FUD FXD forming small crystals after time?

[Scottl]

Just so I am clear, people use virgin Bestine each time and they clean the parts repeatedly?  If you use the same Bestine and only clean once, I'm actually not surprised there is residual wax.  As per my previous post, we have this issue with porous material and solvent replacement of a miscible liquid.  It may not require the 10 replacements that we have to use, but I would not be surprised that the wax residual is substantial.

[DKS]

I never re-use the Bestine for cleaning FUD. But I do keep the used solvent for other, less-critical applications, like removing barcode (and other) stickers. Excellent for this.

[Jbub]

What about cooling the Bestine in attempt to remove the wax residual?

[Scottl]

I never re-use the Bestine for cleaning FUD. But I do keep the used solvent for other, less-critical applications, like removing barcode (and other) stickers. Excellent for this.

That is good to know, I think it is a key detail.  I do suspect though that repeated cleaning applications are likely needed.  A lot of work unfortunately, and without a way to measure how effective it is, unlikely to clearly result in a solution to the problem with the crystals. 

It occurred to me that perhaps a solution is to wash the painted models with Bestine to remove the crystals?  Not sure what it would do to the paint...

[Lemosteam]

I do let the parts rest for a little while in the UC to let floating wax settle.  When I drain the vat in my UC with a bulb syringe, I filter the fluid through 6 ply folded paper towel back into the can. 

I reuse the fluid and I still have no issues.  If there is further cleaning necessary I use an ultrasonic brush dipped in bestine and then rinse the part in warm water.

I have not tried the cooling method yet.

I have no issues to date on any of my painted parts.

[C855B]

I use the cooling method, refrigerating the jar after every soak (after the model has been removed, of course). Enough wax is deposited on the glass to give it a cloudy appearance. It's then cleaned out with paper towels once the recycled Bestine is poured through a paint filter into a can labeled "recycled".

I also soak for 24-48 hours. I have not seen the problem being discussed here in four years of messing with FUD.

[Scottl]

So is the wax dissolved in the Bestine, or is it melted and only miscible in this state?   If it is dissolved, which is what I expect the solvent would be doing, then filtering it will not necessarily remove the wax completely.  When I used Bestine (once, admittedly), I soaked the part several times and discarded the solution afterwards and have not had any of the reported problems.  I assumed at the time that was what people were doing, but I am not sure that is the case now.

DKS suggested that he did not re-use Bestine, and given what I understand is going on here, I would imagine that is the best practice.  In the case of removing water from a porous material (sediment) with acetone, we are removing about 40% of the water in the first soaking and about 90% total after 10 repeats.  We actually recycle the later stage acetone which is "low water" (2-4%) during the initial application on other samples.  It reduces our acetone consumption two-fold.  I know that sediment is not a perfect analogy for the porous nature of the FUD, but it has complex and low permeability so I suspect it is not far from the mark.  It is reasonable to expect incomplete dissolution of the wax with a single application of solvent, and the symptoms of the white crystals may be due to a low residual level of wax.

[C855B]

I'm presuming it is dissolved. The reason I filter is apparently the cooling the solution precipitates the wax, and therefore filtering (more like "fine screening" with the paint filters) is an additional step to prevent loose precipitate from making its way into the can, redissolving into solution as it warms up to room temp during storage.

It might be possible to analyze this with basic quantitative analysis techniques in weighing residue once the solvent has evaporated from each of the sample states, but I'd have to acquire a precision scale and turn the whole thing into another big project. Have enough of those already.

[Sokramiketes]

So ProJet/FXD/FUD needs the wax removed in order to not cause this wax leeching.  Yet removing the wax creates an awful, grainy surface.  What to do?

Use the RP models just for masters for resin castings.  Make use of that great surface finish with wax on it, and convert it to a stable, well known material like resin.

Here's a recent example.  This is an O scale end, drawn by @wcfn100, that was part of this year's RPM Chicagoland Mini-Kit, a CGW 10'-0" boxcar.

The Shapeways part looked like this:

You can see some wax crystals!  Panic!

With no prep, no soak, no cleaning, I sprayed it with Tamiya fine surface primer to confirm surface quality.  Then shipped it off for castings.  The resin parts came out beautiful. 

Here's the same part after fine surface primer was rattle canned on:

[DKS]

You can see some wax crystals!

Nope, in fact I can't see anything...

[wcfn100]

With no prep, no soak, no cleaning, I sprayed it with Tamiya fine surface primer to confirm surface quality.  Then shipped it off for castings.  The resin parts came out beautiful. 

Wow, that O scale one turned out real nice.

For some reason your pics aren't loading.

http://cgwrr.com/RPMConference/O-End-Shapeways.png

http://cgwrr.com/RPMConference/O-End-Primed.png

Jason

[peteski]

Just so I am clear, people use virgin Bestine each time and they clean the parts repeatedly?  If you use the same Bestine and only clean once, I'm actually not surprised there is residual wax.  As per my previous post, we have this issue with porous material and solvent replacement of a miscible liquid.  It may not require the 10 replacements that we have to use, but I would not be surprised that the wax residual is substantial.

Use the trick used by painters to clean brushes: use 2 Bestine bath containers. The first one will dissolve the wax, then blow off or just dry the part and immerse it in the 2nd bath. The 2nd bath will just end up with traces of the wax in the solution and remaining on the part. If you really want to go all the way also have a 3rd bath. At that point you can consider the part pretty much wax-free.   Then as you keep using the baths shift them after a while. So discard the Bestine in the 1st bath and move the other baths down the line filling the last bath container with clean Bestine.

[peteski]

So ProJet/FXD/FUD needs the wax removed in order to not cause this wax leeching.  Yet removing the wax creates an awful, grainy surface.  What to do?

Use the RP models just for masters for resin castings.  Make use of that great surface finish with wax on it, and convert it to a stable, well known material like resin.

Here's a recent example.  This is an O scale end, drawn by @wcfn100, that was part of this year's RPM Chicagoland Mini-Kit, a CGW 10'-0" boxcar.

The Shapeways part looked like this:

You can see some wax crystals!  Panic!

With no prep, no soak, no cleaning, I sprayed it with Tamiya fine surface primer to confirm surface quality.  Then shipped it off for castings.  The resin parts came out beautiful. 

Here's the same part after fine surface primer was rattle canned on:

I can't see the images in your post.  I was able however to view them by directly going to the URL.

The wax only masks the true surface texture of the printed parts. I'm really surprised that the primer stuck to part and stayed adhered. Maybe because it became like a shell encasing the entire part?  Since the wax is soft the paint/primer should not really have any "tooth" to grab onto.  You used those parts for making a master mold, but if you used those parts for the final model do you think the primer coat would withstand the handling, or would it start coming off in sheets from the wax coated surfaces?

[narrowminded]

Use the trick used by painters to clean brushes: use 2 Bestine bath containers. The first one will dissolve the wax, then blow off or just dry the part and immerse it in the 2nd bath. The 2nd bath will just end up with traces of the wax in the solution and remaining on the part. If you really want to go all the way also have a 3rd bath. At that point you can consider the part pretty much wax-free.   Then as you keep using the baths shift them after a while. So discard the Bestine in the 1st bath and move the other baths down the line filling the last bath container with clean Bestine.

In our shop we used that exact practice to clean silicone lubricant from valve parts going into a critical water based floating process to deposit a thin silver layer on x-ray film.  The solvent was trichloroethane, 3 steps as described, wash tubs also rotated as described, and a final wash in trisodium phosphate rinsed with distilled water. That was the only process that passed a rigid laboratory test after many others who were using a typical oxygen cleaning procedure had failed.  Both of those chemicals are frowned upon these days but the concept remains.  Maybe a final soap wash is warranted if folks are having trouble. 

[SandyEggoJake]

Soooo....

Yesterday AM Otto (our own @Cajonpassfan) got advice from an Italian designer of SW FUD parts to use caustic soda (aka lye or sodium hydroxide), and when seeing this, as Otto knows, my reply on that board was much the same as @peteski retort here...

...which all can check above, and I quote, he said...

"Wha?!  He told you to use WHA?????  Dat ***** is bad, man.  Don't do it, Bro!" 

Or something like that... 

And he his quite right.  Remember that scene in Raiders of the Lost Ark?  When the Gestapo Agent's head melts?  I have it on higher authority that the Ark of the Covenant sprayed his face with lye.  True story.

But seeing this topic again here, something tickled a wrinkle in my brain.  So I grabbed my keys and headed over to my local 3DP print shop.  Turns ourt they DO use  sodium hydroxide to clean parts as a step in post production... BUT NOT THE TYPE OF PARTS WE ALL BUY FROM SW! 

Yep... lye.  The tech doing it has the scars to prove it, including a particularly nasty wound on is leg he got this past summer from a spill that won't heal quite right... and he really needs to see someone about that. Yikes.

BUT they use it as that is the recommended process for parts printed using Stratasys Fused Deposition Modeling, or FDM.  First they scrape the worst of the support off, then it gets run in a sodium hydroxide bath in an ultrasonic cleaner, then a run in an acetone / ultrasonic cleaner, followed by water rise and dry. 

But they DO NOT use sodium hydroxide / acetone / water for parts off their Stratasys SLA or OBJect (PolyJet) rigs, that use different build tech and materials.  While SW is FUD/FXD, and printed using 3DSystems Multijet, the Stratasys OBJEct (Polyjet) tech is very similar, main difference being the SW/3DS uses a wax support that is easier to remove and results in better/ smoother characteristics than what is produced in a Polyjet rig of the same resolution.

Sooo... what did we learn?  Yes, lye is used in SOME 3DP post-production processes.  But NOT in those akin to the SW FUD/FXD.

Again, SW/3DS recommendation for FUD/FXD remains warm corn oil (to above the melting point of the wax), followed by warm water w/ mild dish detergent.  SW/3DS recommends against any use of solvents.  But to be clear, SW/3DS does not make ANY recommendation for how to etch as a painting prep either. 

MEK & Acetone seem to harsh for FUD/FXD.  But it seems - at least till be learn more about these crazy crystals - it seems fine to continue to use Bestine.

-Jake

PS:  WARNING.  If preparing a lye bath for some reason, know that adding sodium hydroxide to water produces a exothermic reaction (produces heat)... and IF you dip your FDM 3DP part in this hot bath it will warp.  So wait till the temp cool.    But again, no lye bath for FUD or FXD.