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Sandblasting (Media Blasting) Shop Tech

Understanding the technology and equipment available

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Types of sandblasting equipment

There are two primary types of sandblasting equipment. They are differentiated by how the blasting media and compressed are are mixed and distributed. The most common type of sandblasting equipment is siphon feed. Siphon feed equipment utilizes a sandblasting gun as the mixing point for the media and the air. The basic manner in which this functions is that the compressed air is passed across a supply tube that is inserted into the media supply. As the compressed air passes over the tube it creates a vacuum effect that draws the media up into the compressed air stream. The mixed stream of air and media is the shot out through the nozzle of the gun where it then impacts the surface to be cleaned.

In contrast to this, the other type of equipment pressurizes a resevoir which contains the media blasting material. In this configuration the sandblaster then uses the overall system air pressure to force the blasting material out of the resevoir at the full speed and rate of the compressed air delivery.

Pros & Cons of Equipment Type

Siphon Feed based equipment

  • Pros
    • Low cost of entry
    • Simple technology, easy to use
    • Capability of the blasting tools is based on capacity of air compressor
  • Cons
    • Suction based equipment is less powerful than pressurized
    • Less options (generally) in terms of nozzle configurations
    • Limited effectiveness of certain types of blast media

Pressurized equipment

  • Pros
    • Rapidly removes significant material
    • Much faster operation than siphon feed
    • Wider options in terms of usable blast media and nozzle configurations
  • Cons
    • Higher cost of entry
    • Requires significantly more powerful air compressor
    • Blasting duration limited to volume of blast unit (and refilling it is a bit of a pain)

Monk says, "Regardless of the type of sandblasting you're doing, personal safety is very important! Always ensure that you have a Respirator, eye protection and hearing protection. If you are blasting out of doors, or outside of a cabinet, make sure to wear clothing that fully covers you and a sandblasting hood. The reality is that sand and dust gets everywhere!

It's all about the CFM baby!

The basic reality, outside of sandblasting equipment itself, is that you can only do as much as your Air Compressor will allow for. So, when looking into the option of doing some of your own sandblasting, ensure that you realistically assess your air compressor before even looking at any sandblasting equipment. The critical aspects to know about your air compressor are: horsepower rating, maximum PSI rating, volume, and CFM ratings.

When all is said and done, the most critical rating of all is the CFM rating for the particular PSI range you're working on. You need to ensure that it, at a minimum, matches the CFM rating necessary for the sandblasting equipment, or, preferably, exceeds it. Now, with a siphon feed based system you can get away with running near the maximum output of your compressor, you'll simply have short durations of work, with extended wait times for the compressor to recycle. If you're attemping to run a pressurized system, you will continually have the issue that the system only operates at peak efficiency for the first few seconds that you run it. Anything after that and you're fighting a losing battle of not being able to maintain enough overall pressure to continue the work.

Now, for most of us, we're not going to be doing huge blasting projets where we take down and entire frame or chassis. There's a matter of economy on projects of that sort of scale. If you're only ever going to restore one car, then it's better to farm out the work to someone else. But there will be times when small scale sandblasting is a good option. As long as you have an adequate sized compressor and a siphon feed gun you're set for 90% of the smaller, simpler tasks.

Blasting Cabinets

When I first started sandblasting my own parts, it was on a small scale with a siphon gun and it was done out in my back yard. While this was cheap, it wasn't easy or neat. Why is this? Well, for starters, when you're blasting out in the open there's no way to control where your blast media goes, and proper media isn't necessarily cheap. Then I advanced to rigging lean-to structures out of spare lumber and a tarp. More efficient because I was able to recover some of the sand, but a pain in the backside to set-up and take down each time I wanted to take care of a small part.

Eventually I broke down and bought myself a blasting cabinet. You can get relatively small/simple ones inexpensively that will meet most needs. No, it won't turn you into a sandblasting shop over night, but you will finally get far enough where you can maintain the equipment in your shop and use it when needed. The things to look for in a basic blasting cabinet is how easy is it to get parts in and out of the unit, how good the visibility is into the unit, and how well it seals. In terms of simple upgrades, a light inside the unit makes a huge difference, and most cabinets now have clear plastic stick on shields to protect the window from abrasion. It's also a dusty, messy process. Look for a blasting cabinet that will allow you to hook up your shop vac to help extract the ambient dust from the unit. (The dust removal also greatly aids visibility.)

In terms of use, the single best recommendation I have (short of learning how to use it appropriately) is to put on a pair of the nitrile gloves before sticking your hands into the unit's blasting gloves. It greatly helps to minimize glove goo from sweaty dusty hands. For more information on Blasting Cabinets (particularly DIY improvements) check out my article on Media Cabinet Modifications.

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Contents copyright 2008, 2009 - Jody F. Kerr

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