EP1317999B1 - Water jet cutting machine having a non-contacting and alternatively a contacting device with a distance and guiding detector - Google Patents

Abstract

With metallic workpieces the non-contact sensing system is inductive with feedback signaling to the drive system. When the work is not metallic a contact method is used with a sliding ring (25) on the work surface connected to a metallic ring (24) and control links (22).

Description

In addition to conventional thermal processes for cutting and separating predominantly metallic, plate-shaped workpieces using oxyfuel, plasma and laser cutting machines, non-thermal abrasive waterjet cutting has become established worldwide in recent years.

Water jet cutting machines with a cutting head drive for the automatic tracking of the water jet cutting head for maintaining a uniform distance during the cutting process, by determining the distance between the Stralhrohrausgang and the workpiece by an entrained inductive sensor, wherein in the main body one or more supply pipes for detergent are introduced are known. Such a device is disclosed in US-A-6049580, which is considered to be the closest prior art.

In this separation method, a continuous thin water jet, exiting at very high speed from a jet pipe at a small distance of a few millimeters to the workpiece, for the abrasive removal of workpiece material is used. The water, which is under very high pressure of a few thousand BARs, is mixed with very fine-grained and very hard abrasives in fine grain just before it enters the blast pipe, which enables both brittle and soft, non-metallic materials as well as almost all metals economically to edit.

In thermal processes, it is important to know the energy source, e.g. the gas / oxygen. Flame of the autogenous burner or the arc of a plasma torch, bring close enough to the workpiece to liquefy this in the separation area.

For water jet cutting, the abrasive energy is greatest in the immediate vicinity of the jet pipe outlet and therefore most effective for the abrasive cutting process.

Both in the thermal separation method as well as in water jet cutting, it is therefore necessary to optimally observe the distance between the machining tool and the workpiece.

In order to maintain the optimum distance, even if the position of the surface of the workpiece does not remain horizontal with vertically positioned tool, as for example not completely horizontal storage of plates, contacting (tactile) or non-contact distance sensor guide systems are used in thermal burning and laser cutting machines, which automatically keep the machining distance during cutting by a tracking drive of the machining tool. As tactile sensors sliding shoes or slip rings are used, the position of which generates an electrical control signal in relation and in the direction of the tool machining axis, which is used via a drive for tracking the machining tool when deviations from the desired distance occur.
Non-contact sensors have been widely used as capacitive, inductive and voltage-dependent systems in thermal cutting machines for decades. Their electrical output signals are also functions of the distance to the workpiece.
Capacitive sensors can not be used with waterjet cutting because they provide reliable signals only in a dry environment. Other non-contact distance sensor systems, such as triangulation lasers, opto-electronic or ultrasonic distance sensors, are out of consideration for reasons of the processing environment (splash water, rebound and abrasive material accumulation).
So far, therefore, water jet cutting machines are operated with tactile distance sensors, the
either determine the distance between the outlet opening of the jet pipe and the workpiece before the start of the drilling and cutting cycle, then be lifted off the workpiece and are not engaged during the cutting,
or slidably supported on the workpiece during the drilling and subsequent cutting operation.
With sliding tactile sensors, cutting processes can be carried out with distance control both for metals and for non-metallic materials of sufficient strength.

However, delicate surfaces of the workpieces, such as visible surfaces of metals or polished or glazed non-metallic materials, suffer from scratching due to deposited abrasives and material erosion on the workpiece surface.

Lately inductive sensor systems have occasionally been used in water jet cutting. Inductive sensor systems work on the principle of the reaction of induced eddy current fields on an inductance. They are insensitive to water and water vapor. It had been shown that the rebound of the high-energy water jet, especially during the drilling process (before piercing the workpiece and thus before the actual cutting) in cooperation with the abrasive, the sensor body extremely loaded and destroyed after a short period of operation.
For non-metallic materials, the inductive method can not be used because there are no eddy current fields.

The present invention relates to a water jet cutting machine having all the features of claim 1. Further preferred embodiments of the invention are disclosed in the dependent claims The invention is explained in more detail below with reference to illustrative illustrated exemplary embodiments.

An embodiment is shown in FIG
Therein, 1 shows the water jet Schneldkopf in a functionally simplified form. 2 designates the valve for the water inlet which is guided through the pipe 3 into the cutting head 4 represents the supply pipe for the abrasive agent, which is supplied to the water in the cutting head, entrained thereby and after emerging from the jet pipe 12 for removing the material on the workpiece 13 is used
The main body 5 with the clamping device not shown is pushed concentrically to the jet pipe 12 on this. He wears the sensor body 6 and wrapped this partially on the side for mechanical protection.
In the main body 5, a tube 7 leads to the connecting cable 8 for electrical connection of the sensor. 6
Another tube 10 leads to an annular chamber 11. This is parallel and concentric to the jet pipe extended until its exit from the sensor body, but with a smaller diameter.
Through the pipe 10, the detergent, preferably water, is pressed at high pressure into the annular chamber 11.
The water then flows parallel to the jet pipe and this enveloping with increasing speed in the direction of the jet pipe entrance. For Fig 1, this is indicated by arrows.
The kinetic energy of the effluent scavenger causes flushes of material to be flushed to all sides by the abrasive abrasive and by material removal above the workpiece. In the case of metallic and non-metallic workpieces, congestion, additional lateral loads on the jet pipe and repercussions on the sensor function are thereby avoided.

When "drilling", ie in the time of the action of the water jet on the workpiece surface to piercing the workpiece, the entire material abrasion is together with the abrasive opposite to the beam direction, ie in the direction of the sensor, thrown back and hits with high kinetic energy to the bottom of the sensor body.
Although the material of the sensor body 6 is as far as possible resistant to these loads, in order to achieve a reliable protection of the sensor body, this is equipped on its underside with a protective plate 14. This is of such a nature that it slows down the particles occurring during the drilling process and also has extensive abrasion resistance. It can be easily replaced as needed with a few simple steps if it has suffered a certain wear. To monitor the degree of wear of this protective plate according to the invention, this plate is equipped with devices that trigger an electrical signal at a certain wear, prompting for replacement.

An embodiment of this protective plate is shown in Figure 2 Av.B.
With 14, the protective plate is designated. It consists for example of a rubber-like material. In its interior, approximately centrally, a strip conductor arrangement 16, preferably in the form of a printed circuit, is placed on a thin carrier 15 or in the form of thin wires in a spiral arrangement, directly embedded. An electrical capacitor 17 connects both ends of the spiral with each other, so that this arrangement forms a resonant circuit having a certain resonant frequency.

In the sensor body is in addition to the sensor arrangement itself another resonant circuit, which is tuned to the same frequency as the In the protective plate accommodated resonant circuit and preferably connected to an oscillator circuit.

Due to the immediate vicinity of the resonant circuit in the protective plate and this oscillator + resonant circuit in the sensor body a close coupling of both circuits is given. The passive circuit in the protective plate removes so much energy from the oscillator resonant circuit that it can no longer fulfill the self-excitation condition. As a result, the oscillator oscillation stops and the oscillator outputs no output voltage for signal generation.
Once the wear of the protective plate has progressed so far that the traces are partially exposed and the attack of rebounding particles are exposed directly after a short period of time interruptions to the traces, so that the damping resonant circuit is separated in the protective plate, then the oscillator no longer is damped and can swing up immediately. Its output voltage generates the prompt signal "exchange protective plate".

This signal is given even if the protective plate is missing. In the machine control it can be used to block the commissioning of the cutting head.
Another embodiment of the protective plate is shown in Fig 3 Au.B.
To monitor the degree of wear, a passive oscillating circuit is not introduced into the protective plate in this embodiment, as shown in Figure 2, but the two ends of the preferably meandering or spiral conductor track are connected to a cable connection, which leads to a monitoring circuit on trace interruption. As soon as the track is interrupted at one point, the monitoring circuit responds and in turn generates the signal "change protective plate".

In Fig. 3A, the protective screen 14 with the interlayer track assembly 18 is shown as a meandering configuration.
The conductor track 18 is guided via the cable 19 via a plug connection, not shown, to the monitoring circuit 20, which detects a conductor track interruption in a known manner. Another example of the design of the electrical connection is shown in FIG. 3B. The contacting of the conductor track is provided here directly on the sensor body. In FIG. 3B, the sensor body 6 is provided with an inner tube 33 made of an insulating material, which is equipped with contacts 34 and the terminals 35. The conductor track 18 leads in the protective plate 14 to corresponding contact surfaces with respect to the contacts 34. FIG Parts of the sensor system required for understanding this training.

The additional device for the distance control with the aid of a tactile addition to the inductive sensor is based on the following operating principle:
In the case of non-metallic or non-electrically conductive workpieces, no eddy currents can form in the workpiece due to the magnetic alternating fields of the inductive sensor, so that the inductance of the sensor or its alternating field distribution through the workpiece is not changed and the sensor can not generate distance-dependent signals.

The tactile addition is now such that a metallic body is preferably a ring or a tube piece, which is movably mounted in the direction of the main axis of the jet tube and connected to a tactile, ie resting on the workpiece, low-wear, preferably annular body. In the case of the ring shape of the metallic body, this is arranged between the workpiece and sensor body parallel to this and can be deflected in the direction of the sensor body.

If a pipe section is used, it is arranged concentrically with the sensor body and laterally between the sensor body and the jacket-like continuation of the metal main body. The pipe section therefore forms a short-circuit ring in its effect on the inductive sensor system, whose electrical values depend on its position relative to the sensor system changed.
4 shows one of the possible forms of embodiment of the tactile attachment as an example of a ring-shaped metallic body between the workpiece and the sensor body, partly in sectional view for better understanding.

4, the tactile additive 21 is placed on the main body 5 of the sensor and fixed in not particularly drawn way.
The tactile addition includes a vertically deflectable side rigid guide means, which is indicated schematically and designated 22. Their design is described in more detail in FIG. It carries supports 23 which carry the metallic ring 24. It can move parallel to the sensor body. The supports 23 continue to slide ring 25, which rests in the working position of the cutting head on the workpiece.

If the workpiece position of the surface changes relative to the vertical position of the cutting head, then the sliding ring 25 or in its place one or more roles or. Wheel guides or pneumatic or hydraulic distance guides also perform a relative displacement toward or away from the sensor while taking the metallic ring 24 so that its distance from the sensor changes.

The sensor then reacts as if there is a metallic workpiece underneath it, so that its output signal is a function of the distance to the workpiece.

The metallic ring 24 can also be provided with a wear protection on its underside, as described in FIG.

During the lateral movement of the cutting head parallel to the workpiece, during the water jet cutting, the ring 25 slides along on the workpiece, wherein the rinsing agent, indicated as arrows, ensures that the abrasive particles can not accumulate on the sliding ring. This is provided with openings through which the particles are washed away to the outside.
Figure 5 shows a similar arrangement of a tactile additive equipped with a tubular metallic body.

Instead of the metallic ring 24 shown in FIG. 4, the metallic tubular body 27 is arranged in FIG. 5, which is positioned concentrically around the sensor body 6. By appropriate arrangement of the coils in the interior of the sensor body is achieved that the vertical displacement of the metallic tubular body 27 causes the same output signals of the sensor, as it would give the metallic ring body below the sensor or a metallic workpiece with the same vertical deflection or change in distance.

In Fig. 5 there is an annular gap between the sensor body 6 and the extension of the sensor main body 5 in which the tubular body 27 is moved.

Fig. 6 shows an example of the guide means of the movable part of a tactile accessory.

The guide device has leaf spring segments 28 arranged multiply in two or more planes concentrically around the sensor body.

Each leaf spring element has a symmetrical slot, which divides the element into two similar resilient strips, so that the resilient length becomes larger.

At the end of the leaf spring segment-Strelfen holes 29 and 31 are provided. Through the holes 29 screw or riveted punch 30 are introduced, which end in the body of the tactile additive above and fix the outer part of the spring segment there.

The holes 31 are also provided with similar punches, which continue in the holders 23 for the slide ring 25. On the top of additional springs 31 are arranged with adjusting screws 32, with which the downward spring force can be adjusted.

A not particularly drawn in Figure 6 stop for the inner spring segment strips limit the travel down.

From Fig 6 is easy to see the function of this slippery guide device. It shows the sake of clarity only the leaf spring segments. The two inner spring segment strips may move toward or away from the viewer at the open end while the outer spring segment strips remain in place. The closed end of the spring segment follows the deflection of the inner spring segment strip about halfway.

By slotted spring segments arranged one above the other in two or more planes, particularly high lateral rigidity is achieved with a large deflection travel.
Of course, in the case of small deflection paths, non-slotted spring segments, arranged in two or more planes, can also be used, as shown schematically in FIG. Through the holes 29 in turn lead stamp to the body of the tactile addition.
The segments 33 are here slotted nihct. In the holes 31 also pistons are arranged, which lead to the sliding ring 25 as shown in FIG.
Of course, this type of attachment is only one possible variant of the clamping on the additional body. Clamping devices can also be used.

Claims (14)

1. Water jet cutting machine having a non-contacting and optionally tactile distance guiding sensor device and a cutting head drive for the automatic trailing guidance of a water jet cutting head (1) in order to maintain a uniform, presettable distance during the cutting operation, by continuously determining the distance between a jet pipe outlet and a workpiece (13) by means of carried-along sensors which generate an electrical control signal for driving the cutting head in the direction away from or towards the workpiece (13), wherein a preferably metallic main body (5) is either pushed concentrically with respect to a, jet pipe (12) onto the latter or the holder thereof and is fixed there by a clamping device, or this main body (5) forms a constructive unit with a jet pipe holder, said constructive unit being concentric to the jet pipe (12), wherein furthermore the main body (5) contains an inner inductive sensor body (6) of cylindrical-tubular design, which has a bore running centrically in its main axis, the diameter of said bore being greater than the diameter of the jet pipe (12), wherein furthermore one or more supply tubes (20) for flushing medium are introduced into the main body (5) in such a way that the flushing medium can exit parallel to the jet pipe (12) in the direction towards the workpiece (13) and at the latter flushes away the abraded material and abrasive particles from the cutting device which were produced during the drilling and cutting operation, wherein moreover an additional device can be placed on the main body (5) and can be fixed there, said additional device being equipped and provided for tactile and/or quasi-tactile sensor devices which are connected directly or indirectly to the workpiece (13), in such a way that it can carry out a relative movement between metallic parts of the sensor device with its movable guide device on the inductive sensor body (6), and wherein this relative movement of the metallic parts has an effect on the sensor body (6) such that the latter generates an electrical output signal which corresponds to the relative displacement.
2. Water jet cutting machine according to Claim 1, characterized in that the metallic main body (5) has in the sensor body (6) an extension which partially encloses said sensor body in an annular manner and protects it against lateral mechanical stress, said extension at the same time being designed as a receiving body for an additional device.
3. Water jet cutting machine according to Claim 1, characterized in that, in order to protect the sensor body (6) against abrasion of material caused by the rebound of abrasive particles and abrasive jet medium, protective plates (14) made of abrasion-resistant, non-metallic material are provided which protect the sensor body (6) from below and from the sides, in that furthermore these protective plates are designed to be replaceable, and in that they are equipped with devices for detecting a certain maximum level of wear which trigger an electrical monitoring signal when this level of wear is reached.
4. Water jet cutting machine according to Claims 1 and 3, characterized in that a conductor track arrangement (16) is fitted inside the protective plate (14) and parallel to the outer surfaces thereof in order to monitor the level of wear, said conductor track arrangement being interrupted when a certain level of wear is reached and triggering a switching signal when it is interrupted, by means of a monitoring circuit of known type.
5. Water jet cutting machine according to Claims 1, 3 and 4, characterized in that the conductor track arrangement (16) has an approximately spiral shape and forms an inductance, in that the two ends of the conductor track are connected to one another by an electrical capacitor (17) so that an electrical resonant circuit is formed, in that a further resonant circuit that is independent of the sensor body (6) is provided in the sensor body (6), said further resonant circuit being tuned to the same resonant frequency, being tightly coupled to the resonant circuit in the protective plate and being connected to an oscillator circuit which, when the resonant circuit in the protective plate (14) is intact, is damped in such a way that no intrinsic excitation can be set provided that this resonant circuit is not interrupted, but after it has been interrupted resonates and generates a report signal which prompts for replacement of the protective plate.
6. Water jet cutting machine according to Claims 1, 3 and 4, characterized in that the conductor track arrangement (16) has an approximately spiral or meandering configuration, and in that its ends lead to a cable or to a contact on the sensor body (6) or on the main body (5) and furthermore to a current monitoring circuit which triggers a report signal when the conductor track (16) is interrupted due to wear of the protective plate (14).
7. Water jet cutting machine according to Claims 1, 3 and 4, characterized in that the conductor track (16) has an approximately spiral shape in the centre which expands outwards into a meandering configuration, in that the two ends are connected to one another, and in that as a result a short-circuit ring is formed which is tightly coupled to a special oscillator circuit which is separate from the sensor function and is accommodated in the sensor head, so that, when the conductor track is interrupted due to a feedback effect on the oscillator circuit, the resonant frequency thereof is considerably changed, and in that this change generates a report signal in a downstream discriminator circuit.
8. Water jet cutting machine according to Claim 1, characterized in that the additional device for tactile or quasi-tactile determination of the distance between the end of the jet pipe and the workpiece in the case of non-metallic material consists of a support body which is pushed concentrically over the main body (5) of the sensor device and can be fixed there by means of screws or clamps, in that the support body is provided with a guide device which guides a metallic ring-shaped or tubular body which can be moved in the main axis and is provided with a tactile sliding or rolling device or with a quasi-tactile hydraulic or pneumatic dynamic pressure device and directly influences the inductive sensor body (6), the movement of said ring-shaped or tubular body relative to the sensor body (6) being brought about by the tactile sliding or rolling device or by the dynamic pressure device.
9. Water jet cutting machine according to Claims 1 and 8, characterized in that a metal ring (24) which is guided by the guide device is movably arranged directly below the sensor head (6), and in that, when said metal ring changes position with respect to the sensor head (6), the latter generates corresponding sensor output signals in the same way or in a similar way as in the case of a metallic workpiece.
10. Water jet cutting machine according to Claims 1 and 8, characterized in that a metal tube (27) which is guided by the guide device is movably arranged around the sensor body (6) in a manner concentric thereto, and in that when said metal tube changes position in the direction of the main axis, the sensor head (6) generates corresponding output signals in the same way or in a similar way as in the case of a metallic workpiece.
11. Water jet cutting machine according to Claims 1, 8, 9 and 10, characterized in that the guide device consists of an arrangement of leaf springs (28), which are arranged in two or more parallel planes above one another symmetrically around the main body (5) in the additional device, and of a ring-shaped body which connects all the leaf springs (28) to one another at their movable ends, and in that the non-movable ends of the leaf springs (28) are connected to the support body of the additional device, in that furthermore the ring-shaped body bears either the metal ring (24) or the metal tube (27) and in the direction of the workpiece the tactile sliding or rolling device or the quasi-tactile dynamic pressure device, and in that the leaf springs (28) can be adjusted in a variable manner in terms of their resilient action by means of additional, tensionable springs (31).
12. Water jet cutting machine according to Claims 1, 8, 9, 10 and 11, characterized in that the tactile sliding body consists of a hard metal or ceramic ring which has slots for the flushing operation on its side facing the workpiece, and in that this ring is replaceable.
13. Water jet cutting machine according to Claims 1, 8, 9, 10 and 11, characterized in that one or more tactile rolling bodies are mounted on the ring-shaped body at regular intervals, said rolling bodies rolling off over the workpiece during the cutting operation.
14. Water jet cutting machine according to Claims 1, 8, 9, 10 and 11, characterized in that a number of hydraulic dynamic pressure tubes are provided which are mounted on the ring-shaped body parallel to the main axis of the additional device and at a regular spacing, through which tubes the water flows at a certain pressure towards the workpiece, and in that, at the outlet of the tubes, a dynamic pressure which depends on the distance from the workpiece displaces the guide device in the direction of the main axis of the sensor body (6), so that the sensor body (6) generates a distance-dependent signal in the manner described above.

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