Waterjet Tips: How to control taper

This month we sat down with Headland Machinery’s waterjet specialist Matt Weaver, and asked him to share some insights into how to control taper and methods to reduce taper without a tilting head. 

Firstly, what is taper?

Taper refers to a difference in the kerf width at the top of a cut and the width at the bottom of a cut. Typically, with waterjet cutting machines there will always be a slight taper, the most common type being the V-shaped taper (as seen in the image below).

How is the V-shaped taper formed? V-shaped taper is created when the jet stream loses some of its cutting energy as it cuts into the material. Where the jet stream enters, there is slightly more material removed compared with the bottom of the cut where the jet stream exits.

The V-shaped taper is generally associated with a fast cutting. The greater the nozzle speed, the more pronounced the taper will be. What happens when you cut slower? A slow cutting speed will produce a reverse taper where the kerf width is wider at the bottom. This can also be the case when cutting soft materials.

The third type of taper is the barrel taper which mainly occurs when cutting very thick materials.

Although it is difficult to eliminate taper without a tilting head, how can you control it? There are various ways you can control taper, check out this helpful list below:

• To reduce V-shaped taper, slow down the cutting speed.
• To reduce reverse taper, increase the cutting speed.
• Stack thin materials. Taper is usually most pronounced in materials less than 1/8” (3 mm) thick. If available, use the stack height calculator in the controller software to determine the optimum number of sheets to stack to make the most parts in the least amount of time.
• Use a low stand-off. The closer the nozzle is to the material, the less the jet stream will spread and the less taper it will produce.
• Use the best quality abrasive available. Lower quality abrasives will tend to have less consistent particle sizes. Different particle sizes will increase taper.
• Ensure the Z-axis is perpendicular to the material in both X and Y directions. If the Z-axis is at a slight angle, it can produce a rhombus taper.

The only way to completely eliminate taper is to tilt the head. Read more about the Tilt-A-Jet from Omax here.

For more information call 1300 592 061 or email marketing@headland.com.au