Water Jets Conventional and Dynamic
Water jet machines come in a variety of shapes, sizes, and styles, with a variety of features, from a variety of manufacturers, for a variety of applications. Their versatility makes them useful in servicing all industries. For the OEM or job shop proposing the purchase of an aerospace waterjet cutting systems, two key considerations involve the selection of conventional or dynamic cutting equipment with subsequent 60,000 or 90,000 high-pressure water pumps.
Conventional waterjet cutting systems are the earliest type of waterjet cutting systems. Cutting heads are fixed, positioned or hung in a manner suitable for general shape cutting. Tolerances are less precise due to the non-movement or fixed nature of the cutting head. Conventional waterjet cutting systems create a natural edge taper during cutting. The faster you cut the more taper that is created, resulting in a lower shape cost (time is money), yet cutting slower will minimize the amount of edge taper; but the result is a higher shape cost. Edge taper can quickly eat up size tolerance, a feature having edge taper of .010”, cannot be held tighter than +/- .010” on size. Costs for a conventional cutting heads vary by manufacturer, but plan on $800 – $1,500 depending on level of consumables.
Technology for dynamic waterjet cutting systems have became available over the past 10-years. Dynamic waterjet cutting uses complex algorithms to reduce edge taper by tilting the cutting head during the cut by up to 7 degrees per side. The resultant part will have little edge taper, while the scrap will have twice that of conventional cutting. Controllable taper is key for precision waterjet cutting services to maintain precise size tolerances. A feature having an edge taper of .001” has a strong chance of being within +/- .002”. Costs for a dynamic cutting head again vary by manufacturer, but are extremely expensive due to the software, hardware, electronics, motors, and actuators needed to perform complex movements. Plan to spend $40,000 minimum over that of a conventional waterjet cutting system.
High-pressure water pumps are available to generate both 60,000-psi and 90,000-psi water pressures. The purchase price for a 90,000-psi pump will naturally be greater when compared to a 60,000-psi pump and in most cases faster depending on the manufacturers processing software. When selecting the appropriate pump it is important to compare the overall process time of the product that will be produced. In some instances, the operational advantages of the 90,000-psi pump do not outweigh the higher purchase price, maintenance costs, and operational costs. Additionally, it is more important to understand; will the higher production costs be supported at the market.
Article prepared by Ron Fairchild of Cutting Edge Water Jet Service; South Beloit, Illinois. Ron has over 20 years of experience in hands-on waterjet applications. Cutting Edge Water Jet Service is a job shop provider of water jet services for all industries in the United States. They offer 60,000-psi, 90,000-psi, conventional and dynamic abrasive waterjet cutting using a variety of multi-head waterjet cutting systems.