After my high school years, I studied engineering. During my years at high school and university, I already spent every free hour at my father's company. I gained my practical experience by working, training and studying for more than 10
years. At that company, we developed and produced the first closed vacuum casting systems in the beginning of the sixties.
In 1983 I founded Schultheiss Heating and Casting Technologies. My new company started with the design and
production of temperature regulation systems for soldering/brazing, soldering/brazing wire feeders and control systems.
These systems were followed by melting, granulating, continuous casting equipment. After this, a series of
Vacuum and Pressure Casting units was developed.
Casting Evolution
More and more the customers demanded better solutions in the Platinum melting and casting field. Our know-how together with extensive experience leads to
the research and to develop solutions for the platinum field. The Platinum- Melting Unit, the Platinum-Jewelry Casting Unit and the Platinum Burnout Furnace with Rotation were constructed tested and put in production.
History of casting
Manual gravity casting has been applied for thousands of years. In the museum of Bahrain, sepia casting of jewelry is shown of the period of 4000 BC. Many hundred years later followed the manual centrifugal
casting. Centrifugal casting with spin axis followed that. The Vacuum assisted casting with open metal pouring and melting, was the next technology to improve the castings. This was followed by the vacuum casting in a closed chamber
under protective gas. A Vacuum and Pressure Casting systems is the latest step in the gold and silver casting.
Target
Target for our development was and still is to offer solutions for the whole field of casting, even
for metals which are difficult to cast.
Demands
We were determined to realize a system which would lead to improved casting results and fewer defects.
Solution
As solution we found the casting of platinum
under vacuum and pressure is only suitable for heavy parts and for small casting trees. Melting is possible open - or under vacuum - or protective gas.
The vacuum and pressure casting unit with rotating flasks allows us to cast
larger trees from filigree up to heavy parts. The spinning of the flasks in their center axe allows us to optimize the usable weight of Platinum to 75 %.
The casting sequence is computer controlled to ensure optimum
reproduction. Program techniques for different metals and sizes of parts are available. The direct documentation proves the high quality of the products; the system is extremely flexible, as all parameters can be controlled.
The
system is open and customer specific software extensions are possible. Diagnosis is possible at the unit or via modem.
System concept
The flask and the melting crucible are built into a closed chamber which allows to
work either in vacuum or in argon atmosphere with over pressure.
The Platinum is placed in the crucible for melting and the melting is started. The flask is placed on a turntable base with own vacuum connection. The chamber is closed by a cover with window for operator inspection and optical temperature control and regulation. The Platinum is melted and the spinning of the flask is started.
System concept
After reaching the casting temperature by unit control:
•The vacuum remains at flask for degassing
•The pressure inside casting chamber goes to set over pressure
•The casting of the Platinum is made by the control
•The speed of flask is set the values set in the program
•The casting sequence is made by the system control which allows 20 casting programs
After end of casting cycle the system opens and the operator takes the flask. The unit is ready for next casting cycle.
Flask and wax tree design
The design of the wax tree is a tube shape. We deliver for the tree
rubber molds for easy production of the trees. Depending on the investment used one of the two flask preparing methods have to be used. For sedimentary investment, the top side preparing is used. For phosphate bonded investment the bottom
preparing is used. We deliver the rubber plate.
Casting trees
Depending on the quantity of the casting parts different length of trees can be used. To achieve a good usage of the Platinum the tube shaped tree can be
made hollow to use just ring sections to apply the parts.
Conditions for using the PPC unit in the new technology:
To obtain optimum casting results, the new shape of casting tree must be accepted.
Moreover, it is important to mix the investment precisely and carefully with distilled water or the prescribed hardener. Larger flasks need accurate investment handling. For some investment we deliver tested mixing and burnout conditions. The flasks burnt out should be in a furnace with precise control (Schultheiss has set up special Flask Burnout Furnace for Platinum flasks.)
The exact metal weight is necessary (tolerance); up to now large cones were quite common because of tolerances. We offer our customers training for easy start of production. All information of the handling of platinum investment
handling should be respected.
V8N3
Vacuum and Pressure Platinum Casting
Georg Schultheiss
Schultheiss GmbH
This is an abbreviated version of the original work. For full technical details, please consult the original paper.