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Aggregate production planning for highly re-entrant production processes is typically generated by finding optimal release rates based on clearing function models. For production processes with very long cycle times, like in semiconductor production, dispatch policies are used to cover short term fluctuations. We extend the concept of a clearing fu...
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Citations
... Specifically, re-entrant production creates the opportunity to set priority rules for the various stages of production competing for capacity at the same machines. This dispatch policy, as it was indicated in [2], typically allows for two models of operations -the so-called push and pull policies. A puch policy, also known as first buffer first step, is typically assigned to the front of the factory. ...
We discuss the optimal control problem stated as the minimization in the L²-sense of the mismatch between the actual out-flux and a demand forecast for a hyperbolic conservation law that models a highly re-entrant production system. The output of the factory is described as a function of the work in progress and the position of the so-called push-pull point (PPP) where we separate the beginning of the factory employing a push policy from the end of the factory, which uses a pull policy.
... Specifically, re-entrant production creates the opportunity to set priority rules for the various stages of production competing for capacity at the same machines. This dispatch policy, as it was indicated in [5], typically allows for two models of operations -the so-called push and pull policies. A push policy, also known as first buffer first step, is typically assigned to the front of the factory. ...
... on the rest production line [x * , 1] can be interpreted as a certain version of a pull policy -the so-called quasi-pull policy. However, the right choice of functions V 1 and V 2 is definitely open question (see, for instance, [5,17,34]). This fact motivates us to consider the functions V 1 and V 2 as controls too. ...
We discuss the optimal control problem stated as the minimization in the L2-sense of the mismatch between the actual out-flux and a demand forecast for a hyperbolic conservation law that models a highly re-entrant production system. The output of the factory is described as a function of the work in progress and the position of the switch dispatch point (SDP) where we separate the beginning of the factory employing a push policy from the end of the factory, which uses a quasi-pull policy. The main question we discuss in this paper is about the optimal choice of the input in-flux, push and quasi-pull constituents, and the position of SDP.
... To our knowledge, none considered integrating the dispatch policies into an aggregate model. An optimization approach, corresponding to an open loop control problem for production planning in aggregate models integrating release and dispatch policies has been discussed in [12]. ...
Typical semiconductor production is re-entrant and hence requires priority decisions when parts compete for production capacity at the same machine. A standard way to run such a factory is to start to plan and to finish according to demand. Often this results in a push policy where early production steps have priority over later production steps at the beginning of the production line and a pull policy where later steps have priority at the end of the production line. The point where the policies switch is called the Push-Pull-Point (PPP). We develop a control scheme based on moving the PPP in a continuum model of the production flow. We show that this control scheme significantly reduces the mismatch between demand and production output. The success of the control scheme as a function of the frequency of control action is analyzed and optimal times between control actions are determined.
