Waterjet Cut
Waterjet cut is very similar to Laser cut, with the following differences:
The cycle time for the Waterjet cut process is calculated from the following times:
• Sum of individual feature cut times
• Pierce time
• Rapid traverse time
Waterjet cycle time calculations depend on the following:
• Cutting horsepower of the pump.
• Selected material
• Thickness of the material
• Types and quantity of holes
• Type of pierce
• Desired surface finish and tolerance.
• Number of parts in the stack (bundle)
Cutting time is computed for each geometric feature (simple holes, child edges of blanks, and complex holes).
Note: For pierce time, the machinability factor is based on the selected material. The factor is most closely related to material hardness and quantifies how easily the waterjet can pierce the material.
It is important to note that cutting speed is decreased as the nozzle approaches tight curves or sharp corners – particularly inside corners . If possible, your CAD design should fillet corners with the largest radius possible for best performance.
Cycle Time Calculations
Overall Cycle Time = (Sum of cycle times for all features + Rapid Traverse Time)/ Number of parts in bundle
Cycle time for the overall part (or part bundle) depends on the following:
• Individual feature cut times (see below)
• Rapid traverse time, which depends on the following:
o Blank size
o Machine’s rapid traverse feed rate
• Bundle count (either computed, or specified by a user override)
Individual Cycle Times = (Cut Time + Pierce Time [ + Corner Adjustment] ) /
Machine Optimization Factor
Cycle time for individual features (simple and complex holes, perimeters) depends on the following:
• Cut time, which depends on the following:
o Cut time for small features
o Cut time for large features
o Cut time adjustment factor
Cut time depends on cut length and feed rate. Default feed rate depends on cut Quality (see the next paragraph) and part thickness, as well as waterjet pressure, water flow rate, abrasive flow rate, and mixing tube diameter. It also depends on whether the feature is large or small (see
Waterjet-Cut-specific Inputs).
Cut Quality (see the previous paragraph) is assumed to be 2 for large features and 3 for small features. Quality 3 provides a good balance between speed, surface finish, corner compensation and precision. For straight line cutting, Quality of 3 cuts use the speed it would take to separate material that is three times as thick as the material being machined, with surface finish the same as the top one-third of a separation speed cut. For straight line cutting, Quality 2 cuts use the speed it would take to separate material that is twice as thick as the material being machined, with surface finish the same as the top half of a separation speed cut. A setup option allows the user to override the default feed rate--see
Waterjet-Cut-specific Inputs.
• Pierce time, which depends on the following:
o Cross-section thickness
o Machinability factor
• Corner Adjustment (for perimeter and complex hole cuts) which is computed based upon:
o A plant variable specifying an adjustment factor
o The number of sharp corners to cut
• Machine optimization factor
o A machine variable used to distinguish between optimization software used by machine manufacturers.