Printed Text: Recessed or Raised?

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Gwhite
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Joined: Tue Jul 11, 2017 3:38 pm

Printed Text: Recessed or Raised?

Post by Gwhite » Tue Aug 15, 2017 2:17 pm

I need to add labels to the side of a print, similar to the "Maker Gear" text on the test bracelet that they recommend for your first print. That text comes out pretty well, and is 9 mm tall. I'm going to try for 8 mm tall letters.

Both in terms of readability and printability, is there any particular advantage to doing the letters raised vs recessed?

To make them stand out more, I was originally thinking about making them recessed & filling the text, or at least running a fine point marker around in the grooves. However, I've had problems labeling test parts with a marker because the thin ink tends to wick along the grooves between layers. Trying to clean it up with alcohol just makes things worse. With raised lettering, I could put down a thin coat of more viscous paint on a surface & then press the raised lettering into the paint.

Any tips or suggestions would be appreciated.

Thanks!

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sthone
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Re: Printed Text: Recessed or Raised?

Post by sthone » Tue Aug 15, 2017 2:25 pm

For recessed you can try nail polish with a pen tip... it suppose to work a lot better than markers or paint because its a bit thicker.

If you get the ones with a combo brush/pen tip you could probably do both recessed and raised.

-Steve
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Phil
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Re: Printed Text: Recessed or Raised?

Post by Phil » Tue Aug 15, 2017 6:15 pm

Nail polish is good, but just remember, it contains acetone which affects plastics, particularly ABS. You can see the shading on these prints.
I have experimented with this to make replacement switch covers for my airplane. The unfortunate part is that I am trying to make very small print, and the parts never come out to my satisfaction.
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Gwhite
Posts: 254
Joined: Tue Jul 11, 2017 3:38 pm

Re: Printed Text: Recessed or Raised?

Post by Gwhite » Tue Aug 15, 2017 8:42 pm

Considering the size, those look pretty good. I will mostly be using PLA. I'm not sure how well it tolerates acetone...

I also have some special lacquer sticks designed for filling engraved lettering & marks on machine dials & such:

http://www.markal.com/solid-paint-markers/lacquer-stik/

However, the lettering will be pretty coarse compared to what these are usually intended for.

One option would be to fill recessed letters, and then sand the flat surface to remove any leakage.

In any event, it sounds like printing the letters recessed, rather than raised, is the usual approach.

Phil
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Joined: Mon Sep 19, 2016 7:49 pm

Re: Printed Text: Recessed or Raised?

Post by Phil » Wed Aug 16, 2017 9:52 pm

I printed some nylon switch covers without lettering that I intend to engrave with a laser. There is a local 'maker space' that has the equipment. It costs $35/month, so I want to try a few things at once to make it all worthwhile.
I will post my results.

Gwhite
Posts: 254
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Re: Printed Text: Recessed or Raised?

Post by Gwhite » Wed Aug 23, 2017 12:39 am

I did a bunch of experiments using recessed lettering, and came up with a result I am pleased with. The model was created using AutoDesk's Fusion360, with 8 mm tall letters. The width of the recessed lines is ~ 0.5 mm or less.

I'm using eSun PLA "Plus" to make a block to hold some deburring tools in my shop. I printed the first attempt at 215C, and as I expected, if you try to fill in the letters with an Ultra-Fine Point Sharpie, two things happen: 1) the tip is too wide to get down into the bottom of a lot of the letters, and 2) the ink tends to wick into the passages left where the filament didn't fuse completely. It's hard to keep the Sharpie in the grooves, and if it bounces out, you have a mark that you have to clean up with alcohol. That thins out the ink even further, and it REALLY wicks into the print, leaving lots of fine black lines embedded in the plastic.

I tried using a "lacquer stick", which is designed to rub into sharp edged engraving grooves on metal dials & such. It didn't go into the grooves very easily because they are somewhat rounded, and it made a mess in the fine grooves between layers. The next dodge was to coat the lettering with "Penetrol", which I had kicking around. This is a very thin clear paint product that (among other uses) can be used to seal things like rusted steel. It's very runny, and wicked into the print very nicely. It takes a day to cure, but it stopped the ink wicking very effectively:
Low Temp Label Test.jpg
I had to re-print the model to fix some minor design issues, so I kicked the extruder temperature up to 220C to try to minimize the little capillaries between the layers. I also ordered some 0.2mm markers (Sakura "Micron" from Amazon) to get down into the grooves better, and printed a subsection with a couple labels to check out before I screwed up my final print job.

Increasing the temperature did make a dramatic improvement in the wicking problem, but it wasn't a complete cure. Using Penetrol on top of the high temperature print worked really well, and allowed cleaning up errors with alcohol without any issues (the "S" done in the Penetrol label was cleaned with alcohol, which is why it looks a bit anemic):
High Temp Label Test.jpg
I coated the face of the final block with Penetrol, and then tried the 0.2 mm markers today. They are a big help in getting down into the label grooves, but I still slipped up a few times & had to clean things up with alcohol. The tops of the grooves are somewhat rounded, so the alcohol cleanup tends to get down into the grooves a little, which leaves very fine letters. I could fatten them back up a bit by going over them with the Ultra-Fine Sharpie. I think part of the trick is to use a cloth or a cotton swab that is only a slightly damp with the alcohol so it only cleans the outer face. The final result is quite readable, and doesn't show any significant streaks unless you look REALLY closely.
Final Labels.jpg
Although the higher extruder temperature helped seal the "pores" a bit, it wasn't a complete cure. I had warping issues that would probably be helped by going back down to the lower temperature. Fortunately, the Penetrol does a good job of sealing up the pores in the low temperature print, so going hot isn't necessary.

Phil
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Joined: Mon Sep 19, 2016 7:49 pm

Re: Printed Text: Recessed or Raised?

Post by Phil » Fri Aug 25, 2017 9:58 pm

I played with the laser engraver for a while. The big adjustments you make on it are speed and power. I used all 50W of the laser, and these are results of speed changes. Note that too slow = melting. I also varied the font size and tried Regular and Bold.
I then used black nail polish to fill in the engraving. I brushed, then wiped off the excess, but this left too little color in the grooves. I put more on thickly, then sanded. This worked pretty well, especially on the PLA, which had more discoloration around the engraving. The nylon parts look pretty good, so I think I have my solution. I may also try an enamel paint. Does anyone know the best paint type for nylon?
I also tried to dye the clear nylon. This is 1/8 TSP of Tan RIT dye per cup of hot water and 1TBSP of vinegar. Not my ideal solution.
Now, if I could find some white or natural colored nylon!
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Phil
Posts: 192
Joined: Mon Sep 19, 2016 7:49 pm

Re: Printed Text: Recessed or Raised?

Post by Phil » Mon Sep 25, 2017 10:01 pm

I have had some luck with a laser engraver. I printed the switch cover in CF-Nylon, then painted it with an off-white paint, then laser engraved it. I also had to design and print the orange jig in order to get the lased surface perpendicular to the laser beam. The switch covers are quite stiff due to the CF, so they had to be whittled somewhat to fit.
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On the engraver.
2017-09-22 15.29.50.jpg
As installed in the airplane.

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