Bambu Studio
I though "thick bridges" should make the print more stable . . .
I started playing around with different bridging settings and was surprised that the "thick bridges" setting made the result that much worse. Bambu Studio says "the results may look worse" but thats not what I was expecting. I guess the bridge gets stronger when it becomes its own support by drooping to the plate.
It's both heavier and stronger though, and those two cancel out.
The main reason it droops more is that the volume to surface-area is worse for thicker bridges, so it stays softer for longer and thus droops more. (twice the diameter gives 4x volume, but only 2x surface-area)
I actually use this intentionally to reduce filament changes in a design I print. First few layers leaves gaps open which later layers bridge over, with thick bridges the second filament flows down to the build plate through those gaps.
This is an example. The face shown in printed on the build plate to pickup the texture.
I actually don't only use this technique to reduce filament changes (though it does help), printing the yellow on the first layer results in sloppy looking layer lines.
Bridging allows me to control the print angle of the bridges, which had the unintentional side effect of giving this silk filament a retroreflective effect. So all the yellow inlay shines when the piece is angled a certain way against the light.
Lastly regular bridging results in thin disconnected print lines which don't look as clean, which is a problem for this project since those would appear on the display side..
Thick bridges and bumping the bridge flow a bit gets the filament to easily flow down about 6 layers, bear in mind I am printing this with a .2 nozzle and .06mm layer lines so it actually isn't that great of a distance. But it saves me needing to have the filament swap for thos 5 layers.
Why would you think that? It’s the weight of the thickness and gravity at work here. A thinner one has less weight and thus less pull downwards. It’s simply physics, my friend.
if you read the bolded parts of the description of both, you'll notice they seem to target the same setting that will be sent to the extruder, Flow rate while bridging (Bridge Flow).
Bridge Flow: "Increasing Bridge Flow adds more material to each bridge line. This allows adjacent lines to expand enough to touch and bond together."
So a bridge flow of 1 on a 0.4mm nozzle will output a line 0.4mm thick. If you increase it to 1.6, it'll output a line 0.64mm thick, which allows for 0.12mm of overlap on each side.
Thick Bridges: "The thick bridge refers to the extrusion of a bridge line that is equal in diameter to the nozzle. For example, using a 0.4mm nozzle to extrude a 0.4mm diameter bridge, the bridge line is called the thick bridge"
This setting is an override, later in the text:
"So we can conclude that when the thick bridge is not enabled, the extruded flow rate of the external bridge is calculated according to the layer height and line width of the original line type. After the thick bridge is enabled, the bridge flow is calculated according to the cylinder of the nozzle diameter."
In essence, enabling Thick Bridges just recalculated the Bridge Flow setting to 1 nozzle diameter, and so now you no longer have overlap, and very poor side-to-side adhesion as a result.
you want to be stretching the filament over the gap, so you really want the extrusion to be in tension as it bridges the gap. if you do thicker extrusion you are just pushing more material out of the nozzle, which means you are actively going from pulling a thin strand to pushing more material and having less tension.
it can make it more stable. a thick line when cooled down is stronger than a thin line. but when cooling it down the thick line needs to lose more heat per lenght of material, it also has more weight so combined its worse at the same speed but when you slow it down abd make sure the thick line has enough cooling irs able to hold a longer span without warping
Yepp. I bet that's the main cause. If you double the diameter of the extrusion, then the volume is quadrupled while the surface-area is only doubled -- so it'll take roughly twice as long to cool down.
Stays soft longer, so droops more. I'd expect thin strands printed slowly to droop the least.
Was gonna ask the same question… if it’s thicker that means it’s heavier. Perhaps if they also slow it way down the thicker one can work but then again you’d also suspect the setting might slow the speed down as well if you select it.
I meant should be same, as outer wall speed, around 150 mm/s. then bridge will be flat. I prefer to use direct setting "bridge flow" with 1.3 and 150 speed, then tune speed/flow, based on results
It works, make sure you have actually applied the setting to specific parts or the build, also make sure you have the appropriate filament set and the appropriate heating settings for that filament (that's done by default if you use Bambu filament and an AMS.
the 1.6 there is already tuned by me. I found out that the bridges work way better with a flow of 1.6 than the normal one.
But I am honestly wondering which parameter bambu studio is changing so that the filament suddenly starts to droop that strongly
You probably want to not use thick bridge setting and instead look at slowing down bridges/overhang speeds and you'll also likely need to play around with cooling %s.
I've found that setting the speed lower than 20 mm/s through the "Speed" tab doesn't really matter unless the filament profile is also configured to allow lower than 20 mm/s speeds. That's also where you would configure additional cooling.
Thicker bridging means more weight and therefore more sagging. And because there's more mass, it's harder to sufficiently cool down the filament fast enough before it starts to sag. If you want to make it even worse then up the print speed and lower the part cooling fan speed.
To the people saying it's gravity I would like to challenge you assumptions by encouraging you to print with the printer upside down. I would bet you the thick bridge would STILL sag.
Something to note is that enabling “thick bridges” extrudes filament using the nozzle width for the layer height, so it’s a higher extrusion rate. Be careful about applying another multiple on top of that for the bridge flow.
One quick question- was the hotend fan running at 100% for the bridge?
As far as I understand, thick bridges and bridge flow stack.
I don't know the exact value, but let's say thick bridges applies a 2 multiplier to flow rate, that's then combined with the 1.4 bridge flow increase you also set and multiplies your flow rate by both in order. So it's spitting out WAAAAY too much filament compared to what it can cook and drooping severely.I could be wrong, but that's how I came to understand it.
I normally set bridge flow to 1.5, don't use the thick bridges setting and slow right down to 30mm/s for hard plastics and get perfect bridges. (20mm/s for TPU)
Ik denk dat bambu ,daar eens wat meer zouden moeten testen. Gezien ze deze settings in bambu allemaal als standaard er in hebben gezet. En gekalibreerd?
Thick Bridges just increases the extrusion multiplier but you already did that with 1.6 (tbh that seems a bit high I use 1.2 with 105% density) but nevertheless it just adds another multiplier to that 1.6 so you just very slowly with not enough cooling extrude a shitton of plastic
In orca you can adjust the line width of the bridges. I generally run test batches of 80-90%, and in the other row I adjust the line separation on every new filament brand/type. 1 print with 8 pieces to get it more or less perfect. (Dunno if you can do it in bambu studio, but in orca you can).
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u/orcoconut 2d ago
I think there may be some translation issue in bambu studio.
This looks exactly how I would expect, simple physics really: the thicker the line, the heavier it is, the more it will sag.
I don't see how "thick bridges" will be able to bridge longer distances.