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!
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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