A Clean Concept
Energy chains for cleanroom use put to the test
Cleanrooms have exceptionally high requirements as far as the resistance of moving components to abrasion is concerned. Energy chains used in such environments must be particularly resistant to abrasion in order to fulfill the norms for these sensitive surroundings - and that isn’t easy to achieve. Two energy chains have now been tested by the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA).
The energy chains which were tested were the E6 and E14 series made by igus in Cologne, Germany. The result: in accordance with VDI 2083 Part 8 (Cleanroom suitability of operating utilities), when operated at the velocities of v=l m/s and v=2 m/s, the E6 Series energy chain which was tested may be implemented in ISO Class 3 cleanrooms (in accordance with DIN EN ISO 14644-1). When operated at a velocity of v=l m/s, the energy chain tested from the E14 Series may even be implemented in ISO Class 2 cleanrooms. That’s the conclusion the IPA came to after completing its rigorous tests. As a result, despite tightened-up norms, these energy chains are able to advance into increasingly sensitive areas of application such as the manufacture of microelectronic or pharmaceutical products. What is special about the four models tested is that they were standard variants, i.e. they weren’t made of special materials.
Testing cleanroom suitability
Based in Stuttgart, Germany, the Department of Cleanroom Manufacturing at the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA) assesses the cleanroom suitability of manufacturing equipment and materials. Test benches which have been specifically designed for use in highly-clean reference cleanrooms are utilized to test materials and operating utilities. Studies and research work carried out over recent years have led to the development of appropriate test procedures which guarantee sound, reproducible results. The IPA’s interdisciplinary organization doesn’t just give customers the chance to test already-established material pairings but also to develop systems suitable for cleanroom use. Udo Gommel, a graduate physicist at the IPA in Stuttgart, has tested the cleanroom suitability of the energy chains made by igus and documented the results in a test report. Below is an interview with Udo Gommel from the Fraunhofer IPA in Stuttgart:
Editor:The operation of your Class 1 cleanroom costs your institute a lot of money. How do your customers benefit from this cleanroom?
Gommel:This can be explained really using the following example. igus came to us to ask in which cleanroom classes the energy chains they supplied us with may be implemented. The tests carried out in our Class 1 cleanrooms showed that the two test objects even fulfilled the exceptionally high demands of Class 2 and Class 3 cleanrooms. The manufacturer is now able to document this fact with our qualification certificates which are recognized worldwide - and still be in a position to supply the best products for individual customer requirements.
Editor:What was the reason for tightening up the cleanroom technology norms US FED Std. 209E and VD 2083 to create the DIN EN ISO 14644-1?
Gommel:That’s quite simple to explain. With the US norm, cubic feet are the unit of measure. One cubic foot is approx. 28.31. With the DIN EN ISO guideline, the cubic foot is converted to the more common metric system. As a result of increased requirements, for example in the semiconductor industry, it became apparent that higher cleanliness specifications needed to be defined in the mid-term. Through the new ruling, they’ve been increased a hundred times. The national VDI guideline is more representative of the current state of the art, whilst DIN EN ISO defines the precise specification details (~ the number of particles per unit of air).
Editor:Which norm is used in technological fields?
Gommel:DlN EN ISO 14644-1 is the norm which is currently applicable internationally for assessing air cleanliness. The American standard US FED Std. 209E has been officially withdrawn.
Editor:Which fields of application demand the highest cleanroom classes?
Gommel:The trend-setter is still the semiconductor industry. The highest requirements need to be met here. However, product miniaturization is steadily advancing in all fields of industry. It starts with CD players which are getting smaller and smaller and goes right up to micro hard disks which are as small as golf balls these days. At the same time, storage densities are also increasing. Other fields of industry such as medical technology and machine and equipment manufacturing also have very high demands placed on them as far as cleanliness is concerned. Even the automotive industry is being forced to manufacture more and more components under cleanroom conditions.
Editor:How do you see the future of cleanroom technology?
Gommel:Cleanliness requirements will continue to rise in all areas of industry. As a result, companies such as igus, which are investing in their products at an early stage, won’t have any problems in the future to hold their market position under these conditions.
Energy chains in use
Brooks needs especially clean air to manufacture its Fixloads. This is due to the highly-sensitive area of use of the loading interface of 300 mm wafer-process devices used in the semiconductor industry. With the loading procedure, a box holding the wafers (silicon disks onto which chips are processed) is placed on the Fixload and clicked into position. The gripper arm of the process device removes the wafers from the box so that they can be processed in the device.
It is vital during the loading process that ultra-pure air cleanliness conditions are maintained in the environment to ensure that the wafer is not contaminated and that no particles enter the process device. For this reason, among other things, the required cleanroom suitability of the energy chains used is especially important. Tests carried out by Brooks have shown that no wear of the energy chains could be ascertained despite even long-term fatigue tests. A zipper-type energy chain made by igus is used in a hanging position. The energy chain is equipped with several air and control lines. With a traveling distance of approx. 290 mm, between 50 and 60 cycles can be performed per hour, usually in a three-shift operation. Apart from their cleanroom-suitable resistance to wear, the energy chains also possess a further advantage: the zipper system enables energy lines to be loaded extremely quickly and offers protection at the same time. That increases both their operating safety and service life.
MSR magazine, May 2004, Number 5
