Mechanical Finishing

SURFACE BLASTING is a process unmatched in the quick removal of adhered surface debris and surface oxidation.  It's an operation that is high speed in nature and can be done with a high volume output.  Surface profile can vary widely but the net affect is a tremendous surface for additional finishing operations. 

The process works by exposing a chosen media to a spinning wheel that propels it at a very high rate of speed towards the surface being prepared.

PowderTech offers two type of blasting - tumble blasting and conveyor cabinet blasting services for excellent metal finishing of parts in any shape or size.

The media employed can be changed at any point to meet customer specifications for surface profile. Mechanical surface finishing can been done as a final finishes or as a pre-finish to other operations.

Blast finishing is a very effective means to removing oxides, casting flash, and smoothing parting lines or extractor pin marks.

These operations use a variety of blast media to provide the appropriate level of surface profile required on the part. These operations can significantly improve the final finish that is applied but are not for improving future corrosion as a stand alone process. Whether it's a plate or organic finish, blast finishing provides an important step in removing surface contaminants that can cause future problems when not addressed.

Media incorporated in either of these two operations are interchangeable and include:
1. Aluminum Oxide  2. Glass Beads  3. Plastic  4. Stainless Steel Shot  5. Walnut Shells

VIBRATORY DEBURRING is known for its low production cost per piece. With the proper application of media and surfactant compounds, very refined surface finishes are possible. Various metal types can be optimally processed and prepared for powder coating, conversion coating and electroless nickel plating. Vibratory finishing can remove flash, smooth burrs and hone parts to a micro surface finish. The process can also serve to remove chips and roughen plastic surfaces for operations requiring superior coating adhesion.

Vibratory deburring works by having the media and parts to mix together. The vibration of the tub or bowl in a circular motion causes a scrubbing action. While the load is scrubbing, the vibration of the bowl causes the load to circulate at a slow rate. This circulation keeps the pieces separated to avoid impinging on each other. The frictional forces work on the exterior surface of the part, and to a lesser degree the inside as well. Cleaners and or special compounds are added for rinsing, burnishing, and rust inhibition.

The choice of media and compound determines the type of finishing operation. Polishing or refining operations for die-castings are usually performed with either stainless steel or plastic media combined with a mild, alkaline compound. The plastic media, being soft and lightweight, can abraid without galling or scratching the surface of the part. The heavier stainless steel media provides a burnished look. These type of processes don't usually provide a highly polished or reflective surface.

Heavier surface abrasion is usually done with ceramic media. It is more aggressive, but does not produce the flatness achieved with plastic media. To obtain a maximum finish on parts with heavy flash or burrs or bad imperfections, rough cutting is first done with ceramic media and then the surface is refined with a short run in plastic media.

Thinly applied coatings (< 5 microns) don't perform well over the dull finish produced by plastic. Ceramic media is used with different compounds to provide a burnished effect while still having abrasive qualities.

High geometry parts with extreme detail typically use very small media to allow penetration on all surfaces. Magnesium casting, such as power tool enclosures, requiring a good finish prior to powder coating are run this way using highly alkaline compounds.

While the parts vibrate, a lubricating surfactant compound is mixed with water and circulated through the vibratory bowl. The vibrating action rubs the parts while churning the compounds onto all surfaces. Chips and dirt are flushed out of the tub as the machine is running. This cleaning is not sufficient to move directly to additional operations like painting or plating but is a great first step in part cleanliness!