Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Precise cut for sparkling jewels

09.04.2008
Rubies, emeralds and tourmalines can only sparkle with the right cut. Since early this year, a fully automatic machine has undertaken this grinding process for Paul Wild GmbH. It saves up to 30 percent of the precious material and grinds the gems with greater precision.

Not until they are given the right cut do precious stones reveal their true value. And they only fetch the highest prices if the facets are even and exact. However, the grinding process – which has hitherto been performed exclusively by hand – leaves little remaining of the valuable uncut stone: 66 to 70 percent fall to the ground as dust, while only a good 30 percent eventually sparkle in the light as a precious jewel. But which of the numerous cuts will make the most of the raw gemstone in question? Experienced lapidaries have an instinct for it.

For the first time ever, a grinding machine is challenging this collected experience: On average, it uses 15 percent more of the volume of the uncut stone. The machine has been in use with Paul Wild gem-cutters near Idar-Oberstein for three months, and has already transformed over a hundred lumps of rough stone into sparkling gems. “The machine – a CNC grinding machine with 17 axes – first maps the surface of the uncut stone,” explains Dr. Karl-Heinz Küfer, head of department at the Fraunhofer Institute for Industrial Mathematics ITWM in Kaisers-lautern, who developed the software for controlling the machine with the help of his colleagues.

“To do this, narrow bands of light are projected fully automatically onto the uncut stone, and its geometry can be determined from their curvature. The computer takes ten minutes to determine the image of the enclosed gemstone awaiting grinding, and sends the appropriate commands to the process control unit. The 17 axes ensure that the milling head can move along any desired path and grind the facets to an accuracy within ten micrometers – the gemstones become perfectly geometrical.” For comparison, hand grinding achieves an accuracy of about 100 micrometers, or the width of a hair. Hand-polished gems appear less exact, their facets and polished edges seeming to be slightly rounded.

The fully automated system takes an average of 20 minutes to give an uncut stone its facets. The machine has to work with extreme care and therefore allows the precious dust to fall rather more slowly than a skilled lapidary who has an instinct for the correct grinding pressure. On no account must the precious stone be allowed to get too hot, as this could cause it to split.

During polishing, however, the machine works faster: Whereas the skilled worker repeatedly has to wipe the stone clean and carefully inspect it, the machine sets the polishing time automatically depending on the size of the facets and the type and weight of the gem. “With uncut gems of average quality, the system will pay off within a year or two,” Küfer estimates.

Monika Weiner | alfa
Further information:
http://www.fraunhofer.de/EN/press/pi/2008/04/ResearchNews42008Topic2.jsp

More articles from Machine Engineering:

nachricht Scientists from Hannover develop a novel lightweight production process
27.09.2017 | IPH - Institut für Integrierte Produktion Hannover gGmbH

nachricht PRESTO – Highly Dynamic Powerhouses
15.05.2017 | JULABO GmbH

All articles from Machine Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Let the good tubes roll

19.01.2018 | Materials Sciences

How cancer metastasis happens: Researchers reveal a key mechanism

19.01.2018 | Health and Medicine

Meteoritic stardust unlocks timing of supernova dust formation

19.01.2018 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>