What are the different types of taper?
V-shaped taper is where the top of the cut is wider than the bottom. It is the most common type of taper found in abrasive waterjet cutting. It is caused by the fact that the jet has more cutting energy at the top of the cut than at the bottom and so it tends to make a wider cut. In general, the faster the cut the more pronounced the taper will be.
Reverse taper is where the top of the cut is narrower than the bottom. This happens during very slow cuts or in soft materials where the material is rapidly eroded. Because the jet stream expands the farther away from the nozzle it gets, it removes more material from the bottom than from the top.
Barrel taper is where the middle is wider than the top or the bottom. Barrel taper tends to occur in very thick materials.
Rhomboid or Trapezoidal taper
Rhomboid taper is actually normal V-shaped taper that has been tilted because the nozzle isn't at right angles to the material.
Note:The amount and type of taper is mostly affected by the thickness of the material and its hardness or "machinability." Although it's somewhat counter-intuitive, thin materials actually suffer some of the worst taper. This is because the jet stream spends little time over each area, so there's no opportunity to evenly erode the material.
The taper in these figures is greatly exaggerated. Typical taper is barely visible to the naked eye and is best detected using micrometer measurements.
How can taper be minimized?
There are a variety of ways to minimize taper:
- Stack thin materials to reduce taper
If you need to work with thin materials, you can stack them to reduce the amount of taper. (The OMAX Make software includes a "Stack Height Calculator" to determine the optimum number of sheets to stack to make the most parts in the least time.)
- Use a new mixing tube and jewel
A mixing tube and jewel in good condition will produce less taper.
- Use the best quality abrasive
Lower quality abrasives will tend to have a wider spread of particle sizes. Different particles sizes will result in uneven edges and increased taper. Higher quality abrasives will produce more uniform edges.
- Use a nozzle with a smaller jewel diameter
Nozzles such as the MAXJET®5i MiniJet Nozzle , produce less taper simply because the jet stream itself is smaller in diameter.
- Use a tilting nozzle head
Use the Tilt-A-Jet to eliminate taper, resulting in nearly vertical edges on the parts and increased taper in the scrap, where it doesn't matter. The Tilt-A-Jet is completely computer controlled and requires no additional programming or input from the operator.
The Tilt-A-Jet nozzle eliminates taper and provides maximum accuracy with a single click
- Use a low stand-off
The closer the nozzle is to the material, the less the cutting jet will spread, and the less taper it will produce.
- Slow down cutting
A slower cut will have less V-shaped taper. The OMAX controller can predict the proper speed to automatically slow down and compensate for taper in critical areas by simply assigning a portion of your tool path to a Quality of Minimum Taper. Note that for many materials and thicknesses the speed required for zero taper is quite slow. For these cases the Tilt-A-Jet taper compensation system is the preferred approach to eliminating taper.