Abrasive waterjets employ a jet stream of water mixed with millions of tiny abrasive particles to cut through a variety of materials. Depending on factors like the shape of the cut, cutting conditions, and the material being cut, the kerf width can vary from the top to the bottom of a cut. The different shapes that the cutting edge can take on are referred to as taper. There are three main types of taper:
- V-Shaped Taper. This is the most common form of taper and involves a greater amount of kerf at the top of the material being cut than at the bottom. V-shaped taper occurs when some of the cutting energy disperses as the jet stream cuts deeper into the material. The stream may not have completely cut through the material, causing buildup and removing more material from the top than the bottom. This type of taper is typically associated with rapid cutting.
- Reverse Taper. In contrast from v-shaped taper, this form of taper is caused by slow cutting speeds. The slow speed causes the jet stream to remove more material at the bottom of the material than the top. This can also occur when cutting softer materials, as the hardness of a material impacts the focus of the jet stream energy.
- Barrel Taper. This type of taper consists of kerf width that is the greatest in the middle of a cut. Barrel taper occurs when cutting thicker materials, because it takes longer for the jet stream to penetrate through to the bottom. It can also take place in laminated materials in which the outer layers are harder than the core of the material. After piercing through the top layer, the energy of the jet stream disperses through the core before continuing through the bottom layer.
The Precision of the Waterjet
As technology has adapted over time, precision has grown increasingly important in cutting. Over the years waterjet cutting has seen a tremendous amount of growth as researchers and scientists constantly work to improve upon the cutting method. One of the reasons waterjets lead the cutting industry is their ability to cut with an extremely high level of precision.
Some cutting jobs allow or even prefer some degree of taper, but with precise cutting the objective is to achieve zero taper, which occurs when the width of a cut is maintained from top to bottom. In order to compensate for taper, the required cutting speed can be slower than what is considered ideal for quick production times. In 1997 Dr. Axel Henning introduced a new way of eliminating taper by tilting the cutting head to produce a high-precision cut while maintaining high speeds, which was revolutionary in helping to compensate for taper.
What are the primary causes of taper?
Taper can arise from a number of circumstances, including:
- The thickness or hardness of the material (soft and/or thinner materials are more likely to see taper)
- Cutting speed
- Type of abrasive used in the waterjet stream
- Distance of the waterjet nozzle from the material (the further away the material is from the nozzle, the more likely it is to result in taper)
- Focus and design of the nozzle
How do you minimize taper?
Tilting heads are key in eliminating taper in waterjet cutting. The tilting head angles the nozzle of the abrasive waterjet as it cuts through a material, ensuring a clean and taper-free cut all the way through. There are several strategies that can be used to control taper if you don’t have a tilting head, such as:
- Use a high-quality abrasive and a large grit size, but not so large that is clogs the nozzle
- Use a small nozzle and mixing tube
- Cut slowly, but not so slowly that you risk winding up with reverse taper
- Use the lowest amount of nozzle stand-off that you can, because the closer you can bring the nozzle to the material, the less taper you will get
- Make sure the Z-axis is perpendicular to the material in both X-axis and Y-axis directions
- If using thin materials, stack them, as taper is most evident in materials that are less than 3 mm thick
- Rotate the mixing tube 90 degrees for every 8-10 hours of use to ensure that it wears more evenly, thus enabling it to last longer and prevent taper
Some waterjet cutting machines have taper compensation mechanisms in place, such as tilting heads, to help ensure more precise cuts. ICS Cuts is dedicated to producing the highest quality of waterjet cutting, therefore only the best tools are used by our team of experts. All Intelligent Cutting Solutions, equipment features automatic taper compensation consisting of an articulating wrist that eliminates kerf taper errors and stream lag, which results in the most precise cuts while moving at higher speeds and guarantees the best quality of service.