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033 How to blast

How to Blast

Here we’ll go over how the machines work and the actual process of blasting.

How the Machines Work

Wet abrasive blast cabinets recycle a slurry of media (such as glass bead or aluminium oxide for example) and water to a process gun where an air jet atomises the slurry and cleans the parts. 

 You are able to blast softer metals, alloys and plastics without destroying them in the process or with a change of media, you can even etch surfaces

The cushion that the water provides means you can keep parts cool and prevent heat distortion. Additives are available to prevent flash rusting on ferrous material.

There are three footpedals involved that make it easy to operate

  1. Pump on/air off
  2. Air on
  3. Stop

This gives the ability to run the machine with or without compressed air which can be useful for creating a slight burnishing effect (covered later)

Applications

The businesses that use these machines are many and varied. You may wonder why you’ve not heard more about them. Many don’t like to advertise the fact that they use these machines as they enjoy being able to supply quality workmanship without the competition knowing how they are achieving it. Some of the more common items blasted are car/ motorbike parts, diesel pumps, jewelry, wheels, aviation components and much more. A superior finish is achieved without the need for precleaning or degreasing.

Getting the most from the machine

The process itself for using the machine is very straightforward and you will become proficient in it in a short period of time.

In fact, the blasting skills themselves are the least important factor in achieving optimal efficiency. Below are the most important contributors to producing the best possible finish in no particular order…

• Having a well-maintained machine with a clear filter, unworn nozzle and airjet etc. A  clear vent to minimise cabinet misting and allow you to see clearly.
• Using fresh media, or at least media that hasn’t been overly-worn (blast using the appropriate air pressure for the job

    • for faster processing, operate with an air pressure of 80-90psi (5.6-6.2 bar).
    •  For gentler blasting or to produce a finer finish, you can operate at a lower air pressure down to  10 psi (0.7 bar). Pressure may be adjusted with the air pressure regulator and gauge on the machine.
  •  Keep the window spray to a minimum level (to avoid excessive media loss)
  •  Check the media level regularly using the supplied media concentration jar. Top up  as necessary 
air regulator

Holding the process gun

If you are processing a larger / heavier component, you will place it on the turntable and hold the gun firmly whilst directing the blast flow at the part.
If, however, you are processing smaller / lighter parts, it may be more convenient to fix the gun to its bracket leaving both hands free to hold and maneuver the component in the blast system.
An adjustable gun mounting bracket is provided inside the machine between the glove ports.

Burnishing effect

Burnishing is the process of smoothing a surface. After you’ve finished blasting with glass bead you can further improve the finish by letting the media flow over the part through activating the pump on/air off footpedal and washing over the finished part for a short period. It is a minor effect but it can further improve the brightness if desired.

Technique

• Hold the gun 10-12cm from the part and move the stream using small circular movements
• Move in a methodical pattern with overlapping strokes to ensure you don’t miss anything
• Clean remaining media off the part using the supplied rinse gun and check for any missed areas and rectify as necessary.

For further reading check out

“10 ways to optimise your Dana-Ridge Wetblaster”