PETG prints got bad, PLA is fine  

RE: PETG prints got bad, PLA is fine

Have you tried a different roll and brand of PETG?

RE: PETG prints got bad, PLA is fine

I tried two rolls of two different brands, one of them new. As I said it did work splendidly before, then no more.

I'm trying longer prints in PLA to make sure that with PLA it works really.

RE: PETG prints got bad, PLA is fine

Ok.  It sounds like you have a partial clog.  This can happen with poor quality or we PETG.  This can happened with any machine.  

You can:

1. use cleaner filament
2. do a cold pull
3. replace the nozzle.  

RE: PETG prints got bad, PLA is fine

Thank you for the answer. However, technically, I don't understand how a partial clog impairs PETG printing but not PLA printing. Just now, a perfect PLA print is finishing. So to me that means the hot end is working OK and the nozzle is not clogged.

RE: PETG prints got bad, PLA is fine

It makes no sense for just PETG to do it unless you have wet or poor quality PETG.  

Posted by: @tcoulon

Thank you for the answer. However, technically, I don't understand how a partial clog impairs PETG printing but not PLA printing. Just now, a perfect PLA print is finishing. So to me that means the hot end is working OK and the nozzle is not clogged.

RE: PETG prints got bad, PLA is fine

Don't throw it away.  This can happen to any printer including a Bambu.  I own two now and trust me that they are not without fault.  The Mk4 is nearly perfect.  Try the three suggestions and chat with support a few time before you give up.

RE:

I like the Bambu line, but Prusa Printers print PETG very well. My MK3S+ is superb at it.. in fact, I print more PETG than PLA. However, PETG is susceptible to absorbing moisture and many countries are going into the humid season. What is the relative humidity in your locale?. I live near the ocean and it is always 70%+. Summer, nearly 90%. I must print from dry boxes and I need to routinely dry filament in a good filament dryer (PrintDry for example). The plastic that filament comes in still will let in moisture (unless you get a metal film or mylar wrap), so even new filament can be 'wet'. However, I do agree with cwbullet, that the MK4 is capable of very good PETG printing and you just need to find the problem. Sometimes you really need to try lots of different things.. When your nozzle clogged, likely something failed.. maybe the thermistor got damaged .. something.. PLA has a much wider range of temps that it will print, and so you could still have a hardware issue. The first easy thing is to change the nozzle.. but it may be a thermistor or heater problem and changing those are a pain.. I haven't had to do one yet.. but my next printer will have a tool head board so I don't need to rewire back to the controller. If you don't have a print dryer, get one or borrow one, dry your filament and see if that is the issue.. but to me it sounds like something in the hot-end is damaged. 

RE: PETG prints got bad, PLA is fine

Too bad.  I have three Mk4s, 1 Mk3S+, 5 Minis, and two Mk3.5s.  All print effortlessly and print PETG just as well as my two Bambus.  

@tcoulon I would not lose faith quickly.  You can get this to work.  

Posted by: @fignutz

Less useless than 7 months of troubleshooting a MK4 with support only to watch a refurbished a1 print the same model much better on the first shot.