SANDBLASTING MATERIAL GUIDE
Sandblasting is an extremely useful procedure in a broad array of applications and industries. Whether a material needs to be cleaned, deburred, prepped for powder-coating, de-rusted, shot-peened or otherwise just have its paint removed, sandblasting is the process for the job.
These devices are useful in the auto industry, in ship and rail yards and in a range of industrial applications. Certain degrees of skill and safety training are required to effectively operate a sandblaster, depending on your intended application.
When a surface is coated in grease, paint or another undesired veneer, a sandblaster can completely remove the residue and restore the item to its original condition. When machining leaves sharp burrs on an object, sandblasters can smooth it until it is safe to handle. Shot-peening is another useful application in which a metal is subjected to a barrage of small but powerful impacts — think of what a ball-peen hammer does — in order to make it more malleable. This gives the surface of the metal a compressive, plastic quality that is less likely to develop tiny micro-fractures.
Let’s look at how sandblasters work as well as the different sandblasting media types.
HOW SANDBLASTING MEDIA WORKS
What does a sandblaster do and how does it work?
A sandblaster or BLASTING MACHINES uses pressurized air to hurtle a beam of tiny projectiles, which range from walnut shells to glass beads and tiny rock particulates.
It all starts with two components: the blast pot and the pressurized air intake. The blast pot is a large container that holds the blast media, whether it is glass beads, corn cob, steel shot, plastic or other material. It funnels the media downward through a set of valves that allow the amount entering the system to be controlled.
This media then joins the pressurized air as it zips into the chamber. Note that air pressure is entirely responsible for the process of sandblasting — it is the force that whips the media around. Adjusting it in turn adjusts the speed of the particles. Sandblaster air requirements are quite strict as a result — you need a remote-control system for both precision and safety.
The air and media travel through the blast hose and out of a nozzle. At this point, they are inside the sandblasting chamber, whether that is a small compartment or an entire room, and usually come out the nozzle of a handheld gun. The particles travel at high velocities and impact the object, stripping it of whatever is on its surface. Depending on the size, texture and density of the particles, they will also leave tiny divots in the material. These divots allow future coatings to adhere to the object’s surface.
What goes in must come out. For the chamber to avoid turning into a pressure bomb, air must escape at the same rate it enters. This is where an abrasive trap comes in handy. At the point where air escapes the chamber, a trap is in place to catch the abrasive media — otherwise it would fly out of the chamber as well.
These two basic components apply to both cabinet and portable sandblaster models.
Let’s move on now to the most important component of sandblasting: the media itself. There are lots of variables in sandblasting media to give users plenty of options to choose from.
SANDBLASTING MEDIA GUIDE: WHAT TYPE OF MEDIA SHOULD YOU CONSIDER?
Looking at a list of types of sandblasting media can be daunting at first. The particles can be organic, metal, silicate, plastic or stone. Why is there such a wide array of options? How do you begin choosing one?
The reason why so many media exist is because they each perform different tasks extremely well. This is due to a number of key abrasive properties of the medium: shape, size, hardness and density.
One important result of sandblasting is what is called the “anchor pattern.” When a particle impacts the surface of a metal, it forms a small crater. This tiny crater will be lined by ridges, which are pressed up on all sides of it. The depth of this crater is typically measured in thousandths of an inch and affects how well the coating will bond to the surface of the metal. The deeper the craters, the better the bond.
However, if the craters are too deep, the ridges may poke out through the surface of the coating. This can cause rusting and weakness in the coating, which means another round of sandblasting.