Why the advice to set first layer to 80-90% in S3D?

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insta
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Why the advice to set first layer to 80-90% in S3D?

Post by insta » Wed Jan 28, 2015 4:30 pm

If anything this has made my first layers even worse since the slightest fraction of bed-levelling messes it up. Why are we not using 250-300%, with a first-layer extrusion width of 200% (which I have tried, and it works exactly as I expect)?
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jimc
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Re: Why the advice to set first layer to 80-90% in S3D?

Post by jimc » Wed Jan 28, 2015 7:16 pm

Bryan, i agree. I think the 90% thing was the old way of doing it to get the plastic squished to the bed. I usually go about 150 on the first layer and 125% width. Nothing too aggressive. Just enough to help with getting a level surface.

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Re: Why the advice to set first layer to 80-90% in S3D?

Post by KiddingMe » Wed Jan 28, 2015 7:41 pm

While we're on the topic, for a part I'm building the main surface or visible side of the part is the side printed to the glass.

I'd really like to make this side as smooth as possible without any visible rings or layers. I noticed some of the printed parts on my m2 have this effect.

So far I've tried adjusting the 1st layer % way above 90% and way below and 15% gave me the best results. This was with extrusion width set to auto. Makergear black ABS. V3b 110/245

What would you recomend.

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Re: Why the advice to set first layer to 80-90% in S3D?

Post by jimc » Wed Jan 28, 2015 7:44 pm

You will always see that to some degree but to reduce it, that is all in tye z height adjustment in the machine and or the extrusion multiplier/ filament dia.

jsc
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Re: Why the advice to set first layer to 80-90% in S3D?

Post by jsc » Thu Jan 29, 2015 8:45 pm

Just a note on Simplify3D first layer adjustment: I recall reading a while ago on the S3D forum that what that setting actually does is not what you would think it does.

For adjustments under 100%, the first layer height stays the same, but the extrusion multiplier is increased by the inverse of the adjustment. So if you said 50% with .20mm layer height, the first layer would still be printed at a .20mm height but with a 200% extrusion amount.

For adjustments over 100%, the first layer height goes up, but the extrusion amount does not. So a 200% first layer at 0.20mm would print at 0.40mm, but the extrusion would be the same as for a 0.20mm layer.

This was a while ago, and I don't know if recent updates have changed matters.

msmollin
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Re: Why the advice to set first layer to 80-90% in S3D?

Post by msmollin » Fri Jan 30, 2015 5:03 pm

90% seems to be the default in S3D (see attached).

So you're suggesting higher values that what's provided in the default profile? I have noticed I have issues every so often with adhesion, and given I print on blue tape I shouldn't really ever have them... was wondering if just putting down a wider first layer might help. (not to take off topic... adhesion issues have plenty of other threads dedicated to that topic).
Screen Shot 2015-01-30 at 11.00.18 AM.png
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Re: Why the advice to set first layer to 80-90% in S3D?

Post by jimc » Fri Jan 30, 2015 11:21 pm

yeah 90% has been the default forever. try bumping it up a bit. 125-140% height and a 125% width. you can go higher on the height if your printing at low layer heights like .1 or something like that. then bounce it up to 200%.

msmollin
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Re: Why the advice to set first layer to 80-90% in S3D?

Post by msmollin » Sat Jan 31, 2015 12:06 am

I have to wonder if that's because ye'olde recommendation (at least with the Makerbot Cupcakes/Thingomatics) was to crush the first layer a bit to force ABS adhesion. So you'd reduce the amount of plastic extruded via the first layer width setting.

That's just pure conjecture though. I will try out bumping these settings tonight!

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