Original Date: 01/26/1998
Revision Date: 01/18/2003
Information : Waterjet Numerically Controlled Machining Center
(equipment: Engine ARMS Robotic Systems from United Technologies, Pratt & Whitney Waterjet Systems, Huntsville, AL)
Prior to 1995, Corpus Christi Army Depot (CCAD) used conventional stripping and machining operations to remove flame/plasma coatings from aircraft engine parts. These processes were costly, and resulted in the need to dispose of hazardous waste products. In February 1995, CCAD purchased a custom built Waterjet Numerically Controlled Machining Center. Major components of the system include a six-axis Fanuc S-240F robot with a waterproof robot protective shroud; RJ- series controller; graphic operator workstation; turntable; Jet Edge 57-150 ultrahigh pressure pump with auxiliary hydraulic power unit for nozzle rotation; stripping end effectors; mist collection system; water reclamation system; chiller; and workcell enclosure (Figure 3-1). All system components interface and communicate through the robot controller. A deionization system removes positively charged ions and negatively charged particles from the potable facility water supplied to the pump. Deionization minimizes corrosion and system maintenance to the high pressure water pump components and nozzle orifices.
With the water reclamation system, water is recycled for reuse in the stripping operation and all solid materials are collected for disposal. The chiller is used for cooling the potable facility water so it can continuously cool the hydraulic system of the ultrahigh pressure pump which minimizes seal degradation and maintenance. The theory of the Waterjet operation is to shoot an erosive force of water at high velocity (Mach 2.5 speed), directed against a coated surface by a rotating nozzle, to remove the coating. Five process parameters are critical for the coating removal: 1) nozzle standoff distance; 2) nozzle angle of attack; 3) nozzle traverse speed; 4) nozzle rotation speed; and 5) water pressure. The robot maintains the first four parameters. The water pressure (25-55,000 psi) is automatically set by operating software or manually by the operator. Coatings are removed by a rapid liquid erosion process. Erosive action at the coated surface occurs in milliseconds. Although there are limitations to the Waterjet system, such as line of sight access and single component processing, the prevention of hazardous waste far outweighs the limitations.
Figure 3-1. Waterjet System
For more information see the
Point of Contact for this survey.