next, I disabled the filament sensor which unfortunately did not fix my issue as it seemed to fix somes.

What ultimately mitigated my issue was a combination of 2 things. The first thing I noticed was that the filament sensor would get very hot even to the touch. Sure, disabling would have fixed the issue completely, but I wanted the functionality. So I moved the 5v fan that is included in the printer to the top opening (originally mounted with zip ties - I am currently working on a part so this can be removed and reinstalled easier). Secondly, I installed a 12v Noctua fan where the old 5v fan on the left side was. I wired it like so: Direct connection to the 24v rail, which then was installed into a voltage stepper which stepped down the voltage to 12v, and then connected to the fan. This allowed for more air to flow over the "heat sink" (I am calling it a heat sink since the actual name for the tube is escaping me at the moment) which ultimately eliminated the heat creap issue.

Ever since doing these 2 (possibly 3, the PFTE tube might have contributed but I still experienced issues after that alone) simple modifications, I can report that I have had many successful prints that were not working prior. I used the same gcode files and everything, so these 2/3 things definitely helped a lot. Hopefully this will help someone else out, because believe me I was very frustrated with this.

RE: Problems printing pure PET after switching from PLA

I got some PET filament from this company

https://re-pet3d.com/

I am having the same problems. I cant print well, first layers run great but then I start getting skipping. I have tried many things.

Any idea what it could be? how how this issue got resolved?

RE: Problems printing pure PET after switching from PLA

Posted by: @ciscolara

[...] I am having the same problems. I cant print well, first layers run great but then I start getting skipping. I have tried many things.

What settings are you using? Save off a 3MF project file, zip it and upload it here and we can take a look. Otherwise, the only advice is "slow way down". If that helps, you know you can fix it in slicer settings.

Printing pure PET

Hi,

I know that this post is quite old, but I am trying to print with pure PET from recycled plastic bottles.

I did get quite good result with the following settings :

1) print temp 270°C

2) nozzle diam 0.6mm

I read somewhere that nozzle diameter must be bigger than regular petg due to a greater viscosity of PET.

I precise that I made my own filament from plastic bottles. I have a lot of pleasure to do this !

More here :

Look at the description and go to thingiverse link to see proper printing at 270°C

JP