Improvability properties of assembly systems

The problem of improvability of manufacturing systems which include the assembly of parts produced is formulated. A simple model with a Bernoulli model of machine reliability is analyzed using numerical simulations. It is shown that there exist improvability properties structural in nature. In particular, an assembly system is unimprovable with respect to the machine efficiency re-distribution if the probability of blockages of each component machines are equal to the probability starvation of the assembly machine caused by this particular component machine. The improvability with respect to the inventory re-distribution is characterized in terms of the average occupancy of the component buffers. The results obtained could be useful to guide continuous improvements project on the factory door and could serve as a source for a formal system-theoretic analysis of production systems involving the assembly.