DE10220755A1 - Cutting tool has conductive strip not electrically connected to base body, transverse to wear direction, arranged so as wear increases contact is made with earthed workpiece at first wear threshold - Google Patents

Abstract

The device has a base with cutting and free areas with wear zones to which at least one sensor is attached to detect wear by monitoring its resistance. The sensor has a conductive strip (30,31,32) not electrically connected to the base, transverse to the wear direction and in a wear zone so that as wear increases electrical contact is made with the earthed workpiece (46) at a first wear threshold. The strip is cut through at a second threshold AN Independent claim is also included for the following: (a) a method of detecting wear in a cutting tool.

Description

The invention relates to a cutting tool for machining processing of workpieces with a basic body, the rake faces and free has areas in which wear zones are located, whereby to record the Condition of wear of a wear zone in at least one surface of the base body, at least one sensor is applied, which has an elect rically conductive, electrically not connected to the base body fen and is in series with an ohmic resistance.

In the cutting tool with sensor known from DE 19 10 674 a conductive strip is provided. It is not transverse to the direction of wear, rather arranged obliquely to it and along its longitudinal direction a variety of individual, different ohmic resistances connected. As long as the slanting conductive strip is intact the individual resistors connected in parallel. As ver This parallel connection will initially wear out a first resistor Cut. After that there will be a second and continuously further contradiction would be separated from the parallel connection if the conductive strip more and more is destroyed.

Cutting tools are generally any tools for processing  understanding of workpieces. Cutting tools in particular include other inserts, for example indexable inserts and drills. The Base body can be made of a metallic conductive material, for example a sintered metal, or from a metallic non-conductive material for example ceramics.

The problem with the cutting tool according to DE 198 10 674 A is that that the local resolution of wear is limited. An advertisement follows only if a portion of the conductive strip that is a verb effect of two resistors has been severed.

On the one hand, the possible width of the conductive strips is limited, so that a detection of the minimum wear by the width of the conductive strip is restricted. On the other hand, the cutting tool did not know several sensors in the direction of wear connect in series so that different sensors step by step increasing wear can be detected. Finally, the electrically conductive strips not perpendicular to the direction of wear, much more necessarily at an angle or in steps. This will only local wear at one point, not wear recorded over a longer cutting line of the cutting tool.

The prior art is also referred to EP 0 258 215 B1 and DE 35 35 474 referenced.

Starting from the cutting tool of the type mentioned with a It is the object of the invention to provide this cutting tool educate that multiple sensors are possible that wear across a wear direction across a longer distance can and that the at least one conductive strip not only in the  Cutting a signal provides, but also a signal at electrical loading contact with the workpiece.

This object is achieved by a cutting tool for machining machining workpieces, with a base body which has rake faces and open surfaces in which wear zones are located, with at least one sensor being applied to at least one surface of the base body for detecting the wear state of a wear zone Total resistance is recorded and the

• a) an electrically conductive, with the base body not electrically ver tied strip, which is transverse to a wear direction runs and geometrically in the area of the wear zone to be recorded is arranged so that with progressive wear when errei Chen a first wear threshold an electrical contact with the results in workpiece lying at ground potential and when reaching a second wear threshold of the conductive strip is cut, and
• b) has a connection area with which the conductive strip on its a first end is connected
• c) has a contact area, which in practical operation has ground potential al lies, and
• d) has a first ohmic resistor R1.1, via which the conductive strip at its other (second) end with a contact area connected is

with the features of claim 1.

This cutting tool is already supplied by a sensor with only one conductive strips two signals, namely on the one hand with electrical contact contact with the workpiece and on the other hand when cutting the conductive strip. Each individual conductive strip provides two signals. The individual signals of a strip can be distinguished. Even the individual  Signals from several strips are individual and therefore separate from one another the distinguishable. Differentiation is made possible by different Wi resistance values of ohmic resistors.

If the cutting tool has no or little wear , one places between the connection area and the contact area Total resistance fixed, which is essentially due to the first ohmic Resistance R1.1 is specified. As wear progresses, that comes Work piece in contact with the conductive strip. Because about the workpiece the conductive strip is now (at least briefly) at ground potential located just like the contact area, the first ohmic resistance bridged. This leads to an abruptly significantly reduced overall resistance, because now the total resistance is practically only through electrical conductor determines, namely the resistance of the conductive strip fens, which is extremely low, through the supply lines and the described benen bridge.

If the wear continues, the conductive strip becomes permanent destroyed. Precisely because the conductive strip is transverse to the direction of wear extends, the destruction can begin in different places. Erin According to the conductive strip is arranged so that the Ver wear zone approaches the conductive strip in several places, so that a Wear monitoring over a certain width, namely the full width a cutting line.

The Ge jumps when the conductive strip is cut for the first time total resistance of a single sensor to a high value. Although is coming it still has touch contact between for short periods of time Workpiece and that portion of the conductive strip that is still with the connection area has connection, but these contacts are only short  in time, so that the breakthrough of the conductive strip is clearly recognizable is.

Several sensors are in wear forming a sensor arrangement Arranged one behind the other, each sensor can be used individually two signals deliver and are the signals (resistance values) of the individual Sensors distinguishable from each other. Is not in the case described above only a single sensor is provided, but a second sensor in Ver direction of wear arranged behind the first, so jumps when piercing the total resistance of the first sensor's conductive strip to infinity or a very high value, but now becomes the total resistance of the second sensor only. Play with the second sensor then the processes are exactly the same as for the first sensor have been described.

The second sensor does not interfere with the function of the first sensor. The second The sensor initially only forms a resistor connected in parallel a fixed value. This value can be used when recording the total are taken into account, the resistance value of the second sensor known. In this way, a clear distinction can be made between individual NEN sensors of an arrangement of several sensors, one after the other individual sensors are eliminated. With suitably chosen resistance values the ohmic resistances is for each individual state, one after the other occurs, a different total resistance achievable.

In a preferred embodiment there is a second ohmic resistance between the conductive strip and the connection area. This second ohmic resistance causes that with electrical contact contact of the conductive strip with a workpiece of the total i the resistance depends on the resistance of the second ohmic resistance R1.2  decreases when the first ohmic resistance due to the contact con clock is bridged. Because of the second ohmic resistance it is possible, the contact of individual sensors of a sensor arrangement to be distinguished from one another, namely when the second ohmic contradiction levels of the individual sensors can be selected differently.

In a further preferred embodiment there is not only one sensor, but also are at least two, preferably three or four sensors in one sensor arrangement provided. How a cutting tool works with Several sensors have already been explained above. The key is that everyone Sensors of the sensor arrangement have a common connection area and use a common contact area. As a result, there are very few Supply lines necessary. Since the supply line generally leads to ground, is basically only one for the ohmic measurement of the total resistance electrical connection to the cutting tool, namely the An to contact the closing area. This simplifies the practical Very high handling.

The ohmic ones are in a further preferred embodiment Resistance outside the wear zone. It shouldn't be that due to wear the ohmic resistances in some form be impaired. Rather, only the leitfä by wear streaks are detected, i.e. in contact with the workpiece arrive and be destroyed later.

The invention makes it possible to detect wear much more accurately than this is possible with the prior art. Because of the double use of a conductive strip, namely on the one hand with electrical contact contact and on the other hand in the event of destruction, the local dissolution of the Wear significantly improved.  

The invention also has the advantage that the cutting breaks tool can now be recognized better. Because the conductive strip extends over practically the entire distance of the cutting line, ie over the entire route on which the machining takes place is a Crack or breakage is safely detected at any point along the processing line occurs. This is not possible with the prior art Lich.

The invention allows a variety of conductive strips in Ver arrange the direction of wear in close succession. To this In this way, the wear can be recorded progressively well. The local resolution solution is higher than according to the prior art.

It is preferred that the conductive strips are transverse to the direction of wear have the smallest possible width. In this way, the ver wear very locally and it is possible to have multiple strips in a short distance next to each other (seen in the direction of wear) NEN. The strips are preferably narrower than 50 mμ.

The conductive strips are preferably in thin film technology on one Surface of the base body applied. Other techniques of application against the conductive strips are possible. For example, it is ion implantation, vapor deposition of metal strips etc. possible.

The ohmic resistors are preferably as metal film resistors applied directly to a surface of the base body. In a another version, SMD resistors are used, so-called upper surface-mounted resistors, which are extremely small, can be obtained cheaply can and can be glued to the surface.  

Techniques such as those used for the manufacture of the sensors are used find use for example in the production of semiconductors for example mask technology with photoresist, vapor deposition of larger areas Areas and etching out individual conductive strips, etc.

In a particularly preferred embodiment, the contact area is as follows educated and oriented that he auto comes into contact with the clamping device. This is one electrical contacting of the contact area takes place via the clamping device and separate contacting is not necessary.

In an advantageous development, the workpiece is metallic, but not necessary maneuverably to ground potential, and there is a short circuit between Lei terbahn and the body of the workpiece formed once the wear is sufficiently advanced. This can also be the case with ceramic work witnesses occur when they are sufficiently coated with metal. It gives the following cases: The workpiece is metallic, but the tool is either which is an insulator (e.g. ceramic) or metal (e.g. hard metal). In the case, that the workpiece and tool are metallic or the isolator is sufficient is coated, the workpiece can also form a short circuit between the body, i.e. with a ceramic tool for the coating and the conductor track.

Further advantages and features of the invention result from the others Claims and the following description of non-limiting to understand embodiments of the invention, which refer to took to be explained in more detail on the drawing. In this drawing zei gene:

Fig. 1 is a perspective view of a cutting insert with a sensor in a simple embodiment,

, Now consists of three Senso ren Fig. 2 is a plan view of an end face of a cutting insert similar to FIG. 1 with a sensor unit consisting,

Fig. 3 is a representation corresponding to FIG. 2, but with three fully formed individual sensors and

Fig. 4 is a side view of a tip of a drill which is equipped with a sensor according to the invention.

Different cutting tools are shown in the figures there is no specific training of the cutting tool in detail on. The tool is used for cutting with a geometrically defined cutting edge according to DIN 8588.

In Fig. 1 the cutting tool is shown in the form of a cuboid cutting plate. It has a base body 20 , which here consists of ceramic. The base body 20 has a cutting edge 22 which delimits a rake face and has a free face. The cutting edge is for an unused tool, so there has not been any wear. Below the cutting edge 22 , a wear zone 24 begins, which is shown in dash-dot lines. A wear direction 26 , which is represented by an arrow, extends at right angles to the cutting edge 22 .

On an end face 28 in the immediate vicinity of the cutting edge 22 and in the loading area 24 Be a sensor is applied, which will be described below.

The sensor has an electrically conductive, with the base body 20 electrically non-electrically connected strip 30 which runs parallel to the cutting edge 22 and thus at right angles to the direction of wear 26 . It is arranged within the wear zone 24 to be grasped. As wear progresses, the cutting edge 22 moves in the direction of the wear direction 26 and thereby enters the area in which the strip 30 is located.

The strip 30 has a first end 34 , which is always shown on the left in the first three figures, and a second end 36 . A connection area 38 in the form of a square contact is formed on the end face 28 ; it is electrically connected to the conductive strip 30 via a connection line which extends transversely to the strip 30 . At its second end, the strip 30 is connected via a first resistor R1.1 to a contact area 40 which is at ground potential. It is designed as a relatively large contact spot, which extends over practically the entire surface with the exception of the edge regions of the upper main surface of the base body 20 , it is also performed in the same shape on the underside of the base body 20 . When the base body 20 is tensioned, a tensioning means comes into contact with this contact area 40 and thereby produces the electrical contact.

In the drawing, only simple cutting plates are shown, it can also be made according to the invention indexable inserts other cutting body, Boh rer, etc. Each edge of the base body 20 can be assigned a sensor, as can be seen in FIG. 1.

Fig. 2 shows an embodiment with three individual sensors, which are arranged in the direction of wear 26 one behind the other at a short distance. In the difference from FIG. 1, three parallel strips 30 , 31 and 32 are now provided, which are connected at their respective first ends together to the connection area 38 . At their second ends they are connected to the contact area 40 via resistors R1.1, R2.1 and R3.1. It can already be seen here that only one connection area 38 and one contact area 40 are provided per sensor arrangement. The resistance values of the resistors R1.1, R2.1 and R3.1 are different. As a result, when strips 30 , 31 and 32 are cut, it can be determined which strips are still in order and which are not. The resistance values of the resistors are graded accordingly.

The values of the resistors are individually chosen and different, that the total resistance R of a sensor arrangement for each one State its characteristic, but not in another state has recurring value. A state is defined by the fact that a conductive strip is grounded and / or at least one conductive Strip is cut.

In Fig. 2 nor dash-dotted line 42 is indicated. If the wear has progressed to such an extent that the first, front sensor is damaged, that is to say its strip 30 is severed, the entire cutting insert is ground down until line 42 is reached. Now the second and third sensors of the same sensor arrangement are still intact. The cutting tool can now be used again.

In contrast, you can also work continuously. It the wear can be advanced until the the first, second and third sensors are omitted. You get a total six sleepers for wear.

In the figures, the leads to strips 30 , 31 and 32 and the ohmic resistors are always positioned on the same end face. However, this is not necessary. It is entirely possible to route at least one supply line to another surface of the base body. It is possible to arrange the resistors on a face 28 other than that shown. Finally, it is also possible to position the two areas 38 , 40 on a surface other than the end face 28 , as can already be seen in FIG. 1.

Fig. 3 shows three individual sensors of a common sensor array connected in series similarly as in Fig. 2, but now with the second to sätzlichen resistors R1.2, R2.2 and R3.2. There are now 30-32 ohmic resistances at the ends 34 , 36 of each individual strip. They have such different and graded resistance values that in all cases that can occur in practice, the combination of the resistors results in a different total resistance.

The total resistance is recorded via an ohmmeter 44 or another suitable device for resistance measurement. As can be seen from FIG. 3, the contact area 40 is grounded. A workpiece 46 , which is in contact with the cutting edge 22 , is at ground potential.

Finally, a tip of a drill is shown schematically in FIG. 4. The drill has a special cutting body in its cutting area, which is designed similarly to the cutting plates according to FIGS. 1 to 3. Again, a strip 30 is provided which runs parallel to the cutting edge. Its first end 34 , which is located on the right, is connected via a resistor R1.2 to a rotating contact, via which the total resistance can be measured. For this purpose, the drill has a metallically conductive ring which is insulated from its base body and is accessible via a grinding electrode (not shown).

The second end 36 of the strip 30 is connected to a resistor R1.1, the other end of which is at ground. For this purpose, a contact point 48 is shown, which makes contact with the metallic base body 20 .

The strips 30 , 31 , 32 are made as metallic conductive strips from a thin metal application, for example by vapor deposition, sputtering, etc. It is also possible to evaporate a larger area and to form the strips 30 , 31 , 32 by etching away the superfluous areas , The strips have any width, preferably they are e.g. B. 50 microns or 200 microns wide.

Claims (11)

1. Cutting tool for machining workpieces ( 46 ), with a base body ( 20 ) which has rake faces and open surfaces in which wear zones ( 24 ) lie, with a wear zone ( 24 ) on at least one surface of the base body for detecting the wear state ( 20 ) at least one sensor is applied, the total resistance of which is recorded and the

• a) has an electrically conductive, with the base body ( 20 ) electrically non-connected strips ( 30 , 31 , 32 ) which extends transversely to a direction of wear ( 26 ) and in the region of the wear zone ( 24 ) to be detected is arranged geometrically so that as wear progresses, when a first wear threshold is reached, there is electrical contact with the workpiece ( 46 ), which is at ground potential, and when the second wear threshold is reached, the conductive strips ( 30 , 31 , 32 ) are severed, and
• b) has a connection area ( 38 ) to which the conductive strip ( 30 , 31 , 32 ) is connected at its one (first) end ( 34 ),
• c) has a contact area ( 40 ), which is at ground potential in practical operation, and
• d) has a first ohmic resistor R1.1 and possibly further ohmic resistors R2.1 and R3.1, via which the conductive strip ( 30 , 31 , 32 ) has at its other (second) end ( 36 ) a contact area ( 40 ) connected is.

2. Cutting tool according to claim 1, characterized in that the at least one sensor has a second ohmic resistor R1.2, which is arranged between the conductive strip ( 30 , 31 , 32 ) and the connection region ( 38 ). 3. Cutting tool according to claim 1, characterized in that a first and at least a second sensor are provided, that the at least one second sensor has a first ohmic resistor R2.1 and possibly a second ohmic resistor R2.2 and that only a common connection area ( 38 ) and only a common contact area ( 40 ) are provided. 4. Cutting tool according to claim 1, whose base body ( 20 ) has an electrical conductivity, characterized in that between the base body's ( 20 ) and the sensor an insulating layer is provided. 5. Cutting tool according to claim 1, characterized in that the ohmic resistances are outside the wear zone ( 24 ). 6. Cutting tool according to claim 1, characterized in that the at least one conductive strip ( 30 , 31 , 32 ) has the smallest possible width measured transversely to the direction of wear ( 26 ), in particular narrower than 50 mµ. 7. Cutting tool according to claim 1, characterized in that the at least one conductive strip ( 30 , 31 , 32 ) is applied in thin-film technology on a surface of the base body ( 20 ). 8. Cutting tool according to claim 1, characterized in that the ohmic resistors are applied as metal film resistors or as SMD resistors on a surface of the base body ( 20 ). 9. Cutting tool according to claim 1, characterized in that the contact area ( 40 ) is selected such that it extends into a clamping area of the cutting tool, on which the cutting tool comes into contact with a clamping means. 10. Cutting tool according to claim 3, characterized in that the Resistance values of all ohmic resistors are not equal. 11. Method for detecting wear on a cutting tool according to one of claims 1 to 10, characterized in that the Total resistance of the at least one sensor is recorded.