use smart overhang slicing

[geraldtrost 0]

 

Hi developers!

slicing overhangs is still a huge issue, even in modern slicers!

Very often we would be able to skip the annoying support

material if only - if only the slicers were smart enough!

Why build a perimeter (shell) in the open air

so that the material all

falls down (driven by gravity)?

THIS IS A REQUEST for an additional expert setting named

"use smart overhang slicing"

Description for the desired feature:

************************

Improvement A

************************

 

The smart overhang slicer should slightly adapt some (up to 3) layers

below and above the currently sliced layer as shown in the figures:

 

fig 1: front view of the print model

 

xxxxxxxxxxxxxxxxxxxxxxxxx <- layer +3

xxxxxxxxxxxxxxxxxxxxxxxxx <- layer +2

xxxxxxxxxxxxxxxxxxxxxxxxx <- layer +1

xxxxx <- layer 0 (currently sliced)

xxxxx <- layer -1

xxxxx <- layer -2

xxxxx <- layer -3

xxxxx

 

fig 2: front view of the adapted print model

 

xxxxxxxxxxxxxxxxxxxxxxxxx <- layer +3

xxxxxxxxxxxxxxxxxxxxx <- layer +2

xxxxxxxxxxxxxxxxx <- layer +1

xxxxxxxxxxxxx <- layer 0 (currently sliced)

xxxxxxxxx <- layer -1

xxxxx <- layer -2

xxxxx <- layer -3

xxxxx

 

Layers +1,+2,+3 become slightly cut while layers -1,-2,-3 become slightly extended.

This is done by "secretly" adapting 3 already sliced layers and by "secretly" adapting 3 "next to come" layers.

 

************************

Improvement B

************************

 

The smart ovehang slicer should first build the overhang infill

in direction INSIDE-OUT and then it should build the overhang

shell upon the cooled infill matter.

This also implies that the infill/shell overlap setting should

be increased for the overhang portion.

This also implies that the infill speed should be decreased for the

overhang portion.

Remark:

Even if this method neglectibly distorts the model I would ALWAYS

prefer this option over using a support material!

yours, Gerald Trost

PS: please, forward this request to the development team.

 

 

 

[IRobertI 521]

If I'm understanding you correctly this would only work for very very small overhangs. Something like <1mm. If the overhang was bigger than that you would have to modify a lot more layers and you would destroy the geometry of the model in the process. For example, if the model had a profile like a staircase, instead of having individual steps it would turn into a diagonal line which is probably not what you'd want. Or even if it was just a single overhang, it would still destroy the intended profile. The green part is the intended model (let's ignore it's printed the wrong side up and the red is what would be added. It would completely destroy the model.

Not sure I understand the second suggestion. Do you mean it should be a concentric infill pattern, building outward? Not sure how the infill could be built without eventually stepping out over the edge if there's an overhang, regardless of order or pattern. The shell is already being printed from inside to out. No matter which order you print in, eventually there will be air underneath the plastic.

 

[gr5 2,224]

Robert, you show 45 degree in red but if you have a .4mm nozzle and a .1mm layer height you can change that possibly to a .1 to .4 ratio or 14 degrees.

 

Why build a perimeter (shell) in the open air

so that the material all

falls down (driven by gravity)?

 

Because often it works anyway - gravity is not a significant force sometimes and sometimes (if the fans are cranking on 100%) you can actually build a shelf hanging over nothing. The UM and UM2 are pretty good at this.

 

[IRobertI 521]

Sure, the angle could be changed but that doesn't invalidate my point. You're still destroying intended geometry.

And you could of course make an argument for: "make it an option". Sure, but in reality, how often will it come into play? If you create the model yourself you're far better off either designing around an overhang or put in strategic supports yourself. If you're downloading the model there's a good chance there's a reason for that particular geometry.

I dunno, maybe I'm being closed minded but to me it feels like it would only be useful in a very select few occasions. Even more so if we're only talking about modifying 3 layers in each direction.

 

[duesentrieb 0]

I don´t like support material. Or let´s say support material how it is being created today in most of the times. There are more intelligent ways and approaches. Mesh mixer is such an approach. Illuminarti wrote about it in his blog:

http://www.extrudable.me/2013/12/28/meshmixer-2-0-best-newcomer-in-a-supporting-role/

Something like this integrated in Cura would be mind blasting. We wouldn´t talk about support anymore.

With the right adjustment and cooling an UM can even print midair! Have a look at Joris videos. Amazing.

http://www.thingiverse.com/thing:257327

Sometimes you really don´t want to print with support and overhangs suck. Gerald I like the idea of smart overhang slicing. But I don´t like the idea of changing the dimensions of the printed part. Most of the times I am printing functional parts. A sharp corner should be a sharp corner. If I wanted it round, I would have designed it that way.

What if the print head would print the infill first, but in a pattern that goes along the solid model, line by line. If the overhang is way to big it would also be an option to print half of the overhang in layer one, then layer 2 and 3 first to stabilize the already printed and then go back to layer one?

With bridging I made the experience that an UM can even print bridges of 4 cm and more, the printed plastic hangs like a rope directly after comeing out, but tightens, when the other pillar is reached because of cooling. Of course you need sufficient cooling for this.

Regards,

Philip

 

[nallath 1,124]

A lot of people seem to think that ideas on how to fix the support structure are the bottle neck. This is not the case, far from it actually. In a broad sense, ideas are very, very cheap.

The main concern is not how to implement a better support structure, nor convincing anyone that it's a good idea to implement a beter version (Because really, it is a good idea). The biggest problem is mainly time. We have limited quantities of it and implementing a good support algorithm takes quite a bit of time.

*edit*

I just re-read this post and might seem negative; It's most certainly not ment to put a damper on your ideas! Please, do keep them flowing. Just be aware of the constraints that we face as active developers.

 

[geraldtrost 0]

@IRobertI

right, smart overhang adaption could only work

for small overhangs, let us say <= 3mm.

but tiny overhangs happen frequently in mechanical models.

to my second proposal (smart overhang infill)

yes, infilling the overhang portion inside-out implies that

some circular or concentric infill pattern would be used.

thanks for your attention!

Gerald

 

 

[Daid 306]

While I see how I can implement idea 1. I do not like the idea of changing the topology of the model (as people already pointed out)

Point 2 sounds a bit like the bridging improvements I'm working on.