Things you need to know about water jets before buying one

Waterjet cutting has several key attributes that set it apart from traditional technologies such as machining, laser, plasma, wire EDM and others.

It mainly includes the following aspects:

Save costs

One of its most outstanding features is that waterjet machines are relatively cheap to operate. After all factors are taken into consideration, the cost to run a waterjet cutter is approximately $14.00/hour.If you need an abrasive mixture (garnet sand), you need to pay extra. Usually the price range of abrasive is 2300 yuan/ton, and it is 20-25KG an hour. The consumption is closely related to the power of the high-pressure pump and the time you spend cutting. Related.

In addition to initial running costs, waterjet cutting offers other cost-saving advantages, such as a short transition time from drawing to cutting, fast cutting speeds, and short setup time.

No chemicals or heat generated

Because this process uses only water and garnet sand (abrasive) to erode the material, it is technically a cold cutting process, and any heat that may be generated during the erosion process is instantly cooled by the water flow. As a result, the warping, deformation and material hardening commonly associated with laser, plasma and mechanical processing are eliminated, minimizing the need for secondary processing.

It is also safer for the operator and the environment as no water vapor or fumes are produced and any dust particles produced during the erosion process are trapped in the water and subsequently safely filtered out.

Versatility/Flexibility

As mentioned before, waterjet cutting is suitable for almost all industries because it can cut almost any material relatively cheaply without changing the material's properties. Everything from 0.010-inch acrylic to 10-inch thick stainless steel can be cut with a waterjet. Thin materials can even be stacked to increase productivity and reduce costs.

The table sizes for these machines range from 0.6m x 0.6m to 2m x 4m, but some machines are custom built to feature large 6m x 12m tables and can run multiple cutting heads.

Characteristics of water jet cutting

• Incision width

  
  

  
  

The kerf refers to the amount of material the cutter cuts away, in this case determined by the width of the jet. The width of the jet is typically 0.04 inches or 1 millimeter. Pure water without abrasive waterjet cutting heads have a smaller nozzle and stream width of 0.02 inches or 0.5 mm. This means that the inside corners of the waterjet cut cannot be perfectly sharp and their radius will match the jet radius. In most cases this is not important, but should still be taken into consideration when designing the part. As a rule of thumb, the inside corner radius should not be less than 1.125 times the waterjet radius, so in most cases 0.03 inches.

• Not cutting through

Waterjet cutting is mainly a tool for overall cutting of materials, that is, cutting through. It is rarely used to cut to a certain depth (without cutting through) because this is difficult to achieve and is often not accurate enough. However, this process has been used to polish the surface of stone that is not very deep to achieve a carving effect.

• Cutting hole diameter

Since the water flow width is 0.04 inches 1 mm, people often think that this is the smallest hole size that can be cut accurately, but this is not the case. Before cutting along the cutting line, the waterjet must first break through the material. In this process, called perforation, a waterjet sprays a powerful stream of water and abrasives onto the surface of the material to create the initial hole. The initial hole is quite rough and only after the piercing has been made the incision becomes smooth. Therefore, it is recommended that the hole diameter be 2 times the waterjet hole diameter to achieve a smooth, precise hole, so in most cases, hole diameters below 0.1 inch are not recommended.

• Cutting exit line Entry line

Small dents are sometimes seen on the workpiece where the waterjet stream begins and ends the cut. The initial piercing of the material is usually done in bulk material that is considered scrap, and only then can the water jet be introduced into the part to avoid leaving the large blast marks on the part that would result from the initial piercing. However, if the cuts meet at the lead insertion-lead extraction point, it may create a nib that needs to be removed.

There are several types of lead-in and lead-out available for different materials and thicknesses to get the best processing quality.

Figure 1 - Schematic diagram of 4 different import/export methods

Type 1 (straight line entry, very short straight line exit) is suitable for any sharp angle.

Type 2 (arc lead-in, short arc lead-out) is suitable for thinner and softer materials.

Type 3 (straight lead without lead) is suitable for thicker, harder materials.

Type 4 is an example of straight line import and short arc export.

• Cutting taper

Materials cut with a regular waterjet will have a slight taper along the cutting line. This is because the waterjet cutting flow spreads (energy loss) farther away from the nozzle and therefore does not travel in a straight line. This produces different types of tapers depending on the material and cutting speed.

V-taper is the most common type of taper and occurs because the jet has more cutting energy at the top of the cut than at the bottom and therefore tends to make a wider cut there. Generally speaking, the faster the cutting speed, the more pronounced the taper will be

Reverse taper occurs during very slow cuts, or in situations where soft materials are being eroded rapidly. Because the jet expands further away from the nozzle, more material is removed from the bottom than from the top. Barrel tapers, on the other hand, usually only appear in very thick materials.

When machining parts 1/8 inch (3 mm) thick or less, taper is not worth worrying about because it is barely noticeable. However, there are some methods you can use to reduce the amount of bevel on larger parts. As mentioned before, the main method is to control the cutting speed, usually calculated by the cutting software program after inserting the material data. Another method is to use a tilted cutter head to compensate for the slope. But this would require upgrading the cutting equipment to be able to track the curve and tilt the cutter head accordingly to maintain a taper-free edge, which would cost more.

• HEAD Waterjet 5-Axis Cutter 

  
  

  
  

Advances in waterjet cutting technology have driven the development of 5-axis waterjet cutting technology. The application of HEAD Waterjet 5-axis cutterheads can solve the taper problem described above, and can apply the advantages of waterjet cutting to more complex 3D parts that would otherwise be time-consuming and costly to process, and HEAD Waterjet can realize the variety of cutting needs you want.