Abrasive Blasting 101
Before we get too far ahead of ourselves it’s crucial that you understand many abrasives used in sandblasting are the same as the abrasives used in sandpaper, abrasive belts, sanding pads and all types of grinding wheels. These abrasives are not to be confused with actual sand and softer slags such as Black Beauty that are used only once. If this comes as a surprise, remember that sandblasting is like hamburger – there’s no “sand” or “ham” involved!
You can probably imagine how quickly sandpaper would disintegrate if it were made of softer abrasive, leaving large amounts of dust in your work area and lots of worn out paper. Abrasive blasting machines aren’t much different in concept. They eliminate the paper used to convey movement of the abrasive grains and use compressed air to move the same grains around and over, just like a looped sanding belt uses the belt itself to convey the abrasive used again and again.
Keep in mind that blasting cabinet dust collectors are designed to mainly collect the material being removed from the parts and not to receive large amounts of spent abrasive. By using poor quality abrasive in any media blaster, you’ll soon overload any dust collector’s capacity to store the spent and exploded softer abrasive. When soft abrasive explodes on impact, it can no longer be used because it’s particle size becomes too small to be effective or flow properly within the cabinet.
As the non-quality, softer abrasive turns to dust it’s ability to remove and clean the part is diminished, meaning that it takes longer and longer to clean the same parts. Additionally, visibility inside the cabinet itself is also compromised. Smaller machines with slower cleaning rates due to the low compressed air usage, low abrasive delivery and lower frictional heat, normally have the smallest dust collectors. These machines can clean up to nine (9) times slower than others. All of these factors compromise productivity and decrease return on investment (ROI).
Even the smaller siphon blasting cabinets will deliver about 5 pounds of abrasive grain per minute to the blast gun. The three hundred pounds per hour of dust from too-soft abrasive will soon plug any size dust collector and overload the filters stopping airflow being removed by the exhaust blower. Quickly the workspace will become very undesirable.
(Video Credit: Pasir Sandblast, Abrasive Blasting)
In practical terms, not using high-quality abrasives can require you to stop and clean the dust collector 5 to 6 times per hour of operation. As production increases, this can mean cleaning the dust collector daily and the real mess soon becomes apparent.
Quality abrasives hit the part, do the work then bounce off the part to be used again and again. The only thing going into the dust collector is the material being removed from the part itself. Glass beads have a maximum impact velocity that relates to blasting pressure and the part itself. They will bounce off a piece of cold rolled or hot rolled steel using a siphon delivery blasting cabinet at 80 to 90 psi or 40 to 45 psi using direct pressure without breaking. (For more on that topic see Why Blasting Cabinets Need a Separator Reclaimer.)
Using quality abrasives, harder types like aluminum oxide, silicon carbide, glass beads and others means four things:
These are all good things that all quickly disappear when you save cost on the abrasive you use. Add in the high number of time you recycle quality abrasives and you soon see the money saved using a higher quality higher costing abrasive inside any abrasive blasting cabinet.
More information is available about the different abrasive types, sizes and hardness by viewing our glass bead conversion chart, grit size conversion chart, or by contacting us directly with your questions.