Introduction to airless blasting
Machines for air less blasting come in a wide variety of styles and perform the job in many different ways. Ranging from tumbling in a barrel or traveling on a conveyor to spinning on a hanger or rotating on a table. Though different in many ways, they all propel the abrasive without air. The airless blast wheel is the “heart” of these abrasive blast systems. The centrifugal “airless” wheels have an internal impeller and blade design which “slings” the abrasive at the at the parts. The blast wheel acts much like a pump. The blast wheel impeller and blades are revolving at around 3600 RPM’s and propel the abrasive from 250 to 300 feet per second. A number of wheel designs have been developed over the years with current models providing the best combination of features for smooth abrasive flow, a tightly focused blast pattern, and controlled impact energy. The efficiency and accuracy at which airless blasting machines perform today provide for a much lower cost per part than air propelled systems .
Variety of airless blasting abrasives :
A large variety of airless blasting abrasives, sometimes called media, are available to accomplish a wide spectrum of tasks. The shape, size, and material of the abrasive used is dependant upon the shape of the product, its base material, and the task performed. Many tasks can be performed by airless blasting, such as stripping of paint and other coatings, cleaning and descaling, derusting, deburring, etching or texturizing. Below are a few examples of the more popular abrasives used today.
- Steel Shot
- This is typically round and is made of annealed high-carbon steel or stainless steel. It has a long service life and high breaking strength thanks to its fine-grained, martensite microstructure.
- Steel Grit
- Produced by breaking the round steel shot. It has very good cleaning properties with an excellent surface finish.
- Aluminum Oxide
- Belonging to the group of electro-alumina. This alumina contains approx. 2.90% titanium oxide and is a tough and extremely resistant, non-ferrous abrasive for extreme requirements.
- Cut Wire
- Made from aluminum or steel wire cut to various lengths. Used in cleaning and descaling of castings and forgings, surface preparation for welding or plating, etching, cutting and polishing of stone.
- Ceramic & Glass Bead
- Their high hardness and spherical form can remove impurities and metal oxides without damaging the treated surfaces. Exellent repulsion factor to shorten blasting time and high gardness for low abrasive consumption.
- Plastic Media
- Made of a wide variety of polymers. Used for cleaning, stripping, and surface preparation of more delicate base materials.
- Cast Iron & Pumice
- During the blasting process, each grain breaks at an angle producing a permanent mixture of sharply angled material. This results in the excellent cleaning properties, and the ability to roughen up the hardest surfaces.
- Other Media
- Includes crushed glass, walnut shells, bronze alloys, silicon carbide, wheat & corn starch, and other exotic compounds.
Styles of airless blasting machines
The variety of styles in airless blasting machines is so great it is beyond the scope of this document. Though, in general, they all contain several basic components. A hopper to contain the media, the blast wheel media accelerator section, the blasting enclosure to contain the media, a part suspension system, dust collector, media recovery system, and an electronic control. The only main difference is thier ‘work handling’ of the parts.
The airless blasting system is also extremely efficient and economical to use compared with other pneumatic, mechanical or chemical means of cleaning parts.