I 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.

What 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!

I 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.

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.
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.
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.
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.
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.
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...

My last post was concerned SLA type 3D printing. There is a variation to the SLA laser beam where a full frame binary B&W image is projected at full frame for each layer of the print. Two variations of this process exist. One uses a video projector and the other puts the video LCD screen up against the resin tank with a bright UV light source behind the screen.

The process is called DLP (Digital Light Processing) and creates higher resolution 3D prints than SLA and can be done in some systems at much lower equipment cost.

This has changed my mind about the affordability of high resolution 3D printing in my world of dimensional art. I made a business decision.

I have a DLP 3D printer ordered. This new printer costs about the same as two of my FMD (plastic filament printers) That does fit within my budget.

The DLP printer can produce ready-for-investment masters for lost wax casting. That is my purpose for this printer. The full frame image permits printing multiple items at the same time and no increase in printing time. One ring or 20 copies all print in exactly the same time.

I chose a low cost simple machine. Not purposed for a high production rate but absolutely suitable for the scope and amount of work I produce. It will be a great learning tool. I will also be experienced to advise others or make upgrades in this first system.

Most of my reporting on this new tool will occur in my 3D printing website: http://rd3dpds.com. Eventually I’ll post more here, when I start producing dimensional cast items.

SLA is Stereo Lithographic Apparatus, most commonly called simply Stereo Lithography.

I have investigated this process for use in jewelry making and any other high surface finish 3D printing. The hardware cost has been coming down, but the cost of materials and the finish work such as UV hardening, and support removal are still cost and labor intensive. With enough production need the cost can be reasonable, but it is a system that should be utilized to its fullest extent.

That means it needs full time operation and not occasional utilization.

The process uses a focused laser beam (a) to “paint” the structure layer by layer, on a surface (c) immersed in a polymer solution (b). The light beam partially solidifies the polymer at the focus/surface point. The build platform (e) moves the item (d) away and usually out of the liquid polymer material as layers are added.

The results are usually the ability to produce a very fine, smooth, and accurate surface finish. Post curing and extensive support removal and detailing by hand are required.

Some of the polymer material is suitable for direct used for investing and casting. Other polymer material can be used in the vulcanized or cold process rubber mold making. Then wax burn-out masters can be produced. Many options are available for producing and using the final print output.

The process although high quality is still expensive and labor intensive. There must be a real purpose and plan to make full use of the technology. If everything I made originated in a CAD drawing, The process would be more attractive for the things I create. I would love a “free ride” to play with the process but to purchase such a system, it would have to pay its own way in increased sales.

I currently don’t produce enough jewelry items for SLA to replace my CNC machining. That’s bottom line reality.