Bridging Speed Enabled for First External Layer

[ajday]

I have noticed that during the transition from infill to the first solid top layer I will get gaps if my infill is too sparse. I don't want to have to increase my infill or add more solid top layers, especially for larger parts, to get a good print (a sacrifice for print time). It seems to me that this transition area is essentially a 'bridge' as the tool passes from one infill line to the next to cover up all the gaps. So why not have the gcode reflect the bridging settings for these areas. The settings are already there, so could there be an option to apply them to cover the infill.

By tweaking my bridge settings to reduce the tool speed and increase flow etc. I can get nice bridges, so it is a shame to see the printer cover a bridge just fine that is 8mm wide but fails when it's covering infill that has only 4mm gaps. If there could be a little check box somewhere that would apply the bridge settings with the layer that covers the infill, you could get really nice surface finishes and save on print time.

-AJ

[ajday]

[kelvin]

I agree that it would be nice to treat the first external layer as a bridge if the infill is sparse. I'm using wood PLA and found that I need to increase the first layer speed significantly to prevent it from dropping into the infill. Even after 4 layers, I can still see dimples where I used the honeycomb infill.

[JoeJ]

If you go to the Other tab, you can set the "solid infill underspeed". That allows you to change the speed for only the solid layers on top and bottom of your part.

[C-line]

A helpful feature in KISSlicer is the automatic generation of what the program calls "sparse infill" layers between the user-specified infill percentage layers and the top solid infill.

So lets say you specify 40% infill and then three top solid layers: KISSlicer will automatically generate a layer of denser infill over the 40% layers as a transition to the solid top layers. If you specify a lower infill percentage, the software automatically generates additional transition layers accordingly.

This would be a nice (optional?) feature in Simplify3D as well

[dkightley]

A helpful feature in KISSlicer is the automatic generation of what the program calls "sparse infill" layers between the user-specified infill percentage layers and the top solid infill.

So lets say you specify 40% infill and then three top solid layers: KISSlicer will automatically generate a layer of denser infill over the 40% layers as a transition to the solid top layers. If you specify a lower infill percentage, the software automatically generates additional transition layers accordingly.

This would be a nice (optional?) feature in Simplify3D as well

This sounds somewhat like the mechanics of this request:
viewtopic.php?f=23&t=2762

And I give a +1 to both!

[bray.christopher]

Yes please!

This similar to the Complex Infill request.

viewtopic.php?f=23&t=2762&hilit=top

[rmcniff]

It would be very useful to have a checkbox added either on the layers tab or the Other tab under the bridging section that would cause the slicer to use bridging settings (speed, extrusion multiplier, etc) for the first top solid layer above infill. I have noticed very frequently that when the infill percentage is low (about 30% or lower) that the first solid top layer often comes out very poorly when printed at normal speed (100mm/s or so). It prints MUCH better if it is slowed down significantly, as with bridging. This layer can sometimes print poorly enough that it takes five or six top layers to recover to a decent looking solid pattern, and I'm sure the part strength suffers as a result.

Even with my printer very well dialed in, this has been the largest cause of print quality issues I have had lately. When the infill percentage is low, most of the time the nozzle is printing over open-air for this layer, so really it would make sense to use bridging settings anyway. It's not an issue if the part being printed slopes upward, because the new top only spans the infill by a single extrusion width or so and has an adjacent perimeter to cling to. For parts with with large, flat, horizontal top areas, however, the problem becomes much more pronounced.

The workaround that I have been using is to create separate processes that runs much slower for that one first top solid layer or two. This works great, but is very tedious to do for each new model being printed. It would be very nice to just be able to click a checkbox to apply bridging settings to the first solid infill layer above the sparse infill. Using bridging settings would have the added advantage over my multiple processes method to also tweak the extrusion multiplier to help fill in the gaps between adjacent lines, without also over-extruding on the perimeters.

Thanks!
Riley

[goldcd]

+1
I think this is the third time I've done this though. Enhancement Request seems to be very popular.

[rmcniff]

Doing a bit more research, it turns out that I'm not the first person to think of this. There are threads on Slic3r's github page about this same issue from all the way back in 2012:
https://github.com/slic3r/Slic3r/issues/240

Additionally, it appears to have already been reported here on the Simplify3D forums, and the thread is flagged as ALREADY ADDED, but the solution provided to use solid infill underspeed is not a good solution. For a large flat print, solid infill underspeed will also unnecessarily slow down the bottom solid infill, as well as the uppermost solid layers. That would dramatically slow down the overall print speed when taken down to bridging speeds, and still would not allow tweaking the extrusion multiplier. Thread here:
viewtopic.php?t=5815

This seems like it would be a relatively simple improvement, with a huge return in print quality. I'm seeing people from all over the inter-webs that have had or are having the same issue, especially for ABS with honeycomb infill, but definitely not limited to that.

Examples:
From 2014: http://forums.reprap.org/read.php?262,434774
From 2014: http://forums.reprap.org/read.php?262,385573
From 2015: viewtopic.php?t=3866
From 2016: https://www.reddit.com/r/3Dprinting/com ... ng_prints/