Have you checked the abrasive in the hopper lately? How often do you add new abrasive to your machine?
A properly balanced abrasive work mix is the key to effective and efficient blast cleaning. An unbalanced work mix can lead to longer cycle times, poor finish on the parts, higher abrasive consumption, and higher maintenance costs due to excessive wear and machine down time. A work mix that is too coarse or too fine can increase the cycle time by as much as 30%.
A coarse work mix is caused by adding large amounts of abrasive infrequently to the machine. A work mix that is too fine can be caused by excessive time lapse between additions.
A proper work mix will contain a balanced distribution of large, medium, and small abrasive. As new abrasive is added to the machine it will begin to work in with the abrasive that is already in the machine that is being worn down in the blast cycle until the smallest fines are taken out of the blast machine by the dust collection system. The size distribution of the work mix undergoes constant change in the blast environment. The key to efficiency is to maintain the work mix at a consistent level of particle sizes and to avoid any radical swings from a coarse to fine work mix or from a fine to coarse work mix.
Rule of thumb
To maintain a proper work mix in most wheel blast environments and with most types of carbon steel shot or grit it is best to add abrasive on a daily basis, depending upon the amount of usage of the wheel blast machine.
But how much do I need to add?
Using the following formula as a rule of thumb will help maintain a proper work mix:ADD ½ POUND OF ABRASIVE PER TOTAL BLAST WHEEL HORSEPOWER ON THE MACHINE TIMES THE TOTAL NUMBER OF OPERATING HOURS SINCE THE LAST TIME ABRASIVE WAS ADDED.
For example: if you have one 15 HP blast wheel on a machine that operates 7 hours per day, then you would add: ½ X 15 X 7 = 52.5 lbs.
Another example: if you have four 10 HP blast wheels on a machine that operates 14 hours per day, then you would add: ½ X 10 X 14 = 70 lbs.
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For more information on each of these applications:
The most versatile type of blast cleaning equipment, Goff’s Table Blast models are ideal for large or heavy parts. Parts that are to be cleaned are rotated on the table, exposing the parts to the abrasive blast pattern.