Shapeways MEM

[Dalhousie]

I ordered a 1:72 scale Shapeways Mars Excursion Module http://www.shapeways.com/model/1091605/1-72-mars-excursion-module-w-ascent-stage.html?materialId=6

It arrived yesterday, it's gorgeous.

I would like to detail it but it is so beautiful and so expensive I am afraid try.  So I will just look at it for a while.

Any experience with working with this type of 3D printed material?  Especially filling, sanding, cutting and gluing, also bonding different types of plastic.

[Ronpur50]

It really is beautiful!!  I may have to get the 1/144th scale one.

[Hobbes-22]

Looks like you ordered it in 'White Strong and Flexible'? It's really tough stuff. You can barely cut it, I resorted to sawing to separate my WSF parts from their sprues. It's also a bit flexible, so no need to worry about breaking it.
Because it's a sintered powder, you can't get a smooth surface by sanding. You'll have to use a filling primer.

I've got some more tips in the assembly instructions for my Falcon 9 model: https://www.shapeways.com/forum/index.php?t=msg&th=14981&start=0

[Dalhousie]

Looks like you ordered it in 'White Strong and Flexible'? It's really tough stuff. You can barely cut it, I resorted to sawing to separate my WSF parts from their sprues. It's also a bit flexible, so no need to worry about breaking it.
Because it's a sintered powder, you can't get a smooth surface by sanding. You'll have to use a filling primer.

I've got some more tips in the assembly instructions for my Falcon 9 model: https://www.shapeways.com/forum/index.php?t=msg&th=14981&start=0

It reminds me of melamine, brittle but strong and slightly elastic.  I have no plans to drop it and find out!  Some parts are really thin.  Good to know they will stand up to use.  What did you saw it with?

Thanks for the filling tip, that's what I figured. How do you mind bonding other plastics, like polystyrene? I was thinking of using a LM kit as a source for things like quads, antennae etc.

Thanks for the link too.

[Hobbes-22]

I used a Tamiya mitre saw.

WSF accepts CA glue. Because it's porous, it'll absorb a lot of glue. I've also used PVC glue to attach WSF to PVC, but this glue will melt polystyrene.

[Dalhousie]

I used a Tamiya mitre saw.

WSF accepts CA glue. Because it's porous, it'll absorb a lot of glue. I've also used PVC glue to attach WSF to PVC, but this glue will melt polystyrene.

I used PVC glue to attach the ascent stage engine to the ascent stage(it comes as a separate piece).  Hasn't fallen off yet, but I noticed the porosity.

[Dalhousie]

I have noticed five issues with the model.

1) The landing legs are fully deployed, which means the model stands about 10 mm higher than it should (scale 72 cm).  This means it will look slightly odd when placed on a diorama setting, which is what I had intended.

2) The eight ascent stage tanks are too spaced compared to the drawings, resulting in the space next to the habitat module being lost.  This space is supposed to be where the airlock hatch would have been. 

3) There are a few other mismatches with the drawings I have of the MEM, although none are serious.  The Position of the landing legs have been rotated, so that two line up with the descent stage thrusters, whereas in the drawings none do.  The thrusters are also smaller.  I wonder which drawings they used.

4) There are no ascent stage thrusters, the drawings show four sets.  Mind you, I don't blame Shapeways for leaving them off, they would have been hard to print and it's not near from the drawings anyway how they are attached.  The look rather awkwardly placed, three between tanks and one on a tank.  It is hard to see how tanks could have separated without taking the thrusters with them.

5) The docking hatch is only 9 mm wide (scale 648 mm).   Measuring of the drawings indicate the docking hatch should be 11 mm (scale 813 mm).  I think this is because the ascent stage cabin is slightly too tall.  From the drawings it should be 41 mm, it is currently 44 mm

Of course this is a 1968 design, by the time the MEM flew in the mid 70s there could have been many detailed changes.

Edit - added fifth point

[Ronpur50]

I used a Tamiya mitre saw.

WSF accepts CA glue. Because it's porous, it'll absorb a lot of glue. I've also used PVC glue to attach WSF to PVC, but this glue will melt polystyrene.

I always use the gel type of CA, and it hasn't absorbed too much.  Painting was trial and error.  But using an epoxy paint worked great the last time I built a Shapeways printed model.

[Hobbes-22]

4) There are no ascent stage thrusters, the drawings show four sets.  Mind you, I don't blame Shapeways for leaving them off, they would have been hard to print and it's not near from the drawings anyway how they are attached. 

That's not a decision Shapeways makes, that's up to the designer who created the CAD drawing. Shapeways just prints what you send them. The only thing Shapeways do is indicate if a drawing contains structures that are impossible to print. 

[roma847]

Hello,

a friend in the ARC Forums (Hotdog) has problems with strange effects of Frosted Ultra Details by Shapeways. The parts looked nice when he first got them, but after rinsing them according to Shapeways suggestion, the surface frosted over in inconsistent patterns.

Have you also observed such effects?   But maybe hanging there together with the size of the parts, his SSME bells are quite small in 1:144, as you can see.

[Hobbes-22]

Yes, I've seen that. Frosted Ultra Detail (FUD) parts are printed using a support wax. This material makes the FUD look translucent. When you wash the part in white spirit, the wax dissolves, and what's left is a white resin with a slightly grainy surface texture.
You can then sand the part smooth and it'll stay that way. I've got a few parts lying around that I cleaned and sanded a few months ago, and they're still smooth.

You can also get parts that dry up part translucent and part white. This depends on the orientation of the part, and where the support wax touched the part. It happens on parts of all sizes. The design of the SSME makes it difficult to sand it down. A toothbrush or cotton swab is not abrasive enough to remove the grains, but sandpaper will take it right off, without removing the model's features.

edit: I see where Hotdog went wrong, he washed the parts in water only. I'll head over to ARC and stick my oar in...

[roma847]

Thank you once want to look over, he is pretty desperate with this sensitive stuff.

[Dalhousie]

Back to the MEM.

I have decided on a mostly Viking look.  The Vikings were mostly bare white surfaces, with gold and aluminium details and thermal blankets on the tanks.  This may reflect the martian thermal environment being quite different to the lunar surface.

I'll have white for the descent stage, aluminium, probably foil if I can manage it for the ascent stage cabin, this will provide a contrast.  I'll go for thermal blankets on the crew tunnel, surface shelter and tanks, which are filled by cryogenic propellants.  The ascent stage core I may paint gold, for simplicity.

I have eschewed gold foil, because of difficulties in working it onto the fixed parts and my lack of experience.  Surgical tape is easier to experiment with.

Suggestions on using surgical tape to make thermal blankets appreciated, especially working on the ends of tanks!  Also what type of surgical tape - paper or fabric?

[Ronpur50]

I like the look of Viking, it is a very  70's look!  Should fit in with the  MEM.
I use a thin fabric tape.  I paint over it with white primer with a brush after I apply it. It bonds it to the surface better, I think. 

[Dalhousie]

I like the look of Viking, it is a very  70's look!  Should fit in with the  MEM.
I use a thin fabric tape.  I paint over it with white primer with a brush after I apply it. It bonds it to the surface better, I think.

That's what I got, I can experiment with it.  I am very nervous about ruining the model, given the cost!

[mike robel]

Experiment on the Heat Shield.  If you make a mistake there it won't be so noticeable.  And when you weather it, it might fit right in.