georgei
Posts: 30
Joined: Tue May 03, 2016 11:02 am
Location: London
Contact: Website

S3D puts bridge on top of supports

Tue Sep 12, 2017 3:31 am

Hi,

I am printing some boxes that they have to print face down and therefore need supports.
The strange is that s3d even though that calculates correct the supports on top of them is putting also a bridge (attached images).

Isn't that a little crazy? What is the point of the supports then?
Capture2.JPG
Capture1.JPG

arhi
Posts: 390
Joined: Thu Oct 06, 2016 5:13 pm

Re: S3D puts bridge on top of supports

Tue Sep 12, 2017 6:41 am

georgei wrote:Isn't that a little crazy? What is the point of the supports then?
not crazy, proper way to do things, this way support supports your bridge from sagging and you have easy to remove support
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gwhite
Posts: 102
Joined: Wed Jul 19, 2017 9:37 am

Re: S3D puts bridge on top of supports

Tue Sep 12, 2017 8:47 am

Although it's only for very short distances, there are gaps between the support material ribs that it technically still has to bridge over. You should be able to back off on any tweaks required for true bridging, which might speed up your print slightly, but it's still printing over thin air for a good portion of the supported region. It's just broken up into short enough gaps that the filament doesn't have a chance to droop or otherwise mess up. It may still be a good idea to play with a little over extrusion to make sure the filament bonds to adjacent passes, because there is nothing for the bottom layer to squish against in the gaps.

georgei
Posts: 30
Joined: Tue May 03, 2016 11:02 am
Location: London
Contact: Website

Re: S3D puts bridge on top of supports

Tue Sep 12, 2017 11:02 am

It will make sense if the supports where not dense.
But the last two layers of supports are 90% infill.
The bridge layer just make a total mess of the surface because it follows of course the bridge settings (which are not for printing over a solid layer).

blackbird2016
Posts: 134
Joined: Wed Aug 02, 2017 1:24 am

Re: S3D puts bridge on top of supports

Tue Sep 12, 2017 1:49 pm

I honestly would not think about it any further.
Although those layers in the preview are indicated as being a bridge, it willmake no difference at all for the overall result.
Laying on supports they never ever will come out exactly as smooth as solid layers on the bed.

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dkightley
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Re: S3D puts bridge on top of supports

Tue Sep 12, 2017 4:38 pm

If you don't want any bridging to take effect, simply set the Unsupported Area threshold to 99999.0 sq mm.
Doug Kightley
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jfkansas
Posts: 84
Joined: Wed Oct 01, 2014 2:12 am

Re: S3D puts bridge on top of supports

Wed Sep 13, 2017 4:38 pm

georgei wrote:It will make sense if the supports where not dense.
But the last two layers of supports are 90% infill.
The bridge layer just make a total mess of the surface because it follows of course the bridge settings (which are not for printing over a solid layer).
No, there should be 1 separation layer between the top of the support and the first bridge layer. The bridge settings are just a slight modification to the extrusion profile.

In your preview verify the bridge layer is running at a non parallel angle to the last dense support layer. 45 to 90 degree difference is preferred.

Harry_D
Posts: 12
Joined: Mon May 08, 2017 2:28 pm

Re: S3D puts bridge on top of supports

Sat Feb 03, 2018 12:35 pm

Just another question on the bridge layer, that's added to supports... I seem to have a height issue, where I now have to sand off the bridge layer, as it won't come off the part.
S3D bridge in print.jpg
Printed item, with Bridge layer in view
S3D bridge.JPG
Bridge layer in S3D
In my support settings, I have 2 layers dense support at 50% - these come out easily, no issue at all. Setting for vertical separation is 1 layer each.

So.... shouldn't a bridge layer come off also, when removing support? This bridge layer is completely fused with the 1st solid layer and I can't seem to be able to remove it (other than sanding it out, that is).

I have a layer height of 0.2mm & the top of the bridge layer is produced on the 20th layer: so that puts a printing surface for the 1st solid layer at 4.0mm height - exactly where it needs to be. But as I can't remove the bridge - I now have to sand the 0.2mm out.

Is there maybe a setting that I've got wrong? If someone could indicate where to look, that would be great! It's good to read, (above post) that I can temporarily switch off bridging - but if there's a better way to do it...

Thanks!

horst.w
Posts: 781
Joined: Fri Oct 17, 2014 5:00 pm

Re: S3D puts bridge on top of supports

Sat Feb 03, 2018 3:40 pm

The bridge is not designated to be removed, it is inherent part of the print.

I'm wondering that the deep inside is minor than the constructed and calculated high. So I think, this layer is not the bridge but the uppermost Separation Layer what is baken to hard.

Regards
horst.w
GER

horst.w
Posts: 781
Joined: Fri Oct 17, 2014 5:00 pm

Re: S3D puts bridge on top of supports

Sat Feb 03, 2018 4:07 pm

I have tested,
with FirstLayer High 100%, a rectangular hole of 20 mm high the support ends exactly to 20 mm

G1 X129.688 Y62.537 E0.5704
G92 E0
G1 E-2.5000 F1800
; layer 100, Z = 20.000
; inner perimeter
G1 X126.039 Y64.810 F4800
G1 Z20.000 F1002
G1 E0.0000 F1800
G92 E0

The Z-high is the top of the last layer before beginning the bridge with layer number 101
so the first layer of the bridge must have Z= 20,20 mm when LayerHigh is 0,20 mm.

G1 X126.447 Y113.499 E1.8153
G92 E0
G1 E-2.5000 F1800
; layer 101, Z = 20.200
; inner perimeter
G1 X126.042 Y62.129 F4800
G1 Z20.200 F1002
G1 E0.0000 F1800
G92 E0
G1 X130.764 Y62.129 E0.1696 F2250

H.
L100-101.png

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