Bridge settings for ABS

[Zbyszko 0]

Hi, I'm a relative novice at 3D printing and up until recently have been printing in PLA without much issue.  I need to print some functional parts with higher temp tolerance so I purchased a roll of Inland ABS and did some test prints.  In general, everything is fine - but bridges are horrendous.  The temp tower in the image used no fans at all.  To try to find some reasonable bridging settings I used the experimental bridging settings in Cura 3.6 and printed seven 5cm bridges with different per-model settings.  I set the min bridge wall length to 5mm and then varied the speed, flow, and fan settings between the models.  As you can see in the second attachment  I was not very successful.  Aside from needing some advice on what are good starter ABS settings for bridging I'd like to ask the following questions.

 

1. Is bridging fan speed influenced by other settings in Cura?  Reason I'm asking is:
   • I had "Enable Print Cooling" set to on with a Fan speed of 0 and bridging fans speeds I used were 20 and 45% but I don't think that the fan kicked on at all.  
   • I tried the fan commands (which I confirmed were present in the g-code) manually and the fan kicked on but it was pretty slow on the 20% setting. 
   • Is there a setting to "blip" the fan for a fraction of a second to ensure that the fan overcomes static-friction?
2. I there a way to highlight bridges and when fan are on in the slicer view?  I would be helpful to check visually without having to look through the g-code.
3. What should I try next?

 

My setup: Wanhao duplicator i3 with Micro Swiss all-metal head, in cardboard/plexiglass enclosure.

Print speed: 50mm/s

Print temp: from 240 - 270  (extruder was struggling at 235 so more recent attempts have been at 240C min)

Bridge settings: varied; on the bridge trial I tried 30 and 60mm/s bridging speed with 70 and 90% flow.

 

Thank you for the help!

[mastory 44]

I am wondering what you may have learned in this pursuit.  I didn't notice when you originally posted.

I can't answer your questions 1 & 2.

 

The parts I print are typically structural working prototypes or final use parts in natural ABS.  Usually parts are geometric enough that I can find creative ways to cut them into pieces with CAD before printing and bond them together post printing with acetone.  I this way, I avoid alot of bridges.

 

Occasionally on horizontal (planar) overhangs, I have had success printing a med or low density support, with a high density, but under-extruded support interface, a support horizontal expansion, and a one layer Z gap.  Printing this way without any bridge settings activated has allowed the support to break loose without high difficulty, leaving a rough but consistent overhang.  I should play around with the bridge settings in this scenario to see if any advantages can be gained, maybe forego the gap layer.  I'm not sure all the bridge settings were available when was initially figuring out how to print this type of part/material.

 

If I pursue unsupported bridging with ABS, I would try a combination of the following (my conjecture based on experience printing ABS, not necessarily bridging);

 

Turn off the fan.  I never use fan (don't have one) with ABS, but watch that layer times don't get too short

Under-extrude by 50% or more.

Set bridge speeds high.  Consider the stringing that happens in travel moves w/o retraction.  I think you want to go fast enough that the line can't solidify (stays elastic) until the nozzle finishes the span.

Maybe use TweakAtZ to bump the temp a few deg for the bridge layer(s).  Probably difficult to control and maybe has to be done in advance of the bridge layer.

Bridge wall coasting seems like a good idea

Try multiple bridge layers

[Zbyszko 0]

Thanks for taking the time to reply and the suggestions.  I've actually not made much progress on the bridging front since I think I may have jumped the gun in trying to tackle that before optimizing other thing like print speed and temp. It would be great if there was a flowchart that covered what to tune and in which order when starting with a new material.  I did find something like what I'm describing on thingiverse but as of this moment I'm trying to figure out why CURA sliced prints are coming out poorly when it comes to fine lines which print fine when sliced with a different app.  I did receive some good feedback and will try the implementing it momentarily.  When I finish with these steps I'll come back to trying bridging again.