This thesis was conducted at Linköping University and SAAB Aerostructures, Linköping, and focuses on the automation of flexible fixturing in machining applications. At Linköping University a project called "Koofix" is conducted with support from Strategiska stiftelsen and several manufacturing industries including SAAB Aerostructures. The purpose of this project is to develop a more cost-effective, flexible, technique for fixation of workpieces during processing and assembly.
Fixtures are an important part during the machining process, especially if you process the parts with high accuracy. Today a large number of fixtures are used at SAAB and they would prefer to reduce the number of fixtures by using flexible fixtures instead. SAAB uses one fixture for each article and this result in a high fixture cost and it also takes time to design and construct a new fixture.
There are several advantages with using a flexible fixture such as that you can process workpieces with different length, height and thickness in the same fixture. Bigger workpieces takes time to fasten in the fixture because the machine operator must tighten the clamps by hand. By automating the fixture with for example grippers or clamping cylinders the set time would be reduced because the clamping process is automatic.
In this report there is also a mapping of various flexible fixture components such as grippers, clamping cylinders and linear units. These components are quite common today in the processing industry and are also used in fixtures. The idea of flexible components is to provide a more flexible and automated fixture then the currently used at SAAB. These components were also linked to a concept idea and based on this idea, several concepts were sketched. The result of the concept idea was two concepts that were generated in the CAD program CATIA.
The first concept uses grippers for the clamping process and for additional flexibility the grippers can also be rotated with rotary actuators. Linear units are used to automatically position the beams to reduce the set time. The second concept uses clamping cylinders and rotary grippers to clamp the workpiece. Beams are positioned by an operator, but linear units could also be used in this concept as well.
Finally, the concepts were evaluated according to a method from Ullman with a so called decision matrix. The concept that fulfilled the criteria best was concept 1, which uses grippers and linear units. Another method that was used from Ullman was a QFD (Quality Function Deployment) chart and this chart shows the design requirements that are important and that should be fulfilled.
The components that are presented in this report have not been tested. This could be a suggestion in an upcoming work to test these components. For example the pneumatic linear units with passive or active brake could be tested to make sure that the braking force is sufficient.
2009. , 58 p.