Stringing and blobs when printing Bambu PETG transparent

I need some help with trying to print clear parts using Bambulabs PETG Basic Transparent.
I followed the guides online for how to print glass-like parts. By Rygar1432 on Printables and Printing tips for transparent PETG on Bambulab wiki

I tried to follow the recommendations online to get as clear of a result as possible. Although I didn’t slow down as much as they recommended online. My prints with old roll of Overture transparent PETG came out without any blobs. But while printing with Bambulabs PETG, I end up with blobs on the print, stringing, and bobs on the nozzle.

Any tips on how to get rid of these blobs while printing as clear? The only other filament I had similar problems with was Bambulabs white PETG.

Print Settings, sliced using Orca Slicer

Nozzle diameter 0.4
Layer height: 0.1
Line Width: 0.5
Top Shell Layers:0
Bottom Shell Layers:0

Sparse infill density:99%
Sparse infill pattern: Aligned Rectilinear
Infill/Wall overlap: 35%

First Layer Speed: 50mm/s
First Layer Infill speed: 50mm/s
Outer Wall:50mm/s
Inner Wall: 50mm/s
Sparse infill:40mm/s
Internal Solid Infill:40mm/s
Gap infill:50mm/s

We are well aware of Rygar’s post and most of us were unable to reproduce his results or even get close. However, thanks to the work done by @ExtremeElementz in October 2023, we nailed it through team work.

Do you want to know how do get this result below? First, ditch the Bambu filament. Second, follow this post.

I experimented with a number of clear PETG and PC. There was only one brand that measure up to optical clarity that Rygar posted. The secret sauce is to use this makerworld settings

And then use this filament.

You will get optimal clarity by post-processing the surface which I describe in that post. However, what you will only get with techniques described is a through-in-through optically clear interior that blows away what Rygar was trying to do.

Here’s an example of using a circular ironing on a cylinder primitive. No post-processing was done on this disk. While it is not perfect, It did achieve optical clarity which Rygar was attempting to do.

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fi it blobs as soon as it comes out of the nozzle and sticks to it my first guess would be a high moisture content in the filament. in other words, your filament might need a spa treatment.

I even left it in my dehydrator overnight before testing and still see stuff like this…

But also, it is not blobbing up right out of the extruder when it is not touching the bed. It seems to build up as the print goes on.

Did you try these:

  1. Lower the nozzle temp by 10c or more.
  2. Set avoid crossing walls to on.
  3. Verify that you part fan is turned to off.

Thanks, that’s a good idea on the temperature. I tested it out with a reduced temperature of 260 this time. With avoid crossing walls turned on, I still got blobs, just this time in the middle of the part. (I always had the part fan off for this profile)

Try 245 then which is a temp I typically use. What I see here is evidence of over extrusion and quite possibly bed leveling issues. I say that because of the filament burns. Have you turned on bed leveling?


Definitely going to try a lower temperature.

But I copied the recorded video of this print from the microSD card and turns out the nozzle did not get completely cleaned in the beginning of the print. It was still hanging from the nozzle when the print started and it just kept making a mess.
I ended up removing the sock and cleaning the stuck and burnt filament from around the nozzle and hotend after this.

This is a very common issue with PETG.
I have seen some printable mods for upgrading nozzle cleaning to help mitigate this issue, but I have not personally tried them myself.

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I will try one of the designs out and see how it goes.