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 machine you have, or need, our Buying Guide can help you choose the right delivery method to fit your needs.
Another key piece of information is that there’s no quick fix for a “too small” 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.)
5 Compressed Air Factors for At-Home Sandblasting
There are Different Types of Air Compressors
- Piston Air Compressors are the most common and the least expensive but always consider the cfm volume at 100 psi and never let the size of the tank be your first consideration.
- Single Stage air compressor pumps turn off at a lower pressure in the tank. If you are considering a single stage make sure it turns off at 150 psi and on at about 120 psi or you will run low on blasting pressure before it turns back on.
- Two Stage air compressor pumps normally produce more compressed air volume but they also cost more. If the electrical power is limited to single phase power you want the most air you can get, try to budget a two stage pump if you can afford the additional expense.
- 100% Duty Cycle compressor can operate 24 hours a day without damage to the compressor because the piston is larger and the speed is slower to lower the piston heat.
- Piston compressors can be aluminum pumps, aluminum pumps with cast iron piston sleeves and cast iron throughout. Cast iron can take more abuse but it’s the stated compressor duty cycle (amount of daily operation measured in ten minute time periods) that tells you what you really want to know about the quality.
- Vertical air compressors require less floor space but they also pump less air than horizontal units, why? Vertical models must pass a vibration test to make sure they stay vertical! Supplying a large heavy tank and a small compressor pump is one way to make sure the safety test is passed but they look massive and often you consider the tank size meaning more air – this normally means less compressed air!
- Rotary Screw air compressors produce more volume than piston types and they are normally used when piston types simple are too big in piston size. Most operate on a servo switch pumping only the air you need. Just like cruise control on new cars you get the power you need for the work you want done at any moment in time.
- Hydrovane are mostly motors and have the smallest footprint but they are also expensive to buy and produce larger air volumes for the motor used. When you look at a Hydrovane compressor what you see is mostly the motor but you can simply think about the Wankel Rotary Engine and you will start to understand the Hydrovane compressor concept.
- Diaphragm air compressors are old technology but they use a bladder to pump the air but they normally don’t have pressures more than 100 psi. Think about your own diaphragm filling your lungs with air and you have the basic idea.
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 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 base 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.
How CFM Affects Sandblasting:
- 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 important 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.
- 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 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.
Things to Know when Comparing Air Compressors
- 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.
Other Factors that Affect Sandblasting Efficiency
- Buying a smaller abrasive blasting cabinet typically means you will have a smaller dust collector, which can result in running the cabinet longer, and exceeding the limits of the dust collector supplied with the blasting cabinet.
- Operating a small gun with the air compressor that could accommodate a larger gun will extend your cleaning time.
- With smaller dust collectors, it’s very likely the workspace will become messy and require frequent cleaning.
To Sum it Up
Compressed air can be confusing so this is what we suggest:
- Look for a vertical compressor if you want to save space but look for one that turns off at 150 and back on at 130 or close to those numbers. Either single-stage or dual stage compressor pumps will both produce these pressures but know that dual stage produce higher pressures so they store more air inside any give tank size or volume. Horizontal tanks normally have higher volumes than vertical tank units and considered true industrial models.
- Look at the cfm delivered – ideally you want 90 to 100 blasting psi performance – then consider the cost of the unit. An expensive cast-iron tank that doesn’t deliver enough compressed air is worth far less than a right-sized tank made from a lower quality material but exceeding the compressor duty cycle measured in 10-minute intervals will wear out the compressor quickly.
- Beware: tank size can vary. Some people only want to operate an air impact tool and some people want to paint an entire car and some want to abrasive blast parts all day and some only a few minutes. If the compressor doesn’t pump enough volume you will run out of air quickly, you can’t use the air inside a tank that’s below 100 psi if you want to blast at 100 psi.
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 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!