Unwanted Supports on Bridging
In the top image I have bridging set to build plate only and on the bottom I'm using a support blocker. How can I get the second result automatically via settings tweaks? Just to give you slightly more context I've printed this already and the results are good enough.
Best Answer by Neophyl:
What version of PS are you using ? The thick bridges tickbox is located under Print Settings>Layers and Perimeters>Quality>Thick Bridges. The 'old' logic of PS is that anything bridging isn't squished against the layer below, so it assumes that the layer height for a bridged section is the nozzle diameter, so in a normal profile that means the bridge layer is 0.4mm thick as well as ~0.45 wide. This assumption is true for a certain degree but there were many calls over many years for it to be dropped as other slicers printed better bridges when that logic is not followed. If you look at a sliced preview carefully you can see the dark blue bridge perimeters are usually double height. Same with any bridge infill.
Prusa devs finally added an option to remove that logic. Basically always have it unticked. It gives much better results on everything I've printed so far. I've yet to find anything where the old thick bridges logic actually works better on.
RE: Unwanted Supports on Bridging
Print settings→Support material→Options for support material and raft→Don't support bridges
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: Unwanted Supports on Bridging
I guess I should've mentioned that I have that enabled and the above image is the result I get without a support blocker.
RE: Unwanted Supports on Bridging
It seems like there is a max limit for the bridge length and when your bridge exceeds that it will force supports. I might just be missing this value, but I don't see anything.
RE: Unwanted Supports on Bridging
Nope, there isn't a max length. I know because that feature has been requested several times on github.
Pics aren't the clearest way to see what problem you are having, the best way to get help is to save your project file in PS (File>Save Project As) and then take the resulting .3mf file, ZIP it up and attach the zip file to a reply here. It must be zipped or the forum doesn't allow the file type. Its very picky on the allowed files.
With a project we can slice it with identical settings to you as a project contains the model(s), any positioning, modifiers, painted areas etc as well as a copy of all 3 profiles you are using. We can then slice and view the preview just as you can and scroll through and examine things.
For example you may not be using a blocker correctly, we cant tell from the pics, there may be hundreds of other possibilities too given the combinations of settings, the interaction of which is not always obvious. Post a project and you will get better help.
RE: Unwanted Supports on Bridging
I imagine a 3mf would be enough I don't have the project open anymore
RE: Unwanted Supports on Bridging
I thought I attached the file at work but now that I've checked it there doesn't seem to be any files with that last message. I'll send it once I get in tmr
RE: Unwanted Supports on Bridging
I saved the project and attached it to this post, hopefully it works this time.
RE: Unwanted Supports on Bridging
Can't see a file. Did you zip it? Or maybe it needs to be a approved by an admin as you're a new member.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: Unwanted Supports on Bridging
I think that must be it I used the attach file option at the bottom. Here is a link for it on google drive. If you don't see a link assume it's because of my new member status.
RE: Unwanted Supports on Bridging
You have a few strange settings. Why set the bridge flow to 0.6 and still have use thick bridges ticked ? Just set your bridge flow to the normal amount of 0.95 and untick thick bridges.
That aside the simplest way to do the support you want for this model is to set For support enforcers only, then select your object, select paint on supports, change tool type to Smart Fill and you can select that outer section with a single click. Takes a few seconds to do and gives you way more control.
Also your support settings can be much improved, set to snug, set first layer expansion to 0, your contact distance is going to weld them to the part making removal very difficult.
With a large flat top surface like you have and 15% gyroid infill its also quite likely that the top surface will have smoothness issues printing too. Needs more infill in that area. If you increase your perimeter count to 3 it will make it stronger while only using 0.5g more filament. The difference in print time is minimal, around 4-5 minutes.
I've attached a zipped up modified version.
RE: Unwanted Supports on Bridging
I don't see a setting called "thick bridges" but that sounds like a nice setting to have. With linear advance you can get pretty whack settings to look good, also I've noticed you can use a much closer contact distance. I do think 0.08 is a bit too close since it requires more effort than I'd like to remove but it leaves such a nice finish. Additionally, I was trying out 0.6 to see whether I could pull the bridges any tighter, but it ended up making them too tight and left a horrible finish. I'll probably go back to 0.7/0.8 but the thin bridges setting you mentioned would probably let me set it back to default if it's meant to be a standard value for good bridging.
RE: Unwanted Supports on Bridging
What version of PS are you using ? The thick bridges tickbox is located under Print Settings>Layers and Perimeters>Quality>Thick Bridges. The 'old' logic of PS is that anything bridging isn't squished against the layer below, so it assumes that the layer height for a bridged section is the nozzle diameter, so in a normal profile that means the bridge layer is 0.4mm thick as well as ~0.45 wide. This assumption is true for a certain degree but there were many calls over many years for it to be dropped as other slicers printed better bridges when that logic is not followed. If you look at a sliced preview carefully you can see the dark blue bridge perimeters are usually double height. Same with any bridge infill.
Prusa devs finally added an option to remove that logic. Basically always have it unticked. It gives much better results on everything I've printed so far. I've yet to find anything where the old thick bridges logic actually works better on.
RE: Unwanted Supports on Bridging
Ah I see the problem I still have 2.3 installed on this system and I've been accidentally using it instead of 2.5 lol. Thanks for the help and tips, now my profile will be that much closer to FDM singularity.
RE: Unwanted Supports on Bridging
Neophyl has pretty much said it all, just two points to add.
Going back to the original pictures, the reason PS is adding the supports in the center is the diamond shaped thin bars going across the top surface. Without supporting them, it would have to bridge to create them, and then bridge the rest of the top surface on top of those bridges, which it won't do.
Also, maybe this is just a proof of principle, okay, but why in the world would you possibly want to print the model in this orientation and not flip it by 180 degrees, which removes the need for any supports.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: Unwanted Supports on Bridging
Flipped 180 would still need 'some' supports for the flexible latching bits. It does add a single interface layer under part and a small column down to the lip around the outside if you flip it. With petg I am not sure how easy it would be to remove as the gap is narrow.
That's one of those things where id excise a single instance out from the full model and do some test prints in the filament to see practically what settings work best. Sure would seem a lot better orientation though.
RE: Unwanted Supports on Bridging
Neophyl got it, I was trying to prioritize the quality of the clips over the back surface of the cover. I also kind of prefer the look of a top filled surface over a bed side surface.