Push and Pull Production Systems - CONWIP

Question

With CONWIP, each departing job sends a production card back to the beginning of the line to authorize release of a new job. Which two implicit assumptions are made, when describing CONWIP in this way?

Answer 1

1. The production line consists of a single routing, along which all parts flow.

2. Jobs are identical, so that WIP can be reasonable measured in units (i.e., number of jobs or parts in the line).

Answer 2

Constant WIP.

Each time a job leaves the line another job is introduced, in order to keep the amount of WIP constant.

Answer 3

MVA stands for mean value analysis.
It is an iterative procedure that can be used to compute certain quantities. In the case of 10.4.2 it is used to ultimately calculate the throughput of CONWIP lines at various levels of WIP.

Answer 4

- Since it is an iterative procedure it can easily be implemented into a spreadsheet

- It can be used to generate performance curves ( TH(w) or CT(w) vs. WIP(w) ) other than the best case, worst case and PWC. This is because the MVA model can calculate performance measures for unbalanced lines or coefficients of variations of effective process times other than 1.