“Optimal” layer height?

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Noren
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“Optimal” layer height?

Postby Noren » Fri Apr 06, 2018 6:36 pm

I see a lot of talk online for optimal layer height based on the stepper drivers step size and the pitch of the lead screw?
Is this something one should “worry” about?
And what is the optimal layer heights for the N1 if so?

I guess that people want the stepper to use full steps. So that all layers get the exact same height.

Jetguy
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Re: “Optimal” layer height?

Postby Jetguy » Fri Apr 06, 2018 9:49 pm

This is a non-issue IMO.
You have to understand where this information came from in the first place. It came from the Reprap community, people building printers what from ever junk pile and surplus electronics sources they could get their hands on. Tuning a stepper driver to proper rated spec motor current- oh no, not these people. I'm not saying all Reprap printers are this way, I'm saying this is the source of the very info on how to combat bad or less than optimal build decisions and attempt to get decent prints. Example https://www.reddit.com/r/3Dprinting/com ... ltiple_of/

So yes, say you built your printer from scrap bin parts. Then yes, this concern means that to minimize the error you have introduced by sloppy component choices, incorrect stepper driver settings, then yes, finding a repeating microstep position divisible by your mechanical and electrical system would ensure minimal error in Z axis position.

Prove it to yourself because I'll just go ahead and do the math for you, that way, you can test both non-divisible and divisible layer heights for artifacts basically proving the theory.
The facts are simple, we use 800 steps per mm for Z axis, and that is found via the touchpanel under the hardware menu.
The stepper driver driving this is set to 1/16th stepping mode, and the motor is a bog standard 1.8 degree stepper (AKA 200 full step/rev).
The leadscrew is 4mm pitch/rev. To check the math, 200 step per rev motor, times 1/16th microstepping is 3200 logical microsteps per rev, then we take the leadscrew pitch of 4mm distance per rev 3200/4=800 steps per mm.

The idea here being, knowing you are using 1/16th stepping, you want to land on the same microstep each and every time or put another way, you want the ideal layer height to be divisible on the full step value (200 steps/rev). If leadscrew pitch is 4mm/rev, and 200 full steps per rev, then 4mm/200 means that one full step is 0.02mm. So you want layer height a multiple of 0.02mm. Example is 0.2mm layer height is evenly divisible by 0.02 as is 0.1mm layer height. However, 0.15 is not evenly divisible, nor is 0.25 layer height. Starting at around 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, 0.30, 0.32, 0.34 these are the divisible layer heights for the N series using a 0.4mm nozzle. Using numbers that end in odd values are not divisible.
Again, I just want you to think about what is being said. Since the motor and leadscrew are connected mechanically in an arbitrary fashion, and when you set your Z homing switch for the proper layer Z gap for the start of the print, every printer is likely to be different what microstep it lands on (1 out of 16 microsteps). However, once past that, we then want to land on an evenly divisible distance so that we keep landing on the exact same microstep.

Jetguy
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Re: “Optimal” layer height?

Postby Jetguy » Fri Apr 06, 2018 10:40 pm

Again, as a test.
If you print at 0.20mm layer height, that is considered "ideal"
If you slice at 0.21 or 0.19mm layer height and print the exact same STL this would expose a non divisible layer height and if there are any differences.

I'm betting most already slice at common divisible heights already without even knowing.
I know I typically do 0.20mm or 0.30mm, and for fine prints 0.10mm anyway.
But the 0.15, and 0.25mm in theory are the ones to avoid if you follow this divisible rule.

zemlin
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Re: “Optimal” layer height?

Postby zemlin » Sat Apr 07, 2018 12:31 am

Jetguy wrote:This is a non-issue IMO.

That was my thought as well. At 800 steps/mm you're talking .00125mm/step. The smallest layer height I've ever used was .025, which is an even 20 steps per layer. Keep a 5 or a zero in that third decimal place and you're good on these machines.


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