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What should be the life of Aluminium Oxide (Alumina) used for shot blasting?

February 23, 2008

We use brown coloured Aluminium Oxide (Alumina) grits of virgin 40 grade for shot blasting of pressed components of thickness 0.4 mm to increase surface roughness. For this process, we use shot blasting machine with compressed air nozzle.

We face problem with wearing out of the alumina grits very often (within 5-6 hours). Due to this issue, productivity & consisitency of desired results is adversely affected. We would like to know--

1. What is the life of such grits?
2. What should be the frequency to replace them?
3. Are there any other materials or methods of shot blasting, which can replace these grits effectively to increase productivity?

Regards,

Sunil Shinde
Employee - Mumbai, Maharashtra, India

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First of two simultaneous responses --

You are experiencing about a normal breakdown. Each pass thru the machine will make about half of the media one size smaller. White aluminum oxide costs a bit more, but is worth it when you consider the longer life and the less time spent on cleaning the machine.
For the longest wear, go to silicon carbide. It is not used that much in the USA anymore because our OSHA says that it can lead to silicosis if not controlled. The paperwork costs more than the controls.

James Watts
- Navarre, Florida
February 26, 2008

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Second of two simultaneous responses --

Shot blasting, like mass finishing has a number of variables that effect the final results. The pressure you use will effect the life of the media, as will the angle to the surface will effect the life, the material you are working and the hardness or grade or the media (source) will effect the results. Normally, you can get more uniform results with a mass finishing system and longer life of the media.

AF Kenton
retired business owner - Hatboro, Pennsylvania
February 27, 2008

If your process allow you can opt for steel ball blasting. It will give you constant roughness and more life.

Rajesh dubey
- Kota, India
April 14, 2008

I think that his material is a bit thin for steel shot blast.

James Watts
- Navarre, Florida
April 15, 2008