Frequently Asked Questions

/Frequently Asked Questions
Frequently Asked Questions2018-08-23T14:38:44+00:00

Questions and Answers from BARTON Experts

Customers often have a variety of technical and application questions about the proper selection, performance, and use of BARTON abrasives.

In addition to the information elsewhere on this site, this section is provided by various experts at BARTON regarding topics that have come up frequently in conversation with customers. We hope you find the information helpful. Of course, if you have a question that’s not addressed in this section, don’t hesitate to call 800-741-7756. BARTON customer service professionals are always ready to answer any questions.

Selecting the proper mixing tube, feed rate, and orifice gemstone

Stephen Podnorszki, Product Manager Waterjet Parts

Which Roctec Mixing Tube Is Right for You?2018-08-15T10:21:10+00:00

Using a high-quality mixing tube (sometimes referred to as a nozzle) such as Kennemetal’s Roctec* 100 and Roctec 500 is vital in maintaining accuracy and peak performance from your waterjet cutting equipment. The mixing tube combines the high-pressure stream of water with the abrasive directing it to the cutting surface.

BARTON carries the Roctec 100 and Roctec 500 mixing tubes in a wide range of sizes at our two waterjet parts warehouses. Roctec mixing tubes are considered the industry standard for waterjet cutting and consistently offer longer life than other waterjet mixing tubes.

Without a high-quality mixing tube, the kerf widens, cutting speed is reduced, and cutting precision is diminished as the original optimum jet pattern and abrasive velocity are lost. Reject rates also increase, and time is wasted replacing the mixing tube.

Superior wear reduces the frequency with which mixing tubes need replacing. That longer life also helps maintain the integrity of the jet pattern and velocity. The result is faster average cutting speeds, greater dimensional accuracy, the ability to perform longer uninterrupted cuts, and less downtime for mixing tube replacement.

The question we often get from customers is, “Which Roctec nozzle is best for my operation?” Here are some key facts to consider about the two models. And, of course, customers can call to discuss their operation in detail to determine the best choice.

Roctec 500

Roctec 500 composite carbide mixing tubes are harder and typically last 30% to 40% longer than Roctec 100 mixing tubes. Using Roctec 500 mixing tubes reduces downtime, maintenance effort, and finished-product losses. It is recommended for 87K to 100K applications, and is especially beneficial for long-duration and unattended cuts on expensive material that could be damaged in the event of a mixing tube failure during the cut. Roctec 500 mixing tubes are better suited for applications where a smaller ID mixing tube is needed to achieve a narrower kerf. They can also be expected to hold tighter cutting tolerances longer, and are typically priced 15% higher than Roctec 100 mixing tubes.

Roctec 100

Roctec 100 mixing tubes are made with the same Rapid Omni-directional Compaction (ROC) manufacturing process as Roctec 500 mixing tubes, but they are made with a composite carbide which is not quite as hard as a Roctec 500.

Roctec 100 mixing tubes are best suited for shorter duration cuts with less demanding tolerances. Roctec 100 mixing tubes come in at a lower price point, but consistently perform better than competitive brands of mixing tubes.

 

* ROCTEC is a trademark of Kennametal Inc.

Determining Correct Abrasive Feed Rates2018-08-14T18:29:59+00:00

The correct abrasive feed rate is essential to optimize the 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 is the largest factor that affects feed rate. So is the type of abrasive being used. For example, BARTON’s ADIRONDACK HPX garnet has extremely sharp edges while our HPA alluvial garnet abrasives have slightly rounder edges. Due to HPX abrasives having sharper edges, HPX tends to flow a little slower through the same size metering disk than our HPA abrasives. 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 the correct 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 anytime 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:

  1. Follow OEM-specified instructions for calibrating abrasive feed.
  2. Remove the abrasive feed line, or feed block if so equipped, from the bottom of the abrasive regulator.
  3. 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.
  4. Weigh the abrasive sample using an accurate scale.
  5. Subtract the tare weight of the bag or container to get the weight of the material. The feed rate is X lbs. of abrasive per minute.
  6. Run this test two or three times using the same test specification and conditions to ensure you’re getting consistent weights.
  7. 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.
  8. Enter the exact feed rate into your software settings.
Choice of Orifices: Ruby and Sapphire vs. Diamond2018-08-09T20:29:14+00:00

The orifice assembly is a key component of the waterjet cutting process. Its function is to direct the high-pressure stream of water through the mixing tube where it draws in the abrasive and delivers it to the cutting surface. Diamond orifices are highly regarded in the industry or waterjet cutting. Ruby and sapphire orifices are also used.

Ruby and sapphire orifices are considered functional equivalents. They are commonly used in less-critical applications because they are susceptible to damage in high-pressure applications when abrasive particles impact the sides of the orifice. The impact of these particles can damage the inlet edge and compromise the quality of the waterjet stream. Ruby and sapphire orifices usually cost between $15.00 and $50.00 and can last anywhere from 1 to 40 hours.

Diamond orifices are known to produce a more cohesive stream than a ruby or a sapphire. A more cohesive stream can result in longer mixing-tube life and increased cutting power. Diamond orifices cost between $425.00 and $500.00 each, are generally warrantied for 500 hours, and consistently meet or exceed the 500 hours. It is not uncommon for an operator to get 1,000 hours or more from a single diamond orifice.

Diamond orifices are recommended for use with 87K to 100K equipment and are typically preferred for long-duration cuts on expensive material that might be ruined in the event of an orifice failure mid-cut. The cost of a ruined part because the cut was compromised by a damaged orifice can far exceed the initial upfront cost of purchasing a diamond orifice as compared to a ruby or sapphire orifice.

Diamond orifices also result in significant cost-efficiency because they require less maintenance and wear longer, requiring fewer changeouts.

Operators running multiple cutting heads can also realize the added value of using diamond orifices. Ruby and sapphire orifices have a shorter, more unpredictable usable life than diamond orifices. That shorter life cycle adds to increased downtime, especially on multiheaded machines.

And while diamond orifices are preferable for a variety of reasons, there are times when less expensive ruby and sapphire orifices are often chosen. Operators who cut a wide variety of materials that do not have exacting specifications, and change orifice/mixing tube combinations often, may prefer to use less expensive ruby or sapphire orifices, since the frequent handling of the components during regular changeouts creates greater potential for loss or damage. More expensive diamond orifices would present greater financial risk to the operation.

Protecting the orifice against damage is always a good strategy. Whether ruby, sapphire or diamond orifices are chosen, the useful life of any orifice assembly (ruby, sapphire, or diamond) can be improved by adding a short-stop filter assembly in the high-pressure line before the on-off valve to eliminate the risk of contaminants entering the line and damaging the orifice. If a short-stop filter assembly is employed, periodic cleaning with an ultrasonic cleaner is recommended to remove calcium deposits and extend the life of the orifice.