Patent Description:
Cutting inserts may for example be employed in machining operations such as cutting, milling or drilling of metal. Different geometries, materials and coatings have been proposed for improving performance of cutting inserts (for example improving the overall durability of the cutting insert, or improving the ability of the cutting insert to withstand heat). In addition to providing cutting inserts with good performance, it is also desirable to be able to manufacture the cutting inserts in a cost-efficient way (for example using a manufacturing method that does not take too much time and/or which does not involve many complicated steps).

In machining with replaceable cutting inserts (such as cutting, milling or drilling of metal), there has been an increased interest in different ways to monitor or measure conditions at the cutting insert during operation, since such conditions may affect performance of the machining. Decisions regarding altering of operation parameters, exchange of cutting insert or repositioning of the cutting insert in its holder can be taken based on measurements of the condition of the cutting insert itself and/or based on conditions to which the cutting insert is being subjected during operation. Due to such measurements, time-consuming manual inspection of the condition of the cutting insert may be avoided, whereby efficiency may be improved and/or a more automated operation may be obtained. Precise measurements/monitoring of the condition of the cutting insert, and correct actions performed at the right time as a consequence thereof, may help to prevent damaging of the work piece due to use of excessively worn cutting inserts or operation of the cutting insert at unfavorable operating conditions (such as operating with large vibrations or at too high temperatures). For actions performed in response to measurements to achieve the desired effect, it is important that the measurements are reliable.

Prior art disclosed in <CIT> describes a cutting tool provided with a sensor circuit for detecting wear of a cutting edge. The sensor circuit is designed to be stable in the sense that it does not easily peel off or get disconnected. A conductor of the sensor circuit is arranged in a recess formed at the surface of a base material. The width of the recess may be <NUM> to <NUM> millimeters. The ability of the conductor to conduct electrical current is monitored to detect wear of the cutting edge. The base material may be made of an electrically conductive material, and an insulating film may be interposed between the base material and the conductor. A hard coating layer may be disposed on the surface of the sensor circuit for protecting the sensor circuit.

<CIT> discloses a cutting insert according to the preamble of claim <NUM>, comprising microchannels that are provided with insulating film and sensor film.

However, it would be desirable to provide new cutting inserts for addressing at least one of the abovementioned issues.

It is an object of the present to provide a cutting insert for addressing at least one of the abovementioned issues.

Hence, there is provided a cutting insert for cutting, milling or drilling of metal according to claim <NUM>. The cutting insert comprises a body, a first layer, and a sensor arrangement. The body comprises a substrate (or base material). The body has an elongate recess (or cavity) extending along at least a portion of the body. The first layer covers interior side walls of the recess. The sensor arrangement comprises a lead extending along the recess. The lead comprises electrically conductive material which is arranged in the recess such that the first layer is located between the electrically conductive material and the substrate. For at least a depth below which at least a portion of the electrically conductive material is arranged in the recess, a width of the recess measured at that depth between portions of the first layer covering opposite interior side walls of the recess is less than or equal to <NUM> micrometers. In other words, the width is defined (or measured) across the recess between a portion of the first layer covering a first side wall of the recess and another portion of the first layer covering a side wall of the recess opposite to the first side wall, and the width is defined (or measured) at a depth below which at least a portion of the electrically conductive material is arranged (hence, at least some of the electrically conductive material is located deeper into the recess than where the width is defined/measured).

The width may for example be less than or equal to <NUM> micrometers, or less than or equal to <NUM> micrometers, or less than or equal to <NUM> micrometers, or less than or equal to <NUM> micrometers, or less than or equal to <NUM> micrometers.

The recess is no more than <NUM> micrometers deep, wherein, if the recess is formed in the substrate, the depth of the recess is measured from a surface of the substrate to a bottom of the recess, and wherein, if the recess is formed in the first layer, the depth is measured from a surface of the first layer to a bottom of the recess. At least a portion of the lead is arranged at a depth of the recess such that there is space within the recess above the lead.

Measurements at the cutting insert may for example be employed to make decisions regarding operation parameters, exchange of cutting insert, or repositioning of the cutting insert. Such measurements may for example be performed via the sensor arrangement.

While a lead placed at (or close to) the surface of a cutting insert may be susceptible to damage, placement of the lead in the recess may provide the lead with at least some degree of protection from damage. Due to the recess, the risk that the lead falls off or gets broken already at an initial stage of machining may be reduced, so that the lead may be employed to make measurements for a longer time than if placed at the surface of the cutting insert. In other words, the placement of the lead in the recess may improve the life time of the sensor arrangement and/or the reliability of measurements performed via the sensor arrangement.

While a lead placed at (or close to) the surface of a cutting insert may be susceptible to accidental short circuits (or unintended electrical connections) caused by chips or debris created during interaction of the cutting insert with a work piece, placement of the lead in the recess may provide the lead with at least some degree of protection from such short circuits or other interference which could affect measurements. This may improve reliability of measurements performed via the sensor arrangement.

Cutting inserts may be post treated using blasting for providing a desired surface smoothness and/or for enabling a tougher edge line performance due to the resulting residual compressive stress as a result of the blasting. Blasting may involve bombarding a surface by particles. The size of particles employed during blasting is often limited (for example, the average diameter of the particles may be below a certain value/threshold) since the kinetic energy of large particles may cause damage to the cutting edge of the cutting insert. Using small blasting particles may for example allow better control of the blasting process than using large blasting particles. Placing the lead in a too broad/wide recess may allow blasting particles to enter the recess and to damage the lead (or even remove the lead completely), while a sufficiently narrow recess may protect the lead during blasting. As an example, the prior art document <CIT> describes use of a recess which may be several millimeters wide. If such a wide recess was to be subjected to blasting, the lead in the recess would be damaged (or removed) unless the blasting particles were several millimeters in diameter or unless the lead was covered by some kind of protective coating prior to the blasting. Use of a narrower recess than in <CIT> allows the lead to be better protected during blasting, and it is therefore possible to use smaller blasting particles than for the cutting insert in <CIT>.

In the cutting insert according to an embodiment, the first layer may for example be more resistant to blasting than the electrically conductive material of the lead. If the cutting insert is subjected to blasting, a width of the recess as experienced by the blasting particles may for example be less than or equal to <NUM> micrometers due to the ability of the first layer to withstand blasting. During manufacture of the cutting insert, portions of the electrically conductive material located outside the recess may for example be removed via blasting, while portions of the first layer located outside the recess may withstand (or remain undamaged by) the blasting.

The sensor arrangement may for example be arranged (or suitable) for performing measurements. Measurements performed via the sensor arrangement may for example include measuring a resistance of a circuit including the lead. Measurements performed via the sensor arrangement may for example be adapted (or suitable) for detecting wear of the cutting insert. In other words, the sensor arrangement may for example be arranged (or suitable) for detecting wear of the cutting insert.

It will be appreciated that the cutting insert need not necessarily comprise all circuitry necessary to perform measurements. External circuitry may for example be connectable to the sensor arrangement for performing the measurements using the sensor arrangement.

The recess may for example extend along one or more exterior surfaces of the body, for example along one or more exterior surfaces of the substrate.

The body may for example comprise one or more layers. The recess may for example be formed in one or more of such layers.

The width of the recess may for example be measured (or defined) in a direction transverse to (or orthogonal to) the extension of the recess. In other words, the recess may for example extend in a longitudinal direction, and the width may for example be measured in a direction transverse to (or orthogonal to) the longitudinal direction. The width of the recess may for example be measured (or defined) in a direction which is substantially parallel to a face (or surface) of the body at which the recess is formed.

It will be appreciated that the recess could for example be relatively wide (for example wider than <NUM> micrometers) at the top close to the surface level of the body, but may be more narrow deeper down into the recess below the surface level of the body.

It will be appreciated that the cutting insert may optionally comprise one or more additional layers, for example arranged between the substrate and the first layer, and/or between the first layer and the lead.

According to some embodiments, the recess may be formed in the substrate. The base and the substrate may for example coincide. The first layer may for example cover at least a portion of the substrate.

According to some embodiments, the body may comprise the first layer, and the recess may be formed in the first layer. The material of the first layer may for example be more homogeneous than the material of the substrate, so it may be easier to form the recess in the first layer than in the substrate.

According to some embodiments, for each depth at which at least a portion of the electrically conductive material is arranged in the recess, a width of the recess measured at that depth between portions of the first layer covering opposite interior side walls of the recess may be less than or equal to <NUM> micrometers. In other words, the width may be defined (or measured) at depths where at least a portion of the electrically conductive material is arranged in the recess. The width may for example be less than or equal to <NUM> micrometers, or less than or equal to <NUM> micrometers, or less than or equal to <NUM> micrometers, or less than or equal to <NUM> micrometers, or less than or equal to <NUM> micrometers.

According to some embodiments, the first layer may be an electrically insulating layer.

If the substrate is electrically conductive, the first layer may for example provide electrical insulation between the substrate and the lead. If there is an electrically conductive layer between the substrate and the first layer, the first layer may for example provide electrical insulation between that electrically conductive layer and the lead.

According to the invention, at least a portion of the lead is arranged at a depth of the recess such that there is space within the recess above the lead.

The space within the recess above the lead may for example reduce the risk that the lead gets into unintentional electrical contact with other leads or electrical conductive layers via chips from a work piece or via debris created during interaction between the cutting insert and a work piece. This may increase the reliability of measurements performed via the sensor arrangement.

The space within the recess above the lead may for example be open space (which may for example be filled/occupied by air from the surroundings), or may for example be at least partially occupied by one or more additional layers.

According to some embodiments, the cutting insert may comprise a second layer arranged in the recess such that the lead is located between the first layer and the second layer. The second layer may be an electrically insulating layer.

The electrical insulation provided by the second layer may reduce the risk that the lead gets into unintentional electrical contact with other leads or electrical conductive layers via chips from a work piece or via debris created during interaction between the cutting insert and a work piece. This may increase the reliability of measurements performed via the sensor arrangement.

The second layer may prevent (or reduce) oxidation of the lead, which could otherwise affect resistance of the lead. Reduced oxidation of the lead may for example increase the reliability of measurements performed via the sensor arrangement.

According to some embodiments, the first layer may be more resistant to blasting than the second layer. Blasting may for example comprise bombarding a surface by particles.

The first layer may for example comprise a material which may withstand (or remain undamaged by) blasting. During manufacture of the cutting insert, portions of the second layer located outside the recess may for example be removed via blasting, while portions of the first layer located outside the recess may for example withstand (or remain undamaged by) such blasting. The more resistant first layer may for example remain outside the recess to serve as a hard (or durable) layer during machining, while the remaining portion(s) of the less resistant second layer may be protected by the recess and may provide electrical insulation for the lead.

According to some embodiments, at least a portion of the lead may be arranged at a depth of at least <NUM> micrometers into the recess. At least a portion of the lead may for example be arranged at a depth of at least <NUM> micrometers into the recess or at least <NUM> micrometers into the recess.

Portions of the lead arranged deep into the recess may be better protected by the recess and/or may remain longer during wear of the cutting insert than leads (or portions of leads) arranged less deep into the recess. Having at least a portion of the lead arranged deep into the recess may for example allow for reliable measurements to be performed even after the cutting insert has been subjected to considerable wear. If, for example, the sensor arrangement is intended for detecting a certain degree of wear, such a degree of wear may for example be detected once a lead arranged at a certain depth into the recess is affected (or damaged, or worn down) by interaction between the cutting insert and a work piece.

According to the invention, the recess is no more than <NUM> micrometers deep. The recess may for example be no more than <NUM> micrometers deep. If the recess is too deep, this may affect the durability of the cutting insert or affect the durability of a cutting edge of the cutting insert.

According to some embodiments, at least a portion of the recess may be located at a rake face of the cutting insert in an area susceptible to be subjected to crater wear caused by chips removed from a metal work piece during operation of the cutting insert on the metal work piece. The at least a portion of the recess may for example be located at most <NUM> millimeters from or at least <NUM> millimeters from a cutting edge defined by an intersection between the rake face and a clearance face of the cutting insert.

According to some embodiments, a cross section of the lead may have a width of at least <NUM> micrometers. In other words, an object obtained by taking a cross-section of the lead may include at least two points from the lead located at least <NUM> micrometers from each other. The cross section may for example be taken in a direction which is transverse (or orthogonal) to the main direction in which the lead extends. If the width of the lead is too small, the lead may for example be more likely to break during manufacture of the cutting insert. A too small lead is also more demanding to produce without breakages due to defects in the lead material.

The lead may for example extend in a longitudinal direction along the recess, and the cross section of the lead may for example be taken (or formed) in a plane transverse to (or orthogonal to) the longitudinal direction.

According to some embodiments, the lead may comprise an electrically conductive layer covering at least portions of the interior side walls of the recess. A thickness of the electrically conductive layer may be at most <NUM> micrometers. The thickness of the electrically conductive layer may for example be at most <NUM> micrometers.

Employing a lead which is thicker than necessary may for example require more material than necessary and/or may increase a production time of the cutting insert.

Wear may for example be more easily detected if a thin lead is employed instead of a thicker lead, since wear to a thin lead may have a more dramatic impact on the resistance of the lead than wear to a thicker lead.

The thickness of the electrically conductive layer may for example be at least <NUM>, <NUM> or <NUM> micrometers. If the lead is to thin it may break too easily, for example during manufacture of the cutting insert.

According to some embodiments, the sensor arrangement may comprise first and second contact regions through which the sensor arrangement is connectable to external measuring circuitry. The lead may be connected to the first and second contact regions.

The external measuring circuitry may for example measure an electrical resistance between the first and second contact regions. Increased resistance may for example indicate that the lead has been affected (or damaged) by interaction of the cutting insert and a work piece (or chips from the work piece) despite being located in the recess. Increased resistance may therefore indicate that the cutting insert has reached a certain level of wear. Decreased resistance during metal cutting may for example indicate that an electrically conductive work piece (or a chip from the work piece) is in contact with the lead despite the fact that the lead is located in the recess. Decreased resistance during metal cutting may therefore indicate that the cutting insert has reached a certain level of wear.

According to some embodiments, the body may have multiple elongate recesses extending at least along respective portions of the body. The first layer may cover interior side walls of the recesses. The sensor arrangement may comprise first and second contact regions through which the sensor arrangement is connectable to external measuring circuitry. The sensor arrangement may comprise first and second leads extending along respective recesses of the substrate. Each of the first and second leads may comprise respective electrically conductive material which is arranged in the respective recess such that the first layer is located between the respective electrically conductive material and the substrate. The first lead may be connected to the first contact region and the second lead may be connected to the second contact region. For at least a depth below which at least a portion of the electrically conductive material of the first or second lead is arranged in a recess of the multiple elongate recesses, a width of the recess measured at that depth between portions of the first layer covering opposite interior side walls of the recess is less than or equal to <NUM> micrometers. Each of the first and second leads may present a free end positioned such that, upon a predetermined wear of the cutting insert, the free ends will be connected to each other by the metal work piece or by a chip resulting from operation of the cutting insert on the metal work piece. In other words, if the cutting insert has reached the predetermined wear, then the free ends will be connected to each other during operation of the cutting insert on the metal work piece since the metal work piece or a chip resulting from operation of the cutting insert on the metal work piece will connect the free ends to each other.

The external measuring circuitry may for example measure an electrical resistance between the first and second contact regions. Reduced resistance may indicate that the predetermined wear of the cutting insert has been obtained.

Furthermore, there is disclosed a method for manufacturing a cutting insert for cutting, milling or drilling of metal. The method comprises providing a body with an elongate recess extending along at least a portion of the body. The body comprises a substrate. A first layer covers interior side walls of the recess. The method comprises forming a layer of electrically conductive material covering at least a portion of the body such that electrically conductive material is provided in the recess with the first layer being located between the electrically conductive material in the recess and substrate, and subjecting at least a portion of the body to blasting such that electrically conductive material located outside the recess is removed from the body while electrically conductive material remaining in the recess forms a lead extending along the recess. For at least a depth below which at least a portion of the electrically conductive material is arranged in the recess, a width of the recess measured at that depth between portions of the first layer covering opposite interior side walls of the recess is less than or equal to <NUM> micrometers (or less than or equal to <NUM> micrometers, or less than or equal to <NUM> micrometers, or less than or equal to <NUM> micrometers, or less than or equal to <NUM> micrometers, or less than or equal to <NUM> micrometers).

The body may for example coincide with the substrate, or may for example comprise one or more layers in addition to the substrate. The recess may for example be provided in the substrate and/or in one or more of such layers.

The substrate may for example be provided via sintering or hot isostatic pressing.

The elongate recess may for example be shaped/formed using a laser. If the recess is formed in the substrate, then the elongate recess may for example be shaped/formed via use of an adequately shaped pressing tool when providing (or producing) the substrate.

The first layer and/or the electrically conductive layer may for example be formed using chemical vapor deposition (CVD) or physical vapor deposition (PVD).

It will be appreciated that while some electrically conductive material located outside the recess is removed by the blasting, some electrically conductive material located outside the recess may for example remain also after the blasting (for example if a protective coating protects it from the blasting). It will also be appreciated that while at least some electrically conductive material located in the recess remains after the blasting, some electrically conductive material in the recess may be removed by the blasting (for example if the recess is wide at the top so that the uppermost electrically conductive material in the recess is removed during blasting while electrically conductive material deeper down in a narrower portion of the recess remains after the blasting).

The blasting may include bombardment of the substrate by particles. The average diameter of particles employed in the blasting may for example be at least as large as the above described width of the recess (measured at a certain depth of the recess between portions of the first layer covering opposite interior side walls of the recess). The average diameter of particles employed in the blasting may for example be at least <NUM> micrometers, <NUM> micrometers, <NUM> micrometers, <NUM> micrometers, <NUM> micrometers, or <NUM> micrometers, or may be in the range of <NUM>-<NUM> micrometers, or in the range of <NUM>-<NUM> micrometers.

The first layer may for example be a layer of α-Al<NUM>O<NUM>, κ-Al<NUM>O<NUM>, ZrO<NUM>, HfO<NUM> or AIN, preferably produced with CVD.

The electrically conductive material of the lead may for example comprise a metal, a carbide, boride, boron nitride or a carbonitride such as one or more of TiN, TiC, ZrC, ZrN, HfN, HfC, CrC, CrN, TiCN, ZrCN, TiB<NUM>, TiBN, AlTiN, Au, Pt,Pd, Cu, Cr and Ni.

According to some embodiments, the method may comprise forming, prior to subjecting at least a portion of the body to the blasting, a second layer covering at least a portion of the body such that at least a portion of the second layer is provided in the recess and covers the electrically conductive material located in the recess.

The second layer may for example be electrically insulating.

The first layer may for example be more resistant to blasting than the second layer. During the blasting, a portion of the second layer located outside the recess may for example be removed while the at least a portion of the second layer provided in the recess prior to blasting may remain in the recess also after the blasting.

In what follows, example embodiments will be described in greater detail and with reference to the accompanying drawings, on which:.

All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the respective embodiments, whereas other parts may be omitted or merely suggested. Unless otherwise indicated, like reference numerals refer to like parts in different figures.

<FIG> is a top view of a cutting insert <NUM> with a sensor arrangement, according to an embodiment. <FIG> is cross sectional view of a portion of the cutting insert <NUM> from <FIG>, showing a recess <NUM> in which a lead <NUM> of the sensor arrangement is arranged. The cross section shown in <FIG> is taken along the line A in <FIG> in a direction orthogonal to the direction of the lead <NUM>, and only includes a portion of the cutting insert <NUM>. A perspective view of the cutting insert <NUM> is provided in <FIG> which also shows a portion of an example cutting tool in which the cutting insert <NUM> may be employed. The cutting insert <NUM> is adapted for use in machining operations such as cutting, milling or drilling of metal.

The cutting insert <NUM> comprises a substrate <NUM> (or a base material <NUM>) having an elongate recess <NUM> (or cavity <NUM>) extending along at least a portion of the substrate <NUM>. While the recess <NUM> is shown in the cross sectional view of <FIG>, it may not be that clearly visible when viewed from above or in a perspective view. For reasons of clarity, the recess <NUM> is therefore not shown in <FIG> and <FIG>. On the other hand, <FIG> and <FIG> show how the lead <NUM> (which is arranged in the recess <NUM> and follows the recess <NUM>) extends along the cutting insert <NUM>. The recess <NUM> may extend along the cutting insert <NUM> similarly to the lead <NUM> shown in <FIG> and <FIG>. The substrate <NUM> may for example be shaped as a parallelepiped, but with a hole <NUM> at the rake face <NUM>. The substrate <NUM> may for example comprise (or be made of) cemented carbide, such as tungsten carbide with a cobalt binder.

The cutting insert <NUM> comprises a first layer <NUM> covering at least a portion of the substrate <NUM>, including interior side walls <NUM> and <NUM> of the recess <NUM>. The first layer <NUM> is an electrically insulating layer and may for example comprise (or be made of) α-Al<NUM>O<NUM> (di-aluminum tri-oxide in the alpha phase). The first layer <NUM> may for example act as a thermal barrier. The first layer may further be a layer of high wear resistance in metal cutting operation. The thickness of the first layer <NUM> is in the range of <NUM>-<NUM> micrometers.

The cutting insert <NUM> comprises a sensor arrangement comprising a lead <NUM> extending along the recess <NUM>. The lead <NUM> comprises electrically conductive material <NUM> which is arranged in the recess <NUM> such that the first layer <NUM> is located between the electrically conductive material <NUM> and the interior side walls <NUM> and <NUM> of the recess <NUM>. The electrically conductive material <NUM> may for example comprise a suitable nitride and/or carbide such as TiN (titanium nitride), TiCN (titanium carbonitride) and/or TiC (titanium carbide). In the present embodiment, the lead <NUM> is provided in the form of an electrically conductive coating or layer arranged in the recess <NUM> over the first layer <NUM>. The thickness T of the electrically conductive layer <NUM> is in the range of <NUM>-<NUM> micrometers.

In the present embodiment, there is an inner layer <NUM> located between the substrate <NUM> and the first layer <NUM>. The inner layer <NUM> may for example comprise Ti(C, N, O), for example TiCN. Other compositions are also envisaged, such as compositions based on Zr(C,N), AlTiN or Hf(C,N). The thickness of the inner layer <NUM> is in the range of <NUM>-<NUM> micrometers. The inner layer <NUM> is advantageous in providing increased wear resistance, such as abrasive resistance of the cutting tool. The first layer <NUM> provides electrical insulation between the lead <NUM> and the inner layer <NUM> which may be electrically conductive.

The cutting insert <NUM> (as well as methods of manufacturing the cutting insert) will be further described below with reference to <FIG> and <FIG>. However, the purpose of the sensor arrangement of the cutting insert <NUM> will first be described with reference to <FIG>.

The lead <NUM> is part of a sensor arrangement provided in the cutting insert <NUM>. As shown in <FIG>, the sensor arrangement also comprises first and second contact regions <NUM> and <NUM> through which the sensor arrangement is connectable to external measuring circuitry. The lead <NUM> is connected to the first and second contact regions <NUM> and <NUM> so that a resistance of the lead <NUM> can be measured via the contact regions <NUM> and <NUM>. Since the sensor arrangement forms a closed loop from the first contact region <NUM>, through the lead <NUM>, to the second contact region <NUM>, the measured resistance may be quite low. However, if the cutting insert <NUM> is subjected to wear in a region were the lead <NUM> is arranged, the lead <NUM> may eventually get damaged or worn down (at least if it is not arranged too deep into a recess). During metal cutting, when the cutting insert <NUM> is interacting with a work piece, the work piece itself or a chip from the work piece may cause wear to the cutting insert <NUM> and may eventually reach down into the recess <NUM> to damage the lead <NUM>.

While damage to the lead <NUM> may increase the resistance of the lead <NUM>, this may not be that easy to detect when the cutting insert is cutting (also referred to as "in cut"). Indeed, the measured resistance could be low even if the lead <NUM> is damaged since the work piece (or a chip from the work piece) may be electrically conductive and may contribute to conveying electrical current past the damaged portion of the lead <NUM>. However, when the cutting insert <NUM> is no longer cutting (also referred to as "out of cut"), damage to the lead <NUM> may be indicated (or manifested) by an increased resistance since the work piece or chip will no longer contribute to conveying electrical current. Hence, wear of the cutting insert <NUM> may be detected via detection of an increased resistance out of cut. When it is detected via the sensor arrangement that the cutting insert <NUM> has reached a certain level or wear, the cutting insert <NUM> may for example be replaced by a new cutting insert.

<FIG> is a perspective view of a portion of an example cutting tool in which the cutting insert <NUM> may be employed. The cutting tool comprises a tool holder <NUM> for holding the cutting insert <NUM>, and measuring circuitry <NUM> connected to the tool holder <NUM> for measuring the resistance of the lead <NUM>. The tool holder <NUM> has electrical contacts <NUM> and <NUM> which are to be electrically connected to the contact regions <NUM> and <NUM>, respectively, of the cutting insert <NUM> as the cutting insert <NUM> is held by the tool holder <NUM>. In the present example, the electrical contacts <NUM> and <NUM> are exposed on a lower side of a projection <NUM> provided on the holder <NUM>, such that they will be in contact with the contact regions <NUM> and <NUM> of the cutting insert <NUM> once the latter has been attached at the holder <NUM>. The measuring circuitry <NUM> is connected to the sensor arrangement of the cutting insert <NUM> through the contacts <NUM> and <NUM> of the tool holder <NUM>. The cutting insert <NUM> has a through hole <NUM> in the rake face <NUM> and there is provided a screw hole <NUM> in the holder <NUM>, enabling fastening of the cutting insert <NUM> to the holder <NUM> by means of a screw <NUM>.

The cutting insert <NUM> described above with reference to <FIG> only has a single lead <NUM>. However, embodiments may be envisaged in which the sensor arrangement of a cutting insert comprises multiple leads. A cutting insert may for example comprise multiple leads and associated contact regions for performing measurements in different regions of a cutting insert, for example at different sides/faces of the cutting insert. A tool at which the cutting insert is mounted may include electrical contacts and measuring circuitry for measuring the electrical resistance of such multiple leads.

<FIG> is a top view of a cutting insert <NUM> with multiple leads, according to an embodiment. The leads of the cutting insert <NUM> are grouped into three pairs for monitoring wear at different locations. Only one of these pairs will be described, but the other pairs of leads are arranged analogously.

A first lead <NUM> is connected to a first contact region <NUM>, and a second lead <NUM> is connected to a second contact region <NUM>. The sensor arrangement is connectable to external measuring circuitry via the contact regions <NUM> and <NUM> in a similar way as for the cutting insert <NUM> and measuring circuitry <NUM> described above with reference to <FIG>. The leads <NUM> and <NUM> may for example be arranged in respective recesses similar to the recess <NUM> described above with reference to <FIG>. The leads <NUM> and <NUM> present free ends <NUM> and <NUM> positioned such that, upon a predetermined wear of the cutting insert <NUM>, the free ends <NUM> and <NUM> will be connected to each other by a metal work piece or by a chip resulting from operation of the cutting insert <NUM> on the metal work piece. In other words, the leads <NUM> and <NUM> end at respective free ends <NUM> and <NUM> which are not connected to each other before the cutting insert <NUM> is sufficiently worn.

The external measuring circuitry measures the resistance between the contact regions <NUM> and <NUM>. Initially, the free ends <NUM> and <NUM> will not be connected to each other so the measured resistance will be high (in other words, the sensor arrangement of the cutting insert <NUM> is an open loop sensor arrangement, in contrast to the closed loop sensor arrangement described above with reference to <FIG> and <FIG>). As the cutting insert <NUM> is subjected to wear, the free ends <NUM> and <NUM> of the leads <NUM> and <NUM> will eventually be exposed (unless the free ends <NUM> and <NUM> are arranged too deep into recesses) and be connected to each other by the work piece or a chip from the work piece. When this happens, the measured resistance decreases, which may be detected in cut (that is, during metal cutting). In other words, there is no need to wait until the cutting insert <NUM> is out of cut for detecting that the predetermined wear has been reached. When it is detected via the sensor arrangement that the cutting insert <NUM> has reached a certain level or wear, the cutting insert <NUM> may for example be replaced by a new cutting insert.

It will be appreciated that the sensor arrangement of a cutting insert may comprise leads of different types, and or positioned in different regions of the cutting insert. A combination of open loop sensor arrangements (as described with reference to <FIG>) and closed loop sensor arrangements (as described with reference to <FIG>) may for example be employed in a cutting insert. A sensor arrangement may for example be arranged to measure wear close to a cutting edge <NUM> of a cutting insert. Leads of the sensor arrangement may for example be arranged at a rake face <NUM> to monitor crater wear, or at a clearance face <NUM>.

Having the leads arranged in recesses (instead of at the surface of the cutting insert) reduces the risk that the leads get damaged or fall off at an initial stage of machining. The leads may for example be arranged at a certain depth so that they only get affected by wear once the cutting insert has been subjected to a certain level of wear.

A method of manufacturing the cutting insert <NUM> described above with reference to <FIG> will now be described with reference to <FIG> and <FIG> is a cross sectional view of the same portion of the cutting insert <NUM> as in <FIG>, but before it has been subjected to blasting. The cutting insert <NUM> may for example be manufactured as follows.

First, the substrate <NUM> is provided, for example via a common production method such as sintering or hot isostatic pressing of metal powder. The substrate <NUM> may for example be shaped approximately as a parallelepiped (with a hole <NUM> in the center as shown in <FIG>).

The elongate recess <NUM> in the substrate <NUM> may be formed during the sintering or pressing by using an appropriately shaped pressing tool. Alternatively, laser (such as a picosecond laser) could be employed to form the recess <NUM> after the substrate <NUM> has been produced. In the present embodiment, the recess <NUM> is tapered (or V-shaped) such that it is wider at the top than deeper down unto the recess <NUM>. Embodiments may also be envisaged in which the recess <NUM> has different shapes, such as a recess with vertical side walls, or a U-shaped or semicircular recess with curved side walls. The shape of the recess <NUM> may for example depend on the method employed for providing the recess. The recess <NUM> may for example be at least <NUM>, <NUM> or <NUM> micrometers deep. The depth of the recess <NUM> may for example be measured as a vertical distance D3 from a surface <NUM> of the substrate <NUM> in which the recess <NUM> is formed, down to a bottom <NUM> of the recess <NUM>. The depth D3 of the recess <NUM> may for example be in the range <NUM>-<NUM> micrometers, preferably in the range <NUM>-<NUM> micrometers, or in the range <NUM>-<NUM> micrometers.

Layers (or coatings) are then applied to the substrate <NUM> using chemical vapor deposition (CVD) or some other method, such as physical vapor deposition (PVD). The first layer <NUM> is formed to cover the substrate <NUM>, including the interior side walls <NUM> and <NUM> of the recess <NUM>. A layer <NUM> of electrically conductive material is then formed to cover the substrate <NUM> such that electrically conductive material <NUM> is provided in the recess <NUM> with the first layer <NUM> being located between the electrically conductive material <NUM> in the recess <NUM> and the interior side walls <NUM> and <NUM> of the recess <NUM>. In the present embodiment, an inner layer <NUM> is applied between the substrate <NUM> and the first layer <NUM>. The inner layer <NUM>, the first layer <NUM>, and the electrically conductive layer <NUM> form a CVD stack covering the substrate <NUM>.

A portion of the lead <NUM> may for example be arranged at a depth D4 of at least <NUM>, <NUM> or <NUM> micrometers into the recess <NUM> measured from the surface <NUM> of the substrate <NUM> in which the recess <NUM> is formed.

The substrate <NUM> is then subjected to top blasting such that those parts of the electrically conductive material <NUM> located outside the recess <NUM> are removed from the substrate <NUM> while electrically conductive material <NUM> remaining in the recess <NUM> forms the lead <NUM> (as shown in <FIG>) extending along the recess <NUM>. For this blasting procedure to work as intended, the width of the recess <NUM> is selected appropriately with respect to the size of blasting particles to be employed during blasting.

The width of the recess <NUM> could be expressed in different ways. A first width W1 could for example be measured between the left side wall <NUM> of the recess <NUM> and the right side wall <NUM> of the recess <NUM>. In the present embodiment, the recess <NUM> is tapered (or V-shaped) such that it is wider at the top than deeper down unto the recess <NUM>. The first width W1 may therefore be measured at the top of the side walls <NUM> and <NUM> to obtain the largest possible width of the recess <NUM>. The first width W1 may for example be less than or equal to <NUM> micrometers, or less than or equal to <NUM> micrometers, or less than or equal to <NUM> micrometers.

However, in the present disclosure, it is more useful to consider the width of the recess <NUM> as experienced by blasting particles employed during the blasting, since a sufficiently narrow recess <NUM> may protect the electrically conductive material <NUM> in the recess <NUM> from the blasting. The width is therefore measured between portions of the first layer <NUM> covering opposite interior side walls <NUM> and <NUM> of the recess <NUM>. In other words, the width is measured from a portion of the first layer <NUM> covering the left side wall <NUM> of the recess <NUM> to a portion of the first layer <NUM> covering the right side wall <NUM> of the recess <NUM>. The width may be measured at different depths of the recess <NUM>. It is useful to measure the width at depths below which there is electrically conductive material <NUM> in the recess <NUM>, so that such electrically conductive material <NUM> may be protected if the width is small enough.

In the present embodiment, a width (henceforth referred to as the second width W2) may for example be measured at a depth D1 corresponding to the uppermost part of the recess <NUM>. If the second width W2 is small enough compared to the size of the blasting particles, this allows more or less all the electrically conductive material <NUM> in the recess <NUM> to be protected by the recess <NUM> during blasting, which results in a lead <NUM> extending all the way up to the top of the recess, as shown in <FIG>. Such a result may for example be obtained if the blasting particles have an average diameter above <NUM> micrometers, and the second width W2 is at most <NUM> micrometers, preferably less than <NUM> micrometers. The average diameter of the blasting particles may for example be <NUM> micrometers, and the second width W2 of the recess <NUM> may for example be <NUM> micrometers, or <NUM> micrometers. It will be appreciated that, as long as the first layer <NUM> and/or the inner layer <NUM> are/is sufficiently thick, the first width W1 could still be larger than the average diameter of the blasting particles.

If the second width W2 is too large compared to the size of the blasting particles (for example the second width W2 is <NUM> micrometers but the average diameter of the blasting articles is <NUM> micrometers), then some of the electrically conductive material <NUM> located in the recess <NUM> may be removed during the blasting. A width (henceforth referred to as the third width W3) may then be measured deeper down in the recess <NUM> (for example at a depth D2 halfway down into the recess <NUM>) where the recess <NUM> is more narrow. If the third width W3 is small enough compared to the size of the blasting particles (for example, the third width W3 may be smaller than the average diameter of the blasting particles), this allows the electrically conductive material <NUM> located below that depth D2 in the recess <NUM> to be protected by the recess <NUM> during blasting, which results in a lead <NUM> located in the recess <NUM> and extending up to that depth D2 where the third width W3 is measured, as shown in <FIG>. In other words, the lead <NUM> does not extend all the way up to the top of the recess <NUM>. This may for example reduce the risk that the lead <NUM> gets into unintentional electrical contact with the work piece, chips from the work piece, or debris created during machining, which could affect the reliability of measurements performed via the lead <NUM>.

During the blasting, the substrate <NUM>, as well as those of its layers which are exposed, are bombarded by particles. The first layer <NUM> is adapted to withstand the blasting, so the blasting particles do not reach the conductive material <NUM> located inside the recess <NUM> as long as the recess <NUM> is sufficiently narrow compared to the size of the blasting particles. The blasting is employed to provide a desired surface smoothness of the first layer <NUM> and to enable a tougher edge line performance due to the resulting residual compressive stress in the first layer <NUM> as a result of the blasting. Hence, the cutting insert <NUM> remaining after the blasting has a lead <NUM> (or <NUM>) which may be employed for measurements, and a first layer <NUM> outside the recess <NUM> which provides the desired machining performance for the cutting insert <NUM>.

The size of the blasting particles should not be too large, since that would involve too high kinetic energy, which may for example risk damaging a cutting edge of the cutting insert. The average diameter of the blasting particles may for example be at most twice as large as the radius of a cutting edge of the cutting insert. The radius of the cutting edge may for example be in the range <NUM>-<NUM> micrometers. Still, the recess <NUM> should be sufficiently narrow compared to the blasting particles so that at least some electrically conductive material <NUM> in the recess <NUM> may be protected from the blasting particles during the blasting.

The manufacturing method described above with respect to <FIG> and <FIG> is an efficient way to provide a cutting insert <NUM> with a sensor arrangement. If the recess <NUM> is formed via use of an appropriately shaped pressing tool (rather than using laser to form the recess <NUM>), the sensor arrangement may for example be provided as part of ordinary manufacturing steps employed for manufacturing CVD coated cutting inserts without sensor arrangements. In other words, there may be no need to use dedicated manufacturing steps (for example including etching or laser) for introducing the sensor arrangement in the cutting insert.

If top blasting is employed to remove electrically conductive material <NUM> located outside the recess <NUM> at a rake face of the cutting insert <NUM>, then electrically conductive material may remain at other faces/sides of the cutting insert (such as a clearance face) after the top blasting. If a too thick layer of electrically conductive material <NUM> remains at the clearance face of the cutting insert after the top blasting, then this layer may affect performance of the cutting insert.

It will be appreciated that the lead <NUM> may for example extend its entire length in a recess <NUM>. However, embodiments may also be envisaged in which some portions of the lead <NUM> (for example located far away from regions where wear is expected) may be provided at the surface of the cutting insert <NUM> rather than in a recess <NUM>. It will be appreciated that a cutting insert may include leads arranged in recesses as well as leads arranged at the surface of the cutting insert. It will also be appreciated that different portions of the lead <NUM> may for example be arranged at different depths into the recess <NUM>, and that the width of the recess <NUM> may vary along the extension of the recess <NUM>. The substrate <NUM> may for example have a certain surface geometry (for example including ridges and valleys) to improve cutting performance and/or durability, which may cause the depth of the recess <NUM> to vary along the cutting insert <NUM>. Different portions of the lead <NUM> may also have different shapes, thicknesses or diameters. The lead <NUM> is preferably sufficient thick (for example a thickness T of at least <NUM> micrometers) not to break too easily during manufacture.

It will be appreciated that in the cross section depicted in <FIG>, the lead <NUM> has a diameter which is at least as large as the second width W2 of the recess <NUM>. It will also be appreciated that in the cross section depicted in <FIG>, the lead <NUM> has a diameter which is at least as large as the third width W3 of the recess <NUM>.

<FIG> is a cross sectional view of a portion of a cutting insert with an extra insulating layer <NUM> compared to the cutting insert <NUM> in <FIG>, according to an embodiment. The extra insulating layer <NUM> may for example comprise κ-Al<NUM>O<NUM> (di-aluminum tri-oxide in the kappa phase) and provides electrical insulation for the lead <NUM>. The cutting insert in <FIG> is manufactured in a similar way as the cutting insert <NUM> described with reference to <FIG>, except that a second layer <NUM> is formed before the blasting, as illustrated in <FIG> (which is a cross sectional view of a portion of the cutting insert from <FIG>, but before being subjected to blasting). Before the substrate <NUM> is subjected to blasting, the second layer <NUM> is formed such that it covers the substrate <NUM>. At least a portion of the second layer <NUM> is provided in the recess <NUM> and covers the electrically conductive material <NUM> located in the recess <NUM>. When the blasting is performed, those parts of the second layer <NUM> located outside the recess <NUM> are removed, while those parts of the second layer <NUM> located in the recess <NUM> remain to form the extra insulating layer <NUM> (as illustrated in <FIG>).

The extra insulating layer <NUM> reduces the risk that the lead <NUM> gets into unintentional electrical contact with the work piece, chips from the work piece, or debris created during machining, which could otherwise affect the reliability of measurements performed via the lead <NUM>. In the present example, all but the upper ends <NUM> and <NUM> of the lead <NUM> are insulated by the extra insulating layer <NUM>. The insulating layer <NUM> also protects the lead <NUM> from oxidation, which could affect the resistance of the lead <NUM>.

<FIG> is a cross sectional view of a portion of a cutting insert with a second layer <NUM> similar to the second layer <NUM> in <FIG>, but where certain portions <NUM> and <NUM> of the second layer <NUM> have been removed, according to an embodiment. <FIG> is a cross sectional view of a portion of the cutting insert from <FIG>, but after being subjected to blasting.

In the present embodiment, the second layer <NUM> (which is an extra insulating layer) is of a type which is resistant to blasting (that is, which is not removed via blasting). The extra insulating layer <NUM> may for example comprise α-Al<NUM>O<NUM> (di-aluminum tri-oxide in the alpha phase). Since the extra layer <NUM> protects the conductive layer <NUM>, laser or etching is employed to remove portions <NUM> and <NUM> of the extra layer <NUM> on either side of the recess <NUM> prior to blasting. This allows conductive material <NUM> located below these removed portions <NUM> and <NUM> to be removed during blasting, so that a lead <NUM> is formed in the recess <NUM>. In the present embodiment, electrically conductive material <NUM> and <NUM> remains on either side of the recess <NUM>, but is not connected to the lead <NUM> in the recess <NUM>.

An advantage of manufacturing cutting inserts according to the embodiment described above with reference to <FIG> is that it does not require use of etching or laser for forming the lead <NUM> (in contrast to the embodiment described with reference to <FIG>). Instead, all the layers may be provided in a CVD stack, and the lead <NUM> may be formed via the same blasting operation that is employed for improving cutting performance of the first layer <NUM>.

In the cutting insert <NUM>, described above with reference to <FIG>, the recess <NUM> is formed in the substrate <NUM>. However, embodiments may also be envisaged in which the recess <NUM> is formed in a layer covering the substrate <NUM> rather than in the substrate <NUM> itself. The recess <NUM> could for example be formed in the first layer <NUM> or in the inner layer <NUM>. <FIG> is a cross sectional view of a portion of a cutting insert in accordance with such an embodiment. In contrast to <FIG> where the lead <NUM> extends in a recess <NUM> formed in a substrate <NUM>, the lead <NUM> in <FIG> extends in a recess <NUM> formed in the first layer <NUM> (which is electrically insulating, and which may be of the same material as the first layer <NUM> described above with reference to <FIG>). In <FIG>, the substrate <NUM>, the inner layer <NUM>, and the first layer <NUM> may together be regarded as a body along which the recess <NUM> extends. Since the recess <NUM> is formed in the first layer <NUM>, the first layer <NUM> covers the interior side walls of the recess <NUM>. The first layer <NUM> is located between the lead <NUM> and the substrate <NUM> (and also between the lead <NUM> and the inner layer <NUM>). The recess <NUM> may for example be formed in the first layer <NUM> via use of a laser.

Claim 1:
A cutting insert (<NUM>, <NUM>) for turning, milling or drilling of metal, the cutting insert comprising:
a body having an elongate recess (<NUM>, <NUM>) extending along at least a portion of the body, wherein the body comprises a substrate (<NUM>);
a first layer (<NUM>, <NUM>) covering interior side walls (<NUM>, <NUM>) of the recess; and
a sensor arrangement comprising a lead (<NUM>, <NUM>, <NUM>) extending along the recess, the lead comprising electrically conductive material which is arranged in the recess such that the first layer is located between said electrically conductive material and the substrate,
wherein, for at least a depth (D1, D2, D5) below which at least a portion of said electrically conductive material is arranged in the recess, a width (W2, W3, W4) of the recess measured at said depth between portions of said first layer covering opposite interior side walls (<NUM>, <NUM>) of the recess is less than or equal to <NUM> micrometers, and wherein at least a portion of the lead is arranged at a depth (D4) of the recess such that there is space within the recess above the lead, characterized in that
the recess is no more than <NUM> micrometers deep, wherein, if the recess is formed in the substrate, the depth of the recess is measured from a surface (<NUM>) of the substrate to a bottom (<NUM>) of the recess, and wherein, if the recess is formed in the first layer, the depth is measured from a surface of the first layer to a bottom of the recess.