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Simulation: Equipment, throughput and product mix

: Wiechers, O.

Dorner, J. ; Fraunhofer-Institut für Produktionstechnik und Automatisierung -IPA-, Stuttgart:
Advanced production technologies in the photovoltaic industries. CD-ROM : Manufacturing concepts and their transferability. 27. September 2005, Stuttgart
Stuttgart, 2005
18 S.
Workshop Advanced Production Technologies in the Photovoltaic Industries <2005, Stuttgart>
Fraunhofer-Institut für Produktionstechnik und Automatisierung (Workshop) <2005, Stuttgart>
Fraunhofer IPA ()
logistic; tool development; Softwareentwicklung; Simulation; Hardware

Improvements during the tool development process are getting more and more important in high-tech industries. In general the equipment development process consists of two basic development phases: hardware and software development. These development phases also include the tests necessary to guarantee the correct equipment operation. This operation is measured against the requirements specification.
The idealized equipment development (see Figure 1) would have the two phases overlapping to minimize the development time. Unfortunately this is not typically like this. More often there is a time gap between the end of the software development and the beginning of the software tests. This can happen when the hardware development takes more time than estimated. In effect this gap causes a financial risk as the planned overall development time might not be kept. Additionally there exists a risk that the software does not fulfill requirements which had to be changed during the hardware test phase. Then additional loops in the software development are required which extend the financial risk for the company and the tool development time.
As the overall tool development times decrease statically the importance of simulation increases more and more important. It can be used in different project phases to reduce project risks, e. g. the risk of not fulfilling the requirements. Simulation is a tool which can support the company before, during and after the development of a new tool.
Before the realization of a new tool the idea can be modeled within a simulation as a realization study to gather KPIs before spending a high amount of money for the development. These KPI often are throughput, cycle times, waiting times, utilization of equipment modules etc. A bottleneck analysis can be performed in very detail before realizing the equipment. In addition to this sometimes design errors appear during the realization of the simulation which can be corrected before realizing the incorrect ones in hard- and/or software. The disadvantage is that financial effort has to be spent while modeling with simulation.
During the development phase the simulation can act as test tool simulating the behaviour of the real equipment for the software. This helps to test the interfaces of the equipment to the outer world which are often a very critical parts of the equipment development. Besides equipment crashes are avoided which might happen when starting software test on the equipment. Correcting these errors will cost money and time as equipment modules might be affected by these crashes and might need physical exchange. The simulation realizes reproducible behaviour which helps validating the equipment as errors and problems can more easily be figured out and their solution can be improved. Simulation often offers a visualization of the simulated equipment so that customers and developers can see what happens and compare it with their expectations.
Furthermore the simulation can be used by the marketing department of the company to assist the marketing and sales stuff. Changing configuration parameters on-site with potential customers can convince them as they will directly get their KPIs calculated.
The experiences in simulation at the department for cleanroom manufacturing have been built up in different research and development projects carried out in governmental funded and industry driven projects. Figure 2 shows different simulations on various levels: equipment level and factory level in particular. The model in the upper left corner shows the graphic of a photolithographic tool whose simulation has been extended in several projects so that it can now serve as test tool for scheduling software but also as stand alone simulation for presentation. The large figure in the center shows the visualization of a case study of a specific factory layout variation. The third case study shows a wet bench simulation used to calculate utilization, throughput and cycle times for various configurations of the tool.