PRODUCTIVITY IMPROVEMENT IN GRINDING SAPPHIRE WATCH GLASSES

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PRODUCTIVITY IMPROVEMENT IN GRINDING SAPPHIRE WATCH GLASSES Powered By Docstoc
					                                                                                                                   Project 10610.2
                                                                                                                     2009 - 2011


 PRODUCTIVITY IMPROVEMENT IN GRINDING SAPPHIRE WATCH
    GLASSES THROUGH SCIENTIFIC PROCESS ANALYSIS AND
SUBSEQUENT PRODUCTION SYSTEM MODIFICATION OR REDESIGN
                                  Ing. Pierre-Marie POCHON, Prof. Jacques GIOVANOLA

                                                           Subject of project
The objectives of this project are to improve productivity and technical performances for the grinding of watch glasses. These
objectives will be achieved by combining a fundamental investigation of the deformation and fracture mechanisms in single crystal
sapphire with a technological investigation of current grinding practices to establish processing maps relating process parameters
and process outcome. The current market position of the company will thus be strengthened and new market segments will open up
in the field of technical sapphire parts.
                                                       Innovative approaches
   Fundamental study of                     Technological study and
                                                                                    Second line of investigation
 deformation and fracture of                  formalization of the
   single crystal sapphire                   manufacturing process
                                       +                                                     Development of improved
                                                                                                 hybrid process

                                                                                To investigate the feasibility of ultrasonically assisted
                                                                                grinding of sapphire, a facility to perform a basic study
                                                                                on this process was designed.
                                                                                Performances:
                                                                                • CNC system, 3 Cartesian axes
 Establishing the fracture behavior.       Machining a specific radius with a
                                                                                • UAG 20 [kHz]
   Brinell indentation, 200 [µm]                small grinding wheel.

                             Modeling and
                            processing maps

                               A statistical experiment planning
                               approach serves to delineate the process
                               parameter     space    that   will    be
                               investigated.
                                                                                Microchipping,100[µm]
                               Relating the basic deformation to the
                               grinding response of sapphire allows us
                               to establish guidelines for process              The workpiece will be excited by a 20 [kHz] sonotrode
                               optimization.                                    with an amplitude of the harmonic vibrations between 2
     Processing map.
                                                                                and 20 [µm] peak-peak.


                          Design specifications

The combination of the processing parameters guaranteeing successful
machining in the shortest time and most economic way will serve to
establish the specification list for modification of the system.
                                                                                Torque on the spindle, machining parameters (feed rate,
                                                                                depth of cut, …) and surface quality are recorded.
                             Redesign of
                          manufacturing system
                                                                                                   PROJECT PARTNERS
In the last phase of the project we will develop and validate redesigns
of production to reach an acceptable rejection rate of 5%.

				
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posted:3/12/2011
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