Shapeways FM switchers: Cleaning FUD

[Sokramiketes]

Where does this question lead?  Is anybody complaining that the items dunked in heptane have become brittle, changed or unusable in some way?

Katfudgirl says that surfaces that don't come near wax come out of the machine clear.  Putting the models in heptane turns them white and rough.  If there is no wax and they're clear, but putting them in heptane makes them white, then what is going on?  I think the parts look pretty smooth when delivered, but rough when "washed".  That is the change being complained about. 

There's an assumption that the whole model is coated in wax... but now we're hearing from a direct source that that is not the case.  If the heptane isn't removing wax, then what is it doing?

[Sokramiketes]

Hm, really? So you're saying the material was never intended to have that kind of transparency? I guess I would be confused by this because when some the models come out of the printer, they are not entirely covered by the wax. There are parts that only have wax on the bottom, and the plastic material that is above it is naturally clear, even having never come into contact with wax at all.

I'm quoting this again since I think some people might have missed it. 

[DKS]

Katfudgirl says that surfaces that don't come near wax come out of the machine clear.  Putting the models in heptane turns them white and rough.  If there is no wax and they're clear, but putting them in heptane makes them white, then what is going on?  I think the parts look pretty smooth when delivered, but rough when "washed".  That is the change being complained about. 

There's an assumption that the whole model is coated in wax... but now we're hearing from a direct source that that is not the case.  If the heptane isn't removing wax, then what is it doing?

There's also an assumption I see growing here that all parts have some surfaces that are not exposed to wax. I have yet to receive any parts where there is evidence this is so. If I had an object where there were surfaces known for certain to have not been exposed to wax, then I could test them with heptane to see if it altered these surfaces. My bet is that there aren't many small, intricate parts that have such surfaces since there is also evidence that small parts are done in batches together with other parts to make best use of the machine's assembly space, in which case there will be few--if any--wax-free surfaces.

The only way to test this reliably is to have objects with known and consistent properties. Otherwise, all bets are off.

I'm quoting this again since I think some people might have missed it.

And I am quick to point out that the statement refers to "some" models, which is vague at best. Again, we need objects with known properties going into any test, or it is all meaningless.

[bbussey]

Good luck "sand-blasting" the White Tower structure with baking soda or anything else and not damaging the window treatments and door hardware.

I've had a handful of White Towers where all the stars are in alignment and sections of the roof are smooth enough on both sides where light still passes clear through.  But it's a rare occurrence.  The surface area of FUD objects, by definition, is not entirely smooth given it is built in layers and that most surfaces of an object are not perfectly parallel with the printing plane.  The wax - especially wax that has melted and flowed into the crevasses of irregular surfaces, including flowing to areas where originally there was no wax support structure due to capillary action - will "smooth" the surface and allow light to pass through.  But the FUD material, when cleaned, exhibits the characteristics of other RP materials such as the PolyJet resins.  Just at a finer resolution.

David just explained it pretty thoroughly.  I've soaked numerous parts in Bestine for days, delicate and otherwise, and never had an issue - no breakage, no hardening, no warping.  Other than the White Tower, I design the ProJet parts for use as casting masters, as polyurethane castings are far more practical.

As an example, the mold separation membrane surrounding the XHD master for the Keyser Valley caboose floor is only .0025" thick.  It is there to save the trouble of blocking off the steps and frame edges manually when pouring the first half of the mold, and it will render as thin flash that is removed easily from the casting.  Soaking the master in Bestine for two days removed all the wax in the steps, which would have been impossible otherwise to remove without damaging the membrane.  Also note that the part was rendered upside down, so that any rough areas would be invisible inside the caboose body.



The roofs also had a membrane designed in to aid in the mold creation.  Note that insets etched from .004" brass provide the smooth curved surface desired for the model.



The ProJet resin is very good at rendering intricate and complex details.  It's strength is not in replicating large relatively flat nondescript surface areas.

[bbussey]

There's also an assumption I see growing here that all parts have some surfaces that are not exposed to wax. I have yet to receive any parts where there is evidence this is so. ...

I have never received a ProJet-rendered part, from Shapeways or any other contractor, that did not have wax on every surface.  Never.

Look at the 1940s White Tower as an example.  There is wax in the window treatments - you can see it.  There is wax on the roof - you can feel it.  There's wax on the underside of the roof (as they are rendered upside-down for reasons stated up-thread) - you can feel it there too.  So to assume that residue wax doesn't flow across all surfaces even though most of it is melted away is not valid.

[Sokramiketes]

Ok, if there is a coat of wax over the whole model.  Then why aren't we leaving that smooth surface alone and using the parts as masters to cast in resin?  Then you're not worried about paint sticking to wax... and you get the smooth surface that all these cleaners are destroying...

[DKS]

Ok, if there is a coat of wax over the whole model.  Then why aren't we leaving that smooth surface alone and using the parts as masters to cast in resin?  Then you're not worried about paint sticking to wax... and you get the smooth surface that all these cleaners are destroying...

Because the residual wax is not consistent. There are areas where there are small globs of it. I just checked a FUD model and found globs of wax all over the place, especially corners. If the residual wax was even fairly consistent, then this would work. But I have yet to see a model with consistent surfaces.

Here's a perfect example. Note the white deposits along the back corner of this Z scale Difco dumper.



Even worse are the ribs on the underside; some of the depressions are entirely filled with waxy globs, while others just have irregular deposits. Notice, too, that the yellowish translucency is consistent across all surfaces; if some areas were never exposed to wax, they would have a different appearance.

This absolutely would not work as a master.

[Lemosteam]

bbussey,  Obviously each part would have to be assesed for danageability before sand blasting.  I was more referring to the OP's original example for removing any wax in those hard to reach areas.  Would sand blasting remove the handrails for instance?

Chris333 thanks for tryin the blacklight.  Crap, it was just a hopeful idea...

DKS, maybe the manufacturinig process makes globules of wax airborn (like overspray) and they just settle there on the part.  This would explain katfudgirl's explanation and the fact that recieved parts are covered in wax.

[DKS]

DKS, maybe the manufacturinig process makes globules of wax airborn (like overspray) and they just settle there on the part.  This would explain katfudgirl's explanation and the fact that recieved parts are covered in wax.

The best hypothesis is that liquid wax runs across all surfaces during the heat-cleaning process. I quite doubt that there would be any airborne wax, let alone any that would adhere to the surface such that it requires soaking in a solvent to remove.

[Chris333]

My stuff is always sticky oily feeling when I open the box. So I wonder just what type of wax it is.

I wonder if giving the cleaned FUD a coat of Future clear would turn it back to clear? (guess any clear spray would work)

[DKS]

I wonder if giving the cleaned FUD a coat of Future clear would turn it back to clear? (guess any clear spray would work)

This might not be a bad idea; it might obscure some fine detail, but it might smooth rough surfaces well enough that it makes up for losses. It would require careful testing to determine what works best.

Incidentally, I just took that Difco dumper and dunked half of it in heptane, and it turned almost perfectly clear. This is to be expected. I also intend to clean only half of it so we have a decent comparison.

[wcfn100]

Now, if you read the literature about heptane, you will learn that wax is one of the very few materials that heptane will dissolve.

Dissolving the wax isn't a requirement to get a clean surface.  It's just a little waxy film that in no way requires a days soak in anything to remove.  I want something that allows me to open the package, clean the part in a few minutes and get ready to prime.

 

Jason

[Chris333]

I think the idea of letting it soak for 2 days is that it's "hands free".  You can scrub the parts in a bath and get just about all the wax off, but in N scale you'll probably break half the pieces off with the scrubbing.

I just "blasted" a piece with Testors wet look clear and it only changed from bright white to an off white. I don't think waiting for it to dry would change anything.

Bryan has the right idea, use an etched overlay. These Nn3 EBT steel hoppers I'm messing with would be soooo much better out of etched brass. But not everything can be etched.

[wcfn100]

Heating may cause warpage or sagging in places . Even if the properties change , and that change is undetectable , ......

Shapeways puts the parts in an oven to remove some of the wax already.  It's supposed to be good up to 176 deg which to me, leaves plenty of room to try and remove the wax with heat as an aid.

Jason

[DKS]

Dissolving the wax isn't a requirement to get a clean surface.  It's just a little waxy film that in no way requires a days soak in anything to remove.  I want something that allows me to open the package, clean the part in a few minutes and get ready to prime.

 

Jason

First, you assume there is only a thin waxy film all over the model. Note the photo I posted above; this is what I see most of the time. I have rarely seen a model with a consistent thin film all over. The dumper is the kind of item that requires days of soaking, since the heptane dissolves the wax slowly. If, however, the part does indeed have only a thin wax film, then the heptane will work perfectly, as it should remove that thin film in just a few minutes; agitation will accelerate the process, too.

There are few alternatives that will reliably remove the wax completely. As I have indicated, heat is ineffective, and other methods either risk mechanical damage, or require a secondary cleaning process to remove residues such as oils or detergents. I welcome evidence that there is a process other than dissolving with heptane that is as safe and effective.

Finally, I feel sorry for modelers who are so impatient that they eschew a process known to be effective. To quote Yoda, patience.