DIMENSIONAL ART STUDIO

"Do what you love for those who love what you do"

3D Print Result

I have succeeded in producing a fairly good cast ring from a 3D print master model. This came after many failed and unsatisfactory attempts. There have been numerous issues but the hardest one to overcome has been the failure of the investment during the model burnout. The resin from the model apparently doesn't totally cure. Especially in a thick section model. The uncured resin combines with or attacks the gypsum in the investment during the investment cure and subsequent burn-out.

I found a written article published over two years ago that confirmed every one of my suspicions. A jeweler in Bellingham, Washington, Jim Binnion (https://mokume-gane.com/about/jim-binnion/) offered a solution. It involves high vacuum curing the model in a heated oven, after ultrasonically cleaning it in water, fresh off the printer. No alcohol is used on the model and a UV cure isn't necessary either. 

Jim is a professional jeweler and has professional grade equipment. I assembled a hobbyist grade equivalent, seen in the following pictures. I can't get or measure the 10 micron vacuum Jim recommends. I did notice the vacuum stop at one level, then about an hour later it dropped anotherl .5 inch WC. An indication there was gassing off of the tiny model, which created the drop in negative chamber pressure. I was heating the chamber to 180 degrees Fahrenheit. There was also some condensation (resin?) on the clear and cool lid of the chamber during the vacuum operation.

This ring is one of my best 3D printed casts so far. So, it looks like Jim's information about using a vacuum was good and I am on the right track to good casting. I will continue using this method. I have also resigned myself to keep the model section as thin as possible. The thicker the model the harder it is to properly cure.

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This is the ultrasonic cleaner I use to clean the model and many other things. After the cleaning, the model is placed in this heated chamber and a vacuum is pulled. I let it run about 2 hours.
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This is the ring after it came out of the vacuum chamber. The sprue is wax. I also touched up a few blemishes on the ring using repair wax and a heated, wax pen.
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The results after kiln firing and casting The ring following the usual after-casting clean up process and shining.
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The ring is quite small. I call it Pave' less the Pave' 3D printing does work when you learn the trade secrets. It is not an easy process.

3DP Works!

DSCN0068That’s Three Dimensional Printing. My first attempt with resin material was not satisfactory. I posted the sad results HERE. However, one attempt does not qualify as a final result. Successful people keep trying what they want to do until they get it right. In this case, find the combination that works. Thomas Edison once said he discovered hundreds of ways not to make a light bulb.oweverH

Luckily, I didn’t have to go that far. There are people other than myself already doing it correctly. The materials for a successful 3D print casting exist. It just a case of sorting out all the variables and putting them together in a production stream that works for my conditions and situation. That’s what I enjoy. Working out the details of a very complex process.

DSCN0069The 3D plastic still doesn’t burn out as well as wax. I continue to see evidence of ash or debris on the resin castings. Not as bad as my first test. The PLA burned out quite well. The results are useable but not as good as I can cast with wax masters. Next run I will extend the 1350F hold from two to three hours.

The "wiggly" thingy was hand carved wax. The Fleuer-de-cross is resin DLP and the ring is PLA via FDM printing. 

The new Plasticast investment powder is a wonderful product. It will be my new preferred investment powder for use with wax as well as plastic. The vacuum de-airing was a bit frightening. It rises over twice the height of my previous powder. I mentioned this in my previous post. Mold release (water quench) is outstanding. I love when a plan comes together, and things start working the way intended. It opens the door to making 3D printing a part of the LWC process and I have a new ability to design and create.

I am not at the point where 3D printing is going to be the only way I create models. Wax carving by CNC milling and hand is not going to go away. I enjoy the manual carving. The “squiggly” pendant is an example. It was completely hand carved. I enjoyed making every curve with files and wax carving knives.

The investment process brings out EVERY minute detail in the model. It hides NOTHING. The 3D prints, especially the FDM with PLA shows every layer line in the model. My first instructor warned me, it is far easier to smooth and detail flaws on the model, than to remove those flaws from the silver casting. How true that is!

I was able to grind and polish out the slight “evidence” of the FDM layers, but that’s doing it the hard way. Resin 3D prints are much smoother, but not perfect. Wax is still the best material for masters but can be fragile to handle. Everything has a compromise to understand and consider.

I may have a use for FDM 3D prints now that I know the PLA can be burned out. I may want that look. I am now feeling better about doing design with my DLP (Wanhao D7) printer.

Full STEAM ahead. (I like model steam engines, too) I am already getting requests for jewelry that can be designed in CAD, 3D printed, and cast is silver!

Plasticast

RandRI just filled three LWC casting flasks using my new investment powder. It’s Plasticast Investment made by Ransom & Randolph, Maumee, Ohio (My birth state.) It is supposed to be a superior investment powder for when waxes and plastic are used in investment casting.

I have been using a R&R investment called Ultra-Vest since day one of my silver casting. It’s been a wonderful investment powder for my work. Always produces good results with wax masters.

My first impression with Plasticast is that it is definitely different material. It LOOKS the same but the mixing and especially the vacuum de-airing is totally different. The mix is extremely smooth when mixing and the rise when under vacuum is MORE than twice as high! The air bubbles stick together very well and just keep rising. Almost frightening compared to what I have become accustomed.

No problem, I was aware of the extreme rise and was prepared. I was also grateful when the second vacuum (in the flask) did not rise, but just came to a boil as it should.

In about 15 hours, I will know how the material works coming out of the kiln and silver casting is attempted. I have a slightly modified schedule for the burn out. It now includes a hold stage for two hours at 700 degrees F. for the better transition of the plastic materials. It was a part of the R&R burn-out recommendation

This first try has one flask with the usual wax master. The second has the resin master made with my Wanhao D7 3D printer. The third flask has a finger ring made from FDM 3D printed PLA plastic.

I love to experiment (a little, not forever) so I am excited to see how this will all virtually come out.

I can work forever, er… the rest of my life, using wax for casting silver, but I really want to do highly detailed work with 3D printing of the masters. Next post will show the results.

The Investment Experiments

DSCN0064What works and what doesn’t? That’s why I must experiment. There is no readily available information about materials other than wax for lost “material” casting. From my LWC training I know biological materials have long been used as master material in casting.

My instructor said bugs (insects) and plant material are commonly used. Maybe NOT so common, but it has been done before. I assume with some success. In my classes, a woman used thorns that looked like tiny crosses and it worked for her.

I am giving the casting resin for DLP printing another chance. I have the recommended investment material and a slightly modified burn out schedule with a hold at the 700-degree level before going to 1350 degrees.

I found a report about a jewelry maker using FDM 3D printing using Polylactic Acid (PLA) filament. PLA is a material made from biological and biodegradable materials. I will see for myself how it performs as burn-out model material. I made a simple round finger ring from uncolored PLA and will test how it burns out and the quality of the casting.

I am also running a standard carved wax model in the same firing to see how it behaves with the revised burn out schedule. I don’t expect the pause at 700 degrees to create any issues.

The jewelry making couple (man and wife) using the PLA showed a lot of examples of their work in their webpages. They displayed very primitive looking castings. I don’t know if that was by design and on purpose. It could be an example of the results from using the PLA and FDM type 3D printing. Their quality is definitely not my desire. That’s why I must test on my own.

I am willing to use whatever works. That’s the key, it has to work and not be unpredictable. There is too much time effort involved to have casting fail because of the material used for the masters. Wax is my de-facto standard, so whatever I use must perform at the same level or have some other overwhelming benefit. Failure is not an option! Ha!

3D Printing for LWC

LWC modelI am an enthusiast for 3D printing. Because of this, I set a goal to use 3D printing to produce master models for Lost Wax Casting (LWC) in my silver work.

One obstacle is the quality of the surface produced by standard Fused Deposition Material (FDM) of the popular plastic filament style 3D printers. FDM is getting good finish when printed at 0.2mm per layer or less. But not good enough for casting LWC model.

Another style of 3D printing using an Ultra Violet (UV) curing resin can produce layer heights as small as 0.025mm (25 microns) This is outstanding resolution. Several versions of this process exist. Some use a LASER beam to scan the layer. It's called Stereo Lithographic Apparatus (SLA). Another process uses a full layer exposure like a B&W negative for each layer. It's called a Digital Light Process (DLP)

Shown here is a Wanhao Duplicator 7 (WD7) I own. I bought it specifically for use in producing casting models. There are resins available that (should) burn out the same or nearly the same as wax in the Lost Wax Process. The key word is "should". More coming about that claim.

For more than several years I have been producing CAD models to produce programming to run my Computer Numeric Control (CNC) wax milling machine. A switch to producing Stereo Lithographic files (.STL) for 3D printing is a no brainier. The only difference is the output file created.

The first step in this new approach to lost wax casting is learning how to operate this new printer. It is totally different than my previous 3D printers. I have done some write up in my 3D Printing website. Here is the link:http://rd3dpds.com/resin-printer I have also posted some blogs on the subject: http://rd3dpds.com/blog

This article describes the outcome of this great experiment.

I have just completed my first casting of silver using the casting material from the WD7 printer. I was able, after some trial and error, to produce very decent quality 3D prints from the WD7. This printer works like a camera and film. The exposure for each layer of the print is critical to getting a sharp layer. The model I used here was as good a surface as I produce using wax carving. A good start. The printer is not a problem.

The issue I have discovered, is getting a clean burnout of the resin used to create the model. It is marketed as "castable resin". I followed the burn out schedule of time and temperature which is the same as I use for wax. The manufacturer claims very low ash, but does not state "no ash". Ash is the solid material left behind when all the volatile material is vaporized by high heat, 1350 degrees for 3 hours.

In the pictures can be seen the result of a non-clean burnout. This is a very disappointing result. This pendant (although I stamped my mark on it) is not of the quality I would offer for sale or as an example of my quality standard. The quality is very poor. It is the worst result I have ever cast. Of course all my other casts were made using wax masters.

At this point 3D printing is not going to be my go-to method for LWC. I will stay with WAX masters for the bulk of my work, thank-you...

I will continue to experiment and research casting resins. The 3D process will allow me to create models for LWC that can't be made by hand or CNC milling. That remains my goal. I am not going to let this failure be my only attempt. But I also don't want to stop doing my LWC until I get it working.

Right now I have a nice, but some what messy, very high resolution 3D printer. But I have a resin burn out that is very far from ideal.

 

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 This is the Wanhao Duplicator 7 DLP 3D printer. The pink is the castable resin. The print is formed on the clear bottom surface of the vat.  I had to experiment to find the exposure times (per layer). This is the first print I got correct.
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 The model prints upside-down on the build plate as it is raised up out of the resin vat. The full print can take 5 to 10 hours depending on height of layers and model.  The resin is quite messy. Here the build plate is taken to a work area to remove the model from the plate. The was the first successful print with casting resin.
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 Additional corrections to size of base and supports produced this castable model. The model quality is excellent.  The model is sprued with casting wax on the flask rubber base. The white film appeared after a wash it in alcohol to remove waxy surface.
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 The model in the flask  Just after 2nd vacuum, a film of water appears on the surface of the investment. This is a good sign of a proper investment.
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 Fresh after quenching the flask. Uh-oh... Not too pretty. The dark is normal fire scale from casting.  After 30 minutes in the pickle. Fire scale gone but still very ugly. Looks like a bad sand cast. Not LWC quality.
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 Did some cleanup, but the porosity is horrible. Lots of cr*p must have been in the mold cavity.  I filed the back and stamped it. Big pit right in the center. Worst cast I have ever made. Totally unacceptable.

The photography makes it look far worse than when I hold the pendant in my hand. It IS as bad as it looks, the camera doesn't lie.

I'll find a way to make this process work. I have spent enough time for now. The white residue from the alcohol wash may have contributed, but I doubt that. I'll try another resin cast the next time I have some wax masters to cast. I may need to try a more expensive castable resin. I have to admit this is the cheap stuff. It is also water soluble which was the initial attraction. Other resins require isopropyl Alcohol to clean up and dissolving of the resin residue.

There are other ways to skin this cat. The 3D printer can make hard models that are then used for making rubber molds that can be injected with wax. The wax is used for casting. The cost is material and another extra step.

Bottom line for me right now. The printer is certainly capable. The model material seems to be less than capable. It could be my technique. I have to decide if the time is worth the investment. I already get excellent cast product using wax. Being a pioneer with a new technique is hard work...

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