Abstract:
The conventional process of cutting stainless steel foils, is plasma beam.
This type of cutting has the following disadvantages: a) It leaves scum. b)
The cutting area is subjected to heating (area affected by the heat [ZAC]),
that originates structural changes and c) In the ZAC an aureole that harms
its aesthetic termination appearance.
The objective
of the following project is to eliminate the difficulties pointed in the
previous process, carrying out the cutting (austenitic stainless steel foils
up to 2 mm of thickness) by means of a jet of fluid to high speed.
The cutting
process can only be carry out mixing with, the flow of water, particles of
abrasive material {M-K}. Can be used as element elevator of the pressure of
the water, a lineal injection pump (Diesel motor), a series of transformations
should be carried out to adapt it to the specific use.
With regard
to the circuit: a) the correct filtering of the water should be carried out
to prolong the useful life of the nozzle {URI}. b) The regulation valve of
pressure protects the circuit of over pressures and c) The accumulator of
gas maintains the constant pressure.
Introduction:
To carry out the cut of a certain material it is needed a certain quantity
of energy. In the cutting process we denominate: transformation of the energy,
to the energy that is delivered becomes deformation of the material to cut.
Now, all fluid in movement is associate with certain quantity of energy (kinetics).
Therefore, this fluid will have a bigger energy or similar to the necessary
one to carry out the cut.
As energy
carrier in general, we can almost use all the liquid elements: oils, alcohols
and also liquid metals for example the mercury. Now, the water presents
a series of advantages with regard to the other ones: a) it Exists in enough
quantity and in required quality (drinkable), in almost all the places. b)
tiny cost, in their employment, with regard to the other fluids. c) Easily
accessible. d) it doesn't generate fire. e) Good conditions of fluency (low
viscosity), otherwise it would be very difficult to achieve the delivery of
the jet through a small hole to high speed.
On the other
hand, the air is also completely discarded as energy carrier for the following
reasons: a) High cost to achieve high speeds beams (tunnel of wind). b) Very
low kinetic energy (Density of the air = Density of the water / 1000). c)
Very difficult of achieving a punctual effect, high dispersion when leaving
the nozzle.
The project
is delimited to the cutting of austenitic stainless steel up to 2 mm of thickness.
Development:
For the cutting of foils of austenitic stainless steel (AISI 310) with 2
mm thickness it is needed a very high pressure of water, this is due to the
drop density of the fluid. When adding an element elevator of the density
(metal particles) to the flow of water, the necessary pressure of the pump
is reduced to a third of the previous value. But it even continues being
high.
The appropriate
alternative is to add particles of abrasive material (alumina, garnet, etc.)
to the flow of water {M-K}, which produce the microcutting of the material
{E-M}. Now the necessary pressure of the pump of water is located in 400
atmospheres.
With regard
to the system blending of water with abrasive, can be said: the suction of
the abrasive, from the chute that contains it, is made by suction (Venturi
effect) through a gauged badge hole, being necessary a depression of a tenth
of atmosphere to obtain the appropriate flow (3.4 gr/s).
{S} The more
appropriate construction for the mixing tube, with alumina like abrasive,
it is the carbide of boron with carbon 5 % (B4C-C 5 %). The interior
profile of the tube should be smoothly convergent from the entrance mouth
(diameter 4 mm) until the exit mouth (diameter 0.8 mm) . A bigger longitude
of the tube (76 mm) it brings harnessed a better acceleration of the particles
of abrasive.
Can be used
as element elevator of the pressure a lineal injection pump (Diesel motor),
it should be carried out the following transformations: a) Change the material
of construction of the pistons, cylinders, valves, valve seats and hole for
martensitic stainless steel (AISI 440). b) The system of variation of the
flow is omitted. c) It modifies the profile of each levy (tree of levies)
so that the flow of water is continuous and non pulsating (characteristic
of the Diesel injection). d) It is carved in each piston a groove circumferential
with that which a hydrodynamic stamp is possible to avoid the fall of the
yield with the elevation of the pressure.
It is fundamental
to carry out the correct filtrate of the water {URI} to prolong the useful
life of the nozzle of water.
A regulating
valve of pressure is placed in the circuit of high pressure for: a) To protect
the circuit of over pressure in the moment of closing (momentarily) the valve
blockade solenoid. b) That the pump works to low pressure during that period.
An accumulator
of gas is placed (type membrane) for: a) To absorb the small variations of
pressure, consequence of the discontinuous flow that gives the main pump,
making it more constant. b) To absorb the picks of pressure due to the abrupt
closing of the valve blockade solenoid and c) To maintain the circuit (between
the anti-return valve and the valve blockade solenoid) on the working pressure
(400 atmospheres), while the main pump works to low pressure (it closes momentary
of the valve blockade solenoid).
In the enclosed
diagram can be observed the main components of the circuit.
References:
1) Filter of
water (particle diameter = 0.45 to 0.5 microns). 2) Auxiliary pump
of the high pressure pump. 3) Loock solenoid
valve (primary). 4) Valve of security
and itdischarges. 5) Gauge. 6 and 7) Tube
of stainless steel . 8) Catcher. 9) High pressure
pistons pump (400 kg/cm2). 10) High pressure
pump electric motor drive. 11) Compound abrasive
bolster for:
a) Nozzle of water
to pressure. Diameter = 0.254 mm, material = sapphire (or diamond).
b) Camera of mixture
of the water and the abrasive (for suction = Venturi effect).
c) Mixing tube or of
acceleration of abrasive particles. Diameter (of exit) =
0.8 mm.
12) Chute with
abrasive (for a capacity of 24 kg). 13) Flexible tube,
bond between the chute and the mixture camera (Nominal Diameter = 6 mm). 14) Itplates tocut (austenitic stainless steel, until a thickness of 2 mm). 15) Accumulator
of gas. 16) Valve solenoid
(secondary).
Results:
To carry out the cutting of austenitic stainless steel foils (up to 2 mm of
thickness) by means of jet of water, it should be added to the fluid a certain
flow of abrasive particles producing what we denominate microcutting of the
material, since this particles they impact on the material to a high speed
(460 km/h).
You can use
a lineal injection pump (Diesel motor) as element elevator of the pressure
of the water, for it should be carried out it certain changes to guarantee
their appropriate acting.
A correct
filtrate of the water prolongs the useful life of the nozzle of water. When
including in the hydraulic circuit a valve regulator of pressure: a) it is
protected to the same one of on pressures, b) it is saved energy and c) it
diminishes the waste of the pump.
On the other
hand, the accumulator of gas helps to maintain constant the pressure of the
water.
Computer book AWJ:
If you are interested in this project, you can acquire the computer Book
(Spanish language) on Machine of cut of foils of stainless steel for jet
of water and abrasive. Here she/he will find, in 88 topics distributed in
94 pages (A4), all the information on this novel cut system, which was topic
of my Final Thesis of Mechanical Engineering.
If you require
additional information in this respect, I recommend download the Demo: Awjd.zip (76 kb).
If on the
contrary, it is convinced of the kindness of this book, you can acquire it
right now by means of some of the following links:
Abstract:
The conventional process of cutting stainless steel foils, is plasma beam.
This type of cutting has the following disadvantages: a) It leaves scum. b)
The cutting area is subjected to heating (area affected by the heat [ZAC]),
that originates structural changes and c) In the ZAC an aureole that harms
its aesthetic termination appearance. 
