No, These Aren’t Birthday Candles

They’re actually rubber impressions of tiny drilled holes. The folks at National Jet in Maryland showed such examples to me when I visited to develop this story about their approach to machining micro-holes for spinerettes (aka polymer extrusion dies).

Some spinnerettes have micro-holes with critical diameter transitions that can't be visually inspected by conventional means. To check these internal profiles, National Jet injects a two-part rubber compound into the holes. After the rubber sets up, it is pulled from the holes to reveal the exact hole profile. These rubber profiles are then examined on a measuring microscope.

This story is part of MMS Online’s growing Micromachining Zone. There you’ll find articles, video and even an expert available to field questions you may about creating tiny parts and features with small tools and precision machines.