What am I doing wrong?

[Schmitty1944]

I don't have a ton of experience 3D printing. I could really use some advice. I am trying to print the RCSUBS.CZ Type XXI in 1/48 scale purchased from Nautilus Drydocks. I'm using an Anycubic Vyper printing in PETG at 235 Head temp 85 bed temp. To begin with the prints where going great. Then I had one that went from good to bad right in the middle of a print (see photos). After that I cleaned the nozzle, cleaned and zeroed the bed several times and switched to a brand new sealed roll of the same filament (Overture PETG). Some prints turned out good, most look like garbage. I tried a new nozzle, no change. I cut off and re-installed the heater end of the Bowden tube as it looked a little black, no change. Filament appears to feed and flow great.

You can see in the photos the exact point the print went from good to bad instantly. It did make some good prints after that though. Some of the sections of hull take a day and a half to print so this is turning into a big waste of time, filament and energy. I would appreciate anyone's experience and input. I have checked over the printer for loose belts etc. and can't find anything wrong.

Many thanks
Jason

[Subculture]

It can be very fussy, much more tricky than pla. MAke sure you're using a silcer profile for your printer and designed for petg, then try dialling in your settings with some test objects like a temperature tower and a calibration cube.

[Marylandradiosailor]

I print a lot in PETG but can't really help you much as I use a different printer (P1S), different brand of filament (inland petg+) etc. That said I have found it important to make sure the filament is very dry for good results, even if I open a new box of filament I don't trust it is dry and always dry it in a heated dryer for several hours, then store it in a sealed bag and redry again before every use, but this may or may not have anything to do with your issues, good luck.

[Surcouf]

Jason,

I agree that drying the filament, even when new is really important on PETG. The extruder and bed temperatures look appropriate. What are your cooling fan settings? Sometimes, they need to be reduced to eliminate some of the issues you are seeing. The closer to the bed, the higher the temperature, so it may still print those early layers at an acceptable level, but then as the height increases, the cooling effect becomes more noticeable.

Tony

[trout]

I have zero experience with your printer and less so with an open frame. I print a ton of stuff on my Bambu P2S, it is enclosed. Heat is both a blessing and can be a curse in our 3D print environments. Have you noticed if an air conditioner has kicked in while printing? My print room is kept hot, originally did it for the resin printers, but now I like it for FDM printing. I am just wondering if something is cooling the print, is it at nighttime as the evening cools that the failures are happening?

[Subculture]

It looks to me that at a point in the print some over extrusion has happened and the nozzle has ended up with some extra material surrounding it and that has messed with subsequent layers. It tends to be more of a problem with petg than say pla, as it’s a more sticky filament prone to stringing etc.

I would look at your speed and extrusion settings, and like I said try some calibration prints, they will inform you far quicker what is going on than a section of Type XXI hull.

[Subculture]

Personally I would not bother with a bed slinger these days for printing hulls. Do yourself a favour and upgrade to a decent core xy printer, and you’ll find is like night and day. The print quality of these newer machines is superb, and they’re fast. Bambu labs is the gold standard or Elegoo Carbon Centauri if you’re more budget conscious gives you a lot of bang for buck.

[Schmitty1944]

Thank you everyone for all the great suggestions. To answer a few of the questions asked. I have tried with the fan set to 0 and also to 30% after I thought the problem might be "heat soak". I could not tell any difference. My problem seems to be inconsistent and at least somewhat random. I think I had the settings dialed in pretty well because some entire print sections turned out great while others are all terrible and some went bad part way through printing.

The room the printer is in is typically around 70-75 degrees in the summer (now). There is AC but it is nowhere near the printer (room is 34 feet long). I have not noticed a relationship between temp or time of day and when I have prints fail.

I have not tried drying filament but definitely worth a shot. I don't have a dedicated dryer but I guess you can use an oven? I have been having this problem over several rolls of filament and seems to come and go even within the same roll. Is that likely to be damp filament?

printing some test parts is a very good idea instead of printing hull sections that take 29 hours.

Buying a new "better" printer isn't out of the question, I'm just a bit reluctant to just keep buying more stuff when I haven't gotten much out of the one I have which is only a couple years old. Maybe if I just made one really great thing and loved the experience I could justify spending more money to upgrade.

Here is last nights print, surprisingly the part of the hull that did print before it went haywire looks pretty good.

Thanks
Jason

[gantu]

I can only say buy an bambu lab printer i had the same problem with anycubic printer.