407 | RWTH Publication No: 443027 2014   IGPM407.pdf |
TITLE | Integrating Release and Dispatch Policies in Production Models Based on Clearing Functions |
AUTHORS | Dieter Armbruster, Michael Herty, Xinping Wang, Lindu Zhao |
ABSTRACT | Aggregate production planning for highly reentrant 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
function to allow control over both, the release rates and priority
allocations in re-entrant production. This approach is used to
improve the production planning problem using combined release
and the allocation dispatch policy. The control parameter for
priority allocation, called the push-pull point (PPP), separates the
beginning of the factory which employs a push policy from the
end of the factory, which uses a pull policy. The extended clearing
function model describes the output of the factory as a function
of the work in progress (wip) and the position of the PPP. Its
qualitative behavior is analyzed. Numerical optimization results
are compared to production planning based only on releases. It is
found that controlling the PPP significantly reduces the average
wip in the system and hence leads to much shorter cycle times.
Note to Practitioners: This study is focussed on the semiconductor production industry where multiple passes through the same machines (re-entrant production) are common. We show that changing priority rules is essentially a re-allocation of spare production capacity which may lead to significantly reduced lead times. In addition, a control scheme that determines the changes in the priority rules is shown to lead to smaller safety stocks for large demand fluctuations compared to a static priority rule. |
KEYWORDS | production planning, dispatch control, partial differential equations, reentrant production |
DOI | 10.3934/nhm.2015.10.511 |
PUBLICATION | Networks and Heterogeneous Media (NHM) Volume 10, Issue 3, Pages 511 - 526 September 2015 |