FID diseñó una Mesa de Corte por Chorro de Agua, para cortar metales, cerámicos y polímeros en forma de placa, la precisión del sistema es de 0.5 mm/m, con velocidades de posicionamiento de 1.127m/s.

El diseño es importante ya que en el año 2001 fue la primera vez que se integro y se termino el proyecto de construcción de un sistema de corte por chorro de agua en México.

si Ud. requiere de una maquina de corte con chorro de agua o desea los servicios de esta tecnología no dude en contactarnos.

Calculus, Selection and Integration of Commercial Parts for

Built a Water Jet Machine, Like a Real Option for Machine Design

In Development Countries or Specific Regions in the world.

Ivan Espinosa

FID

A water jet cutting machine is designed using commercial components. The jet cutting machine has been designed to meet the following specifications: a) positioning average speed of 0.127m/s, b) precision

0.42 mm/m, c) working area 1.22 x 2.44 m, d) competitive cost. The paper describes the selection procedure of the main parts like: hydraulic, power transmission, positioning and control, Our propose is enhance the integration of commercial parts for built machines as an specific strategy for development countries or specific regions in the world for obtain such technological independency.

The water jet cut is a technique well stablished since 1970 [1], thi technique is generally realized at the same pressure for hard or smooth materials the average pressure of cut is 3795 bar, for cut hard materials like the ceramics or metals is necessary the include an abrasive inside of the water jet beam like silica sand [2]. In comparission with other cut techniques like the plasma or laser, the water jet cut has several advantages being the principals the wide variety of materials and thickness that it’s possible to cut (ceramics, plastics, metals) [3], the low heating that the processes causes to the target material, that is < 260° [4] and the few waste of material [5].

The actual commercial systems are been designed using the concept of integration of different parts, the correct use of the integration of this parts, produce confidents and functional machine systems, this paper approach this same concept of the integration of commercial parts and also discuss the selection of components. First the machine form is described, after that the different selection systems are justified, and for ending the machine plans are showed. The machine must fulfill the design specifications that are in table 1. The complete analysis of this work can see in [6] and also the complete set of plans can be requested to the authors.

The form of the machine, must reduce the different operation dead times, the size space that occupies in the workshop floor must be small as possible , the structure must has low special requirements, and it must have a competitive price. The number of bases that load the structure of the machine defines the form of the machine, if the machine has no bases, implies a system embedded in the ceiling of the workshop, if it has 2 bases, the system has a cantilever form, and if it has 4, is a conventional system. It is possible to stablish a decision matrix with basis on the functionality of the machine, the decision matrix is showed in the table 2

Especificaciones de la máquina.
Precision	±(0.417) mm/m, ±(0.005)in/ft
Average speed of positioning	0.127 m/s (300 in/m)
Work space	1.22 x 2.44 m (4 x 8) ft
Controller	2 axes
Motor Pump Power	37285 W (50 hp)
Intensifier	Dual pistons
Work Pressure	3796 bar (55000 psi)
Number of head cuts	1 head
Shape of the material to cut	Plate

3.1 HYDRAULIC SYSTEM.

The water jet cut requires a flow of 3.78 l/min with a pressure between 3800 and 4100 bars at the exit of the fuze, the hydraulic system is formed with the next components: pressure intensifier, attenuator tank, flexible high pressure piping and a water head cut. The intensifier increase the pressure generally from 207 bar a 3796 bar, with a mechanisms of an hydraulic press that presents an area ratio of 18:1, 19:1.

The attenuator of pressure fluctuations tank is a high pressure vassel, able to diminish the fluctuations that produces the intensifier, generally its shows pressure variations of 6% of the work pressure value (3800 bar). The exit flow of the atenuator is connected to the water head cut, via, a high pressure flexible piping, finally the head cut sends a water jet beam that impacts the material to be cut.

For this application it had been selected a dual pistons intensifier mod WA50 Water Service inc, of 50 hp, and work pressure of 3800 bars. The pressure attenuator, the high pressure flexible piping and the head cut can be acquired with the same manufacturer, there also exist several others manufactures.

Because of the cantilever form the sliding rails will bend, in this application the maximal torque for one rail has the value of 299.8 N.m, the selection was a set of rectangular rails that can stand 590 N.m and a normal force of 79500N , the rail has a rigidity constant EI = 15392 N/m² .

The fundamental part of the structure is the subjection triangle that avoids the bending of the rails see figure 2, that system must has the enough rigidity for obtain the precision required in the cut a cause of the structure bending

The calculus of the displacements of the subjection triangle has the assumption that all the stresses that presents the triangle are promoted by the gravitational force, there is no consider the inertial force, because of the value of the linear acceleration, 160 times lower than the gravitational acceleration, the free body diagram is showed in the figure 3

Figure 2. Triangular subjection that enhance Figure 3. Free body diagram of e bars that constitute

If the displacements that undergo the nodes can be described by the Hooke law, the system can be modeled by F = KU where F are the general forces that actuates in the subjection triangle, K is the constitutive relation associated to the subjection triangle and U is the nodal displacements so:

The nodes 1 and 3 don’t present displacement, it follows that the displacements in the node 2 are:

With the value of the displacement

its can be calculated target beam error promoted for the displacement that suffer the subjection triangle, from figure 4 the target error from the beam can be expressed by:

The addition of the positioning error of the screw ball e and the target error D gives the total error of positionament of the water jet beam

= 0.221 mm/m, that accomplish the precision requirements of design of table 1.

The controller is a 2 axis commercial controller SMC-200 of 32 bits, the controller has a CAM option, that can easy read the cad draws in DXF extension, the sigma SGDB/SGDA is the amplifier and the servomotors have an encoder of 2048 samples per revolution and a torque of 0.3 N.m, all the control system is fabricated by the same supplier.

The water jet cut technique is well established since long time, nevertheless in Mexico no exist any local or national manufacturer, the example of integration that the paper discuss is one, in a world of options for start our own developments, really necessary for the regions that have a lack of technological independence. In the other hand when it was realized the quotations with the several suppliers it can be observed that the inversion cost can be reduced in a 40% in comparison of the cost of the actual commercial systems. [6] The explosives of the system are showed in figures 5, 6, 7, also the complete set of plans can be requested to the authors.

The integration of commercial systems is sometimes an easy task, that permit design machines with characteristics just as sophisticated as it desired. In this work it had been described the selection process of the systems for built a water jet cut machine, that accomplish with the initial design requirements. The fabrication of machines using the integration of parts permits that regions that have not obtain it’s technological independence, have an option to advance to it, with fabrication cost much lower than purchase costs of the commercial systems and with allot of benefits for the region that where developed.

Figure 5. Explosives of the system, 1 Base of the cut machine, 2 Cantilever arm, 3 cover of the system, 4 Pressure Intensifier.5 Cut tabl

Figure 7. Explosives of the base of the machine. 1 Bases of the structure, 2 Platform of the structure. 3 Brakets of the coverture., 4 Rowlock, 5 Inferiors rails 6 Sliding brackets with stockings, 7 Screw of preloaded spheres, 8 Motor.

platform, 7 Cable tensor system. 8 Subjection triangle, 9 Structure of the subjection triangle, 10 water head cut cut.

[2] Fairhurst R.M, Heron R.A, and Saunders D.H, “Diajet a New Abrasive Water jet Cutting Technique” 40, 8^th International Symposium on jet Cutting technology, Durham UK, Sept. (1986).

[3] Carlson L.D, and Huntley D.T, “The Adventages of High Energy Beam Processing Over Conventional Methods” MS89, Nontraditional Machining Conference, Orlando USA, Oct. (1986)

[4] Neusen K.F and Schramm S.W, “Jet Induced Target Material Temperature Increases during jet Cutting” E4, 4^th international Symposium on jet Cutting Technology, Cantenburry, UK (1978)

[5] Brown J, “Modern Manufacturing Processes”, Industrial Press. InC., N.Y. (1991)

[7] Thomson Saginaw, “Advanced Linear Actuator Guide” Reference Manual (2000)