May/June_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A Y / J U N E 2 0 1 8 2 7 TECHNICAL SPOTLIGHT HOW TO MAKE SAMPLE CUTTING MORE EFFICIENT New designs of precision cutters are optimizing sample preparation for greater efficiency, consistency, and precision. P recision sample preparationofmet- als and composites is the key to re- liable, high volume product testing anddiagnostics in awide variety of indus- tries. In aerospace manufacturing, for ex- ample, metals are being combined with advanced plastics and composites to ad- dress stringent performance demands. In addition to the need to cut flawless sam- ples to meet exacting dimensional speci- fications, changes are taking place in the overall quality control/quality assurance environment. Some of these include sat- isfying the continuous demands of high volume testing and the ever increasing precision of components and parts. In a high volume production environment, hundreds of samples from production batches must be run through the lab on a daily basis. For metallographic studies, the process often requires parts to be sec- tioned, a destructive technique by ne- cessity. Sectioning, the first step in the metallographic preparation procedure, creates a damaged layer at the cut sur- face. The extent of this damage is a function of the sectioning technique, machine design, material being cut, nature of the wheel or blade selected (including the abrasive type, size and distribution, bonding agent, and thick- ness), and the cutting parameters uti- lized, including the feed rate, blade rpm, coolant flow, and other variables. Sectioning inherently causes some level of damage to the specimen. As demands for higher sample quantities increase—along with stricter quality benchmarks—companies are seeking ways to minimize damage caused by sectioning. Precision sectioning reduc- es kerf loss, is exact enough to be used when specimens must be sectioned at precise locations, and is delicate enough for use with fragile or friable specimens. Surface finish is also bet- ter than that produced by other cutting methods. Time savings is another factor to consider: After precision sectioning, The goal of precision cutting is to minimize damage to the sample andmaximize the flawless surface area available for analysis. Fastener integrity is crucial to aircraft safe- ty and performance. Integrity is verified by stringent sample analysis. there is no need for coarse abrasives to remove the kind of damage produced by other sectioning techniques. The goal with precision cutting is to mini- mize damage to the sample and maxi- mize the flawless surface area available for analysis. Other benefits of high vol- ume sample testing include: • Less rework on sample cuts, saving both sample material and lab time • More samples cut in a single day, enabling lab staff to focus on other tasks SAMPLE CUTTING VARIABLES Three main factors impact the sample cutting process: blade speed, blade composition, and control of heat and cutting load. Here we consider each of these variables: Blade speed. Power hack saws, band saws, and shop abrasive saws (generally run without a coolant) are