Machine Tools And Devices For Special Technologies

Water Beam Machining

Slovak University of TechnologyFaculty of Material Science and Technology in Trnava

Machining by water beam

ecologic without impact effective cold cut Various materials

metal, ceramics, plastic, foods, others...

Principle of machining by water beam Erosion influence of water – small flash,

high pressure (more than 400 MPa),

Water is in the cut place like solid material.

In the cutting of hard and brittle materials is into water mix in abrasive.

Principle of water beam machiningAccording by cutting material are realised two

mechanisms of material removal:

brittle material – begining and extension of cracks originated by influence of tension by impacted water beam,

tensional material – begin of sliding fracture by shearing stresses.

Kinds of water beam

Continually Linear,

clean, cryogenic,

cavitation, abrasive,

AWJ Abrasive Water Jet (around 500 MPa), ASJ Abrasive Suspension Jet (till 100 MPa),

Discontinually Low-frequency, High-frequency

Clean water beamClean water without

substances.Preparing of water –

recommended.

Material with low firmness (textile, foods, gum).

Diameter of beam 0,1 till 0,3mm, jet distance from surface maximum 15mm

Cryogenic water beam

Into water beam the frazils of water or CO2 of sferic shape are mixed in during expasion.

Using in food industry and in medicine for bio materials cutting.

Cavitation water beam

In water beam are cavitation bubbles that can influence into material local 10 multiply increase of pressure during impact.

Glass cutting, rocks and etc.

Abrasive water beamInto water beam is mixed in suitable abrasive.It is

used for strong brittle, hard machining materials (300 – 500 MPa, clean water above1000 MPa).

Abrasives: Heavy:

granat, Carbide of silicon (SiC), Steel scobs,

light: Silica sand, glass.

AWJ – side mixing in of abrasivea – water input,

b – abrasive input,

c – water beam abrasive output,

1 – water,

2 – mixture room,

3 – abrasive,

4 – jet with colimator,

5 – cutting material,

6 – water beam with abrasive

Usage of abrasive: 0,5 till 20 kg/min

ASJ

Abrasive is into pressure water mixed in in pressure container. This suspenzion is directed into special jeet.

Abrasive usage: 1 till 3 kg/min

Discontinual water beamPressure generated by impact of water beam is

particular multiply higher than pressure generated by continual water column.

By impact of discontinual (pulsing) beam originated impact pressure that next decreased to zero. This cycle is repeat with the frequency.

Pulsation with low frequency, Discontinuous beam, modulated beam.

Water beam cutting process

Cutting process consist of two phases:

By water pressure influence become hollow that is transformed to hole,

Creating of sawed joint.

Process of water beam cuttingAreas in cutting surface:

In the side of the input – mat aspect with roughness Ra = 2 till 5,5m

In the side of output – gaining with wave lenght 1 till 2mm

Quality of cutting surface

More quality cutting surface: Increasing of cutting speed, Increasing of pressure, Increasing of volume flash of abrasive, Increasing of dynamic beam stability.

By various parameter setting we achieve quality of cutting surface that be suitable for requests.

Quality of cutting surface

Q1 – dividing cut, Q2 – rough cut, Q3 – intermediate cut, Q4 – fine cut, Q5 – the best cut.

Cutting surface shape

Cutting speed is with respect to hardness of cutting material small. Water beam comes in time for erode cutting sawed joint into his natural shape.

Cutting surface shape

Cutting speed is correct, cutting surfaces are without scarf.

Shape of cutting surface

Cutting speed is with respect to hardness of cut material high. Water beam is not coming in time for particularly eroding of bottom cut part and that is in down direction closed.

Devices for water beam cutting Water preparing:

filtration, deionisation, softening,

High-pressure pump: Low-pressure oil cycle, High-pressure water cycle,

Cutting station: Cutting desk, portal, support, Cutting head with cutting jet

Water preparing filtration – mechanical preparing, removing

elements of size around 1m, deionisation – removing of the ion waste

elements, ion transmission, softening – water hardness preparing is

recommend to using of soft water. Back osmose – water is pressed through the

semipermiable membrane that is stopped soluble materials.

High lifetime of device (jet, pump), increased quality of cutting surface.

High-pressure pump

Low-pressure oil cycle – oil pressure is 15 till 35MPa. There are used standard generators.

High-pressure water cycle – created water cutting pressure of asked rate (100 till 500MPa). There can be individually a few.

Exclusively high-pressure elements!!

High-pressure pump

Processing of high-pressure pump

Cutting desk

Filled in with water that stopped the energy of water beam,

Filling in and filling out of water, Firm construction, Type of construction:

In the floor is assembled system with dividing cutting desk, Integrated system desk-portal, Console system with dividing cutting desk, Integrated system desk– console.

In the floor assembled system with dividing cutting system

Iintegrated system desk - portal

Console system with dividing cutting system

Integrated system desk - console

Next parts of cutting device

Portal – makes possible to moving of support above desk, can has several cutting heads,

Support – holds cutting head above desk, positioning by servomotors, cutting heads is setting in the vertical axis Z, cutting head can be rollovering.

Cutting head – is imbed by jet, there can by various shapes of jets.

Cutting heads

For cutting by clean water,

For cutting of abrasive water beam

Cutting head jet

For clean water beam – diameter 0,05 till 0,5 mm Sintered carbide, Synthetic sapphire, Synthetic diamond,

For abrasive water beam – diameter 0,8 till 2,2mm Wolfram carbide (WC) Cubic nitride of boron (KBN) ceramics

Lifetime around 100hours.

Jet shapes of cutting head

Stair-step, conic, combinated.

Examples of technology using

Examples of technology using

Example of desk with two cutting heads