Abrasive Blasting 101
Are you wondering which is the best abrasive delivery method for Maximum Media Blast® Cabinet Production? This question is answered incorrectly more often than correctly mostly because people don’t understand the question or the equipment. Direct pressure abrasive delivery appears to clean faster than siphon abrasive delivery, but often the comparison doesn’t keep the abrasive speed, and the cfm being used the same.
If a siphon abrasive blasting cabinet is using the same cfm as a pressure blast cabinet, and both are using the same abrasive with the same abrasive speed, the two machines will have almost the same pounds of abrasive delivered to the part per minute. The two abrasive delivery types will need different nozzle sizes and different blasting pressure to achieve the same speed of the abrasive impacting the part surface. This means when it comes to the maximum Media Blast® cabinet production – either delivery method can achieve the maximum production output depending on several factors.
Pressure has the compressed air pushing against the abrasive like a gun bullet and shell, with the abrasive weight having no affect. The siphon is using an injector gun to pull the abrasive, siphon it, into the gun body where the inside air jet flicks the abrasive out the nozzle.
Real World Example: Direct pressure abrasive delivery is like using a pool cue to hit a ball into the pocket. Siphon abrasive delivery is like using a cue ball to hit a second pool ball into the pocket which means losing some energy. Siphon delivery loses some abrasive energy and direct pressure does not, so siphon requires the higher blasting pressure. Both delivery types can exceed maximum impact speed of almost all abrasives.
To dive deeper into the differences between these two types of abrasive delivery, check out Siphon Abrasive Delivery vs. Direct Pressure.
It seems like we could simply turn up the direct pressure to achieve more maximum Media Blast® cabinet production output. Unfortunately, this isn’t possible because almost all siphon delivered abrasive can explode when it impacts a part at 100 psi. So, turning up the pressure on the direct pressure cabinet, which creates twice the abrasive speed as siphon, will greatly increase the cfm being used and destroy the abrasive in a single pass through the system when blasting above 50 psi. You cannot turn up the pressure beyond maximum abrasive impact velocity, and you must maintain the same cfm usage. People that do this with direct pressure will destroy the abrasive.
Pro Tip: The blast pattern of the siphon is wider than the direct pressure using the same cfm volume.
To understand which abrasive delivery method gives the maximum Media Blast® cabinet production output we have to think bigger than just the part processing time. The siphon delivery Media Blast® cabinet can run continuously, which is why most automated machines use siphon abrasive delivery. If direct pressure was faster, then all cost engineers would favor direct pressure. The direct pressure has a smaller more concentrated abrasive delivery pattern with a higher frictional heat, and it normally has to stop operating to have the pressure pot re-filled after minutes. Nothing is an absolute, but for most applications these facts are rock solid.
Real World Example: What would you rather do: paint a car with a spray gun with a wide pattern, or a garden hose? Would you rather mow a lawn with a lawn mower or an aggressive weed eater string mower? The siphon pattern is all you need for most blasting applications and easy to overlap the blasting pattern.
Direct pressure abrasive delivery cabinets may not always achieve the maximum Media Blast® cabinet production output. But these cabinets can do something that siphon delivery media blasters can’t. With the pneumatic push of the direct pressure behind the abrasive, you can use heavy steel shots and grits to peen at a much higher intensity. You can’t possibly siphon large shot to the gun of a siphon delivery cabinet because it’s simply too heavy to siphon convey. And turning up the siphon pressure to 200 psi to increase the abrasive velocity will also stop the injector gun from delivering abrasive.
Each machine delivery type can do something the other can’t and it takes all the different models to make sure the user is getting the right machine, and maximum output, the first time. If you’re looking for the maximum Media Blast® cabinet production output, then give us a call and we’ll make a recommendation based on your specific application.
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