Puasment PETG oddness... please help.
I am very new to this forum, but I have been reading through it before posting and, even though I couldn't find a similar thread to my issue, I do believe that there is someone out there who can cast some light on my problem.I am having some weird build-up when printing PETG. I don't really know how to describe it (probably why I couldn't find reference to it on the forum!) so it's probably best if I post some images of the offending print. (below)
The model is a set of 'creature' teeth... but it looks like a mouth full of tiny trees!!!!
I would really appreciate anyone's input on this as the main 'bulk' of the print is perfect and the problems start as the print get closer to the tips of the model.
Thank you in advance
Best Answer by Steve:
Kieran,
I've seen what you referred to as "branching" on particularly wet PLA when the printer is printing small features like horns on a dragon head. The printhead slows down due to the feature size and then when the layer ends a large blob oozes off of the nozzle, due to steam generation from the heat in the nozzle, and gets stretched as the print head moves toward the next location. If you are using aligned or nearest seams they can stack from layer to layer and get pretty bulky as you saw.
The extrusion multiplier is not exactly rocket science. The number is literally a correction factor for filament extrusion applied to the calculated number. 1 represents 100% of the calculated extruder move so larger number more filament (i.e. 1.04 equals 4% more filament extruded) smaller numbers less filament (i.e. .94 equals 6% less filament). The extrusion multiplier is usually used to correct for over/under extrusion impacting dimensions, hence the complex adjustment procedures to "calibrate" for a given filament.
In your particular case if you are printing with a high flow nozzle the superior heat transfer ability of the nozzle exacerbates the PETg tendency toward blobbing and stringing so reducing the nozzle temperature offsets the effect of the better heat transfer. Reducing the extrusion multiplier by a few percent (i.e. perhaps 0.96) will result in a slight under extrusion which means less residual pressure on the filament during print head movement also leading to less blobbing and stringing.
One final thought, if you have an air fryer or filament dryer handy you might put your spool of PETg in for a few hours to make sure it is as dry as possible to eliminate that one more factor in ooze/stringing.
Good Luck,
Steve
RE:
These 'branches' seem to be some kind of seam build-up on the teeth? As though the print head has finished is extrusion at that point befor moving on to the next one (and doing the same thing!)
They are not 'bound' into the print and, with a little effort, can be scraped off (picture below)
If anyone has any thoughts at all, I'd love to hear them as I need to get a few of these printed out, at a good enough quality for painting.
it's been a tough job getting it even this clean (I know how dentists feel now!!) and I can use this print to test the paint on... so all is not lost, but I would love to know how to prevent it from happening.
I will go to my studio on Monday and get the slicer setting for the print, it might give someone an idea of what it is I am doing wrong.
Thank you all again
RE: Puasment PETG oddness... please help.
I am a little surprised that you have not received any reply yet. I don't have a lot of experience with PETg printing on the Core One but there are several other threads about PETg printing indicating that the default profiles are too hot and extrusion multipliers are too large for PETg with these printers especially if you are using a "high flow" nozzle. Your issue looks and sounds like a classic "ooze" problem. The PETg filament is continuing to ooze once the extrusion stops and the result is blobs and strings as the print head moves from point to point.
Perhaps someone with more PETg experience will chime in here with some specific recommendations or you can just search this forum for PETg printing issues.
Regards,
Steve
RE: Puasment PETG oddness... please help.
Thank you for your thoughts Steve, your diagnosis makes a lot of sense.
I have been scanning the forum for PETG related threads but, aside from stringing I didn't really see anything that resembled the 'branching' anomaly that I'm getting.
In some of the threads I read I did notice the comments about extrusion heat and multipliers... The heat bit I got my head around, and will try varing it by plus/minus 10 degrees. However, the extrusion multiplier!!... I read someones very thread that suggested tweaking this, but when I followed their link and began to read about how this works, and should be adjusted, I got completely lost very quickly, if this is my problem, I hope someone can offer a 'preset' or something because I'm far to unsure of myself to be trusted with making adjustments myself.
I'm kind of now thinking that this particular model might be more suitable for resin... if that is not a heretical thing to say!?!
I do love my Core One but I need to get a product out, one way or another!
Thanks Again Steve.
RE: Puasment PETG oddness... please help.
Kieran,
I've seen what you referred to as "branching" on particularly wet PLA when the printer is printing small features like horns on a dragon head. The printhead slows down due to the feature size and then when the layer ends a large blob oozes off of the nozzle, due to steam generation from the heat in the nozzle, and gets stretched as the print head moves toward the next location. If you are using aligned or nearest seams they can stack from layer to layer and get pretty bulky as you saw.
The extrusion multiplier is not exactly rocket science. The number is literally a correction factor for filament extrusion applied to the calculated number. 1 represents 100% of the calculated extruder move so larger number more filament (i.e. 1.04 equals 4% more filament extruded) smaller numbers less filament (i.e. .94 equals 6% less filament). The extrusion multiplier is usually used to correct for over/under extrusion impacting dimensions, hence the complex adjustment procedures to "calibrate" for a given filament.
In your particular case if you are printing with a high flow nozzle the superior heat transfer ability of the nozzle exacerbates the PETg tendency toward blobbing and stringing so reducing the nozzle temperature offsets the effect of the better heat transfer. Reducing the extrusion multiplier by a few percent (i.e. perhaps 0.96) will result in a slight under extrusion which means less residual pressure on the filament during print head movement also leading to less blobbing and stringing.
One final thought, if you have an air fryer or filament dryer handy you might put your spool of PETg in for a few hours to make sure it is as dry as possible to eliminate that one more factor in ooze/stringing.
Good Luck,
Steve
RE: Puasment PETG oddness... please help.
Kieran,
This is a re-post of the PM I just sent to you. I hope you get your forum issues resolved.
Your model is a challenging one for PETg (I think) is there a reason that it must be printed with PETg? There are some other things that you can try to reduce those artifacts such as increasing retraction length on moves and playing with settings such as "wipe while retracting" and retraction/deretraction speeds can help as well as reducing printing speeds overall. Also, with the High Flow nozzle you can probably realistically reduce nozzle temperatures to a few degrees below the minimum indicated. Too low and you will get "stuck" filament as the hotend is not melting material fast enough but PETg is very "runny" when it is melted and controlling the blobbing and ooze can be a challenge as you are discovering.
One last thought, are you printing with the door open or closed? Depending upon your ambient temperature you may want to leave the door open so that the filament cools more quickly once it is extruded.
Good luck,
Steve
RE: Puasment PETG oddness... please help.
Steve, My friend, you are a superstar!
I set a print going last night using a variation on your suggested settings. To be honest, I was hold out much hope (not because I didn't trust your judgement, but because I'd had too many disasters to have nothing but trepidation!)
Anyway, check out the images below... not much sign of 'braching', your suggestions are begining to work. Thank you.
It is not perfect but it shows a huge amount of promise. I will go back in and run a few more test with additonal slight 'tweaks', and this time I will be doing so with hightned expectations.
Thanks you again steve. 👍
RE: Puasment PETG oddness... please help.
Kieran,
That looks really good. I'm glad that I was able to help.
Regards,
Steve
RE: Puasment PETG oddness... please help.
Hey Steve,
Yes indeed mate. After a couple of hours with a steady hand and a fine needle file, they are definately good enough to go to paint.
Being the sucker for punishment, I am going to send a couple more tests going, just to make sure that this particular pass was not a 'fluke', and I am very interested in your suggestion of tweaking the "wipe while retracting" settings. (I can relax and have a little play, now I have a 'use-able' product)
I will take a copy of my setting (based on your suggestions) and print it here, then mark the topic 'Answered'.... er, You don't happen to know how you mark a topic 'Answered' do you??
Cheers Steve, you're a gent.