“ABRASIVE WATERJET MACHINING (NON CONVENTIONAL MACHINING)”

Abstract:- IPR has procured a 3 axis precision abrasive Waterjet cutting system of approx. 3.2 meter x 1.5 meter XY travel. The machine can cut complex flat parts out of most materials (and wide range of thickness) including metal, plastic, glass, ceramics, stone and composites. Extremely hard, reflective and nonconductive materials can also be cut. The machine does not create heat-affected zones or mechanical stresses. The aim of this project work is to learn the basic abrasive Waterjet cutting application on R&D purpose. Studies on the various dependent parameter such as Water Pressure (Pw), Cutting Speed (V), Nozzle diameter (d),Abrasive Index, Machinability Index of the material, Quality to be cut and depth of cut etc. Each cutting process has significant depended on these parameters.

ABRASIVE WATERJET MACHINING Introduction:-

Waterjet process provides many unique capabilities and advantages

The Waterjet process is recognized as the most versatile and fastest growing process

compliment other technologies such as milling, laser, EDM, plasma

True cold cutting process – no HAZ, mechanical stresses or operator and environmental hazards

Not limited to machining – food industry applications

History:-

Dr. Franz in 1950’s first studied UHP water cutting for forestry and wood cutting (pure WJ)

1979 Dr. Mohamed Hashish added abrasive particles to increase cutting force and ability to cut

hard materials including steel, glass and concrete (abrasive WJ)

First commercial use was in automotive industry to cut glass in 1983

Soon after, adopted by aerospace industry for cutting high-strength materials like Inconel,

stainless steel and titanium as well as composites like carbon fiber

PROCESS OF ABRASIVE

WATERJET CUTTING

JET LAG Angular Edge shape

(Common Abrasive) (Hard Rock Abrasive)

Garnet is hard, tough and inexpensive

80 Mesh – Most common general

purpose Garnet water jet abrasive

ATTACHMENTS FOR OMAX 60120:

Tilt–A-JET :Taper removal attachment

Terrain Follower : To maintaining stand off distance for non planner surface

Rotary Axis: 6-axis Path to create 3D shapes,

Precision Optical Locator (POL): To determine the precise location of parts,

Variable Speed Solid Removal System (VS-SRS) : Optimal abrasive removal during

operation using VFD.

Drill Head Attachment : 100% reliable piercing of composites and laminates

Bulk Abrasive Delivery System : Feeds abrasive from 600lb abrasive Hopper to the

machine

A-Jet : Allows bevels cutting up to +- 60 degrees

SUMMARY OF THE PROJECT:

The basic on Waterjet technology and its Applications area is studied.

Studied the benefit of the CNC abrasive Waterjet machining , its advantages over other

machining techniques. A best example is almost all materials can be cut using AWJM with

zero HAZ.

Studied the capabilities of the OMAX 60120 Abrasive Waterjet Machine and understood the

various features of the Attachments such as Tilt-A-Jet, Terrain Follower, Rotary Axis,

Variable Speed Solid Removal System (VSSRS), Precision Optical Locator and Drill Head

attachment.

Installation requirement for OMAX 60120 machine and its safety concern. As material and

pump technology advances faster cutting rates, longer component life and tighter tolerances

will be achievable

Analytical approach to calculate various parameters such as cutting speed, depth of cut etc.

for SS304 material.

REFERENCE: [1] M. Hashish, A model for abrasive water jet machining, J. Engg. Materials Tech., Vol.111, (1989), pp.154-162. [2] J. Zeng and T. J. Kim, An erosion model of polycrystalline ceramic in abrasive water jet cutting, Wear, Vol.199(2), (1996), pp.275-282. [3] http://www.omax.com/waterjet-cutting/machine/model/60120. http://waterjets.org/index.php?option=com_content&task=view&id=81&Itemid=51. [4] http://waterjet-cutting.blogspot.in/search/label/maintenance%20waterjet

ANALYTICAL APPROACH

Used to cut much harder materials

Water is not used directly to cut material as in Pure, instead water is used to accelerate abrasive

particles which do the cutting

80-mesh garnet (abrasive) is typically used though 50 and 120-mesh is also used

Standoff distance between mixing tube and workpiece is typically 0.010-0.200 – important to keep

to a minimum to keep a good surface finish

Orifice is made of Sapphires, Rubies with 50-100 hour life

Diamond Orifice has 800-2,000 hour life

Standard Tungsten Carbide lasts 4-6 hours (not used much anymore)

Premium Composite Carbide lasts 100-150 hours

Consumables include water, abrasive, orifice and mixing tube

Summer School Programme, Institute For Plasma Research, Bhat Gandhinagar, Gujarat (July 2014)

SUMMER SCHOOL PROJECT 2014, INSTITUTE FOR PLASMA RESEARCH, BHAT, GANDHINAGAR

1 • Over Head Tank (OHT)

2 • Water Purification System (R.O System cum Water Softener)

3 • Chiller Unit (To protect the High Pressure Pump from excess heating)

4 • High Pressure Pump (20ksi - 60 ksi)

5 • Control Valve & Flow Regulator

6 • High Pressure water from Orifice (Jewel)

7 • Abrasive Mixed at Mixing Tube

8 • Pressurized mixture from Nozzle

9 • To Work Piece

]}1.15 V = {

- Zeng Modified Cutting Speed Equation Where, P = Stagnation pressure of the Waterjet in thousands of PSI (KSI), typically 55 KSI. d = Orifice diameter in inches, typically 0.014 Ma = Abrasive flow rate in lb./min., typically about 0.8 fa = Abrasive factor (1.0 for garnet) Q = Quality, Set to 3.0 to calculate clean cut speed H = Material thickness in inches D = Mixing tube diameter in inches, typically 0.030 to 0.040 V = Traverse speed in IPM M = Machinability of material

0

0.5

1

1.5

2

2.5

3

3.5

4

0 1 2 3 4 5 6

Cutt

ing

Spee

d V

(IPM

)

Finish Quality (Q)

Cutting Speed vs Finish Quality

SS 304 material by taking H = 2 inch

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 100 200 300 400 500

Cu

ttin

Sp

ee

d V

(lP

M)

Machinability

Cuttin speed vs. Machinability

Carbide SS 304

Titanium

Aluminum

Glass

Nylon

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 10 20 30 40 50 60 70

Citt

omg

S[ee

d V

(IPM

)

Water Pressure Pw (Ksi)

Cutting Speed vs. Water Pressure

0

0.005

0.01

0.015

0.02

0.025

0 1 2 3 4 5 6 7

CU

TT

ING

S

PE

ED

H(DEPTH OF CUT)

CUTTING SPEED VS. DEPTH OF CUT

HOW HIGH PRESSURE IS GENERATED:

Direct drive pump

Intensifier pump

Direct drive pumps are gaining acceptance in the Waterjet

industry due to their simplicity and high efficiency.

Abrasive

Pw=55ksi,H=3 inch

SS-304 material by taking H=3 inch

Pw=55ksi,ss-304

material

JET LAG

Produced 3800 bar to

4100 bar by 60 ksi, 40

Hp Direct drive pump