EUREKA JUNE 2007 COVER FEATURE STORY

Manufacturing base keeps on shrinking

.....but in this case it is to be encouraged.
Tom Shelley reports on technologies that allow manufacturing in smaller and smaller areas and at lower and lower cost

Manufacturing cells for making small parts are becoming smaller and smaller. So-called 'Desktop Manufacturing' cells are being superseded by manufacturing lines that fit on a small desktop - while the latest idea is 'Square Foot Manufacturing' where the whole factory occupies a space only 30cm x 30cm.
Technologies such as those currently being developed and marketed by companies such as Robert Bosch, who call their idea 'Desktop Factory', are based on standard rack manufacturing units in a basic frame and lead to marked savings in capital investment, factory space and overall energy consumption.
But these are almost nothing compared to the next stages in small scale manufacturing being developed and researched.
Bernd Feirabend, manager of production procedures and construction machinery at the Robert Bosch plant in Waiblingen, Germany, says: "We are trying to reach overall investment savings from 10-20% throughout the product service life. In some cases, it may even be 30%."
The rack units are 220, 330 and 440mm wide. The basic module consists of a base frame, a security enclosure, and slide in modules. There is one process per module. The modules are re-usable and re-configurable. Typical products manufactured are up to 100 x 100 x 100mm in size and up to 500g in weight. Cost savings arise in various ways. As regards setup time, Feiraband said: "We were thus able to design a completely new platform within just three months."
The company also claims that required surface area is reduced by up to 75%, energy costs by up to 20%, and re-usability is up to 50%.

Smaller still
On show as a working demonstration at the recently held Hannover Fair, the TUT Microfactory, with a complete assembly line around 1m long, has been developed by the Automated Manufacturing and Assembly Laboratory at Tampere University of Technology in Finland, under the direction of Professor Reijo Tuokko.


"The Microfactory is all in separate modules so we don't need cabins," Prof Tuokko explained.
Each module occupies a space 300mm x 200mm and 220mm high wide, and was sealed to the next to ensure maximum cleanliness. The line of modules we saw was producing loudspeaker assemblies for mobile phones. Each module was internally lit by arrays of LEDs.


When we asked why one would want to do this, Prof Tuokko said that mobile phones and other consumer and medical products will have more and more features in the same small package.
"Our idea is to go away from huge machines to make small devices. The Japanese have been initiators by building the first prototype microfactories. We started work in 2000 and built a mini factory to make assembly and disassembly of small gears."
This approach, he says, is more sustainable: less material is needed to build small machines, and energy requirements also are reduced.
"Transformations due to temperature changes are smaller, so we see better performance in terms of speed and accuracy. There is also a solution of the clean room problem for making medical and consumer products, such as medical implant manufacture - even in a clean room, if humans are working we need extra sterilisation of products."
Items inside the cells were being handled by miniature, cell ceiling mounted, six strut, "Microdelta" parallel robots, developed by the Centre Suisse d'Electronique et de Microtechnique company, (CSEM). Specifications for these machines are: Workspace XY: 60 mm, Z: 30 mm; 3 degrees of freedom, 4th axis optional; acceleration up to 10 g and repeatability less than 2 microns. Control was by a wireless user interface.
Regarding commercialising the technology, Prof Tuokko said: "We are building our first production line to make ear implants on demand. The line will be 1m long and 0.3m wide. Such implants are presently supplied in packets of different sizes and doctors choose the right size for the patient. We have five cells in our plant. The next step we are starting to research is to use it in real world production environment."
The micro factory has been developed as part of M4 (Micro-Meso Mechanical Manufacturing) and NEXT (Next Generation Micro Factories for Challenging Processes) projects. Funding has comes from the European Union, the Finnish Funding Agency for Technology Tekes, and Finnish industry.

Even smaller
However, this was nothing to what was being demonstrated on a nearby stand by the Institute of Production Engineering (LaFT) directed by Professor Jens Wulfsberg at Helmut Schmidt University in Hamburg - a cell in which a work piece stayed in a carrier, to be worked on by five different special purpose machines that were pick-and-place inserted in the cell, each machine being located using pins.

Helmut Schmidt University is in fact, the University of the Federal Armed Forces, but as researcher Florian von Scotti explained: "Most of our work is not for defence, but tasks such as hydro forming small buckles and structures in tubes for endoscopy."
The Square Foot Factory is evidently at a much earlier state of development than the Finnish Microfactory. Von Scotti said: "Movable machine tools can be realised by micro machine tools in combination with a carrier device. Instead of the work piece, the machine tool can be placed on the carrier device so that not the work piece but the machine tool is replaceable on the module. Coupled or cascaded working areas can be generated in this way in order to bring micro structures into macro work pieces. The difficulty in micromachining is analysing the process. We install specially developed sensors that allow us to see if the tool is working properly and tell us whether the edges are machining the work piece or rubbing. There are already sensors like this on the market but they have a huge problem for us - their natural frequencies are similar to the signal frequencies produced by the machine tool working at high rotation speeds [60,000 to 160,000 rpm]".
He said the team was investigating piezoelectric 1D and 3D force sensors. The 3D sensors, he said, allow a wider range of measurements "but are not so accurate". Working on machining such small parts we learned, required paying to attention to grain size and microstructures of the parts being made, as well as bulk properties.
At the present time, the individual machines are being placed by hand, instead of by a pick and place robot, as they would be in a commercial application. Nonetheless the way forward is clear, and von Scotti said that their approach should "end up being very cheap compared to a five axis conventional machine tool".

Pointers

*"Desktop Factories" can be set up using modular parts in as little as a quarter of the space required for conventional assembly lines

* Close to commercialisation are "Microfactories" where entire production lines can sit on the top of a small desk

For more technical developments see www.eurekamagazine.co.uk

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