The continuing trend towards producing individualised products leads to process time fluctuations, different process sequences and continuous integration planning in industrial assembly. Furthermore, in the assembly of large and complex components increases in automation are desired. This is often not economically feasible within the framework of conventional, line-based assembly systems and increased changeability.
Within this thesis, a new form of organisation for industrial assembly and an a priori performance evaluation method is developed. Based on an analysis of changeability paradigms in manufacturing and assembly, Line-less Mobile Assembly Systems (LMAS) are defined. Three core principles characterise LMAS: (1) clean floor approach, (2) mobilisation of all assembly relevant assets, and (3) the highly flexible assignment of resources to jobs and jobs to locations considering process requirements. LMAS are characterised by job routes describing a tuple of resource allocation, order of assembly processes, time sequence, and spatial allocation on the shop floor within sequence restrictions.
A reference architecture model is developed for the design, evaluation, and control of LMAS. The model provides additional usage levels and a hierarchy for the model's assets through abstract modelling. Based on this reference architecture model, a mathematical formalisation of an LMAS is provided.
Rough planning of assembly systems requires the low-effort assessment of key figures such as throughput, lead time, and resource utilisation. This thesis presents a method to transfer LMAS into a closed queueing network form and determine relevant key figures using an analytical solution procedure. Topology conflicts are resolved by assuming stochastic process distribution instead of process sequences for long periods. Thereby it is not necessary to consider the assembly sequence. The occurring project conflicts are solved using randomly generated stochastic schedules and Monte Carlo simulation. Evaluation criteria are used to determine the result's quality.
The developed evaluation method is validated regarding internal validity, convergence, and system behaviour plausibility using sensitivity analysis are used to support validation. Additionally, a comparison with a discrete event simulation model is carried out. The validation shows that the developed model is suitable for estimating the suitability of an LMAS a priori in the context of rough planning.
Fertigungsmesstechnik und Qualitätsmanagement
Model-based A Priori Analysis of Line-less Mobile Assembly Systems
The trend of individualized production requires changeability in assembly systems. This thesis develops the novel paradigm of Line-less Mobile Assembly Systems based on the core principles: clean floor approach, mobilization of all relevant assets, and highly flexible assignment of resources to jobs and jobs to shopfloor locations. It provides a method for performance estimation during assembly system design that assists resource selection. Validation demonstrates the model’s applicability.