JPH0469198A - Cutting method for precision shape in water jet cutting - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] <Industrial application field> The disclosed technology uses high-pressure water jets to clean plastics and rubber.

Water jet cutting, which cuts materials such as FRP and metal materials up to relatively thick plates with high precision and efficiency, or high-pressure water jets and silica sand.

It belongs to the technical field of net shape or near net shape cutting using an abrasive type water jet mixed with abrasive grains such as garnet sand or alumina.

<Summary> Therefore, the invention of this application cuts a material to be cut, such as a metal material, with high precision using a water jet of high-pressure water itself, and furthermore, an abrasive type water jet mixed with a predetermined abrasive grain. This invention relates to a precision shape cutting method using water jet cutting that cuts into shapes, and in particular, water jet cutting that improves dimensional accuracy, enables high-speed cutting, is economically stable, and increases cutting efficiency. This invention relates to a precise shape cutting method.

Prior Art As is well known, modern society relies heavily on a variety of mechanical, electrical, and other devices, and these mechanical devices are becoming increasingly complex and precise through various research and improvements. As a result, the manufacturing and assembly of such equipment has become increasingly complex.

The manufacturing, maintenance, and maintenance of these devices and equipment must be performed in such a way that their functions do not change over time, and the degree of precision is becoming more and more demanding. It is becoming.

Units and parts of these mechanical equipment have many cutting and machining surfaces, and as durability is required, the precision of these machining surfaces and cutting surfaces is increasing. It is strongly sought after.

Furthermore, in order to meet these demands, there is a strong need for research and development of new materials, and cutting, cutting, and peeling technologies are about to enter a new phase.

As a means of cutting and peeling in the conventional technology, mechanical means such as a cutter, thermal cutting using a cast burner arc, etc., and physical cutting using plasma etc. have been developed, but the requirements are not met. In order to avoid deterioration of the base material and non-contact machining is required, the requirements for cutting complex-shaped parts and peeling of molecular bonds are becoming stricter. Technical means have various bottlenecks, and some aspects are becoming unsuitable for actual use.
Water jet cutting technology, which uses a high-pressure beam-shaped water jet to remove paint, cut materials, etc., has been brought into close focus. However, in order to use high-pressure water jets, there are various problems that need to be solved in hardware and software. Many problems lie ahead.

Cutting with such a tarjet generates almost no heat during processing, so it has the advantage that an extremely smooth cut surface can be obtained as designed without deterioration or deformation of the material to be cut.

Therefore, it is a very promising cutting method for so-called net shape or near net shape processing, and various research and developments have been carried out for a long time, and some of them have been put into practical use to a considerable extent.

However, in reality, water jet cutting,
In particular, abrasive type water jet cutting is
Conventionally, it has not been widely used for cutting that requires high precision.

For example, since cutting with an abrasive type water jet is a jet process using free abrasive grains,
Since the jet diameter cannot be ignored, it is difficult to match the cutting center (nozzle center) with the actual cutting line, and there is also the inconvenience that the cutting line changes over time due to nozzle wear. Since the width is generally different on the front and back sides, there is an inconvenience that the cut surface has a tapered shape, and in addition,
The leading edge of the cut on the lower surface is pulled and lags behind the upper surface (cutting delay), which is an undesirable characteristic that leads to cutting errors such as the lower part of the cut expanding into a fan shape and the radius of curvature increasing when cutting a curve. This is because it has

Here, to explain the factors that cause cutting errors in water jet cutting, FIG. ) 2, the nozzle center 3 is shifted by 1/2 of the cutting width W, but in the case of water jet cutting, especially the abrasive type, the nozzle and jet diameter are relatively large, so the cutting width is ignored. It is not possible.

Fig. 13 shows cutting error factors based on surface inclination of the cut surface. in many cases.

This surface tilt angle depends on the plate thickness and the cutting speed, and as shown in Fig. 14 (upper surface 1', lower surface 1'), the cutting speed U (ul...kuu5) is sufficiently slow. (For example, U+
), the cutting width is larger on the lower surface 1' side than on the upper surface 1' side, and in the case of high speed (for example, US), the cutting width is the opposite. At this intermediate speed (for example, L12), the cutting widths of the upper and lower surfaces match, and the inclination angle east of the cut surface becomes O. However, this speed U is 1710 to 1710, which is the cutting limit speed for ductile materials such as metals. The speed is 1/20, and brittle materials such as stone and ceramics are on the lower speed side.

FIG. 15 shows the error factor based on the cutting delay. In terms of the cutting phenomenon, the cutting leading edge on the lower surface 1" side advances slightly later than the upper surface 1' side, causing a cutting delay, which appears as a drag line 6. The cutting delay becomes more noticeable as the thickness of the material 1 to be cut increases and the cutting speed increases.

The cutting error caused by this becomes noticeable when the thick plate material 1 to be cut is cut at high speed with a small radius of curvature R.

As can be seen from Fig. 16, the cutting error Δ purely due to cutting delay is given by the following formula (A is the center of the jet on the 1' side of the upper surface, B is the center of the jet on the 1'' side of the lower surface, and 0 is the radius of curvature. center of R, δ is the time delay).

Therefore, cutting errors such as tilting of the cut surface and cutting delay greatly depend on the cutting speed, and especially when attempting to cut with high efficiency by increasing the cutting speed, the effect becomes more pronounced. It begins to affect people.

Therefore, when attempting to cut as accurately as possible with current waterjet technology, a mode of cutting at a slow speed is generally used, which is compared to the cutting speed limit (for example, cutting metals). In the case of materials, as mentioned above, the speed is extremely slow (about 1/10 to 1,720, etc.), and the efficiency is extremely low.

<Problem to be solved by the invention> The cutting groove width W is a countermeasure for actively correcting the above-mentioned cutting error.
It is being done for. That is, it is a means of moving the cutting center (nozzle center 3) toward the scrap side by 1/2 of the cutting groove width W, and in this case, the cutting groove width W will wear out if the cutting conditions are constant. Since it depends only on the diameter of the nozzle 4, it is sufficient to change the correction at the time interval of over-prize.

At this time, if an NC (or CNC) system capable of advanced control is used, these corrections may be made automatically.

However, although this type of countermeasure is effective to some extent when the material to be cut is thin plate, etc., when the material to be cut is thick plate, as mentioned above, the effects such as tilting of the cut surface and cutting delay become large. There is a disadvantage that it is difficult to ensure a predetermined dimensional accuracy by only correcting the cutting groove width, and the range of possible conditions is extremely limited.

As mentioned above, cutting using a water jet is a type of jet processing, so firstly, when processing at high speed, the cutting width has a surface inclination in the thickness direction, resulting in a dimensional difference between the front and back surfaces.

In addition, when cutting curves due to cutting delays, the upper part of the cut expands into a fan shape, increasing the curvature and reducing dimensional accuracy, so it is currently not used for precise cutting. There are no limits.

Second, cutting equipment that performs cutting using water jets blows out water under high pressure from small-diameter nozzles at high speeds such as supersonic speeds, so they are susceptible to wear, especially when cutting by adding an abrasive to the high-speed jet. In abrasive type water jet cutting that increases performance, the abrasive nozzle part that mixes and accelerates the abrasive material into a high-speed jet is subject to significant wear.As a result, as the abrasive nozzle wears out, cutting width.

The taper angle and cutting delay increase, and cutting accuracy deteriorates economically, making stable continuous cutting for a long time impossible, and in order to maintain accuracy, the abrasive nozzle must be replaced. The disadvantages are that the frequency must be increased, a great deal of labor is required, maintenance is cumbersome, and the operating rate is reduced.

<Purpose of the Invention> The purpose of the invention of this application is to solve the problems of precision cutting using a water jet such as an abrasive type based on the above-mentioned prior art, and to solve the problems related to the material and thickness of the material to be cut. It is an object of the present invention to provide an excellent precision shape cutting method using water jet cutting, which can perform precision cutting as designed with high efficiency in a stable state, thereby benefiting the field of processing technology in the manufacturing industry.

<Means/effects for solving the problem> In order to solve the above-mentioned problem, the structure of the invention of this application, which is summarized in the above-mentioned claims, is to cut the material to be cut according to the cutting shape. Cut the center with groove width W of 172
The axial direction of the nozzle is set to the outside in the normal direction (cutting width correction), and the nozzle axis direction is tilted by the necessary angle to correct the cutting surface inclination in the direction perpendicular to the cutting direction (cutting surface inclination correction).
In addition, the axial direction of the nozzle is tilted in the cutting direction by an angle necessary to compensate for the cutting delay (cutting delay compensation), and these compensation means are set at the same time in consideration of the cutting speed, plate thickness, and nozzle wear. In addition, by three-dimensionally controlling the nozzle position and posture, it is possible to achieve various predetermined dimensions in the thickness direction of the material to be cut.

A technical measure is taken to obtain a shape cut.

The above correction amount is based on the material, thickness and pressure of the material to be cut.

The influence of cutting parameters such as the nozzle diameter, standoff distance (distance between the material to be cut and the nozzle), and, in the case of ABRAIN 1 type, the type of abrasive, the particle size of the abrasive, and the amount of supply, are usually considered. is pressure.

Parameters such as nozzle diameter, standoff distance, abrasive material, etc. are determined by the workpiece to be cut, and are often held at a constant value during cutting, so they need to be changed depending on the cutting location. The only parameter that exists is the cutting speed.

Therefore, in normal cutting, the correction value can be determined only from the cutting speed determined by the plate thickness at the cutting location and the amount of nozzle wear. In addition, when cutting the material to be cut two-dimensionally, the two-dimensional figure data and the coordinate data for 5-axis machining can be made to correspond using a relatively simple coordinate transformation formula, so it is easy to be aware of complex 5-axis machining, etc. High-precision machining can be performed with the image of 2-axis machining without having to do so.

<Example> Next, an example of the invention of this application will be described below with reference to FIGS. 1 to 11.

In order to perform water jet cutting according to the invention of this application, a processing machine having a degree of freedom of five axes or more is usually required, and the embodiments shown in FIGS. 1 to 5 show system configurations using simultaneous five-axis control. ing. Position control is X, Y, 23
In the orthogonal coordinate system with the axis as the basic axis, the posture control of the nozzle axis is performed by two axis: the claw axis (rotation around the X axis) and the C axis (rotation around the Z axis).
This is done using the rotating shaft diameter of the shaft.

The embodiments shown in FIGS. 2 and 3 show the machining head in this embodiment (R is the position control point, P is the tool tip position, H is the C-axis rotation radius, L is the claw axis rotation radius, (Q is the center of rotation of the six wheels), the processing head is a zero offset type in which the tip position of the head does not change even if a rotation command is given as shown in the figure (in this case, point P and point R coincide), Although the position of the tip of the head also changes, causing interference between head posture control and head tip position control, either an offset type can be adopted, which has a simple mechanism and a wide posture range.

Then, offset the cutting center by 172 points outside the normal line with respect to the cutting groove width W with respect to the cutting shape of the workpiece of the material to be cut 1,
Further, the axis of the nozzle 4 is tilted in the right angle direction by the surface tilt correction angle, and the nozzle axis is also tilted by the cutting delay angle,
These are combined and corrected three-dimensionally.

FIG. 4 shows the relationship between the advance angle (cutting delay correction angle) α, the taper correction angle β, and the attitude control angles φ and T when the nozzle axis 5 is attitude-controlled using the above system. The angle φ is the angle between the tangent to the cutting line on the work plane (xy plane) of the material to be cut and the projection line of the axis 5 of the nozzle 4 on the same plane. rotation angle (around the Z axis). The angle γ is the angle between the workpiece plane and the nozzle axis 5.

As shown in FIG. 5, φ and T are expressed by the following relatively simple equation using α and β.

For zero offset type machining head, use the above φ.

The attitude can be controlled by directly giving a rotation command to γ (note that mutual interference between φ and γ must be taken into consideration).

FIG. 5 shows the coordinate transformation mode in the offset type machining head. The coordinate transformation formula in this case is a transformation formula between the tip position P of the nozzle 4 on the two-dimensional (including quasi-two-dimensional) work plane and the three-dimensional coordinates of the position control point R. If the tip position of is set to a position shifted by approximately 172 of the cutting groove width W in the outside normal direction of the cutting line, and the coordinates of this point are (X, V), the coordinates of the position control point R (X
.

y, z, φ, γ) are given by the following equations.

x=-Hcos(e+φ)+Lcos7-5in(θ
+φ)+Xy=-H5in(e 1φ)-LCO
37”-cos(e+φ)+yx=Lsi
nγ Figure 6 shows cutting width correction, Figure 7 shows cutting surface tilt (taper angle)
Correction: FIG. 8 shows a cutting delay correction method. FIG. 9 schematically shows these correction effects. As shown in the figure, as a result of the correction, the shape of the cutting leading edge protrudes at the center of the thickness of the material to be cut, and this part becomes the cutting advance δ', causing an error. As shown in the comparison, the error due to this cutting advance δ′ is the cutting delay δ
It is so small that it can be ignored compared to that of

FIG. 11 shows another embodiment of the invention of this application, and this embodiment is a mode in which an articulated robot with six degrees of freedom is used. Although the method of commanding the position and attitude is different from the orthogonal type of the above-described embodiment, the attitude control angle of the nozzle axis is the same.

Although the above-mentioned embodiments have shown only typical embodiments of the invention of this application, the essence of the invention of this application is to reduce cutting errors by using both the position control of the nozzle tip and the posture control of the nozzle axis. All the cutting methods that are included in the spirit of the invention of this application belong to the technical scope of the invention of this application.

<Effects of the Invention> As described above, according to the invention of this application, it is possible to perform high-precision cutting processing without causing the surface of the cut surface of the material to be cut by the water jet to be tilted and without cutting delays. This makes it possible to commercialize products without using any of these methods, and has the excellent effect of increasing the reliability of the product.

In addition, since the degree of finishing processing can be reduced,
This has the effect of reducing the number of man-hours, increasing efficiency, and improving yield.Furthermore, the cutting speed is also improved compared to the conventional method, so there is an advantage that production costs can be reduced.

In addition, since the deterioration in cutting accuracy due to nozzle wear can be compensated for through control, there is no need to shift the position or stop the production line due to nozzle replacement, and stable cutting is possible for a long period of time, which improves the operation of the facility. Qin also has the effect of improving efficiency.

[Brief explanation of drawings]

1 to 10 are explanatory diagrams of one embodiment of the invention of this application, in which FIG. 1 is an overall block diagram thereof, FIGS. 2 and 3 are schematic diagrams of the processing head of the same device, and FIG. Figure 4 shows the forward angle,
FIG. 5 is a schematic perspective view showing the relationship between the taper correction angle and the attitude control angle of the nozzle axis with respect to the taper correction angle. FIG. Figure 6 is a schematic diagram of the correction of cutting groove width.
Fig. 7 is a schematic diagram for correcting the inclination of the cut plane, Fig. 8 is a schematic diagram for correcting cutting delay, and Fig. 9 is a quantitative representation of the effects of these corrections.
Fig. 10 is a diagram showing the relationship between the error due to cutting progress caused by correction and the error due to initial cutting delay, Fig. 11 is a mechanism diagram of another embodiment, and Fig. 12 is a cutting error factor caused by cutting groove width. Fig. 13 is a schematic diagram of cutting error factors caused by tilting of the cut surface, Fig. 14 is a schematic diagram of cutting speed and cutting groove width shape, Fig. 15 is a schematic diagram of cutting delay phenomenon, and Fig. 16 is a schematic diagram of cutting error caused by tilting of the cut surface. It is a quantitative schematic diagram of errors. 1... Material to be cut 3... Nozzle center position 5... Nozzle axis 2... Cutting center line 4... Nozzle 6... Drag line

Claims (3)

[Claims] (1) In a precision shape cutting method for water jet cutting that performs optimal automatic control of the position and posture of a nozzle for precision cutting during water jet cutting, position control for cutting groove width correction, surface tilt correction of the cut surface, Furthermore, there is provided a precision shape cutting method using water jet cutting, which is characterized by combining cutting delay correction and nozzle axis attitude control in parallel. (2) A precision shape cutting method using water jet cutting according to claim 1, wherein each of the correction amounts is variably controlled in accordance with the plate thickness and shape of the cutting location. (3) Precise shape cutting by water jet cutting according to any one of claims 1 and 2, characterized in that each of the above correction amounts is variably controlled in a predetermined manner according to the degree of wear of the nozzle used. Method.