Stripping FUD

[BCR751]

Well now that it's ruined you can test all sorts of stuff on it!

Good idea!

Doug

[Lemosteam]

FUD and FXD are very porous.  FUD more so than FXD.  This is because of the printing process.  With each hardening of each layer, the outline of the cross-section is hardened first.  Then the fluid trapped inside that section is hardened by the laser making cross hatching paths across the surface.  FUD cross hatching has larger spacing than FXD so there's more porosity.  Think of it as a fluid filled honeycomb.  The final process is to cure the remaining minute amounts of fluid that is trapped in between the hatching and each layer, and depending on how long Shapeways cures the part, some fluid may not be fully cured.

When you paint the model it embeds into those honeycombs because it is so thin and essentially becomes part of the material. 

Treating the current paint as a primer and cleaning it up as was suggested, you may have been able salvage the surface.

[BCR751]

FUD and FXD are very porous.  FUD more so than FXD.  This is because of the printing process.  With each hardening of each layer, the outline of the cross-section is hardened first.  Then the fluid trapped inside that section is hardened by the laser making cross hatching paths across the surface.  FUD cross hatching has larger spacing than FXD so there's more porosity.  Think of it as a fluid filled honeycomb.  The final process is to cure the remaining minute amounts of fluid that is trapped in between the hatching and each layer, and depending on how long Shapeways cures the part, some fluid may not be fully cured.

When you paint the model it embeds into those honeycombs because it is so thin and essentially becomes part of the material. 

Treating the current paint as a primer and cleaning it up as was suggested, you may have been able salvage the surface.

Thanks for the explanation, John.  I had no idea how the process works.  One other thing I noticed during this fiasco is that the paint, the top coat, never really appeared to dry thoroughly.  It always felt a bit tacky.  I don't know if this is related to the manufacturing process or not but I found it interesting.

What does the final product of the FXD look like?  Does it have the same surface texture problems that FUD has?  I plan on getting another shell done and have the choice of either medium.

Doug

[Lemosteam]

Yes but on a much finer scale.  FXD has more  and thinner cross sections and may also use a finer laser diameter.  This is why it costs more- it is simply a function of time.

The paint not drying may be a function of weeping, uncured resin that mixed with the paint.  The resin can only be cured by UV light.  I think some folks let the part cure in a sunny window (heat will warp so be careful) but i have never had to do this myself.

[peteski]

The reason for paint remaining tacky could be that some of the wax was leftover on the object  being painted.  It contaminated the paint, inhibiting the cure/drying.

As far as FUD vs. FXD resolution goes, quoting my own post ,

If the printer they use is ProJet HD 3000Plus (as Bryan Bussey mentioned), it is interesting to note that the only difference in resolution between FUD (UHD) and FXD (XHD) modes it the thickness of the layers (the x and y resolution is the same).

UHD Mode 750 x 750 x 890 DPI (xyz); 29μ layers
XHD Mode 750 x 750 x 1600 DPI (xyz); 16μ layers

The data sheet is available at http://www.priorityengineering.net/Documents/ProJet_HD_3000_Brochure_USEN.pdf

So depending on the orientation of the printed part, the layering effect on some surfaces might be as coarse as with FUD.

[Lemosteam]

Fair enough, but don't assume that all of the resin is fully cured during the process.  I have run the models prior to PRojet and I can tell you that there is a post curing process and that process cannot get to all of the resin.  Wax typically repels oil and water based products no? 

[BCR751]

I don't think wax was the problem in this case.  I left it in the Bestine for three days and scrubbed the bejeezus out of it with warm water and dish soap after it came out.  I think it was likely uncured resin as John says.

So, for the next shell, I guess there's no real advantage to FXD over FUD since I have no control over how the part is oriented during printing.  So, being basically cheap, I guess I'll go with FUD...again.

Doug

[BCR751]

I see there is something called "Black Hi-Def Acrylate" being used on Shapeways now.  Any idea how that would print?  It says it's smooth plastic.

Doug

[C855B]

There's a thread somewhere around here discussing it. I recall much unhappiness - warping and dimensional accuracy to mention a couple.

[wcfn100]

Yeah the black acrylic is prone to warping, but I don't know if anyone has tried to design around that just like some have designed around FUDs support material issues.  It does give a smoother surface for sure. 


Jason

[peteski]

Fair enough, but don't assume that all of the resin is fully cured during the process.  I have run the models prior to PRojet and I can tell you that there is a post curing process and that process cannot get to all of the resin.  Wax typically repels oil and water based products no?

Yes, wax will repel water, but wax, oil, and even heptane are all petroleum derivatives so I suspect that could mix just fine.

[Lemosteam]

I have been somewhat successful using an air eraser to smooth put some surfaces. If you have one, it might just work down those corrugation rows on the roof and sides, but sometimes a scrape with the right shaped tip does wonders.

[peteski]

I have been somewhat successful using an air eraser to smooth put some surfaces. If you have one, it might just work down those corrugation rows on the roof and sides, but sometimes a scrape with the right shaped tip does wonders.

That is an abrasive process and I'm not surprised that it works well to abrade the fuzz or paint off the surface.