Modelling of a Flow Shop using OntoGui

Case Description

The flow shop is composed of 4 machines and 4 buffers which are connected accordingly.

formal model

The processing time of each machine varies according to the part(classes).

Process times:

	Part A	Part B	Part C
Generation	1 part/sec	0.5 part/sec	0.8 part/sec
M1	2.1 sec	1.3 sec	1 sec
M2	1.2 sec	1.2 sec	2.5 sec
M3	5 sec	1 sec	3 sec
M4	1.5 sec	5 sec	1.3 sec

Buffer capacity:

Buffer	Size
B1	10
B2	7
B3	9
B4	4

Each of the machines has failure modes with different mean time to repair and mean time to failure. M1, M4 have two failure modes and M2,M3 have only one failure mode:

Machine	MTTF_1	MTTR_1	MTTF_2	MTTR_2
M1	300 h	15 min	200 h	20 min
M2	200 h	20 min	-	-
M3	250 h	5 min	-	-
M4	100 h	2 min	250 h	10 min

Modelling of Flow shop (Using OntoGui)

Control panel

control panel

1. A new ontology module Flow-shop has been created.

2. System design tool is selected under the ontology tools.

System Design

System design window is opened

Part Types

part type part A

1. A new part called Part-A of the class Workpiece type is created

Process Plans

process plan part A

1. A process plan process-plan-a is created for the Part-A

Process Steps

process step part A

1. m1a is the process step of the machine M1. The processing time of 2.1s is entered using the set time option and Manufacturing task is selected under the set class option.

2. m2a is the process step of the machine M2 with a processing time of 1.2s

3. m3a is the process step of the machine M3 with a processing time of 5s

4. m4a is the process step of the machine M4 with a processing time of 1.5s

Successors of process step

successor of m1a

1. m2a is selected as a successor of m1a using the add button under add successor. m3a is the successor of m2a and m4a is the successor of m3a.

Systems

create system

1. A system called production.sys1 of the class Manufacturing system is created.

adding machines

adding buffers

1. The machines M1,M2,M3 and M4 and buffers B1,B2,B3 and B4 are created under this system using the Add new option.

Managing connections of selected machine

manage connection in system

1. For M1, B1 is in upstream and B2 is in Downstream. For M2, B2 is in upstream and B3 is in Downstream. For M3, B3 is in upstream and B4 is in Downstream. For M4, B4 is in upstream and B1 is in Downstream.

Manage properties of Buffer

adding buffers

1. The buffer capacity of each buffer was entered in the box.

Manage failure modes of machine

add failure modes

1. The failure mode properties of each machine is entered. The failure type is "ODF". Time to fail is recorded in terms of hour and time to repair is in terms of minutes. The value is entered in properties value dialog box.

2. The procedure is repeated for all the other machines as well. M1 and M4 have two failure modes

3. The value can be modified later by using the set button

Assignments of process step

Assignment of process step

1. The machines are assigned to respective process step. M1 is assigned to m1a, M2 is assigned to m2a, M3 is assigned to m3a and M4 is assigned to m4a.

Part Types

part b system design

1. A new part called Part-B of the class Workpiece type is created

Process Plans

1. A process plan process-plan-b is created for the Part-B

Process Steps

1. m1b is the process step of the machine M1. The processing time of 1.3s is entered using the set time option and Manufacturing task is selected under the set class option.

2. m2b is the process step of the machine M2 with a processing time of 1.2s

3. m3b is the process step of the machine M3 with a processing time of 1s

4. m4b is the process step of the machine M4 with a processing time of 5s

Successors of process step

1. m2b is selected as a successor of m1b using the add button under add successor. m3b is the successor of m2b and m4b is the successor of m3a.

Assignments of process step

1. The machines are assigned to respective process step. M1 is assigned to m1b, M2 is assigned to m2b, M3 is assigned to m3b and M4 is assigned to m4b.

Part Types

part c system design

1. A new part called Part-C of the class Workpiece type is created

Process Plans

1. A process plan process-plan-c is created for the Part-C

Process Steps

1. m1b is the process step of the machine M1. The processing time of 1s is entered using the set time option and Manufacturing task is selected under the set class option.

2. m2b is the process step of the machine M2 with a processing time of 2.5s

3. m3b is the process step of the machine M3 with a processing time of 3s

4. m4b is the process step of the machine M4 with a processing time of 1.3s

Successors of process step

1. m2c is selected as a successor of m1c using the add button under add successor. m3c is the successor of m2c and m4c is the successor of m3c.

Assignments of process step

1. The machines are assigned to respective process step. M1 is assigned to m1c, M2 is assigned to m2c, M3 is assigned to m3c and M4 is assigned to m4c.