Achieving the thinnest successful first layer

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dwallersv
Posts: 5
Joined: Tue Mar 26, 2019 3:11 pm

Achieving the thinnest successful first layer

Post by dwallersv » Sun May 05, 2019 2:25 pm

The standard Lulzbot 0.43mm first layer for pretty much all profiles works great if you don't have any feature detail on the bottom of the print. Much of the time, this is the case, so no problem. Sometimes, though, you have a feature -- like a fillet on an edge -- that is completely ruined by a first layer 2-3x as thick as all the others. Yes, sanding can largely correct this, but not completely, and sometimes that just ruins the appearance.

So, I've been working on getting well-stuck, thinner and thinner first layers as possible, trying to get to the regular print layer thickness. I've been able to squeeze this down to .2mm first layer with a .1mm print layer size, and get repeatable good prints. It's not easy, though.

I've had to shim the corner washers between the plate and the washer, to get the surface "truly" level during the probe at the beginning of the print. Some of this may be tolerances in the thickness of the glass/PEI sheet across its surface. Using 0.05mm thick parchment paper for shims, I was able to get a nearly symmetric print of 1-layer calibration squares with one corner adjusted (little triangle of paper inserted in between the washer and the plate on that corner).

Also, it is CRITICAL that you carefully clean the corner washers and the nozzle thoroughly before starting the probe. It takes only a tiny spec of dust, extra plastic, a hair -- anything -- to throw off things on the scale of 0.05mm. You won't see these errors with a 0.43mm layer thickness. Take it down to 0.2, or even 0.15 (got that to work too, but not consistent), and the smallest particle messing up the leveling probe will have the nozzle running on the glass in on or more quadrants.

So, that's my story to date on ultra-thin first layers. I've purchased some precision plastic shims with a range of thicknesses from 0.0005in (0.0127mm) to 0.0300in (0.762mm). These should allow me to dial this in very precisely.

Interested in a general discussion about this if anyone else has taken this challenge. How thin have you gotten with a successful first layer? What techniques did you use?

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mwester
Posts: 102
Joined: Sun Nov 26, 2017 8:02 pm

Re: Achieving the thinnest successful first layer

Post by mwester » Sun May 05, 2019 3:56 pm

I just use a raft.

kmanley57
Posts: 1111
Joined: Sun Feb 01, 2015 3:53 pm

Re: Achieving the thinnest successful first layer

Post by kmanley57 » Sun May 05, 2019 10:59 pm

I am lucky to get a PEI film/sheet that is or has a thickness tolerance of better than .1MM across it usually. I have had several that were pretty 'wavy' at times.
I will express my CRAZY ideas at any time! So you have been warned. None of my opinions are Lulzbots and can be wrong at any second.

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