Production is characterized by batch-size becoming smaller and smaller and greater variety of products. Assembly, being the last production step, is particularly vulnerable to changes in schedules, batch-sizes, and product design. This situation is forcing many companies to put more effort into extensive rationalization and automation of assembly that was previouslyextensive rationalization and automation of assembly that was previously the case. Although the development of flexible fixtures fell quickly behind the development of flexible handling systems such as industrial robots, there are, nonetheless promising attempts to increase the flexibility of fixtures. The fact that fixtures are the essential product - specific investment of a production system intensifies the economic necessity to make the fixture system more flexible.
Fixtures can be pided according to their flexibility into special fixtures, group fixtures, modular fixtures and highly flexible fixtures. Flexible fixtures are characterized by their high adaptability to different workpieces, and by low change-over time and expenditure.
There are several steps required to generate a fixture, in which a workpiece is fixed for a production task. The first step is to define the necessary position of the workpiece in the fixture, based on the unmachined or base pan, and the working features. Following this, a combination of stability planes must be selected. These stability planes constitute the fixture configuration in which the workpiece is fixed in the defined position, all the forces or torques are compensated, and the necessary access to the working features is ensured. Finally, the necessary positions of moveable or modular fixture elements must be calculated- adjusted, or assembled, so that the workpiece is firmly fixed in the fixture. Through such a procedure the planning and documentation of the configuration and assembly of fixture can be automated.
The configuration task is to generate a combination of stability planes, such that fixture forces in these planes will result in workpiece and fixture stability. This task can be accomplished conventionally, interactively or in a nearly fully automated manner. The advantages of an interactive or automated configuration determination are a systematic fixture design process, a reduction of necessary designers, a shortening of lead time and better match to the working conditions. In short, a significant enhancement of fixture productivity and economy can be achieved.
References
[1] Ji, P., 1999, An Algebraic Approach for Dimensional Chain Identification in Process Planning, International Journal of Production Research, 37:99–110.
[2] Mbang, S., Haasis, S., 2004, Automation of the Computer-aided Design –Computer-aided Quality Assurance Process Chain in Car Body Engineering,International Journal of Production Research, 17:3675–3689.
[3] Denkena, B., Rudzio, H., Brandes, A., 2006, Methodology for Dimensioning Technological Interfaces of Manufacturing Process Chains, CIRP Annals –Manufacturing Technology, 55:497–500.
[4] Denkena, B., Schurmeyer, J., Eikotter, M., 2011, Linking Total Costs and Benefitsof Ownership (TCBO) and Process Chain Simulation for Integrated Assessmentof Manufacturing Technologies and Processes, Production Engineering – Researchand Developments, 5:557–564.
[5] Brecher, C., Vitr, M., Wolf, J., 2006, Closed-loop CAPP/CAM/CNC Process Chain Based on STEP and STEP-NC Inspection Tasks, International Journal of Computer Integrated Manufacturing, 19:570–580.
[6] Heusinger, S., Rosso Jr R.S., Klemm, P., Newman, S.T., Rahimifard, S., 2006,Integrating the CAx Process Chain for STEP-Compliant NC Manufacturing of Asymmetric Parts, International Journal of Computer Integrated Manufacturing,19:533–545.
[7] Monostori, L., Viharos, Z., 2001, Hybrid, Al- and Simulation-supported Optimisation of Process Chains and Production Plants, CIRP Annals – Manufacturing Technology, 50:353–356. 基本加工工序和切削技术英文文献和中文翻译(8):http://www.751com.cn/fanyi/lunwen_56493.html