In their quest for quality, the personnel at Ford’s Dunton Technical Centre in Brentwood, Essex, England, use a scanning electron microscope. Explained Roger Davis, who performs materials engineering and testing at the site, “We need to investigate possible reasons why a development part may not meet our stringent requirements. In some cases that reason can be the smallest anomalies, something that can be found by using the scanning electron microscope. The machine can magnify a part by up to 200,000 times and make it look quite surreal, but to the trained eye any defects become quickly apparent at these levels of magnification.”
The SEM works by using electrons rather than light waves, as is the case with conventional microscopes. Parts are placed in a vacuum chamber, and then an electron beam is scanned across the part surface through the use of a series of electromagnetic coils. The beam of electronics knocks secondary electrons off the surface of the part, which are amplified, then displayed on a cathode-ray tube.
When you look at the accompanying images, realize that 100 µm equals 0.1 mm. The diameter of a human hair is approximately 80 µm.