Poor bridge anchoring

Having some minor issues with bridging.

The point of origin is not anchoring well. Sometimes it falls off.

Have tried a wide range of speeds and flow rates. Always the same problem with little change.

Running out of ideas. currently trying again with lower print acceleration rates in marlin.

After that I'm out of ideas and looking for suggestions.

---

If you can't fix it with tape and tie wire. Its broken. You need a new one.

[www.youtube.com]
[plus.google.com]

Moderators and RepRap Wiki editors have my full and unconditional permission to use any original photo's I upload for the wiki or any other way they may be of benefit to others.

I had the same issue. You need to tune the extrusion rate of the bridge, speed and the acceleration, of those 3, most important is extrusion rate / speed. I use slicer and my setting is: bridge speed 50 mm/s, extrusion 1 / 0.95 depending on the filament I use. And of course an excelent cooling, 100% for bridges (and I have a beatiful cobra fan shroud witha radial fan, that thing really blows air!)

Also using Slic3r.
I've tried speeds from 20mm/s to 120mms. and flow rates from 0.4 to 1.5. Had good results going slow with less flow and fast with extra flow. The photos above where at 80mm/s with 1.2 flow. I have a big radial fan, but still working on the shroud. Can't get much air on print of it cools the hotend and causes a bunch of other problems.
Although probably not a problem as not getting saggy bridges.
Never once had good origin anchoring. I think there is an accelleration setting I can't find for bridges?
What is really annoying, is that my regular perimeter and infill settings work fine. For some reason there seems to be extra acceleration on bridges that I can't seem to turn down.

---

If you can't fix it with tape and tie wire. Its broken. You need a new one.

[www.youtube.com]
[plus.google.com]

Moderators and RepRap Wiki editors have my full and unconditional permission to use any original photo's I upload for the wiki or any other way they may be of benefit to others.

Why dont you try my exact settings and test that? 50mm/s speed , fan at 100%, bridges accel 200, flow 1/0.95
It is really important the fan shroud, to me, once I got it running, I can print 15 cms long bridges, with no saggying
If you look for a food shroud, look at this: [www.thingiverse.com] .
I have a prusa I3 and I could adapt it to me wade extruder. It works GREAT for bridging

How do I set bridge accel?

Other than that tried all that. Excpt fan at 100% lol. that would blow the part of the bed.

---

If you can't fix it with tape and tie wire. Its broken. You need a new one.

[www.youtube.com]
[plus.google.com]

Moderators and RepRap Wiki editors have my full and unconditional permission to use any original photo's I upload for the wiki or any other way they may be of benefit to others.

LOL. Nevermind.

Bridge acceleration setting in the speed tab. Down the bottom.
That was the answer I needed. Thanks for making me look again

edit. Also just noticed there is a pressure advance setting, which may solve a few other minor problems I have

Edited 1 time(s). Last edit at 10/05/2016 09:49PM by Mongrel_Shark.

---

If you can't fix it with tape and tie wire. Its broken. You need a new one.

[www.youtube.com]
[plus.google.com]

Moderators and RepRap Wiki editors have my full and unconditional permission to use any original photo's I upload for the wiki or any other way they may be of benefit to others.

Oh bugger.

Cant just set bridge acceleration in slicer without screwing up all the other acceleration settings.
Its greyed out unless I change default acceleration. Which I have done before and is really bad for non print acceleration and results in huge dagging problems.

A little more info here would be much apreciated.


Had a play with pressure advance. Interesting result. Not good, but interesting.

---

If you can't fix it with tape and tie wire. Its broken. You need a new one.

[www.youtube.com]
[plus.google.com]

Moderators and RepRap Wiki editors have my full and unconditional permission to use any original photo's I upload for the wiki or any other way they may be of benefit to others.

Forget about pressure settings, still experimental and you need to have volumentric extrusion set I think.
Regarding accel setting, it wont break anything: in default extrusion set the value you have in your firmware, set the desired value in the bridge section, and all other set them to 0 (cero mean default, so all values with a cero value will use the defaul, and since the default is the same as in frmware, no change at all )

My firmware has different settings for print and non print. Setting the default in slic3r to the print value also sets the non-print value to the same speed. Which does indeed mess stuff right up. I have been down that path before. As I already mentioned. Its a total disaster. Resulting in either huge banding problems for a decent xy non-print accel, due to too much Z accel on non print. Or huge stringing and dagging problems if I set a good Z accel. Spend a few days with all that not going there again.

Getting serious improvement with the pressure setting. Still got a few more tests to do, Started at 2, then 1 both of which was way too much. Now I'm down to 0.1 and its really close. Had to stop for the night. Will be trying 0.05 next. With bridge speed at 80mm/s and flow at 1.2, which is probably a bit low. once I have the advance right I'll probably bump flow up. Getting massive improvements on overhangs and a under extrusion problems I was having with speed changes.

Its the setting I should have played with weeks ago. No need for volumetric to be set. Although I have been meaning to play with that. Its all been stable for some time according the the release notes.

---

If you can't fix it with tape and tie wire. Its broken. You need a new one.

[www.youtube.com]
[plus.google.com]

Moderators and RepRap Wiki editors have my full and unconditional permission to use any original photo's I upload for the wiki or any other way they may be of benefit to others.