What is the Best Process for Micro-Deburring?

Question

One of our main difficulties in micromachining is micro-deburring. We have aluminum parts with lots of intricate features machined at 30,000 rpm that require an edge break of no more than 0.002 inch and no visible burrs under a 10X microscope. In your experience, what is the best process for deburring small features?

Response from John Bradford, micromachining R&D team leader for Makino

As you know, this is one of the most challenging aspects of small feature machining, especially in soft materials. We have several techniques that we have applied successfully for deburring. They include:

● Miniature tumbling using various media—such as walnut shells and polymer pyramids. The parts are generally tumbled in these media materials with a liquid. A useful site for reference is www.kingsleynorth.com/skshop/search_results2.php?catID=823

● Micro glass bead blast. We use a Renfert micro bead blast unit that is designed for dental applications. This unit provides us excellent control of the media flow and pressure. Also, the media type and size can be switched easily per the application requirement. Our unit has nice foot pedal controls that immediately start and stop media flow as needed.

● Nitric acid etching. This is a last resort. Depending on the material, it can be aggressive. Nitric acid etching is effective for removing smaller burr remnants immediately, but then if left active, it will begin to remove parent material. Use this one carefully.

We also occasionally perform "deburring" machining passes that offset the cutter by a certain amount radially and axially (for example, 0.0005 x 0.0005 inch)—so we effectively notch out the corner where the burr is hanging on. In many cases, this machining pass will remove the burr without affecting the performance of the remaining feature.