Abrasive Blasting 101
Blog updated November 22, 2021: Before you buy an air compressor for your home garage blast cabinet, there are a few things you should know. First and foremost, it’s the compressed air that actually powers the blasting for any directional abrasive blasting cabinet or hand held gun. Whether you’re using a siphon or direct pressure abrasive delivery method, you’re going to need the right air compressor for your application.
Pro Tip: If you’re not sure which media blasting machine you have, or need, our Buying Guide can help you choose the right abrasive delivery method to fit your needs.
Another key piece of information is that there’s no quick fix for a “too small” air compressor. Abrasive blasting requires more than 100-psi tank pressure, and anything less than that (regardless of the size of the tank) will add time to your project. Why is this the case? The Rule of Coefficient of Friction states that if you reduce the blasting pressure to only half the maximum pressure cleaning time increases 4 times. This means a 10-minute cleaning time at 100 psi will turn into 40-minute cleaning time at 50 psi. (Fun Fact: using half the volume of compressed air with a small gun size will do the same and turn a 10-minute job into a 40-minute job.)
1. There are Different Types of Air Compressors
2. Home Garage Power is Different than Industrial Power
Most home garages have residential (208 to 230 volt single-phase) electrical power. If you can operate a home dryer, range or large heat pump you have a 208-to-230-volt single-phase power supply and will want access to your home’s electrical panel for the air compressor.
Single-phase motors are normally no larger than 5 hp and they come in standard sizes such as 1, 2, 3, 5 etc. You will find motors rated at 6-1/2 or maybe 8, but this will be rated horsepower based on a different test. The real importance is the motor amperage being used, where the 6-1/2 or the 8 hp rating will be about the same as a basic 5 hp motor and use the same amperage.
3. Did you know Cubic Feet per Minute (CFM) Affects Sandblasting
Cubic Feet per Minute (CFM) in the context of HVAC and compressed air affects sandblasting. Lots of factors affect CFM, but generally the more compressed air the higher the CFM.
Some companies supply abrasive blasting cabinets said to operate using a 120-volt air compressor, but these are normally using about 6 cfm. This is a very small gun size, but more importantly each different gun size produces different amounts of frictional heat at the same blasting pressure.
This means a larger gun size will not only blast more quickly but it will also operate at a higher frictional heat making it exponentially faster. Just think about an orbital sander – the more you push down the higher the frictional heat and the faster it sands.
ProTip: Doubling a cabinet’s gun size will normally reduce the cleaning time by more than 2/3rds. This will save you two hours blasting on a 3-hour job!
One exception to the rule of thumb above is the sandcarving industry; they use the direct pressure delivery and a small nozzle size to eliminate frictional heat to help preserve the mask material. Media Blast offers a large line of CrystalBlast sandcarving machines that are direct pressure models but we also offer the 3030 Savage sand blaster that is a direct pressure cabinet made to operate in home shops with an industrial dust collector for clean operation.
4. Air Compressors with Higher PSI Clean Faster
All air compressors have two different volumes of compressor airflow shown in the printed specifications. One is displacement (mathematical formula for the piston size vs. the pump rpm with zero pressure in the tank pumping in a vacuum). The other is what we call the working compressor number, which is basically the usable air volume. This number is normally between 90 to 100 psi.
Higher psi means faster cleaning. There are piston air compressors on the market that will deliver 25 cubic feet of air per minute at a tank pressure of 150 to 175 psi and operate on 220-volt single-phase power. While these are more expensive, your application may require this output or you may feel the cost is worth the time saved.
5. Larger Might be Better
Purchasing an air compressor can be confusing so this is what we suggest:
The air compressor is one of the biggest factors determining cleaning speed on a blast cabinet. For more information about buying an air compressor check out Air Compressor 101: Everything You Need to Know.
Pro Tip: One air compressor is not right for everyone but you can buy a good 16 cfm air compressor for $600 or one that is less desirable for $1000 depending on how much homework you do ahead of time.
Media Blast manufactures 170 different blasting cabinets models, Wet, Dry, Siphon, Gravity Feed and Direct Pressure, Light Duty, R&D and Production, with special blasting cabinets for Steel Shot, Plastic and Soda. We have a complete line of smaller micro units for special low frictional heat.
We want to help you buy the right machine the first time – contact us today!
– The Media Blast & Abrasive Team