Abrasive Blasting 101
Daily Duty Cycle (DDC) is the amount of time a blasting cabinet can operate before it needs to be serviced. We measure DDC using the gun cfm, the dust collector blower, and the filter storage area. Consider this, a 5% DDC typically translates to less than 30 minutes of total operation in a single 8-hour period. If your application requires more than 30 minutes of machine operation you may need to size-up your dust collector. And you may possibly need to upgrade the cabinet’s support features.
Dry blasting cabinets are all built to operate with an integrated dust collector. The size of the dust collector should be matched to the daily machine operation. It is possible to purchase a dry blasting cabinet without a dust collector. However, it’s not legal to operate a cabinet without one. Some people try to cut corners by hooking up a small shop vacuum to their abrasive blast cabinet. This is almost always a recipe for disaster. Considering that small, inexpensive blasting cabinets are almost always 5% DDC or less. You can imagine how ineffective a machine with a shop vac as a dust collector would be. The low volume vacuum blower and filter are not equipped for abrasive blasting.
Yes, you can operate a machine longer than it’s DDC. Unfortunately, you must then increase the number of times you clean the dust collector. Remember, a 5% DDC normally allows less than 30 minutes of total operation in a single 8-hour day using a single dust collector cleaning cycle. If you’re working more than 30 minutes, you’re spending time cleaning and servicing your dust collector between blasting sessions.
These low DDC blasting cabinets normally use less than 18 cfm of compressed air, which means they offer a much lower abrasive frictional heat temperature. This lower frictional heat combined with smaller cfm and abrasive volume can almost geometrically increase the time it takes to clean a part. Many higher DDC models using 80 cfm of compressed air can process parts 9 times faster than a 5% DDC machine. Another way of saying that is: nine hours of operation using a 5% DDC cabinet can be processed in one hour using a higher DDC blasting cabinet.
Poor machine maintenance and service is one of the most common factors that contributes to poor dust collector performance. It’s one of the most common reasons that a blast cabinet’s surrounding area becomes dusty and messy.
Real World Example: Let’s compare the relationship between a car’s gas tank and a 5% DDC dry blasting cabinet dust collector. If your car has a one-gallon gas tank, you must stop at a gas station about every 20 miles. Driving 200 miles means stopping 10 times to fill the tank, and adds significant time to your trip. Exceeding your cabinet’s DDC means you will either frequently service your dust collector, or face a messy workspace.
Maintenance can also relate to abrasive maintenance. 5% DDC cabinets are often used at blasting pressures above maximum abrasive impact speeds. This will blast parts faster, but destroy the abrasive because it is moving and exceeds maximum abrasive impact velocity. As soon as the abrasive impacts the part being blasted, it explodes into fragments which plug the dust collector filters. Again, a messy area is inevitable, but not the fault of the cabinet itself.
A dry blasting cabinet can never really have too much dust collector! Buy the largest dust collector you can find, even if you are looking to purchase a 5% DDC Cabinet.
In our more than 45 years of experience, no customer has regretted buying a bigger dust collector. That’s because usually people start blasting and aren’t ready to stop after just 30 minutes. And rather than stop to maintain the machine, people push the limits beyond the DDC. Additionally, if you have access to more compressed air, spending more for a higher DDC blaster can pay for the machine with labor dollars saved in less than one year.
If you are thinking about adding a blasting cabinet, WET or DRY, give us a call, we can help you get the right blasting cabinet the first time based on your application’s DDC.