Electronics LP2000_VAR - Manual (Page 13)

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The advantage of using the Almen strip method lies in the ability to detect the many changes
that can occur in a blast machine cleaning operation. Many quality departments are demanding
real time process control to satisfy customer requirements for documentation. Instead of relying
upon the operator’s judgment of cleanliness, the Almen strip method provides a scientific basis
for qualifying the machine. The following are the changes that can be detected by the Almen
method:
a.
Wrong shot size added to machine (check the bag or drum for correct size)
b. Wrong shot size, dust collector not removing all small or broken shot
c. Wrong shot hardness (check the bag or drum for correct hardness)
d. Incomplete coverage, due to exposure time, shot flow rate adjustment, or improper tar-
geting
e. Improper targeting caused by worn wheel blades or control cages out of adjustment
Almen strips are an inexpensive way to demonstrate that the blast cleaning machine is running
properly. It is similar to taking your temperature each morning and charting the results. If your
temperature is abnormal, you may not know exactly what is wrong, but you certainly know that
something is wrong and additional investigation is needed. If the Almen strip readings are not
the same each morning, then something is wrong and additional investigation is needed. Al-
men strips provide clear evidence of proper (or improper) machine operation and can contribute
to an ISO 9002 or QS 9002 quality program as a standard operating procedure.
For additional information on the Almen method see SAE J-443 “Procedures for Using Standard
Shot Peening Test Strip” available from SAE or from Electronics Incorporated.