Shot Blasting Measurement Kit
Many people may think that the Shot Blast Cleaning process can not be quantified and qualitified to meet ISO 9000 requirement and therefore should be excluded from the purview of SPC program for ISO 9000.
This is not true, we can develop a simple technic to measure and control blast cleaning process.
Some organization starts their SPS program by keeping a record of motor amperage, however, this will not tell you the factors like blast wheel targeting, hot spot pattern shifting, poor working mix etc.
A better method of SPC Control is to use almen strip. In every shift, the strip is passed thruoug blast stream and its curvature is measured by almen gauge and recorded. The cirvature of strip is decided and standardized for job to job after controlling all the factors as mentioned above for ontaining statisfactory finish and output. Threafter in every shift one strip is passed to record the curvature reading with help of almen gauge and SPC chart is made.
Normally the curvature of strip is affected by control cage wear, impeller wear, blade wear, the waer and tear of these parts will shift hot spot location and intesity. The cahnge in media quality will also have affect upon the curvature. The cleaning rate will also affect the curvature of strip. On the basis reading generated and recorded, the corrective measure is taken on the above mentioned factors. The sequence of event is listed as under:
1. Mount the Almen strip onto the special holder.
2. Mount the Almen holdeer and strip onto a dummy part.
3. Pass the dummy part through the blast cleaning machine.
4. Remove the alen strip from the holder.
5. Measure the curvature ‘arc height’ of the strip.
6. Record the value or plot the data onto the SPC chart.
7. Repeat on a periodic basis (daily).
This is the way by which blast stream intensity is quantified for quality control purpose.
Normally, almen strip block holder is fitted on the job and passed under the blast stream for exposure purpose. If the almen SPC reading is at variance then we must check the following and corrective measure is taken to restore the standard reading:
a. Working mix.
d. Availability (hopper clogged or empty).
a. Wheel Hot Spot Pattern Shift.
b. Part Placement
3. Blast Exposure Time
a. Conveyor Speed.
b. Cycle Timer Setting.
4. Motor Amps
a. Ammeter Calibration.
b. Media Flow Rate.
5. Wheel Speed
a. Speed Setting.