First Layer Width - M3 SE help needed

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First Layer Width - M3 SE help needed

Postby Evan » Wed Nov 29, 2017 7:45 am

Hi All,

I have yet to work this one out and after months of trying thought I'd ask here. When printing, my very first layer is always wider then the walls/outline above it. I have calibrated Z-Height time and time again, both manually and with the MakerGear "test patch" process through Octoprint. I've leveled, calibrated extrusion flow following the thread here on the forums, etc. But I always have a slightly wider first layer. I use S3D for slicing. PLA is less noticeable, and I can live with it but when I print with ABS it is more apparent. Also, when printing the 20mm x 20mm x 2mm calibration object my widths and heights are always slightly under. Would anyone have any idea's on what I might be missing or doing incorrectly?

Thanks!
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Re: First Layer Width - M3 SE help needed

Postby sthone » Wed Nov 29, 2017 3:34 pm

Your first layer is usually always going to be a bit wider (they call this elephant's foot) because you are squishing the first layer into the build platform so you get good bed adhesion. You can play with the bed height to try and eliminate this but you will give up some bed adhesion. The best way to eliminate the problem if you are the one designing the parts is to add a chamfer (say .02" or .5mm) to the bottom edge and this helps eliminate the problem.

If the height of your calibration cube is off you can try playing with the first layer height maybe? Although If the dimension of you calibration cube are off over the entire width of the cube too it might be an extrusion problem.

Keep in mind you are pushing around melted plastic so your dimensions are only going to be so accurate.
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Re: First Layer Width - M3 SE help needed

Postby Evan » Wed Nov 29, 2017 10:37 pm

Ok, thanks sthone. Good to know and it seems I might not being doing anything terribly wrong after all. A relief. I'd still like to reduce that first layer width with ABS, hopefully without compromising adhesion. Oh, mostly I am printing customers own designs, so no real chance to modify the bottom to help reduce that first layer width. Appreciate the help, thank you!
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Re: First Layer Width - M3 SE help needed

Postby zemlin » Fri Dec 01, 2017 2:08 pm

Regarding dimensional accuracy, you might take a look at this thread: viewtopic.php?f=3&t=3885&p=32417#p32417
For every new material or setup (nozzle size, significantly different print speed, layer thickness, material/supplier) I will print one of the calibration cross models and calculate new scaling and offset numbers. I found the Z to be pretty consistent as one would expect, but on my M2 it still needs to be scaled to be accurate.

This works very well for me.

How much you need to squeeze the first layer also depends on the build surface and how fast you are laying down the first layer. I normally run at 50% speed on the first layer, but have gone as slow at 25% if a material isn't laying down well. I can normally be close to zero spread on the first layer.
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Re: First Layer Width - M3 SE help needed

Postby willnewton » Sun Dec 03, 2017 2:18 pm

Two replies with different takes on solutions and both are correct.

The last step in my design process for 90% of my prints is to add a micro chamfer to the surface touching the bed face. If it is another persons design, you could request thay integrate a microbevel if it is needed.

The first step in my printing process is determining appropriate ratio of squish to print base complexity and overall print design.

The balance of dimensional accuracy vs. adhesion is something you will learn as you print more. I find myself leaning either way as the print demands.

Sometimes that base needs to be very accurate and sometimes you are trying for the third or tenth time to get a difficult print to work out and you just have to say “You are gonna stick this time you son of a ...”
I'm finally back to where I started two days ago!

A thread with some stuff in it I update every once in a while. http://forum.makergear.com/viewtopic.php?f=8&t=9
See some of my stuff http://www.thingiverse.com/willnewton/about
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Re: First Layer Width - M3 SE help needed

Postby zemlin » Mon Dec 04, 2017 6:30 pm

willnewton wrote:The last step in my design process for 90% of my prints is to add a micro chamfer to the surface touching the bed face.
I often do this too. A chamfer of 1 or 2 layer thickness will often hide any first-layer-spread issues. Plus I figure it will lay down the second layer of perimeters (and third or more, depending on the chamfer size) centered between the first perimeters which should yield a better perimeter bond at bottom face as well.
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