Selecting the Right Waterjet for Your Operation
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Selecting the Right Waterjet for Your Operation Growing Popularity Of Waterjet The waterjet process is recognized as one of the most versatile and fastest growing cutting processes used in manufacturing across the globe. Waterjet complements or replaces other technologies such as milling, laser, EDM, plasma and routers. Because of its many advantages, waterjet is fast becoming the process of choice for many fabricators and machine shops. Cold Cutting The process generates little heat so materials are never altered. Versatility Waterjet does things no other technology can do from cutting whisper thin details in stone, glass and metals to cutting food products or thick titanium. Benefits Of Waterjet No Stress Added Waterjet cutting doesn’t induce warp on the target material. The advantages of using a waterjet cutting system include: Fast Turnaround Waterjets typically vary only cut speed going from one material to the next, and cutting forces are very low resulting in very short part-to-part timeframe. Environmentally Friendly No noxious gases or liquids are used in waterjet cutting, and waterjets do not create hazardous materials or vapors. These benefits are driving increased adoption of waterjet cutting technology. Its versatility, quick set up, easy operation, and high quality part production make it an ideal choice for any manufacturing organization looking to reduce costs and improve efficiency. Getting Started While making the decision to incorporate the waterjet process into your operation may be clear, selecting the right machine configuration requires some evaluation. You need to assess the requirements of your business and customer base and balance that with the practical concerns of space, personnel capability, and budget. This paper will help guide you through the decision-making process by providing questions you should be asking to help you select the appropriate waterjet system. What materials are you cutting? The first step in determining the right waterjet is to define the kinds of materials you work with or plan to work with in your operation. When it comes to materials, the major considerations are: current and potential future material types, material stock size, material thickness, and part shape (flat, bevel, or 3D). Types of Material A good place to start is to determine what materials you work with 80% of the time. For many job shop contract cutters, mild steel might be more typical, but cutting less common materials such as titanium, glass, steel alloys, or stone can really allow the waterjet process to shine and yield higher margins The versatility of waterjet is key here. The ability to use the same equipment for all materials greatly enhances machine utilization and your return on investment. Pure Waterjet Handles soft materials that can be cut with a knife: gasket, foam, and plastic. Switch between Pure and Abrasive with a simple two minute head conversion. Abrasive Waterjet Handles tougher materials: metals, glass, stone, and composite. Material Size and Thickness The size and thickness of the materials you intend to cut determines the power and number of cutting heads, the pump requirements, and the size of the work bed you’ll need. Thin sheet metal under .25” (< 6 mm) and especially down to the 8-12 gauge level can usually be stacked and cut with waterjet to increase your production – and profits. Optimal thickness for stacked sheet material is approximately 0.6” (15 mm) regardless of sheet thickness. If the thin material is not stackable because of small batch size, you can improve efficiency by putting power through two cutting heads with smaller jets. With thin material, you don’t need larger jets because, surprisingly, they don’t cut much faster than smaller jets. However with thicker material over .25” (6 mm), going to a larger single head and increasing horsepower increases cut speed proportionally. The size of the work bed, or material support catcher, should be big enough to handle the largest sheet or plate that you commonly cut. An occasional oversized piece of material doesn’t justify an enormous and expensive machine tool since you can hang larger material off an end of the catcher. Although not optimal, it is a more cost effective solution. If you plan to cut metal and/or stone, the most common sheet and plate sizes often dictate a 6.5 x 13 ft. (2 x 4 m) work bed size. In North America, aluminum is sometimes available in 12-foot lengths, so the 13 ft. bed allows for easy loading. Similarly, the 6.5 ft. wide bed accommodates stone slabs that are sometimes delivered with a width of 6 feet. You should get a work bed slightly larger than the stock material you intend to cut so that loading and fixturing is easy. It is not surprising that the most common machine size is 2 x 4 m, or 6.5 x 13 ft., since this size covers nearly all North American and European material plate sizes. A less obvious reason to obtain a relatively large work bed even when cutting smaller stock material is that the large bed provides room for installing multiple, semi-permanent tooling locations to enable quick changeover from one job to another. If you’re cutting brittle materials like stone and glass, you should equip your machine with UltraPierce™, a vacuum assist device that allows piercing of these materials without breakage. Typical Customer Decision Consider a shop currently doing a lot of mild steel fabrication work. They have a large bed plasma table, welding equipment, bend and break equipment but they don’t have CNC chip making equipment (mills or lathes). Because the common, relatively lower tolerance fabrication work is extremely competitive, they decide to add a waterjet to expand to more material types and greater thickness and to eliminate grinding off of the heat affected zone left behind by the plasma cutter that is required on many of their jobs. They believe they can cover the workload in one shift. As a fabricator, they are used to working with large plates, utilizing an overhead crane and fork lifts to load any machine easily. They work with steel and sometimes aluminum sheets and plates up to 1 inch (25 mm), with the most common between 1/8” and 3/8” (3 to 9 mm) thick. They very rarely work with material thicker than 1 inch. They purchase stock material in sizes 4 x 8 ft., 5 x 12 ft., or occasionally 5 x 20 ft. (1.2 x 2.4 m, 1.5 x 3.6 m, or 1.5 x 6.1 m). They have room in their shop for a medium or large waterjet so this fabricator would likely choose a unit with a minimum bed size of 6 x 12 (1.8 x 3.6 m) because nearly all plate sizes can fit on the table. When they need to work with an oversized plate they can hang it over the edge (safely with proper support) to work on one end, or cut it in half on the plasma. The incremental cost of going from a 4 x 8 ft. to a 6 x 9 or 6 x 12 ft. table is small. However moving up to a 6.5 x 24 ft. (2 m x 7.3 m) table is more costly. They also decide to forego investing in a heavy-duty catcher capable of holding a 6 inch thick piece of material since they had never worked with material thicker than 1 inch in the past. On the rare chance such a need arises, they could support the material with blocks to enable thick cutting. In the end, they choose a single head 6.5 x 13 ft. (2 x 4 m) machine with medium power (50 hp) because they know they can upgrade later to a larger sized pump and add a second head when productivity becomes key. What level of precision do you require? Another factor to consider when choosing a waterjet is the level of accuracy and tolerances you need. Most operations are either fabrication or machine shops. Each have different needs when it comes to the level of cutting precision required. In general, machine shops normally need more accuracy than fab shops but some shops have both the precision chip making equipment of a machine shop and cutting, forming, and welding equipment of a fab shop. Flow waterjet systems are available with different levels of precision capability. A machine tool equipped with a basic waterjet cutting head, sometimes called a conventional waterjet head, can cut a +/- 0.005” accurate part out of any material up to approximately three inches thick. Beyond that the finished part accuracy will be less. To cut to +/- 0.005” (+/- 0.13mm) tolerance with this conventional head the machine cut speed must be reduced to approximately 15% of maximum cut speed. This slow speed is needed to minimize corner washout caused by stream lag, and part taper caused by the V-shaped kerf created by the jet at high speed. Slower cutting reduces these errors, but takes longer so is more expensive. Most systems Flow provides are equipped with Dynamic Waterjet® with Active Tolerance Control. Dynamic Waterjet is patented technology that automatically tilts the cutting head impingement angle to compensate for stream lag and taper in a behind the scenes operation based on cutting speed and type of material being cut. The result is two to four times faster cutting and finished part precision of +/-1 to 3 thousandths of an inch (+/- 0.03 to 0.08mm). The technology allows the machine to move very fast, create a taper and stream lag, and then compensate for it automatically by tilting the head by up to 10 degrees.