Deflashing Plastic Parts

Molded plastics often contain flashing that needs to be removed. While there are many methods ranging from a sharp knife to cryogenic deflashing, vibratory tumbling is an effective and cost efficient method.

Flash sticking above edge
Flashing removed - smooth edge, matte finish


The part was vibratory tumbled with Ceramic Media for only 30 minutes. A non-abrasive tumbling compound solution was used to keep the process lubricated and clean. Even after this short cycle time, the flashing was completely removed and the edge was smooth. The surface had matte, tumbled finish. At a 30 minute cycle time the general purpose media should be able to be re-used for 250 or more batches to spread the operating cost over many parts.

Choosing Tumbling Media for Deburring, Deflashing or Polishing

Choosing the proper tumbling media (vibratory tumbling or barrel tumbling) for any deburring, deflashing or polishing application requires balancing the aggressiveness of the operation with the surface finish specifications. As long as a rough, tumbled appearance is acceptable a more aggressive media can be used to remove burrs and 'smooth' a surface resulting in a shorter cycle time . If the surface finish is important (i.e., for anodizing or thin-coat plating), a less aggressive media and longer cycle time is necessary. Often a multi-step process is used with progressively less aggressive media to achieve a deburred and smooth part or even polished part.

Generally, Ceramic Media are used on harder metals like steel or titanium. Plastic or Synthetic Media are better for softer metals like aluminum, brass and copper. Within each type of media, a variety of formulations (or bonds) are available from ultra aggressive to general purpose to polishing.

Crushed Glass Grit - Uses (2)

Both Medium (40-70 mesh) and Fine (70-100 mesh) Crushed Glass Grit can be used for many different applications. Below are examples of some of the more popular uses - some may even surprise:

Medium Crushed Glass Grit

• Auto restoration - rust removal, more aggressive than soda
• Log home - rough hewn logs, aggressive on wood
• Masonry restoration - brick, cement block
• Tanks - mill scale removal
• Graffiti removal - concrete, asphalt (no damage on surface)
• Consumer - metal (iron): lawn furniture, fencing, decking

Fine Crushed Glass Grit

• Log home - smooth finish, alternative to Corn Cob Grit
• Aluminum surfaces - no pitting, good strip rate
• Auto restoration - body panels, engine parts (smooth, etched finish)
• Boats - fiberglass, no media embedding
• General parts cleaning - less than 1 mil surface profile

Obviously, the list of potential applications is much longer and limited only to the imagination and expertise of the user. Please share other applications in the comments section.

Crushed Glass Grit - Uses

A quick list of applications and uses for Coarse (10/40 mesh) Crushed Glass Grit:

• Bridges - heavy paint and coatings
• Tanks - outside welds, rust
• Pipelines - rust and oxidation
• Water towers - paint, rust
• Ship hull blasting - welds, paint, oxidation
• Barges - clean-up, surface preparation
• Heavy, industrial equipment - tractors, front-end loaders, snow plows
• Structural steel - surface profiling, oxidation removal

Coarse Crushed Glass Grit can be used for many applications and reasons (not just the short list here). The 10/40 mesh size is the most aggressive and can provide a 2-3 mil profile on many surfaces. Please share your experiences with Crushed Glass Grit in the comments to this post.

A list of applications for the finer sizes to come on the next post.

Powder Aluminum Polishing

Aluminum powder products offer many advantages over other metal powders due to aluminum's inherent corrosion resistance, lightweight density, machinability and non-magnetic properties. After pressing (at lower pressures than other metals) and sintering (at lower pressures) the parts needed to be deburred and prepared for surface finishing/coating or anodizing.

The parts in the picture were vibratory tumbled with a light cutting Synthetic Media to remove burrs and create a uniform, matte surface finish (2 discs on left). A second step to polish the parts (2 discs on right) also involved vibratory tumbling but with a polishing Ceramic Media. Appropriate neutral pH compounds were used to remove and prevent oxidation of the surface. Cycle times were only 1-2 hours for each step.

Silicon Carbide

Silicon Carbide is manufactured from a high heat reaction of silica sand and carbon. While silicon carbide and silica share similar chemistry, Silicon Carbide used in abrasive blasting contains less than 1% free silica. Free silica or silicon dioxide is the compound that should be avoided (due to risk of silicosis) and not inhaled as a fine particulate. Details about Silicon Carbide can be found on a previous post.

Blasting Stone with Sand

Question: I am thinking of purchasing a small business doing stone engraving. My only concern is blasting with the silica sand which is what is being used right now. We plan to use a blasting room and filtered breathing system but I don't know how safe I can be using silica sand. I am curious about alternatives like silicon carbide and aluminum oxide and could use any tips and advice on how I can do this kind of work safely.

Response: Blasting with silica sand is definitely NOT recommended - even with a breathing apparatus. Both Aluminum Oxide and Silicon Carbide are more aggressive blasting media than sand and will provide quicker results and a better surface finish on stone. Both of these media can be used with standard abrasive blasting systems without modification. Of course, always minimize breathing any kind of dust when blasting.

Steel Bluing

The process of bluing steel creates a micro finish on the steel surface to prevent corrosion and rust. Putting this type of finish is very popular with guns as the process improves the surface finish, protects it and reduces the glare off the metal. While not nearly as durable as plating or painting, bluing is an inexpensive and simple surface finish.




There are a few different ways to blue a surface but all involve creating a very thin 'coating' of iron oxide on the surface. This coating prevents oxygen from further attacking the steel. This is similar to the way the green 'coating' (copper oxide) coating on the Statue of Liberty protects the underlying copper. Bluing gets its name from the coloring of the iron oxide (magnetite) the process creates. This is a different chemical compound than the reddish color typically associated with rust (also iron oxide).