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Trepanning
Trepanning, also known as the circular cutting method, is used for producing larger holes. With this method, the dimension and precision of the drill hole diameter is determined by the relative motion between the workpiece and the laser beam. This technology roughly corresponds to laser cutting. An additional increase in precision by further decomposing the drilling process in ever more individual steps becomes possible by the so-called twist drilling, developed from trepanning drilling. Various scientific investigations have proven that a drill-hole quality that has never been achieved in ceramics and steel is possible with this method.
The centerpiece of the trepanning optical system consists of three specially designed beam splitters for aimed deflection of the laser beam. During the process, all three beam splitters rotate around the fiber optical axis. This allows one to adjust a desired phase shift proportional to the radius of the helix on the material. Integrating the trepanning optical system into the polarization adjustment will further improve quality. Drag lines will be avoided, the outlet cross-sectional area will be circular, and process efficiency will increase due to higher absorption.
(Springer Handbook of Mechanical Engineering, Springer Handbook of Mechanical Engineering,p672)

Proximity Sensors
Proximity sensing using optical or acoustic techniques is useful when a robot tool is brought into contact with a workpiece. Since the robot is designed to be very stiff and the workpiece is usually quite rigid, the contact force between them builds very rapidly when the robot contacts the workpiece with finite velocity. Even if force sensing is used, the contact force may build to damaging levels before the system can respond. Proximity sensors are short-range, noncontact sensors which allow fine control of tool velocity shortly before contact to avoid severe impacts. Optical systems based on triangulation or simply the intensity of light reflected off the workpiece have been tested. Ultrasonic rangefinders using a sonar-type principle offer an alternative technology.
(Standard Handbook of Machine Design, Robots and Smart Machines, Kenneth J. Waldron, Ph.D.,p47.20)

Digital-to-Analog Converters
Analog-to-Digital and Digital-to-Analog Converters
Most sensors transmit data in analog form. At some point this must be converted to a digital format to allow the computer to read it. This is done by means of an analog-to-digital converter. Conversely, the driver circuits of actuators require analog input. Thus, the digital output of the computer must be converted to an analog signal by a digital-toanalog converter. Transmission of an analog signal requires only a wire pair, often in the form of a coaxial cable. With the recent advent of relatively inexpensive and compact analog-to-digital converters, considerable flexibility is possible in selecting the appropriate place in the system to perform the conversion. However, the limited number of output lines available on a microcomputer processor board usually requires that digital-to-analog conversion be done in the computer on circuit boards designed for the purpose. The outputs from the digital-to-analog converters are amplified and transmitted as analog signals to the actuator drivers.
(Standard Handbook of Machine Design, Robots and Smart Machines, Kenneth J. Waldron, Ph.D.,p47.25)

Tool Wear
Grinding wheel wear may take place in the grains and the bond. The wear phenomena can be related to dulling or grain/bond breakage. In dulling, wear flat areas are formed on the edges. They lead to increasing grinding forces and temperature. This normally happens when the abrasives are submitted to gentle grinding conditions. When the abrasive grains are under higher loads the grain/bond breakage mechanisms will lead to higher volumetric wear resulting in constant grinding forces and temperature. Surface finish quality may deteriorate and form errors may increase.
(Springer Handbook of Mechanical Engineering, Springer Handbook of Mechanical Engineering,p641)