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.
