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Specifications of the precision engineering centre at CMTI [20]

Metrology laboratory 20 02 C < 02 k/05 h < 01 k/m < 03 k > 30 Hz < 02 m 50 5% 10,000 5 (VDI 2083) > 10 Pa < 02 m/s 400 lux < 45 dB (A) 200 m2 4m Precision machine shop 20 05 C < 05 k/05 h < 02 k/m < 05 k > 30 Hz < 02 m 50 5% 100,000 6 (VDI 2083) > 10 Pa < 03 m/s 700 lux < 60 dB (A) 214 m2 44 m

Basic Temperature Maximum temperature change, T/dt Temperature gradient Differential temperature of the floor to the air Resonant frequency of the foundation Permissible ground vibration amplitude (peak to peak) Relative humidity Clean room class Differential air pressure Air velocity Illumination Noise level Floor area Head room

The design of clean rooms can be improved by using a combination of various methods such as analysis of experimental data, rules of thumb and experiences, empirical equations and computational fluid dynamics or the so-called air flow modelling [8] Each of the methods has its own advantages and drawbacks The rule of thumb allows designs to be completed very quickly and inexpensively, but these rules are very general and may require large safety margins to ensure that the design is successful On the other hand, empirical equations can be used to quickly predict the conventional usage of the design However, when the parameters of the design vary, the uncertainties of solutions can often be significant In physical modelling, designers can see and feel the environment governed by this design, but this advantage comes at a very high cost By using computational fluid dynamics (CFD) which is less expensive, some potential design flaws can be predicted so that they can be remedied before the facility is constructed In addition, it can quickly explore the possible opportunity for improved performance and can model a variety of options for both planned and operating designs so that the most economical solutions can be pursued with a high degree of confidence in their validity In some applications, physical modelling is still required after flow modelling However, flow modelling can reduce the number of prototypes The important features that are employed in the precision engineering laboratory at CMTI are shown in Table 86 Table 86 Features and solutions employed in the precision engineering laboratory at CMTI [21]

Solution provided Independent massive monolithic RCC floor blocks resting on high density expanded polystyrene and anti-vibration mounts for machineries Through course filters, prefilters and superfine filters, maintenance of overpressure in the conditioned space, antistatic PVC flooring, dust trap, smooth polyurethane paint on the wall surface of return air ducts and air shower As shown in Figure 845 and Figure 846 Water proof layer of slate slabs with waterproof cement for joints outside the retaining walls Optimum proportion of preconditioned fresh air to circulate air and the use of intelligent Direct Digital Control (DDC)

Certain precision engineering laboratories such as the Mitutoyo Laboratories in Kiyohara, Japan, Moore Special Tools Laboratories in Bridgeport, USA, Dixi Laboratories in Switzerland, are all constructed underground to take advantage of the constancy of the subterranean temperature

Microelectro-mechanical Systems (MEMS)

1 2 1 Cement plaster (30 mm) 2 Brick wall (115 mm) 3 Bitumen coating 4 Expanded polystyrene (50 mm) 5 Air gap (50 mm) 6 Brick wall (115 mm) 7 Cement plaster (20 mm)

Fig 845: Wall insulation of a precision manufacturing shop [21]

irrespective of the atmospheric temperature [21, 24] It is proven that at depths of 6 m, the earth s temperature is constant irrespective of the variation in the atmospheric temperature Therefore,

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