maker2
Posts: 140
Joined: Sun Jul 19, 2015 9:05 am

first layer of solid infill sometimes as Bridging

Mon Jul 19, 2021 3:39 am

When using larger extrusion widths (eg 0.75mm) infill (eg 10%) can end up producing quite large gaps (eg hexagonal infill).

I normally print solid infill (0.2mm layer height, 5 top layers) quite fast (100mm/s) and normally that works fine. However in the above case the first layer of solid infill is going to be quite messy as extrusions tear in the gaps between infill structures on the faster (i.e. longer) runs. To create a blanket reduction in solid infill speed can have too higher cost in part time. However the problem would easily resolve itself if S3d could recognise that, in certain circumstances (gap >= bridging distance) the first layer of solid infill should be categorised as "bridging" and the "bridging speed" applied.

Tx.

maker2
Posts: 140
Joined: Sun Jul 19, 2015 9:05 am

Re: first layer of solid infill sometimes as Bridging

Thu Jul 22, 2021 2:18 am

Yep I've confirmed this over a couple of prints. Stand by the printer and reduce Speed to 50% for first layer of top layer solid infill and it resolves a lot of problems when infill is rendered sparse by extrusion width.

(In detail on last print was extruding at 100mm/s with 0.6mm nozzle, 1mm extrusion width and 0.2mm layer height. Infill was 10% (as high as was necessary for part strength) so set infill underextrusion to 60% - as low as could reasonably go = nozzle diameter - yet till the hexagonal infill was much too sparse for printing over. However 3 bottom and 5 top layers were all printed at 50mm/s that would be a big time waster and necessitate fiddling with hotend temperature as well. A fiddle. Bridging speeds auto-activating for sparse infill would save the day.)

ps as a further refinement could even have Bridging speeds auto activate for first layer of solid topfill plus X (parameter-able) additional layers. There might be some advantage in keeping for the second layer as well since gaps might well remain.

airscapes
Posts: 374
Joined: Tue Mar 06, 2018 10:35 am
Location: Philadelphia PA Area

Re: first layer of solid infill sometimes as Bridging

Thu Jul 22, 2021 4:32 pm

so create multiple process and adjust your speed at the layer you want it adjusted .. Personally I would just use a higher infill with rectilinear pattern, wait the extra couple of minutes and forget about the issue your are creating to save s dibble of filament and minutes of time.. but that's just me.. I use a .75 nozzle most of the time to save time and make stronger parts. I understand what you mean and I have experienced it. I just never go below 25% infill.. Not sure how you keep the filament melted at 100mms .. but glad you can. BTW this software is dead so there won't be any new features or updates..

You could also change your infill percentage in a second process 2 or 3 layers below the first solid and see if that would fix the issue.. never tired it but maybe the bridge would kick in.
You may also want to adjust the Unsupported threshold to see if you can trigger the bridging settings to kick in for the first solid layer.

maker2
Posts: 140
Joined: Sun Jul 19, 2015 9:05 am

Re: first layer of solid infill sometimes as Bridging

Thu Jul 22, 2021 4:51 pm

Thanks for the tips.

100mm/s x 1mm width x 0.2mm height = 20mm3/s which is at the upper end of what a standard Slice Mosquito can do.

Out of interest, with your 0.75mm nozzle, what width do you extrude infill? It seriously bothers me to make something that weighs like a brick just in order to get an acceptable top layer.

airscapes
Posts: 374
Joined: Tue Mar 06, 2018 10:35 am
Location: Philadelphia PA Area

Re: first layer of solid infill sometimes as Bridging

Thu Jul 22, 2021 10:53 pm

My parts are all mechanical parts so they need to be strong, weight is not a problem. I extrusion width for everything is .8 and I normally do .5m height for most things. There are a few items I have printed at .3 but I don't think ever .2 with a big nozzle.. If I am using a big nozzle it is a big part.. Don't need millions of tiny thin layers want the part as solid as I can get it..

maker2
Posts: 140
Joined: Sun Jul 19, 2015 9:05 am

Re: first layer of solid infill sometimes as Bridging

Fri Jul 23, 2021 2:19 am

Nice. Love chunky parts. Once made under and over supports for a weighscale load cell somewhat in the way that you described, with lots of tapering I-beam structures and adored the solidity, resilience and, frankly, look of those toothpaste-like extrusions. Currently quite a lot of originally shaped electronics enclosures destined for ABS smoothing: 0.2mm height is good for that and 2 x 0.75mm or 2 x 1mm for wall features. At low height the 1mm extrusions seem to present friction to the nozzle which, in certain circumstances, stimulate resonance in the hotend carriage (my printer has a 45Hz susceptibilty) that shows up as an up/down waviness that, since it solidifies on the underlayer, builds up with successive layers. But apart that, works well.

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