Abrasive Waterjet Machining

Abstract

The abrasive waterjet machining process was introduced in the 1980s as a new cutting tool; the process has the ability to cut almost any material. Currently, the AWJ process is used in many world-class factories, producing parts for use in daily life. A description of this process and its influencing parameters are first presented in this paper, along with process models for the AWJ tool itself and also for the jet-material interaction. The AWJ material removal process occurs through the high-velocity impact of abrasive particles, whose tips micromachine the material at the microscopic scale, with no thermal or mechanical adverse effects. The macro-characteristics of the cut surface, such as its taper, trailback, and waviness, are discussed, along with methods of improving the geometrical accuracy of the cut parts using these attributes. For example, dynamic angular compensation is used to correct for the taper and undercut in shape cutting. The surface finish is controlled by the cutting speed, hydraulic, and abrasive parameters using software and process models built into the controllers of CNC machines. In addition to shape cutting, edge trimming is presented, with a focus on the carbon fiber composites used in aircraft and automotive structures, where special AWJ tools and manipulators are used. Examples of the precision cutting of microelectronic and solar cell parts are discussed to describe the special techniques that are used, such as machine vision and vacuum-assist, which have been found to be essential to the integrity and accuracy of cut parts. The use of the AWJ machining process was extended to other applications, such as drilling, boring, milling, turning, and surface modification, which are presented in this paper as actual industrial applications. To demonstrate the versatility of the AWJ machining process, the data in this paper were selected to cover a wide range of materials, such as metal, glass, composites, and ceramics, and also a wide range of thicknesses, from 1 mm to 600 mm. The trends of Industry 4.0 and 5.0, AI, and IoT are also presented.

Keywords: abrasive waterjet; composites; cutting; drilling; glass; metal; milling; surface finish; titanium; trimming; waterjet.

Figure 1

Waterjet system components.

Figure 2

AWJ parameters.

Figure 3

Waterjet orifices.

Figure 4

Waterjets with different upstream conditions at 350 MPa pressure.

Figure 5

Waterjet flow, power, and orifice size relationships.

Figure 6

Abrasive particle shape indices and preferred zone (upper left corner).

Figure 7

AWJ nozzle and suction hose characteristics [24].

Figure 8

Example of mixing tube wear.

Figure 9

Geometrical attributes of waterjet cutting.

Figure 10

Erosion model.

Figure 11

AWJ cutting model showing step and cutting stages.

Figure 12

Idealized model of surface waviness.

Figure 13

Effect of abrasive particle size on surface roughness.

Figure 14

Trailback geometry for several cuts in titanium.

Figure 15

Universal kerf shape and data from Figure 14.

Figure 16

Theoretical waterjet kerf profiles.

Figure 17

Kerf width profile in 150 mm thick titanium.

Figure 18

AWJ cuts showing kerf top, bottom, side, and surface morphology.

Figure 19

Cutting speed zones.

Figure 20

Gain in speed due to dynamic jet tilting.

Figure 21

Undercutting at the bottom of cuts.

Figure 22

Examples of AWJ applications in jet engines.

Figure 23

Composite use in aircraft.

Figure 24

CFRP parts on the Airbus 350.

Figure 25

Examples of cutting microelectronic parts.

Figure 26

Examples of AWJ glass cutting and milling.

Figure 27

AWJ stone cutting and inlay.

Figure 28

Examples of automotive applications.

Figure 29

Example of thin sheet metal cutting data.

Figure 30

AWJ end effector with height sensor and vision camera.

Figure 31

Sample holes for vent screens.

Figure 32

Titanium screen cutting.

Figure 33

Precision robotic cutting of glass domes for solar panels.

Figure 34

Microblaster abrasive feed for fine abrasives.

Figure 35

MicroSD singulation using AWJ technology.

Figure 36

EHC before and after AWJ cutting.

Figure 37

Trailback curve rotation with lead angles in glass.

Figure 38

Kerf width profile rotation in 100 mm thick titanium.

Figure 39

Example data on kerf width and trailback.

Figure 40

Thick glass cutting of small demo parts. The arrows show the cutting path.

Figure 41

Cutting 600 mm thick glass using a 900 mm long mixing tube. The arrows show the cutting path starting from the center.

Figure 42

Maximum cutting speeds and trailbacks in titanium.

Figure 43

Surface waviness as a function of cutting speed.

Figure 44

Near-net shaping of integrated jet engine rotor blades.

Figure 45

Potential integrity problems faced when using solid tools.

Figure 46

Stringer trimming for the Boeing 787 aircraft.

Figure 47

Stringer trimming machine for the Boeing 787 wing stringers.

Figure 48

AWJ composite machining systems.

Figure 49

Focal point C-frame end effector for composite trimming.

Figure 50

Sample AWJ-cut taper and finish.

Figure 51

Examples of small composite parts.

Figure 52

Robotic trimming of small composite clips.

Figure 53

Geometry of fan blades and a blade trimming test.

Figure 54

A varying thickness portion of an AWJ-trimmed fan blade.

Figure 55

Cuts made in sapphire and SiC/SiC composite material.

Figure 56

Effect of the cutting speed on the taper of the cut in SiC/SiC material.

Figure 57

Micro AWJ with a 177-micron mixing tube [78].

Figure 58

Cutting results with a micro AWJ tool.

Figure 59

Patented micro AWJ cutting heads [81,82,83].

Figure 60

Micro AWJ sizes from the literatures [60,78,80,85,86].

Figure 61

Micro AWJ cutting head, Craigen and Hashish [81].

Figure 62

Example features machined with micro AWJ technology.

Figure 63

Micro sidefire AWJ cutting head for groove milling.

Figure 64

Hole piercing progression examples.

Figure 65

Possible hole shapes with AWJ piercing.

Figure 66

Cross-sections of holes drilled in aluminum and steel (d_n = 0.18 mm, d_m = 0.51 mm, P = 345 MPa).

Figure 67

Drilling times for steel and aluminum at different depths.

Figure 68

Effect of pressure on the drilling time for 12.7 mm thick steel and aluminum.

Figure 69

Small-diameter holes drilled in a 20 mm thick steel block.

Figure 70

Hole depth progression in steel at different eccentricities.

Figure 71

Holes drilled in glass.

Figure 72

Drilling rate in thick glass under different conditions.

Figure 73

Repeatability of hole drilling in thick glass.

Figure 74

Possible problems of drilling a TBC using AWJ technology.

Figure 75

Accurately drilled hole at 30 degrees.

Figure 76

AWJ-drilled holes in TBC.

Figure 77

AWJ-drilled hole in an alumina/alumina CMC with no adverse effects.

Figure 78

AWJ-drilled shaped hole in SiC/SiC material.

Figure 79

Hole circularity measurement in an alumina CMC.

Figure 80

Potential failure modes in AWJ drilling.

Figure 81

AWJ piercing through a 25 mm thick composite at a shallow angle.

Figure 82

Cutting head for precision cutting and drilling.

Figure 83

Matching holes drilled in aluminum and carbon fiber composite.

Figure 84

Closely packed AWJ-drilled holes in 1 mm thick CFRP.

Figure 85

Example of pierced shaped holes.

Figure 86

Hole boring pilot and reaming AWJ tools.

Figure 87

AWJ-bored holes.

Figure 88

Milling methods using masks.

Figure 89

Isogrid milling (radial and cylindrical).

Figure 90

Milling of jet engine exhaust heat shield tiles.

Figure 91

Milling of telescope face sheet glass.

Figure 92

Deep pocket milling examples.

Figure 93

Typical composite joint designs.

Figure 94

AWJ-milled composite repair joints.

Figure 95

AWJ grooving examples.

Figure 96

Turning operations.

Figure 97

Example samples of turning operations.

Figure 98

Example turning trends using Ti-Al target material.

Figure 99

Turning process parameters used for modeling.

Figure 100

Segmental turning.

Figure 101

Example of early multi-operation machining.

Figure 102

Shaping of titanium aluminide blades.

Figure 103

AWJ cuts for a 3D laminated object.

Figure 104

Stent polishing.

Figure 105

Waterjet texturing of automotive cylinder bore.

Figure 106

Effect of waterjet impact of fatigue parameters for 7075-T6 aluminum.

Figure 107

Examples of pure waterjet cutting at elevated pressures.

Figure 108

Effect of pressure on non-delamination cutting speed.

Figure 109

Mechanical–waterjet hybrid composite machining system.

Figure 110

AWJ-EDM hybrid machine.

Figure 111

Effect of upstream cooling on nitrogen jet structures.

Figure 112

Steel plate cut with a liquid nitrogen ACJ.