Problems with Shapeways "Frosted Detail" 3D printing plastics

3Dsf

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So I thought I'd like to get a conversation going on this one to share people's experiences. And basically, it's the problem of cleaning the wax off "Frosted Detail" acrylic plastic used by Shapeways. (Frosted Ultra Detail/FUD and Frosted Extreme Detail/FXD) And the problem of FD crystallization.

FUD/FXD 3D printers

The FD products are interesting in that they use dual materials to print. The printers produce plastic parts using an ultraviolet-cured liquid resin. But with 3D printing technology that uses liquid resin you've got a problem if you have any overhanging areas. The resin would just flop down while it hardens, making overhangs impossible. So you normally have to include a bunch of support sticks to carry the weight of the model, which you have to cut off - and which leaves little ugly nubs. Or you use what Shapeways' "Projet" brand printers use - a wax support material.

It's a pretty ingenious approach. And expensive, as you need dual jets. The wax is used to support the weight of any overhanging plastic during the printing process. When the objects are printed, Shapeways techs take them to an oven and the wax is mostly melted away. They're then cleaned in an ultrasonic cleaner.

The first problem - cleaning

The first issue is that the parts are never totally free of residue when you receive them. There's always a bit of oil or flaky wax stuck to the parts when they arrive. So before you paint your parts it's pretty important to give it a good clean. The difficulty is how to do it without damaging the parts. I generally find that running really hot tap water, over a sieve to avoid part loss down the drain, and brushing everything with a medium coarse paintbrush, works fairly well. It just takes bloody forever, though.

I've experimented with ultrasonic cleaners. The first was one of those plastic ovoid cheap pieces of garbage, but it did nothing other than make noise. I have a more heavy duty one now, with a built-in heater, and it seems to do a better job. Especially with hot water.

However, even with the ultrasonic cleaner you still need to do a lot of physical cleaning afterwards with a brush. There's just something about the physical brushing action to loosen the material that ultrasonic cavitation can't seem to do. If you don't, then the wax seems to turn into this pure white crumbly strange sort of material that you definitely don't want to paint over. (the white crumbly problem is worsened by soaking in water) The wax remains especially on rough surfaces, such as curves.

I tried using an ultrasonic cleaner with isopropyl alcohol (suspending the loosely covered alcohol container in a water bath, to avoid the risk of explosions from alcohol fumes) and that made the plastic more brittle and a pure opaque white colour, which isn't reassuring. I haven't tried any other solvents.

The best results I've found have involved subsequently scraping of all accessible parts (especially flat surfaces) with the flat edge of a sharp blade, then brushing with a stiff bristled brush dipped in isopropyl alcohol. Again, huge amounts of time.

The second problem - crystallizing

This is the more troubling issue. After FD parts have been sitting around for a while, they seem to generate these odd whiteish crystals of material. I've definitely seen this on parts that I haven't cleaned yet that were stored in their original Shapeways ziploc bags. The big problem is that nobody seems to know exactly what's causing this.

So. Is it wax residue? Is it oxidizing or being exposed to ambient air moisture? Does it worsen if kept in a sealed ziploc bag, or kept out in the open?

Worse, is it the actual resin breaking down? Is it because the resin didn't get enough UV light to harden? Is it the wax interacting with the resin and causing longterm damage? (ie: are the crystals purely on the surface of the resin, or is the resin eroding?)

The really bad part is reports that people have seen the material migrating through a paint layer. So sealing it with primer may not be adequate to prevent the problem.

I'm really hoping it's basically problems with the wax. Since the wax and the plastic are similar in colour and translucency, people may not always realize that there's still residue on their models before they paint. The problem of crystallization seems to occur in complex and rough surfaces on my models, which is where you'd expect wax residues to remain. But who knows?

Anyway. This is all new territory as it's still pretty new technology. Any thoughts on these issues? Thanks!
 
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The resin from that type of printer can use a bit more time curing so it can help to put it in the sun for a little bit. Part of the weird surface is due to the support material being a different resolution from the resin.
 
I've had no issues whatsoever, apart from breakages caused by the delicate nature of the prints I had made. My Palomino and Cygnus antenna are all fxd -primed and painted- with no issues.
I didn't attempt to scrub anything, just painted as is. In my experience, if shapeways clean it- it's clean!
 
Here are some examples of the issues.

After cleaning with hot water and a drop of detergent in an ultrasonic cleaner. You'll notice that there's a lot of white crusty powdery buildup on the interior of the snowspeeder canopy (the upper part). This appears to be wax residue breaking down in the water, but adhering to the plastic.

crusty-wax.jpg

After cleaning with heated alcohol in an ultrasonic cleaner. The translucent material has turned pure opaque white, which is a bit concerning. The plastic is pretty clean, but less flexible, and has the weird transmogrified outer layer.

I need to see how it holds up after being primed and painted.

alcohol.jpg

The ideal situation. This is a piece that I cleaned with hot water and a drop of detergent in an ultrasonic cleaner. I then manually scraped off all the white powder residue, using a knife. This has yielded pretty perfect clean plastic, but took forever.

cleaned.jpg

Now this is the really troubling situation. This is a piece which is experiencing crystallization. It's hard to tell in this photo, but if you look closely you can see a ton of white speckles. These are reflective, slightly rainbow-sheened, crystals of mystery material.

crystals.jpg
 
That little desk looks great.The top two pictures I could live with, but the bottom.......
That looks a mess.
Have you shown the image to shapeways- they may be interested.
If a fault is shown, they are generally pretty quick to print out a replacement.
 
I have zero experience with these prints or material, but just a thought. If it's a paraffin based wax, that is soluble in White Spirit (I think you call it Mineral Spirits in the US) so it might be worth letting the part soak in that for a while before washing off with detergent.

it would be prudent to check that the resin itself isn't affected - maybe on a spare/sacrificial piece.

Could the white material that is appearing just be a thin layer of wax that is being roughened up by the cavitation process?
 
I haven’t tried anything harsher than isopropanol. I know a lot of people who have tried various solvents report issues with damage to the plastics. I have enough random test prints that I could sacrifice some bits to test, I suppose.

It could be that the cavitation is causing minor surface damage to the resin, softened by the hot alcohol. That’s a possibility as it’s occurring on flat clean surfaces as well. All pretty uniformly.

Problem is we’re all just guessing here. And Shapeways have just said, “we’re looking into it” for over a year.
 
Fascinating. If I'm not mistaken, alcohol tends to attack acrylic, fogging or even cracking it. So if this is an acrylic material, your alcohol-based cleaning methods might be a dead end that's actually making things worse. I'd stay away from solvents in general, but the mineral spirits may be worth a try.
 
I have made a ton of parts using these materials from shapeways. I tried the tire cleaner solution and didn't find it worked any better than warn soapy water and a toothbrush. Parts that don't require a wax support don't seem to get the crystallization, so I'm blaming the wax and interaction with cleaning. I do have a part that has the crystals coming through primer, but after brushing it off it hasn't returned. Since I started the toothbrush\warm water/ dish soap, I haven't had any issues.
 
Okay. So I did some further tests with mineral spirits/paint thinner. Basically soaked some test prints for maybe 15 minutes.

The good news is that the piece with crystalline sparkles came out perfectly clean without any scrubbing.

cleaned.jpg

Of course, I have no idea if the crystals will recur.

It also seemed to loosen some of the crusty crud on the snowspeeder canopy, though there's still a lot of white discoloration.

Bad news: a thicker plastic cylinder appears to have cracked internally from the treatment. So that's not great. It also didn't remove the buildup of wax on the interior curved surface - I still had to scrape it.

cracking.jpg

Plus now I have a bloody headache from the stink of the chemicals!
 
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I soak my parts in Nitro spitit and use a brush to wipe off the wax. After drying I use MRP primer and then what ever paint I need...np problems what so ever so far.

cheers
Uwe
 
What is Nitro spitit?

Sent from my Nexus 10 using Tapatalk

Here in Germany it is called "Nitro Universal Verdünnung"... a universal thinner that you also use to wash brushes or to wipe off already dried paint to a certain degree. It smells bad, is not healthy but very good! ;-)
 
>Have you tried methylated spirits?

Nope. I've never thought of ethanol as the greatest cleaning solution. Isopropanol evaporates more cleanly.

Have you given it a go?
 
Here in Germany it is called "Nitro Universal Verdünnung"... a universal thinner that you also use to wash brushes or to wipe off already dried paint to a certain degree. It smells bad, is not healthy but very good! ;-)

It's known as cellulose thinner in UK/US.
 
For my Falcon parts, I went with soaking and agitating in isopropyl alcohol and rinsing in luke warm water. Very hard to get into the struts for the dish and it’s too delicate to scrub. However, most seemed quite quite clean so I will find out if that was enough (they are now primered). Sounds like the cleaning approach may definitely need to differ depending on the shape.
 
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