Shot Blasters are some of the toughest machines known to mankind. It is not uncommon to find 30, 40 and even 50 year old machines still running and in production. There are not many metal working machines around that can claim that.
Yet for all their toughness, they are also delicate. Not delicate in the sense that if you touch them they fall apart. Delicate in the sense that they need nursing along and require lots of TLC to get the best out of them.
The following 8 Ways will help you get the most out of your machine; more production, less downtime and less consumption costs.
8 Ways to Improve Wheel Blast Machine Performance:
- Hot Spot Test
- Dust Collector Performance
- Separator Settings
- Abrasive Consumption Record
- Preventative Maintenance
- Abrasive Working Mix
- Blade, Control Cage and Impellor
The ammeter is your viewing window to performance of your blast machine. The ammeter indicates the quantity of abrasive being thrown by the blast wheel. As abrasive flow is increased to the blast wheel, the amperage consumed by the motor will rise. Conversely as abrasive flow is reduced to the wheel, the amps will drop.
All electric motors have have a full load amperage rating. This is the maximum amps that can be drawn for that particular motor.
Consult your machine operating manual or the motor data plate to determine the maximum amperage rating for your motor.
In most cases the machine will have been designed to run the wheels and motors at full load. The machine control panel will be fitted with ammeters to easily monitor the amperage being drawn.
Just a small reduction in full load amperage can have a big effect on the cleaning speed. So check to ensure maximum load is being used and the wheels are operating at 100% efficiency. Do not increase abrasive flow over the motor full load rating, as this will shorten the motor life.
In most cases a low amperage reading is the result of insufficient abrasive flow. However it can also signal wheel flooding. This is when the abrasive flow metering is opened too far, and excessive abrasive floods the wheel and prevents the motor operating and full speed or full amps.
If you are not sure if low amperage is the result of low abrasive flow or flooding, a simple test can quickly determine the cause.
1. Start the blast wheel and turn on the abrasive to the wheel. Run for a short while. 2. Close of the abrasive flow to the wheel and at the same time watch the ammeter. 3. If the amperage immediately drops, the cause is not enough abrasive flow. 4. If the amperage increases for 2-3 seconds and then drops, the cause is flooding. 5. Adjust and reduce the abrasive gate accordingly to set correct amperage.
During the blasting cycle the motor amps should remain consistent with only slight variations in the amperage reading. If the amperage reading is fluctuating wildly up and down it is a sure sign of inconsistent abrasive flow.
The most likely causes for this are either, not enough abrasive in the storage hopper (in this case when starting blasting the amperage will be stable, but after blasting for a short while it will start to fluctuate) or there is a blockage somewhere in the piping between the storage hopper and the wheel feed spout.
Always keep the abrasive storage hopper 2/3 full and clear any trash from feed pipes.
In order to run your machine at its maximum efficiency, monitor and maintain correct wheel amps settings.
2. Hot Spot Test
The setting of the blast stream is one of the most important settings on your machine. If the thrown abrasive is not hitting the part correctly, the cleaning efficiency is sure to decrease. Natural wear on blastwheel internal parts will affect the position of the blast stream, so this is something that needs constant checking and re-adjusting.
Except in exceptional circumstances, ie you are dumb enough to climb inside a running machine, it is not possible to see the blast pattern of abrasive coming off the blastwheel. And if it is not visible, it can easily be out of adjustment, but unnoticed.
So in order to ensure the abrasive is hitting the right place, a Hot Spot test is performed. This is a simple test that uses heat to determine the where the main concentration of thrown abrasive is hitting the part.
Refer to illustration 1. It can be seen that the majority of the abrasive thrown by the blastweel is concentrated in a relatively small area. Ahead and behind this concentration lesser abrasive is thrown. This is a function of all correctly designed blast wheels.
This area of higher abrasive concentration should be blasting onto the part, and blasting onto the the correct area of the part. If it is missing the part and blasting the cabinet wall, or blasting the wheel housing liners, production rates will decrease and abrasive and wear costs will increase.
Get it right, or you are throwing money down the drain.
When the blast stream hits a stationary work piece the area of concentrated blast will generate heat. This is referred to as the “Hot Spot”.
The Hot Spot test involves placing a plate (or other steel object depending on the machine configuration) in front of the blast stream and blasting it for 1 minute, with the test plate stationary.
By running your hand over the area just blasted it is easy to determine the hottest area, see illustration 2. This is the Hot Spot. Determining this indicates where the concentration of the blast stream is. The control cage can now be adjusted accordingly to get the Hot Spot in the correct position.
Remember a small adjustment in the control cage can have a big effect on the Hot Spot position, so don’t over adjust.
Generally several tests are conducted. Blast, feel, adjust. Test again. Rinse and repeat until the correct setting is found.
Once the correct Hot Spot position is established it should be regularly checked. Just a small amount of wear on wheel parts can throw out the Hot Spot alignment.