Any tips in Bridging with PETG?

Hello,

Trying to bridge PETG Inland. The Bridge is maybe .6" long. All I can get is a lot of sagging.

Printing at 235 extruder and 80 bed. Using Simplify 3d and my bridging settings are
Unsupported area threshold =10
extra inflation distance = 1
Bridging extrusion multiplier 140%
Bridging speed multiplier 80%


Thanks for any tips, ask if you need more info.

Quote:

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Originally Posted by SpragClutch

Hello,

Trying to bridge PETG Inland. The Bridge is maybe .6" long. All I can get is a lot of sagging.

Printing at 235 extruder and 80 bed. Using Simplify 3d and my bridging settings are
Unsupported area threshold =10
extra inflation distance = 1
Bridging extrusion multiplier 140%
Bridging speed multiplier 80%


Thanks for any tips, ask if you need more info.

---

Need to Lower the extruder Temp.
Try about 210C , (actual temp at nozzle)
(also worked at 200C, but 210 is better temp)

I've bridged 36mm at 210C, using PETG, with only one loose pass.

Note: Indicated temp at printer may Not be actual temp at nozzle,
it's probably Hotter than printer display says

Thanks!

That is exactly what I'm learning. Its all about cooling!. My previous settings were to hot and to fast. Did not let the PETG cool down enough. I switched from the right extruder to the left (closer to the active cooling fan). I've lowered the temp to 230 degrees and I've lowered the bridging speed multiplier to 50%. I set the Bridging extrusion multiplier to 70%. I got rid of the extra inflation distance.

Here are the results so far. The middle is the most recent settings. Going to play around with it some more to try and get better.
Attachment 8038

Quote:

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Originally Posted by EagleSeven

Need to Lower the extruder Temp.
Try about 210C , (actual temp at nozzle)
(also worked at 200C, but 210 is better temp)

I've bridged 36mm at 210C, using PETG, with only one loose pass.

Note: Indicated temp at printer may Not be actual temp at nozzle,
it's probably Hotter than printer display says

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Do you still get a good strong bond at that temp?

230C still sounds a little too High to me
but your printer may be different than ours.
(nozzle size, etc.)

Note: I'm noticed that too many people set their nozzle-temps way too High,
for all filament types.
And I don't understand why they think they Have to do that ??
(There's No need for nozzle-Fan if they just lowered the temp setting)

I tried 220 but the bonding was not that great. So I'll have to stick in the 230 or + range. I tried turning active cooling off except for bridging operations but I did not get good results. Seems like having active cooling on makes a better looking print. Going to play with bridging speed now that I got the temp set as low as I can to get a good bond.

Nice results so far. Please let us know what you end up with for your final settings. I just got a role of PETG....going to try and play with it this weekend.

Here are my settings that I will be using. I'm printing from a Flashforge Dreamer using S3D. Printing Blue PETG Inland brand.

Printing with Left extruder (Closes to Active Cooling Fan)
I'm running the Active cooling fan starting at the 5th layer
Extruder temp I set at 245 to start, then gradually reduce by 5 degrees each level till I reach 232.
Bed Temp is set at 80. I'm liking how PETG sticks really well at 80, but as soon as it cools 10-20 it just pops right off.
I'm using 1.5mm for retraction distance.
Running 4 top solid layers and 4 bottom layers. (This is because my model has a few bridges and I want it water tight.)
Going with 2 outline shells.
I'm leveling the bed as normal and running the first layer height at 90%, width 100% and speed 20%.
I'm printing at 50.0 mm/s.
Bridging settings are,
Unsupported area threshold set at 10.0 sq mm.
Extra inflation distance set at 0.
Bridging extrusion multiplier set at 80%
Bridging speed multiplier set at 50 %.

Now this is what I have learned so far. To get good bonding you need high temp. To get a good bridge you want lower temp. So you have to find that fine line where you get a good bond and then a decent bridge. To me, bridging is temp. sensitive. If I set the extruder at 235, I get a noticeable sag in bridging compared to when I set it at 232. Its not terrible at 235 but not great either. So for my printer and the model I'm currently printing the perfect temp seems to be 232.

I'm no expert, but this is what I've learned so far. I've also found the below article to be helpful.

http://www.3dgeni.us/a-bridge-too-far/


Cheers!

Here is the bridge with these settings,
Attachment 8043

One more thing, At least on a flashforge Dreamer, bridging along the X-axis comes out better then along the Y-axis. I'm thinking its because of the way the active cooling fan blows at the nozzle. My model has a bridge at the top of a circle. The bridge will be along the Y-axis. I had to adjust the "Extra inflation distance" to 0.50 mm. Otherwise the extruder would not touch both sides due to a small amount of warping. Here is a picture of a test sample. The one on the left is without the extra inflation distance, and the one on the right is after. But you can see that the bridging is not as good as previous bridging due to it being along the Y-axis.
Attachment 8044

Hopefully all this work is good. I'm starting the actual print that will take 26 hours.

Cheers

Thanks for sharing! I'll give a try soon

Another thought in why the top of the hole is worse is because the bridge distance is shorter, so there is less time for the plastic to cool before the extruder comes back and extrudes next to it. It is still hot and flexible so it stretches and droops.

I stayed at 240 because less than that and I can pull the layers apart on a FFCP, but doing the bridges *really* slowly (20mm/s at 0.2 mm layer height) and with a print cooling fan going. I've heard 240 and above is bad for the interior Teflon so I have the Micro-Swiss all metal hot end upgrade, but haven't installed it yet. Waiting for a free moment to take the hot end apart.

Attachment 8050