The optimal abrasive feed rate is essential to achieve ideal cutting efficiency, precision and reliability of any waterjet operation. The abrasive feed rate directly impacts the quality of the cut, cutting speed and the volume of abrasive used. Improper feed rates can result in clogging in the mixing tube, overuse of abrasive, slow cutting and poor edge quality.
Abrasive feed rates will vary depending on a variety of factors. The mesh size, or grade, of abrasive being used as well as the type of abrasive are the two largest factors that affect feed rate. Other factors that affect abrasive feed rates include humidity changes and the condition of the abrasive feed hoses.
Abrasive feed issues can also occur if the abrasive regulator is not grounded. Ungrounded abrasive regulators can build static in the feedline to the cutting head and slow or stop abrasive feed.
The abrasive metering charts provided by OEMs are a great starting point to ensure use of the optimal abrasive feed rate for a specific application. However, it is always good practice to perform an abrasive calibration test and physically measure the amount of abrasive being fed from the abrasive regulator. Most OEMs recommend performing this test weekly or any time there is a change to the abrasive mesh size, abrasive type, equipment change, or other factor that is known to affect feed rate and overall cutting performance.
A simple feed rate test can be performed by following these steps:
- Follow OEM-specified instructions for calibrating abrasive feed.
- Remove the abrasive feed line, or feed block if so equipped, from the bottom of the abrasive regulator.
- Using a stopwatch, or test function available in some OEM software, turn on the abrasive feed and run the abrasive for exactly one minute into a container such as a plastic sandwich bag. Weigh the container prior to feeding the material to get its tare weight.
- Weigh the abrasive sample using an accurate scale.
- Subtract the tare weight of the bag or container to get the weight of the material. The feed rate is X kgs. of abrasive per minute.
- Run this test two or three times using the same test specification and conditions to ensure you’re getting consistent weights.
- Adjust metering disk sizes up or down to get to the desired feed rate, and repeat steps 3, 4 and 5 to once again ensure that the proper feed rate has been achieved. Test until you are confident that you have an exact feed rate.
- Enter the exact feed rate into your software settings.