martincho
Posts: 14
Joined: Wed Sep 04, 2019 12:45 am

How to use "First Layer Settings"?

Wed Sep 04, 2019 9:27 pm

Trying to get a better first layer. It seemed obvious that "First Layer Settings" is where this might happen. However I am seeing some weird behavior.

First, if I change "First Layer Height" to, say 50%, what I get is a thinner first layer AND I also get about half the extrusion thickness printed. In other words, instead of the lines being smooshed they are thin little hair-sized lines that don't touch each other.

I tried leaving "First Layer Height" alone and only changing "First Layer Width" to 125%.

The preview window shows the lines smooshed together as one would expect. However, the machine is printing thicker lines farther apart from each other. So, it looks like the actual G-code has lines that are 125% wider but also spaced 125% farther apart (or something like that)...which means the infill consists of a bunch of thicker lines that don't bond to each other.

"First Layer Speed" seems to work as advertised. I don't actually know if it is affecting anything else as the other two settings seem to. I have it set to 20% and that seems to be what I am getting.

Are these known bugs?

If not, how do these settings work?

How do I smoosh down the first layer, get the first layer infill lines to bond to each other if not with these settings?

I found the "Global G-Code Offsets" in the G-Code tab. I can use that to drop down the first layer. However, this drops down the entire part by whatever value I put into the "Z-Axis" field. Which means that my part becomes that much thinner.

Color me confused.

Thanks for your help.

wirlybird
Posts: 1216
Joined: Sun Jul 17, 2016 1:32 pm

Re: How to use "First Layer Settings"?

Thu Sep 05, 2019 9:53 am

When you reduce first layer height below 100% it also reduces the extrusion multiplier I believe.
Use the global offsets to get more squish.
I usually have my first layer height at 100-120% depending so to compensate for a bed that isn't perfectly flat in all areas.


When you increase the first layer extrusion width it also increases the spacing.
I think the idea of increased first layer extrusion width is to help get better adhesion with a wider extrusion.

martincho
Posts: 14
Joined: Wed Sep 04, 2019 12:45 am

Re: How to use "First Layer Settings"?

Thu Sep 05, 2019 11:22 am

wirlybird wrote:
Thu Sep 05, 2019 9:53 am
When you reduce first layer height below 100% it also reduces the extrusion multiplier I believe.
Use the global offsets to get more squish.
I usually have my first layer height at 100-120% depending so to compensate for a bed that isn't perfectly flat in all areas.

When you increase the first layer extrusion width it also increases the spacing.
I think the idea of increased first layer extrusion width is to help get better adhesion with a wider extrusion.
If that's the case this feature is seriously broken. At the very least it should have a clear indication of what it does. For example, there's plenty of space there to show the adjusted extrusion multiplier value.

Now I am wondering if the "First Layer Speed" setting also has unintended consequences. This would actually explain some of what I am seeing. If that's the case I think the only safe way to deal with the first layer would be to create a new process with settings unique to the first layer and then add processes as needed to address the rest of the print.

I don't necessarily like the global offsets option because it shoves the entire part down by whatever amount you enter. In other words, if I am printing a part that is supposed to be 10 mm high, and I set a Z global offset of, say, -0.25 mm, my part comes out at 9.75 mm of height, at best.

One ought to be able to deal with the first layer without affecting overall part accuracy. And it should not be that hard.

wirlybird
Posts: 1216
Joined: Sun Jul 17, 2016 1:32 pm

Re: How to use "First Layer Settings"?

Thu Sep 05, 2019 12:03 pm

I think you need not over complicate the first layer settings.
Personally I use first layer height of 100-120%. I move up toward 120% if I see minor low spots and I might add a little -Z offset to give a little more squish.
I generally leave the first layer extrusion width at 100% unless I have a specific reason for more such as a large ABS print and I want to try to improve the adhesion a bit.

First layer speed is what it is and seems to be fine. I generally use 40-50%.

On the global offset. If you are trying to get more squish on the first layer by going to 50% then what is the difference of entering that number into the global offset?

If you have a 0.2mm layer height and do 50% for the first layer then you move down 0.1mm.
If you leave the first layer height at 100% and add a -0.1mm Z offset (50% of layer height) you have done the same thing except you are still at your normal extrusion multiplier so you get the squish you are looking for.

martincho
Posts: 14
Joined: Wed Sep 04, 2019 12:45 am

Re: How to use "First Layer Settings"?

Thu Sep 05, 2019 12:09 pm

I've been using 100% but the results have not been consistent. My build plate is ridiculously flat for a 3D printer (I machined it flat on my Haas VF-2 industrial CNC mill)...so that's not the problem. There's some math voodoo happening somewhere that I don't yet understand.

Not sure I understand going to 120% height for the first layer. Wouldn't that mean less squish? Or do you do that and then add a negative g-code z offset to push it down?

Thanks for your feedback.

wirlybird
Posts: 1216
Joined: Sun Jul 17, 2016 1:32 pm

Re: How to use "First Layer Settings"?

Thu Sep 05, 2019 12:16 pm

If my first layer extrusions look good but maybe have a little gapping between I might add a -0.01 Z offset and see.
Then maybe increase to -0.02 etc but first I make sure my leveling is giving a proper nozzle to bed gap.

Going to a higher first layer height will allow you to squish it a bit more and account for any little low spots on the bed.


Mostly though you need to analyze the first layer and determine what exactly is an issue.
Are the extrusions not touching? Check the nozzle to bed gap set in the printer is not too big.
Mostly adjust the first layer by fine tuning the bed level, depending on the printer of course, then fine tune more with the software.

martincho
Posts: 14
Joined: Wed Sep 04, 2019 12:45 am

Re: How to use "First Layer Settings"?

Thu Sep 05, 2019 12:41 pm

OK, I'll go through some of these points and see what results I get.

For reference, I am printing using a 0.8 mm nozzle. My z home position is set to somewhere between 0.10 and 0.15 mm using feeler gauges, not paper. My z-home limit switch is repeatable within about 0.0025 mm (0.0001 in). Finally, I use an optical sensor to mesh level the bed before every print. I run all calibrations after both the bed and hot end have achieved operating temperature and had plenty of time to stabilize (2 to 5 minutes).

My gut feeling right now is that I am fighting the interaction between S3D settings and possibly Duet firmware math as well. The fact that the first layer height and width settings actually modify the extrusion multiplier sure didn't help.

wirlybird
Posts: 1216
Joined: Sun Jul 17, 2016 1:32 pm

Re: How to use "First Layer Settings"?

Thu Sep 05, 2019 12:50 pm

Width doesn't modify.
Height only changes multiplier if you go below 100% first layer height.

martincho
Posts: 14
Joined: Wed Sep 04, 2019 12:45 am

Re: How to use "First Layer Settings"?

Thu Sep 05, 2019 1:49 pm

Sorry. Width changes the spacing. So, if you had lines that did not touch and you change the First Layer Width parameter both the extruded width and the spacing between lines increases.

BTW, this is not displayed at all in the preview window. Regardless of the width setting the traces are the same size and they always touch each other.

CORRECTION: What isn't displayed in the preview window are the gaps between traces. No matter how you set width the lines always touch.
Last edited by martincho on Thu Sep 05, 2019 2:23 pm, edited 1 time in total.

martincho
Posts: 14
Joined: Wed Sep 04, 2019 12:45 am

Re: How to use "First Layer Settings"?

Thu Sep 05, 2019 1:53 pm

Forgot to mention this. I've been reading through the "Simplify 3D Settings" PDF by Clint Goss. In it he states (page 34):
If your First Layer Height is below 100%, the extrusion amount will remain the same, only the Z-will
change, but if you increase First Layer Height above 100%, the extrusion amount will scale accordingly.
http://www.breathflute.com/pdf/S3D_SettingsCG.pdf

Given my experience so far and what's been said in this thread this assertion seems to be wrong. Did these settings work differently in the past?

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