The distance from the work surface to the tip of the cutting nozzle in water jet machining is called the Stand-Off Distance (“SOD”). The optimal SOD depends on the type of cutting being performed, the material being cut, and the desired cut quality.
As a starting point, the optimum SOD guidelines for the highest cut quality suggest:
- 3-axis Abrasive Waterjet Cutting SOD: 0.125” – 0.250”.
- 5-Axis Abrasive Waterjet Cutting SOD: 0.125”
To ensure a consistent cut finish through the entire cut cycle, the SOD should be consistent at each point. Cutting too close to the material can cause back pressure, which can clog the abrasive line or worse, the nozzle can come in contact with the material being cut. A standoff that is too high can cause dimensional problems if the spray pattern enlarges and the delivered cutting pressure is reduced with the extra distance.
Functionally, the Surface Mapping option creates a 100 x 100 point mapping grid and records the distance between the laser sensor and the surface of the material. The data is used to create a topographical map of the surface undulations which a cutting head can follow to ensure the cutting head remains the optimum cutting distance from the surface of the material being cut.
Laser Surface Detection
WARNING – Be aware of where the laser sensor is pointed. Never look directly into the laser beam. Eye damage may result.
The Surface Mapping, factory installed option, has a laser sensor that mounts near the cutting head during mapping operations and is stored in an enclosure with a laser controller during cutting operations. When a Surface Map is being created, the laser will follow a defined serpentine path across the area to be mapped, recording surface variations up to a ±0.6 inch (±15 mm) range. This surface map data is imported into the part program via the Aquavision DI controller and used to maintain the desired Stand off Distance during the cut cycle as surface heights vary.
LASER MAPPING BENEFITS
Keeping a constant distance between the cutting head and the sheet surface improves the cutting accuracy especially when using beveling or 5-Axes cutting. With the nozzle closer to the surface cutting speeds can be increased while still delivering the required quality. Avoiding the cutting nozzle from touching the sheet surface reduces the risk of clogs and expensive nozzle breakage. The laser map can be overlayed on the piece part for pre-cut viewing.
LASER MAPPING LIMITATIONS
The entire work surface or a specific area can be mapped with up to 100 data points for the x-axis and the y-axis for a total of 10,000 data points. The laser sensor has a detection range of ±0.59 inches (±15 mm) and does not detect variations beyond that range. Since the Surface Map is created prior to the actual cutting starting, any material changes that occur during the cut are not detected and compensated for.
OTHER SURFACE DETECTION OPTIONS
Other Surface Detection Options
Overcome Fluctuations in Material Flatness
Jet Edge’s Contact Height Sensor contacts and rides on the work piece, providing real time feedback on surface variation. Stand off Distance adjustments are made to the nozzle height as it cuts, assuring consistently accurate and quality cuts. The sensor will stop the cutting process if it comes into contact with a previously cut part that has tipped up after being cut. This avoids risk of having the nozzle coming into contact with it.
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Jet Edge is a leading manufacturer of waterjet cutting machines, intensifier pumps, and accessories. Whether you’ve got a demanding application due to tight tolerance precision requirements, you need non-stop grit, power, and hard work for heavy-duty cutting, you need a custom solution to optimize your process, or you simply want a capital equipment supplier who acts like a partner seeking your long term success—it’s time to get in touch with Jet Edge.