Can support increase accuracy/definition of small features?

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Re: Can support increase accuracy/definition of small featur

Postby Phil » Tue Mar 14, 2017 8:11 pm

[quote="Jules"...print the text raised on the design in a different color.[/quote]

I think I will try that anyway.
The biggest PITA I had printing the covers on their sides was aligning the lettering into the cuts. There seems to be no way to align the pieces without lots of zooming in and very slightly hand-moving them.
I have yet to figure out why the STL files drop onto the S3D simulated build platform in an unorganized fashion. I build two CAD files along the same axes and at the proper depths from one another, and when they are imported, they end up at odd angles, and S3D's alignment tools do nothing to help.
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Re: Can support increase accuracy/definition of small featur

Postby ednisley » Tue Mar 14, 2017 10:24 pm

Phil wrote:fill in the lettering the black filament missed


It looks like the lettering extends only one thread width into the switch body, which means the black extruder must start and stop very accurately. That rarely works as well as I'd like.

If you extend the letters from a large black block embedded within the white switch body, then the extruder will run long enough to build up the proper pressure and produce better threads. Set the slicer to build the black infill first, then wrap the final black perimeter thread around the outside, and it should be just about perfect.

Switch legend printing.jpg
Switch printing: small vs. large legend areas
Switch legend printing.jpg (13.51 KiB) Viewed 1602 times


Of course, that means it must print small white areas. Because the layer consists mostly of white threads, maybe the extruder will do the right thing without any further attention. If not, move the black block further into the switch body, make the letters extend further, and the white areas can have two or three thread widths between the surface and the embedded black block.

If the switch must be illuminated from the rear, then an embedded black block won't work very well.

Also: will PLA get all melty in a summertime clockpit?
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Re: Can support increase accuracy/definition of small featur

Postby Phil » Wed Mar 15, 2017 12:46 am

"It looks like the lettering extends only one thread width into the switch body, which means the black extruder must start and stop very accurately. That rarely works as well as I'd like."
I made the lettering depth 0.003" I did not calculate how many lines that would be, but I can make it, say, three deep next time.

"If the switch must be illuminated from the rear, then an embedded black block won't work very well."
It is not illuminated, so no matter, there.

"Also: will PLA get all melty in a summertime clockpit?"
Definitely. This is the proof of concept phase; the real things will be made from something else.
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Re: Can support increase accuracy/definition of small featur

Postby ednisley » Wed Mar 15, 2017 3:35 pm

Phil wrote:lettering depth 0.003"


That's 0.076 mm, which explains why the letters look like crap.

You're working at the limits of 3D printer resolution, believe it or not, where getting good results requires incredible attention to the whole process. Folks printing Yodas from Thingiverse don't run into these problems …

The smallest printable feature must be larger than the thread width, maybe 0.40 mm (or whatever you told the slicer to use) for a 0.35 mm nozzle. The slicer may be reducing the extrusion rate to the absolute minimum and the plastic barely dribbles out of the nozzle.

make it, say, three deep


You'll get better results with even multiples of the thread width (0.80, 1.6 mm, etc), because then the slicer can lay in a complete loop of perimeter thread. If you make it two threads, maybe plus a little bit, then it should become a single closed loop with no infill. Getting the dimensions exactly right will require tedious fitting and previewing, because the slicer must consider more than just the nominal clearances: don't print anything before previewing the G-Code to verify that the slicer is doing what you expect.

Also, I think a single black lump inside the body with extensions to the surface for the letters will produce better shapes than you'll get from tiny isolated letter sections, because the extruder won't start and stop as frequently with either filament and you'll get better adhesion between the layers.
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Re: Can support increase accuracy/definition of small featur

Postby ksevcik » Wed Mar 15, 2017 7:22 pm

Any reason those have to be a solid piece? The letters would print MUCH nicer flat, so maybe you could have a generic cover base and print panels that you can glue on top.
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Re: Can support increase accuracy/definition of small featur

Postby Phil » Wed Mar 15, 2017 8:38 pm

[/quote]You'll get better results with even multiples of the thread width (0.80, 1.6 mm, etc)[/quote]

Looks as if I was off by a factor of 10. 0.8mm = 0.031" I will have to fix the file and try again.
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Re: Can support increase accuracy/definition of small featur

Postby ednisley » Wed Mar 15, 2017 8:50 pm

ksevcik wrote: The letters would print MUCH nicer flat


That means each stroke within each letter must be 1 thread = 0.40 mm, which is kinda chunky for small letters. The space between strokes and between adjacent letters must also be multiples of that width for good fill.

Assuming those switches are finger-sized, that makes the letters maybe 5 mm tall and they're packed very close together. I think there's not enough room for 3D printing at that scale: it's hard to draw a good-looking M, for example.

Doing the letters sideways makes the stroke width equal to the layer height, maybe 0.20 mm, and the between-stroke spacing will be multiples of that, so you get about twice the resolution. That's still on the hairy edge of being OK, but uppercase letters in a simple stick font should be do-able.
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Re: Can support increase accuracy/definition of small featur

Postby Phil » Mon Mar 27, 2017 3:10 pm

Here is another try. The switch cover is shelled to be 0.065" thick, so I made the black lettering the entire thickness. I also increased the size of the font, and I know, the NAV LITE needs to be centered. See what you think. (I find the back might look a little better than the front.)
Attachments
2017-03-27 09.04.48.jpg
2017-03-27 08.46.01.jpg
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Re: Can support increase accuracy/definition of small featur

Postby zemlin » Mon Mar 27, 2017 3:27 pm

If the back looks better ... is that related to where the printer starts the outlines? What happens if you flip the part 180 degrees on the bed?
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Re: Can support increase accuracy/definition of small featur

Postby Phil » Mon Mar 27, 2017 5:09 pm

zemlin wrote:If the back looks better ... is that related to where the printer starts the outlines? What happens if you flip the part 180 degrees on the bed?


Great question! I think I will try again with 0.25mm nozzles, and maybe make four, each rotated 90 degrees from the last.
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