Can Bridging Make This Part?

I'm just wrapping my brain around bridging (printing unsupported material) and I'm wondering if all bridges need to be straight.

Would it be possible to use bridging to print the object in the attached image? Obviously in this particular case the correct approach would be to print it upside-down, so the 'bridge' became the 'base', but just for the sake of learning about the limitations of bridging, I propose printing it right side up, as shown in the image.

Has anyone tried or had any luck printing a bridge that goes around a corner like this?

Even if that object was 1mm in size you still wouldnt be able to pull off a bridge with 90 degree angles or any angles for that matter. bridging is point to point only. Anything else would need support material.

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-Tom

Try experimenting with support material. I've been surprised by how well it works. I've found that kisslicer does a much better job than slic3r as the support material is much easier to remove and appears to hardly touch the object.

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Using ABSPrusa Mendel Zaphod with Pronterface and slic3r 1.3.0. Printing well with 3mm PLA and ABS through 2 x J Head Mk IV b and Wade Geared Exruders. Controlled using RAMPS1.4 board running Marlin_v1.1.9

Thanks for the input, Tom. I hadn't heard of or seen any such bridges being done, but I thought it was worth asking about directly.

Just to play devil's advocate, let me ask a question...

Suppose you are starting a bridge, and when the bead has extended halfway across the span, you stop extruding and pull the nozzle away. Wouldn't you have a single strand sticking out into thin air? Assuming that it has been cooling and stiffening as you extruded it, wouldn't it be able to stand on its own?

Suppose you then did the same thing with the next bead over, and stopped the same distance out. Then again and again, et cetera. Eventually, you would have a platform sticking out, unsupported, wouldn't you?

This thought suggests that 'bendy bridges' might be possible under some circumstances. Theoretically. Maybe?

Ok I already know how you feel about editing gcode manually, but given the hypothetical I'd say this would be necessary or else you'd have to extrude the whole bridge somehow with manual commands.

Supposing you did do that for the entire bridge what would happen is the filament would not stick together and you'd get a bunch of seperate strands rather than a fused filament extrusion. also unless you stop the extrusion half way like you said and then waited for around 15 seconds per strand, the strands would still be so hot that they woud just plop to the ground like loose strands of yarn.

Hope this doesnt come off too discouraging, your really keeping me entertained here at work! haha

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-Tom

Yes, it would definitely not be possible with standard slic3r output...

So, it sounds like you're saying two things:

[1] Although the bead that is being drawn across the gap is cool enough and stiff enough not to droop, it's still warm enough and soft enough that if it was disconnected from the extrudate coming from the nozzle, it would fall.
[2] The beads drawn across next to each other over empty space will not be bonded to one another, ie side-by-side, which means that the first layer of a bridge is basically just a collection of individual strands lain next to one another, and they don't become fused until they are bonded together by the next layer up.

These thoughts seem reasonable enough in the lack of any opportunity to try them out in the real world. I'm building up quite a list of 'crazy ideas to try' while I'm waiting for my next delivery of filament.

And don't worry about sounding discouraging.. if I didn't want my thoughts critiqued, I wouldn't post them here

Here you go. A mid-air 90-degree print. Did this a few days ago, so the part has been cleaned up with a dremel. If you saw the original you wouldn't think much of it. The first layer droops to the ground acting like support material and the layers above it print fine.

Also these pictures uploaded sideways for whatever reason

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-Tom

from the look of the part in your picture, DGC PartWorks; why don't you just flip the part over with the "bridge" as the starting layer of the print. in other words print it upside down.

edit: DOH! Carry on.

Edited 2 time(s). Last edit at 10/26/2012 03:57PM by Evogenius.

Evogenius you should probably read his first post.

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-Tom

sometimes i leap before i look. oh well. good luck with the bridging!