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Media Blasting Basics

Media Blast manufactures a complete line of abrasive blast machinery including Light Duty, General Purpose and an extensive line of Siphon and Direct Pressure Production models. In addition to common dry blast machinery, Media Blast also manufactures a complete line of dry Micro siphon and Direct Pressure models. If you have a special application that requires a wet abrasive blasting machine, look to our Hurricane model. The following basic information about blasting machinery will help you select the right machine for your application. Please use the Buying Guide or the Machine Comparison Matrix to help you decide which machine is correct for your application.

CLEANING SPEED

Cleaning speed varies based on the amount of compressed air used. The greater the cfm used, the higher the frictional heat created at any set blasting pressure.  Always allow for existing needs when determining the amount of compressed air required for an abrasive blasting cabinet, and know that compressed air is measured in Cubic Feet per Minute (CFM). Our compressed air basics covers has more detailed information about how air affects blasting.

The construction and quality of air compressors can differ greatly and CFM can vary within the same horsepower rating, still the following rule generally holds true. What takes a 5 HP compressor 1 hour to process, will take a 10HP compressor 20 minutes, and a 20 HP compressor 7 minutes. When you double the cubic feet per minute of compressed air, you triple the Production capacity or reduce the blasting time by two-thirds. This is the single most important reason that Production machinery will make up for its additional cost, resulting in reduced labor time and increased Production output.

Abrasive gun sizes operate at temperatures that increase in Frictional Heat, as the abrasive gun size increases in air CFM usage. Larger guns generate more Frictional Heat during the blasting process, which in turn, greatly reduces the processing time. The increase in Frictional Heat, added to the increase in abrasive flow, results in a tremendous decrease in blasting times. Faster blast cleaning rates require additional machine features to maintain proper operation of the equipment. Production machinery may cost more, but simply put, it does more!

Light Duty machines cannot operate with abrasive guns larger than 20 CFM because they lack the support features required to operate the larger blast guns. Light duty machines are excellent choices when the parts being blasted are small and daily continuous operation is not required. Production machines using larger guns can compress 8 hours of blasting into less than 1 hour. If unlimited compressed air is available a Production machine can pay for its increased cost by saving labor at a nearly geometric rate.

CABINET SIZE

Never choose a blasting cabinet based on part size alone. Increased inside work area for part movement and operator visibility will result in faster cleaning times. Larger cabinets produce better visibility inside by allowing the abrasive to expand to a lower particle density inside the cabinet. A larger cabinet size also increases part mobility, allowing for movement and rotation when blasting 100% of the part surface. Consider painting the part: if you need to flip or turn the part to paint it you will need to do the same inside the cabinet when blasting. Keep in mind, the more three-dimensional the part, the more rotation required. An easy way to wrap your head around this that works regardless of the part's shape is to picture it inside a box, and then flip it visually in your mind to determine the required cabinet size. Look to the Shop Standard line for larger cabinets with smaller non-Production dust collectors when you require a large cabinet for non-Production blasting.

DUST COLLECTOR FILTRATION

What makes a Production cabinet suitable for Production work is the dust collector. Negative pressure dust collectors are the cleanest and most efficient to operate. In a negative pressure dust collector the Exhaust Blower is located on the clean side of the dust collector filters. This creates longer blower life because the air drawn through the blower has already been cleaned. Media Blast's negative pressure dust collectors offer larger filter areas for maximum use between filter cleanings. As dust and spent abrasive collect on the dust collector filter surface, blower performance is decreased. Therefore, the more filter surface you have, the longer a machine will operate before filter cleaning is required.

Media Blast's Production machines are easy to service and offer self-cleaning dust collector filter assemblies. If dust collector cleaning is easy the operator can clean the collector faster and more frequently. If cleaning is difficult and time consuming, the operator often neglects this important duty. Media Blast's hopper bottom dust collectors are the easiest to drain and they allow for environmentally safe dust removal.

Keep in mind Production is a word that describes many things, but applied to blasting it refers to operating a machine daily for periods of 1 hour or more. Even small 5 HP abrasive guns will discharge almost 3,000 pounds of abrasive in 8 hours! If your compressed air is limited to 20 CFM, Light Duty machines are great tools, but are not well-suited for applications requiring daily use. Production machines can also operate with smaller abrasive guns and this creates an operation that requires very little maintenance and reduces labor time.

SIPHON OR DIRECT PRESSURE MODELS

All blast machines, whether siphon or Direct Pressure, use compressed air to force the abrasive against the part being cleaned. Siphon machines use suction to pull the abrasive into the blast gun while pressure machines use a pressurized pot to pneumatically push the abrasive to the blast nozzle. Siphon machines use an abrasive gun with two hoses, one for compressed air and one for abrasive delivery to the gun. Pressure machines use a single hose with a mixture of compressed air and abrasive.

Siphon machines are the most common type of abrasive machinery. A siphon machine can run for very long periods of time while Direct Pressure machines must be stopped about every five to seven minutes to allow the Pressure Pot to recharge. Siphon machines never have to stop unless the cabinet runs completely out of abrasive. Siphon machines have an inherent advantage over pressure machines in that they can operate with a much wider range of abrasive sizes. The only abrasive a siphon machine cannot use is large or heavy type abrasive like steel shot and steel grit.

Pressure machines are the right choice if the blasting process requires a heavy abrasive or blind hole cleaning. A pressure machine works with heavy abrasive in the same way a pressurized paint pot works with thick paints. A pressure machine will blast into blind holes or deep pockets because it concentrates the abrasive and compressed air into a smaller nozzle area and pneumatically pushes the abrasive into the hole or pocket. A pressure machine creates a higher abrasive particle velocity than a siphon machine at any given blasting pressure. Pressure machines also increase the blasting frictional temperature of the abrasive by creating a higher abrasive particle density on the part.

While Direct Pressure machines create higher abrasive particle velocity and greater blasting frictional temperatures, their efficiency is significantly reduced by the interruptions required to recharge the Pressure Pot. In addition most abrasives can be destroyed upon impact using both types of machines with normal air compressor line pressures. The information above is general in nature please keep in mind that features are available that eliminate some of these conditions. The cost of Direct Pressure machines are greater than siphon machines, but the Direct Pressure delivery system offers distinct advantages for certain applications.

WET BLASTING MACHINE

Because of the water used, a wet machine has the ability to eliminate the frictional heat that can damage certain materials. In addition, wet machines can operate with ultra-fine abrasives, i.e. (4,000 mesh), creating new possibilities that are not available using dry machinery. Usually, the wet process is a user recognized application, but more and more applications are evolving that require these models such as the medical implant field. One of the main advantages of wet blast cabinets is chemically clean part surfaces can be achieved using wet machines. Media Blast offers the Hurricane stainless steel product line. The Hurricane machine uses a seal-less slurry pump system (not to be confused with simple air agitation) to suspend and agitate the abrasive and water into a slurry solution. The pump then keeps the abrasive suspended and delivers the mixture to the blast gun where compressed air accelerates the mixture.