טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentNelkenbaum Bernardo Dov
SubjectThe Tradeoff between Fixture and Tool Change Time in a
System Based in SSMS
DepartmentDepartment of Industrial Engineering and Management
Supervisor Mr. David Sinreich (Deceased)


Abstract

Single-stage multifunctional machining systems (SSMSs) are an important integral part of automated, flexible manufacturing systems. However, the SSMS frequently becomes the bottleneck of the entire manufacturing system due to internal setup requirements. A key to achieving full SSMS utilization is the ability to reduce internal setup activities even at the expense of increasing the external setup activities. To achieve this all the factors involved in the setup process need to be considered. Till now, fixtures and fixturing have not received much attention in the FMS related literature. Nevertheless, fixtures are in some cases a limited resource which may affect the shop scheduling decisions and the shop performance and as a such can not be omitted.

This study introduces a method which takes into account the tools and fixtures required for the production of each job type as well as the tool magazine capacity to determine a job sequence minimizing the total cost of lost time due to internal setup operations. The model also recommends purchasing additional fixtures when economically justified.

The method is put to the test using a small job demand example and a real industrial setting. A lowest cost sequence is determined for each of the examples. Several conclusions can be drawn over the subject.

The analysis demonstrates that the following resources have a direct effect on internal set-up costs:

1.      The tool magazine capacity of an SSMS.

2.      The total number of tools required for the production of a set of jobs.

3.      The number of different part types in a set of jobs.

4.      The total number of jobs.

The model is very flexible and therefore may be further applied in a range of job sequencing problems which involve SSMSs.