Planning in production systems

Operation scheduling

Slovak University of TechnologyFaculty of Material Science and Technology in Trnava

Operation scheduling the lowest level of planning detailed description of that, what would be

produced, when and on which machines

Heuristic methods: they are not optimizing methods these methods in majority of cases find

suitable solution, which suits to limiting conditions

it is not obvious, to what extent the solution is good, because optimal solution is not known

they are based on experiences, using knowledge from some previous action

Main aims of scheduling maximum utilization of machines maximum degree of completion and

minimal continuous time minimize of inaccuracy function

Scheduling objectives1. assign operations to production facilities –

entering into production with aim to design a removal profile of capacity units Two basic approaches:

forward loading backward loading

2. to define processing order of individual products in process of production – sequencing

Forward loading it starts with actual point in time, products

are assigned to workplaces towards future on the workplaces the capacity demands

which are under consideration time periods are cumulated; it is possible to consider of final or unlimited workplace capacity

time scheduling horizon could be overrun – no fulfilment of product delivery time

Backward loading products are starting to assign into

workstations from the term of their eduction backwards, in actual term, assigning starts at latest possible term, minimalization of working out, short continual periods

it is possible to over step capacity border of workplace

terms of overrun are not over stepped

Assignation order of processing production task it is necessary to define superior selection

rule – according it the products are chosen from line and are assigned to working places

it is necessary to assign rule for choice of machine, that performs right operation

Hand made Gantt diagram - forward loading

Hand made Gantt diagram - backward loading

Techniques and methods of scheduling Conventional methods

Mathematical programming approaches – linear programming, dynamic programming

Heuristically oriented approaches New methods

Techniques of artificial intelligence and knowledge systems

Techniques with use of neuron netsTechniques with use of modeling and

simulations

Place of scheduling in PPS systems Source

requests of plan

Aggregate production planning

Rough capacity planning

Operation planning

Capacity requests of

plan

Material requests of

plan

input/output

analysis

Workshop system of scheduling

Dynamic management

Offer management

Required input and output information

Input information Output informationProduction plan Input in productionProducts structure, components Production orderProduction procedure, operations Working sheetsTechnologies used, productionsources

Production currency

Working sourcesCalendar of changes