Uneven "Flashing" on First Layer Using Color Resin with Form 3


#1

Using Form 3 machine - I’m getting about 1 mm of uneven, rippled “flashing” on my first layer using Formlabs Color resin (mixed as “Walnut” brown). It appears to be only the very first layer, as the rest of the models look perfect. I wanted to print these models directly on the build platform, but the models are so small that the 1 mm halo really affects the appearance. Trimming it off would be too labor intensive and result in a scuffed bottom. So I really need to figure out how to remove the flashing.

I checked the LPU and bottom of the tank and both are free of dust. Rigid 4000 resin prints fine with no flashing.

PXL_20210210_141911129_2


First Thoughts: Resin Color Kit
#2

I have some better photos that show the flashing on parts after removal from the build platform.

For troubleshooting, I did try both the Beta and the Default profiles for Color resin at 100 microns. Both exhibited the same problem.

Any ideas?


#3

I have been troubleshooting this issue on my own, as Formlabs support advised that it may be a faulty tank, which does not appear to be the case. They then said that models printed directly on the build plate may have this “skirting,” as they called it. Buy why?

My working hypothesis is that the additional laser power applied to the first layer, combined with reflections on the build plate surface, can work together to create an uneven perimeter.

To test my hypothesis, I modeled a circle with a chamfered bottom which was sliced in 0.1 mm increments and arrayed 14 times on the build plate, as illustrated below (the first 3 layers are not chamfered):

I then printed this file on several different substrates, each with the intention of testing the hypothesis that excess laser energy is being reflected around the perimeter of the first layer:

  • Direct to standard build plate
  • On shiny 3M aluminum tape
  • On green polyester tape (used for powder coating)
  • On amber-colored Kapton tape

As expected, the more reflective the surface, the more likely and worse the flashing/skirting. I also want to add that it is ONLY the first layer that is affected.

Printing directly to the build plate produced some skirting, as the surface is roughened. Yet, being aluminum, there were still some reflections.

Printing directly onto shiny aluminum tape produced the worst skirting, jagged, non-uniform, and extending > 1 mm from the first layer model perimeter. In fact, the first layer of the circles were not perfectly circular. Because the surface is shiny, more energy is reflected and distortions occur to the laser dot. Printing on shiny aluminum results in a first layer like this:

Printing on green polyester tape produced a small amount of smooth and uniform skirting. Because it is green in color, some of the UV energy was allowed to reflect off the aluminum on the back side. Unfortunately, standard resins do not adhere well to this tape, so it is not a viable option. Rigid 4000 resin does adhere well enough, at least for small models.

Printing on the amber-colored kapton tape produced < 0.1 mm of skirting–practically zero–as the excess energy reflected off the aluminum build plate is absorbed by the red color. Unfortunately, like the green polyester tape, standard resins adhere poorly to this material, making it unsuitable for use. See in the below photo, none of the models from the second column adhered to the tape.

I will next experiment with altering the aluminum build plate by oxidizing/anodizing the surface in an attempt to darken it and minimize its reflectivity.


#4

Nice work! What I can also recommend is checking the LPU window for dirt/smears, very often this kind of print defect is a result of optics that are not perfectly clean.


#5

In my most recent test, I applied a strip of 3M 3340 aluminum tape to the build platform, used isopropyl alcohol to remove the red ink from the surface of the tape, and then treated the tape with Birchwood Casey Aluminum Black, an acid solution that oxidizes and blackens aluminum.

This tape is normally very shiny and produces an extreme amount of skirting/flashing as the UV laser scatters and bounces off the reflective surface. However, the black oxidized layer prevented this and produced a perfect first layer with no skirting. The only problem is that the oxidized layer is very thin and is poorly bonded to the unaffected aluminum underneath, resulting in models potentially peeling off the oxidized layer and failing to adhere to the build platform. In the image, you can see one of the discs did just that.

Based on the tests so far, I would speculate that a properly anodized aluminum build plate dyed with a dark color would likely resolve the flashing issue with minimal effect on part adhesion.

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#6

The below photos show the problem in practice when parts are placed directly on the build platform.

For this, I used a brand new and unused build platform with the color resin I’ve been using.

As you can see, even though the amount of skirting/flashing on the first layer is minimal with a new build platform on account of the matte finish, it is still present and affects small parts a great deal.

Of note, the matte finish on the build platforms is not abrasion resistant and rubs off easily with a paper towel and isopropyl alcohol, eventually wearing down to an increasingly shiny layer of aluminum. So the skirting will only worsen as the build platform is used.

Also notice how the skirting is not a consistent width around the perimeter.