Managing WIP buffer with combination of feeding materials scenario and conventional control theory of single type of hospital bed production

Abstract

The trend of customer today in many industries is in customized products. The implication to this is in the production floor especially in the assembly plant, where the flow of materials must be managed to ensure that every machine or workstations are supplied with complete materials and volume (quantity), in the right time, so that throughput can be achieved as scheduled. This study is being conducted in a hospital bed industry which uses a special workbench to assemble the beds. This paper attempt is made to model the production scheduling and control system to manage the work in process from the single workbench to complete one type of product. The main objective of the control is to manage WIP buffer in every stage of production so that it is available completely in the right time and able to achieve lean level of inventory buffer. Scheduling of material feeding implement “ Day minus1” method and controled use conventional control theory. The day minus 1 is the production scenario with the ” Day 0” being time scheduled to assembly the finished goods. Day -1 is day scheduled on the upstream buffer WIP materials supply, consecutively implemented for every upper stream of the workstations buffer. Raw components supplied in lot and downsize in batch in WIP buffer to supply the welding stations, welding buffer in batch supply to paint shop and feed queuing in hanger. Coming out from paint shop, the components are arranged in racks, trolley or box in batch of WIP buffer.This batch materials is sent to assembly station together with standard components supply from warehouse arranged in kiting form. For this production case the system able to manage demand of delivery one container every week which consists of 134 beds with zero defect. The stability of the process controlled using time constant<= 1 with proportional gain 1.