FUD FXD forming small crystals after time?

[Cajonpassfan]

Soooo....
...

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. 
...

Well, following the above-mentioned SW recommendation, I obtained a 40 oz. bottle of said corn oil, the smallest one in stock at our local Smart & Final, for the princely sum of $2.49 and am eagerly awaiting arrival of my next shipment from SW.

Yet there seems something fundamentally counterintuitive about dipping expensive models in cheap corn oil, but I'm willing to give it a try, once. Needles to say, I do not intend to recycle the corn oil like I did Bestine, which is pricey and has to be smuggled into California across interstate lines under cover of darkness, and which I learned here is bad in that when reused, may cause our exquisite models to become afflicted with the dreaded "crystal rash".

The first cheap corn oil victim may be one of the new not-too-cheap Harriman roofs by our own John LeMerise.
(I'm not cornoiling the unique and long awaited Descanso funeral car just yet, its Italian designer is the one who recommended use of the caustic soda, and his designs are beautiful).

Jake, just what temperature does SW say the oil needs to be to melt the wax (and presumably not the print)? And how long does one leave it in??

Okay UPS, you can deliver now...the corn oil awaits.
Otto K.

[Maletrain]

... I obtained a 40 oz. bottle of said corn oil, ... for the princely sum of $2.49 and am eagerly awaiting arrival of my next shipment from SW. Yet there seems something fundamentally counterintuitive about dipping expensive models in cheap corn oil, ...

You could always try extra virgin olive oil if you feel the need something expensive.

But, seriously, if it is correct that SW already bathes the parts in corn oil and then detergent, is it really just a matter of doing it again or longer to avoid this problem? 

It would be a big step forward to just know if the "crystals" that are penetrating the paint are really the wax that wasn't removed, or the by-products of a chemical reaction with a solvent wash, or some sort of break-down of the basic structural materials unrelated to either.  Trying to figure that out by trial and failure takes too long and ruins too many expensive prints.  I am surprised that SW hasn't asked for some samples and performed an analysis, because this could kill their model print business if it becomes wide-spread.

[SandyEggoJake]

@Cajonpassfan

Too be clear, your SW FUD/FXD parts already have had oven bake (to melt/drip off most of the support wax), then an ultrasonic baths of warm corn oil,  then warm water w/ detergent, then inspected to see if it needed another round of cleaning.  So I would ONLY advise the warm corn-oil bath if you find wax residue on the surfaces to be painted.  I would try the warm water w/detergent first to see if that removes what concerns you before going back to warm oil, then warm water bath again (to remove the corn oil). 

And take care to differentiate the wax from what might be sticky areas of a model, which might be uncured resin.  For such, the recommendation is additional UV exposure.... a few hours in direct sunlight (not through a window glass) should do the trick (print shops like SW uses a UV light box). 

The purpose of the corn oil seems to be at least three fold.  1) It is an effective heat transfer fluid, 2) an effective way to separate residual now melted wax from the part, as the lighter density wax will float on the surface of the oil, and 3) given the melted wax is attracted to the polyunsaturated structure of this type of oils.  Getting the temp right also seems to be desired.  Too hot and you risk warping your part.  But below the temp of the wax melting point, and it may not be effective at all.

BTW, I've never had a problem getting Bestine (heptane) here in California.  It is a (relatively undesirable) component of gasoline after all .... which is a blend of petroleum distillates that includes it's more expensive and famous cousin, octane.   Heptane is undesirable in fuels because it burns explosively and causes the dreaded engine knock.  I'm also not convinced reuse of Bestine is "bad", but like any solvent, it would have a solubility capacity that eventually will be saturated.  If one starts to see wax precipitate out of a hexane solution, even after cold filtered, it is time to use it for another purpose....

I'll see if I can dig into the 3D Systems specs for a bath temp recommendation, and edit this post if I find such.

EDIT: "The recommended temperature for melting support wax from most parts is 60°C (140°F). Using a higher temperature will accelerate melting, but caution is required to prevent part warping."

[havingfuntoo]

Why corn oil? What are it's properties that make it the recommended oil for the removal of the wax over other types of oils?
Has any one here looked at the wax formula and if so what is it? Petro chemical base or plant base?
The caustic approach has me a little baffled and I suspect we are about to learn how devastating NaOH can be from those who choose to try out that material. KOH is also worth a look if you are going down this path and equally dangerous. If you don't understand or know either of these products then you should not be playing with them. For those who are going to give it a go can I suggest you check out your local supper market for an oven cleaner that has it as one of its active ingredients before you go diving into making up your own brews.     

[SandyEggoJake]

Corn oil, is because that is the recommendation of SW, given that is the recommendation of their material and tech supplier, 3D Systems, for post production of FUD parts (apparently made using the 3DS resin SR200).

I suspect they use it as corn oil is heat stable, non toxic, low allergenic, has the right density, and works.  But again, corn oil is a polyunsaturated oil, so better at stripping wax holding of the melted wax away from the part.
And also, it is cheap... the 3DS recommended tank size to post processing to vendors (not us end users) is a 25 gallon vat! 

SR200 SDS  ===>  http://infocenter.3dsystems.com/materials/sites/default/files/sds-files/professional/VisiJet_SR200/23100-S12-04-A_SDS_English_VisiJet_SR200_Natural-Gray-Blue_M3_ProPlast_Navy_TechPlast.pdf


Best I can determine, the type of support material (aka, the Hydroxylated Wax) used with SR200 is S100 or S200, a proprietary wax mixture.  But 3DS also has other wax formulations specific for use with different resins and machines.  All seem to be admixtures (the clue being each has a melting range between 55 to 65C rather than a specific melting point.)

The 3DS "wax" is apparently a key differentiating point between the tech of 3DSystems and that of their major competitor, Stratasys, which use a different type of "support" for their similar machines, the latter being more a crumbly silicone like substance, which is apparently more a challenge to remove (requires use of uses solvents) and leaves a less smooth regions on surfaces in contact with their support. 

[thomasjmdavis]

Wondering whether its possible that it is corn oil trapped in the pores from the bath/wax removal that is causing the crystals and/or part of what we are identifying as left over wax or uncured resin is corn oil leaching out of hidden places. Let corn oil sit on your counter for a day or two and see if it isn't sticky.

Whatever the answer, I have a bunch of Shapeways parts coming from a couple vendors that will find their way into several locomotives and passenger cars, and I sure would like to have some resolution to "how can I make paint stick and still look good a year from now" that is superior to the current info from vendor, which is along the lines of... some users think this is a good idea, so why not try it and let us know if it works....

So far, best advice seems to be- clean up shapeways product as best you can, fill and sand to smooth surfaces, use as master and make casting mold, cast parts in resin, wash resin in warm water with dishsoap, paint resin.

[C855B]

...(the clue being each has a melting range between 55 to 65C rather than a specific melting point.)...

And that, in my mind at least, works against DIY using the warm corn oil method. The large vat you noted has a boatload of thermal mass, so keeping temps stable and within range is easy. A pot on the stove, not so much. It's going to have hotspots on the burner and lose temp fairly quickly when removed from heat. This works against FUD/FXD, because I've found it gets soft and maybe a little too pliable as low as 70-75C.

IOW, there's a moderately small "sweet spot" for removing the wax with the warm corn oil method. You certainly can build your own vat setup (five gallons or so?), but this seems like a lot of work in light of our not really having determined whether the heptane soak is good, bad or indifferent, or even has anything to do at all with the wax leaching problem... if that's what it is.

[SandyEggoJake]

@C855B Agreed.  But I would think even 5 gal of corn oil is vast overkill for our small parts in a one off bath.  Yes, thermal mass is easier to maintain with more oil, but a quart or even a pint of oil on a hotplate with mixing and eye on a thermometer might work.  The key would be to get the oil to a stead temp first.  (Note the 3DS recommendation suggests ultrasound cleaning is optional add to the heated bath. )


Also... the resin is getting thicker on this FUD crystal hunt.

Yesterday I stopped in to the exhibit floor of "Inside 3D printing Expo".  Unfortunately, I was not able to find anyone from 3DS (they didn't have a booth - it was a small show) but did talk with the Stratasys folks... (sales guys - mostly useless).  Yet scored when I met an ex 3DS guy.  He mentioned that 3DS did have issues of "sweating" with material leaching over time out of its SR200 prints.  He said it seems to me it was thought to be wax leaching out of the pores, not a crystal or degradation... and he recalled this issue has been "corrected" with some change.  He has offered to help us get an technical reply from former colleagues at 3DS, and I'm following up on that lead as so far I've heard only crickets from my notes to SW & 3DS.

BTW, did check out several of the next gen printers.  Some with multicolor, but 100 micron Z resolution, so not likely a fit for N scale miniatures.  But was intrigued by the new rig by Envisiontec and some others.

Also, learned a bit more of the formulation of SR200... might be related to a formulation change?  Might not.  But I noted discrepancies in the composition of SR200 comparing the old MSDS to the new (post 2013) SDS forms.

The (older) MSDS on SR200 from SW includes UA (35- 45%) and TEG-DMA (45-55%) and well as trace photoinitiators.  (see chrome-extension://ecnphlgnajanjnkcmbpancdjoidceilk/content/web/viewer.html?source=extension_pdfhandler&file=https%3A%2F%2Fwww.shapeways.com%2Frrstatic%2Fmaterial_docs%2Fmsds-frosted.pdf)

But I found a newer (June 2017 revised) document on the 3DSystems page for SR200 doesn't list TEG-DMA and rather notes Isobornyl acrylate (7-10%) as well as UA (25-35%). 
chrome-extension://ecnphlgnajanjnkcmbpancdjoidceilk/content/web/viewer.html?source=extension_pdfhandler&file=http%3A%2F%2Finfocenter.3dsystems.com%2Fmaterials%2Fsites%2Fdefault%2Ffiles%2Fsds-files%2Fprofessional%2FVisiJet_SR200%2F23100-S12-04-A_SDS_English_VisiJet_SR200_Natural-Gray-Blue_M3_ProPlast_Navy_TechPlast.pdf

Understand aim and requirements of the old MSDS and the new SDS forms are slightly different, so it is possible TEG-DMA is still in SR200, but listed anymore as it is not considered a hazardous material.  And the isobornyl acrylate might have been in the old soup too... perhaps it was the undisclosed "reactive monomer (CAS# proprietary) 26%" of the UA mix... the numbers work out so this is my guess... but now required to be specifically listed as it is hazardous. 

This revelation that FUD contains isobornyl acrylate might be a smoking gun so far not discussed.  Such may be the "Free Radical" that SW mentioned causing the oxidation degradation of the FUD, producing the crystals (it or something else) when leached out. 

[Sokramiketes]

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?

It stayed on through shipping across a couple states, so short term it was OK.  Long term, the T-gauge shell I mentioned earlier still has the paint well adhered (not coming off in sheets) but the leeching wax is an issue.  I should try cleaning it sometime to see if the paint is durable underneath the leeching.

[Cajonpassfan]

@SandyEggoJake,

Thanks Jake, for your detailed and thoughtful responses. Much appreciated, it seems I misunderstood the initial post.  Looks like I'm out $2.49 because I'm not about to cook with it, either

The last shell I did was using Simple Green followed by warmish Dawn dish soap scrub and it seems to have worked well. It also seems that the more recent Shapeways prints come much cleaner than what I was used to few years back.
Letting the shells dry out in direct sunlight for a day or too seems like a prudent way to go also.

Otto

[havingfuntoo]

If you are heating the corn oil use a water bath to heat it, that way you will be able to maintain the temperature at a constant 65 degrees, a water bath can be as simple as a large pot holding the water and a small container in the pot holding the oil making sure it is not sitting on the bottom of the pot.   I will investigate the information presented by Eggo on the wax formulation, thank you for the data.   

[MK]

65C I'm assuming?

[Chris333]

So I should still zap it a few times with the corn oil and then clean it further with Bestine?

[SandyEggoJake]

@MK

Oddly, the 3DS specs call for 60C, not 65C.  Even as 65 seems to be the upper band of the S100/200 MP.  I think they stick with 60C out of part warp concerns.

@Chris333

Unless you have massive amounts of wax on a part AND are committed NOT to use Bestine, Bestine alone has been proven to be adequate to remove the wax.  Remember, use of 60C corn oil and no solvent is the SW/3DS recommendation for wax removal from FUD.  Yes, the jury remains out on the long term issues - if any - from Bestine exposure on FUD.  But I'm still using it - just not soaked for hours as I used too. 

Personally, I've not seen any FUD parts from SW recently that have so much wax that I've felt any need to set up a corn oil crockpot or double boiler.  Rather I still use ~60 degree water with dish soap and/or Bestine.
 

[MK]

Has anyone tried deep frying????