waterjet cutting machine

7/30/2019 Waterjet Cutting Machine

1/36

WATERJET CUTTING MACHINE

BY : KANISHK BUGALIA

SHRIYA KANNAUJIA


2/36

WHAT IS WATERJET CUTTING

Water jet cutting is exactly what it says, it involves using

an extremely fine jet of water travelling at high velocity,

into which an abrasive material is mixed for cutting hard

materials such as granite and titanium. This process makesa very fine cut into the material, known as a

kerf.


3/36

PRINCIPLE OF WATERJET CUTTING

A high pressure pump produces water at pressures upto 4100 bar .

The high pressure water is delivered to a cutting headby a small bore stainless steel pipe.

At this point it is passed through a very small orificemade from sapphire or diamond which produces anextremely thin, high velocity jet of water.

A metered amount of abrasive particles, such as sand,is then mixed with this high velocity jet of water andfocused in another nozzle called the focusing tube.


4/36

The work piece to be cut rests on support gridsover a tank of water.

The water jet penetrates through the materialand moves relative to the XY coordinates of thebridge supporting the cutting head.

The excess water jet energy that exists after the

jet has cut through the material, is absorbed bythe tank of water.

The cutting water and sludge can be filtered byan optional sludge removal system.


5/36


6/36

WATERJET CUTTING MACHINE

DIAGRAM OF A WATER JET

CUTTER

1 - high-pressure water inlet2 - jewel (ruby or diamond)

3 - abrasive (garnet)

4 - mixing tube

5 - guard

6 - cutting water jet

7 - cut material


7/36

MAJOR PARTS

HIGH PRESSURE WATER INLET

Fixed displacement piston pump.

This type of pump as used in some entry

level machines, uses a set of high speed

pistons driven directly by an electric motor

to compress the water and generate the

pressure. This type of pump develops a

cutting pressure of 1500 2000 bar which

is adequate for an entry level machine. It

also has the advantage of being cheap to

manufacture .


8/36

Fixed displacement piston pump


9/36

INTENSIFIER PUMP

This type of pump uses hydraulic pressure

developed by an electric .Motor driving a

hydraulic pump, which in turn drives a single

piston backwards and forwards in a long slowstroke, compressing the water and

developing pressures up to 4100 bar. This is

the most common type of pump found onwater jet machines.


10/36

INTENSIFIER PUMP


11/36

CHOICE OF NOZZLE

It mainly depends on three factors

Whether you are cutting with water only i.e. softmaterials like Foam, rubber, cardboard, foodstuffs,leather or textiles, or water and abrasive i.e. hard

materials like metal alloys, glass, ceramics, stone,laminates or Granite .

Quality and speed of cut required

Volume of cutting- In the case of a fixed

displacement pump, there is only one choice ofnozzle as the volume of water delivered is constantand the pressure delivery is influenced by the orificediameter. Therefore the nozzle diameter and thefocusing tube diameter must be chosen so that the

pump delivers the required cutting pressure.


12/36

NOZZLE


13/36

MIXING CHAMBER


14/36

ABRASIVE

The abrasive used in water jet cutting is typically a Garnet type of80 up to 120 microns in diameter. The quality of this abrasive has a

great influence on the cutting power of the water jet. The abrasive

must have a high cutting efficiency, but cause low wear on the

focusing tube and mixing chamber, create very little dust and be

environmentally friendly.The following factors must be considered in determining a suitable

abrasive :-

The grain of the abrasive must be less than half the focusing tube

diameter. The hardness of the abrasive has a direct effect on the cutting

power of the water jet.

The dust content of the abrasive must be low or it creates sludge

in the waste water.

Quality and repeatability of the cutting results .


15/36

Schematic illustration of the abrasive-jet machiningprocess.


16/36

Advantages of Waterjet Cutting

There are no heat affected zones (HAZ)

The material does not get warped, discolored or

hardened

Ability to manufacture burr-free parts

No jagged edges or burrs

Near net shape cutting

Eliminates the need for secondary operations

Can cut through thick materials

Up to 12 in thickness


17/36

Cuts Complex Shapes without discoloring or melting metal

Minimal Tolerances (at 0.003")

Can Pierce Material directly without the need for a pre-

drilled starter hole

High or Low Speed surface pressure flexibility for thick or

sensitive materials No Dust or Toxic Fumes Garnet is easily disposed or re-

cycled

Single or Multiple Cutting Heads

Thick or Thin, Waterjet cutting is the most flexible process

in manufacturing


18/36

It does not produce any dust or particles that are

harmful if inhaled. It can be easily automated for production use

High precision - no need for costly recutting.

No need for resharpening tools

Very fast implementation from drawing board to

cut piece .


19/36

SPEED AND QUALITY OF

WATERJET CUTTINGAs the water pressure increases, the cutting depth achievable

increases proportionally.The quality of the cut surface also

increases, however, so does the wear and tear of the seals in the

pump. Pressure changes also result in wear and tear on the seals,

so if the material needs to be pierced at a lower pressure e.g. glassand laminates, then all the piercing operations should be carried

out prior to increasing the pressure for cutting operations.

Abrasive quantity must be optimum for the material to be cut. Ifthe abrasive flow is not high enough then the cutting power of the

water jet will not be sufficient. If the abrasive flow is too high, then

the water jet becomes sluggish and reduces the cutting power


20/36

The cutting depth attainable decreases withincreasing cutting speed. The quality of the

cut surface also decreases with an increase incutting speed. The pressure and abrasivequantity are set for a particular material toensure optimum piercing and cutting power.

The cutting speed i.e. the speed in m/min atwhich the cutting head is driven, is varieddepending on the thickness of material beingcut and the quality of cut required.


21/36

The surface cut by a water jet is that the cutting stream at the bottom lags behind the point of

entry to the material at the top, causing the characteristic curve. This effect worsens with an

increase in speed and improves with an increase in pressure or abrasive flow, up to an optimum

setting. Taper of the cut is also a problem which gets worse with speed and can be virtually

parallel at the optimum feed rate.


22/36

CUT QUALITY


23/36

CUTTING TABLE

Commonly known as the table, this is the part of themachine that is generally a large tank of water, overwhich the work piece is supported.

A gantry driven in the x and y axes (and in some casesthe z axis) moves the cutting head in relation to thework piece to cut the programmed shape

. There are generally two types of system, thecantilever, where the cutting head is supported and

driven from one side of the table and a gantry typewhere the cutting head is driven along the longestdimension by a rack and pinion guide on both sides ofthe table.


24/36

The most important function of any cutting

table is to guide the cutting head rapidly and

smoothly and isolate any vibration from thecutting process.


25/36

1D-2D-3D CUTTING

ONE DIMENSIONAL CUTTING

In production applications, slitting and continuous waterjetcutting is often used. The frame of the system is usuallyquite simple, cutting speeds are quite high .

The very important criterion in this application is the highreliability and short stand still times of waterjet cutting overlong cutting periods. In contrast to roll cutting, the materialis not moved to the side and no airborne dust is created.

Many cutting heads can be applied and controlled at the

same time. Application areas: Paper and Plastic production, Gypsum

boards, Raw drywall plates, sheet metal, Cake, Frozen pizza,etc


26/36

TWO DIMENSIONAL CUTTING

The most popular application is the 2D cutting

table. The cutting head is located above thecutting tank, moves in X-Y axes, according to the

outputs given by the CNC-Controller.

In many cases the Z (height) axis is controllable, in

order to adapt to non-flat surfaces.

The controller is more complex and most of the

cutting speeds lie below 15 m/min.


27/36

Three Dimensional Cutting:

There are two subgroups of 3D applications: Robotic

applications, where the cutting head is mounted on a robotic

arm and cutting tables, where, in addition to the 3 X, Y, and Zaxes, a rotation and swivel axis are added.

Robotic applications are able to cut automotive soft materials

such as headliners, dashboards, door panels, cutting out

shapes not accessible to presses. A cutting head with 5-Axies can perform conical cuts of flat

material sheets and cut chamfers as well as perpendicularly

situated holes in tubes.

In engineering applications, the bottom end of titanium tubesused in chemical reactors can be cut without weakening the

material.


28/36

3D WATERJET CUTTING


29/36

CHALLENGES TO WATERJET

Keeping in mind the wide spectrum of possibleapplications there are a few areas, which aresomewhat challenging for this cutting method.

The jet does not like large openings in hard

materials. When cutting a multi-layer profile at thetop of the workpiece, a slowdown in the velocity ofthe outside of the jet is observed, while at the sametime, the centere of the jet maintains the highkinetic energy.

As a result, upon exiting the first layer of thematerial, an increase in width of the jet occursresulting in inferior cutting quality and parameters .


30/36

When cutting piles of sheet metal, it is importantto make sure the plates are as flat as possible in

order to prevent the creation of pockets betweenthe layers .

By tube cutting, the jet on the lower side of the

tube is somewhat wider. A solution here can be arotating system facilitating the rotation of thetube in the process of cutting.

Keeping these considerations in mind, waterjet is

very well suited to cut multi-layer materials.


31/36


32/36

Application & flexibility


33/36


34/36

WATER TREATMENT NECESSARY

Inlet water should be treated for either the removal of hardness or thereduction in Total Disolved Solids (TDS). A water treatmentproducing TDS content of less than 0.5 ppm is not recommendedsince the aggressiveness of the purified water may damage theintensifier pump components. Treated water must have a pH valueof 6 to 8.

If your water has low TDS (200 ppm), water quality is considered

poor and should be treated with DI or RO equipment. If your water has high silica concentration (>15 ppm), dual strong-

base DI is recommended.


35/36

WATERJET ABRASIVE RECYCLING

SYSTEM

The system is designed to remove sludge from anabrasive water jet cutting tank or integrate into anexisting abrasive removal system. The recycled abrasivecan be placed in the hopper for use again with theoptional abrasive transport system. The abrasive isremoved from the tank using patented nozzles thathave no moving parts. The nozzles work best whenburied under approximately 12" (30 cm) of sludge. Thesludge is sent to the top of a series of vibrating screens

where usable abrasive larger than 100 mesh isseparated. This is then dried and made ready to useagain


36/36

Waterjet-A technology on rise

A very quickly guided waterjet, which just manages to cut throughthe material, has a V-shaped profile, creating a uneven surface atthe bottom. Should the jet be guided in a slower fashion, theprofile will be more even. As a general rule at one fifth of themaximum cutting speed, a perfectly perpendicular with a near

perfectly polished surface is achieved. A further slowing of themovement speed, leads to a loss of guidance in the material,erosion in the lower sections of the work piece, and a creation ofan A-shaped profile.

Plastic coated iron, plastic foil covered aluminum, styrofoam

covered gypsum board ... Waterjet technology was used for theremoval of the Russian Kursk nuclear submarine from thebottom of the sea. The steel body was covered with a thick layer ofrubber. And this gets us to yet another advantage of this methodit is not affected by moisture, working also under water.

waterjet cutting machine

Documents