The type and degree of surface finishing varies widely from part to part. A part may require one, or several surface finishing operations including, de-burring, polishing, surface texturing, sharp edge breaking, and preparation for coatings.
Any type of manufacturing which uses a tool to cut metal, including milling and turning, will create a bur. This bur may not be easily visible to the naked eye, but will almost always be present under magnification. When dealing with micro sized parts imperfections which would typically be considered undetectable become a big problem. We employ a range of strategies to remove burs.
Micro abrasive blasting, as used in dental labs, is one of the most versatile de-burring tools. By using extremely fine blasting media (down to 20 microns) and choosing the appropriate type of media, this tool can be fine tuned for a multitude of tasks. Soft plastics can be de-burred without effecting the delicate geometry of the part. The same goes for the hardest of metals. Even glass and ceramics can be processed by micro blasting.
De-burring is not the only use. Micro abrasive blasting is also perfect for producing a uniform dulled finish or preparing a surface for a particular type of coating, such as anodizing. With the correct type of media tooling marks can be erased without putting a part out of tolerance in most situations.
Another surface finishing tool is mass media vibratory finishing. Parts surrounded in a particular type of media, ranging from ceramic triangles to walnut shells, are vibrated at high frequency until the desired result is achieved. Again, Media choice is everything. An aggressive media can be used to remove tool marks and gently round sharp edges. A softer media with an abrasive compound can bring surfaces to a polished finish.
For extremely delicate nonferrous parts, magnetic pin burnishing can have excellent results. The parts are bombarded by thousands of tiny stainless steel pins being spun in a magnetic field. the parts are burnished instead of abraded, so nearly no material is removed. The result is effective de-burring and surface enhancement while still keeping very tight part tolerances.
And of course, sometimes, with the most delicate and precise pieces, only hand finishing will suffice. Hand finishing each part can be time consuming, especially when done under magnification, but sometimes there is no substitute.
The most important aspect of these different finishing procedures is knowing when and how to implement each one. We have the knowledge to employ the correct process with the proper media to deliver the desired results.
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