GB2577077A

GB2577077A - A tool module for real-time tool condition monitoring during precision machining

Info

Publication number: GB2577077A
Application number: GB1814840.3A
Authority: GB
Inventors: Lay Matthew
Original assignee: Element Six UK Ltd
Current assignee: Element Six UK Ltd
Priority date: 2018-09-12
Filing date: 2018-09-12
Publication date: 2020-03-18
Also published as: GB201814840D0

Abstract

The tool module 10 includes a tool holder 12 and a replaceable cutting tool 14 detachably mounted to the tool holder. The cutting tool comprises an integrated sensing element (22, Figure 5). The tool holder also housing a control unit (not shown) for the acquisition and processing of signals generated by the integrated sensing element into data. A communication unit (not shown) is for transmitting data relating to a condition of the cutting tool from the control unit. The tool module may be connected to a tool assembly on, for example, a mill or a lathe. The data may be transmitted from the control unit to a data management platform using wireless technology. A tool retention system 38 may be used to selectively retain the cutting tool in place on the tool holder. Spring-loaded connection pins (36, Figure 7) adjacent the cutting tool reception zone 16 may be in communication with the control unit. The cutting tool material may be polycrystalline diamond (PCD) or polycrystalline cubic boron nitride (PCBN).

Description

(54) Title of the Invention: A tool module for real-time tool condition monitoring during precision machining Abstract Title: Tool module for real-time condition monitoring during machining (57) The tool module 10 includes a tool holder 12 and a replaceable cutting tool 14 detachably mounted to the tool holder. The cutting tool comprises an integrated sensing element (22, Figure 5). The tool holder also housing a control unit (not shown) for the acquisition and processing of signals generated by the integrated sensing element into data. A communication unit (not shown) is for transmitting data relating to a condition of the cutting tool from the control unit. The tool module may be connected to a tool assembly on, for example, a mill or a lathe. The data may be transmitted from the control unit to a data management platform using wireless technology. A tool retention system 38 may be used to selectively retain the cutting tool in place on the tool holder. Spring-loaded connection pins (36, Figure 7) adjacent the cutting tool reception zone 16 may be in communication with the control unit. The cutting tool material may be polycrystalline diamond (PCD) or polycrystalline cubic boron nitride (PCBN).

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

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A TOOL MODULE FOR REAL-TIME TOOL CONDITION MONITORING DURING PRECISION MACHINING

FIELD OF THE INVENTION

This disclosure relates to a cutting tool module, and in particular to a cutting tool module which is used in the real time monitoring of the condition of a cutting tool during machining e.g. turning or milling.

BACKGROUND

Cutter inserts for machining and other tools typically comprise a layer of polycrystalline diamond (PCD) bonded to a cemented carbide substrate. PCD is an example of a super hard material, also called super abrasive material, which has a hardness value substantially greater than that of cemented tungsten carbide.

Components comprising PCD are used in a wide variety of tools for cutting, machining, drilling or degrading hard or abrasive materials such as rock, metal, ceramics, composites and wood-containing materials. PCD typically comprises a mass of substantially inter-grown cubic diamond grains forming a skeletal mass, which defines interstices between the cubic diamond grains. PCD material comprises at least about 80 volume % of diamond and can be made by subjecting an aggregated mass of diamond grains to an ultra-high pressure of greater than about 5 GPa, typically about 5.5 GPa, and temperature of at least about 1200°C, typically about 1440°C, in the presence of a sintering aid, also referred to as a catalyst material for diamond. Catalyst material for diamond is understood to be material that is capable of promoting direct intergrowth of diamond grains at a pressure and temperature condition at which diamond is thermodynamically more stable than graphite.

Examples of catalyst materials for diamond are cobalt, iron, nickel and certain alloys including alloys of any of these elements. PCD may be formed on a cobalt-cemented tungsten carbide substrate, which may provide a source of cobalt catalyst material for the PCD. During sintering of the body of PCD material, a constituent of the cemented-carbide substrate, such as cobalt from a cobalt-cemented tungsten carbide substrate, liquefies and sweeps from a region adjacent the volume of diamond particles into interstitial regions between the diamond particles. In this example, the cobalt acts as a catalyst to facilitate the formation of bonded diamond grains. Optionally, a metal-solvent catalyst may be mixed with diamond particles prior to subjecting the diamond particles and substrate to a high pressure high temperature (HPHT) process. The interstices within PCD material may at least partly be filled with the catalyst material. The inter-grown diamond structure therefore comprises original diamond grains as well as a newly precipitated or re-grown diamond phase, which bridges the original grains. In the final sintered structure, catalyst/solvent material generally remains present within at least some of the interstices that exist between the sintered diamond grains.

In drilling operations, a cutting tool insert is subjected to heavy loads and high temperatures at various stages of its useful life. In the early stages of drilling, when the sharp cutting edge of the insert contacts the subterranean formation, the cutting tool is subjected to large contact pressures. This results in the possibility of a number of fracture processes such as fatigue cracking being initiated. As the cutting edge of the insert wears, the contact pressure decreases and is generally too low to cause high energy failures. However, this pressure can still propagate cracks initiated under high contact pressures and can eventually result in spalling-type failures. In the drilling industry, PCD cutter performance is determined by a cutter's ability to achieve high penetration rates in increasingly demanding environments, and still retain a good condition postdrilling (hence enabling re-use). In any drilling application, cutters may wear through a combination of smooth, abrasive type wear and spalIing/chipping type wear. Whilst a smooth, abrasive wear mode is desirable because it delivers maximum benefit from the highly wear-resistant PCD material, spalling or chipping type wear is unfavourable. Even fairly minimal fracture damage of this type can have a deleterious effect on both cutting life and performance.

With spalling-type wear, cutting efficiency can be rapidly reduced as the rate of penetration of the drill bit into the formation is slowed. Once chipping begins, the amount of damage to the diamond table continually increases, as a result of the increased normal force now required to achieve a given depth of cut. Therefore, as cutter damage occurs and the rate of penetration of the drill bit decreases, the response of increasing weight on bit can quickly lead to further degradation and ultimately catastrophic failure of the chipped cutting element.

Similar problems exist in the machining industry. PCD may be used to machine non-ferrous materials in operations such as cutting and turning. Again, chipping greatly affects the lifetime of the PCD cutting element and also the quality and finish of the workpiece being machined.

When optimising PCD cutter performance, increasing wear resistance in order to achieve better cutter life is typically achieved by manipulating variables such as average diamond grain size, overall catalyst/solvent content, diamond density and the like. Typically, however, as PCD material is made more wear resistant it becomes more brittle or prone to fracture. PCD elements designed for improved wear performance will therefore tend to have poor impact strength or reduced resistance to spalling. This trade-off between the properties of impact resistance and wear resistance makes designing optimised PCD structures, particularly for demanding applications, inherently self-limiting.

PCD cutting elements are typically provided with a usable lifetime (which may be measured in terms of time, metres cut, number of operations etc.). As chipping is a brittle process, the performance of an individual cutting element may greatly exceed that of another individual cutting element, and this effect is difficult to predict. In order to avoid damage to tooling or workpieces, this usable lifetime typically has a cautious value that is significantly lower than the actual lifetime a given tool may achieve.

Known tool condition monitoring systems include online inspection systems in which the tool is inspected for defects after each cut or cycle. These tool monitoring systems typically use optical sensors or laser optical sensors, which measure the geometry of the tool after each cut. However, on-line tool condition monitoring can only detect catastrophic failure of a tool after a cut and cannot monitor the gradual wear of a tool during real time or predict the tool's failure.

It is an object of the invention to provide a tool condition monitoring system that monitors in real time the condition of the tool and provides virtually immediate feedback to the process or user as to whether any operating parameters, such as feed rate, need to be altered. Such operating parameters may then be adjusted accordingly, manually or automatically, without having to interrupt the cut or cycle.

There is currently a drive to apply sensors to tools to measure parameters such as temperature, chipping, vibration and so on. The data obtained by these sensors can be used to more accurately measure cutting element life, leading to less risk of damaging workpieces and a greater usable lifetime for each cutting element.

It is an object of the invention to provide a fully versatile tool condition monitoring system, in which the tool holder can receive and work with any cutting tool which has an integrated sensing element.

SUMMARY

According to a first aspect of the invention, there is provided a tool module for real-time tool condition monitoring during machining, the tool module comprising a tool holder and a replaceable cutting tool detachably mounted to the tool holder, the cutting tool comprising an integrated sensing element, the tool holder housing a control unit for the acquisition and processing of signals generated by the integrated sensing element into data, and a communication unit for transmitting data relating to a condition of the cutting tool from the control unit.

With this tool module, advantageously any cutting tool with an integrated sensing element can be utilised with the tool holder with little or no further modification.

Preferable and/or optional features of the first aspect of the invention are provided in dependent claims 2 to 13.

According to a second aspect of the invention, there is provided a real-time tool condition monitoring system comprising a tool module in accordance with the first aspect of the invention and a data management platform for receiving and analysing data received from the control unit.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting example arrangements to illustrate the present disclosure are described with reference to the accompanying drawings, in which:

Figure 1 is a perspective view from above of a tool module in accordance with the first aspect of the invention;

Figure 2 is a perspective view from below of the tool module of Figure 1, showing in particular a slidable cover to conceal an internal chamber;

Figure 3 is a perspective view of the tool module of Figure 2, with the cover removed to reveal the internal chamber;

Figure 4 is a top view of a tool ready to receive a sensing element, and shows in particular a recess in the surface of the tool into which the sensing element will be received;

Figure 5 is a top view of a tool complete with integrated sensing element and wires;

Figure 6 is a bottom view of an alternative tool, with a pair of integrated electrical contacts;

Figure 7 is a close up perspective view of one end of the tool holder, and shows in particular a reception zone into which the tool is received;

Figure 8 is a further perspective view of the tool holder, and shows in particular a releasable clamp used to secure the tool in the reception zone of the tool holder; and

Figure 9 is a close up view of the rear of the tool holder with the cover removed, and shows in particular the location of a further sensing element.

DETAILED DESCRIPTION

Referring to Figure 1, a tool module for the real-time condition monitoring of a cutting tool is indicated generally at 10. The tool module 10 is connectable to a tool assembly (not shown) on, for example, a mill or a lathe. The tool module 10 is portable, handholdable and self-contained. It will now be described in more detail.

The tool module 10 comprises an elongate tool holder 12 and a replaceable cutting tool 14 detachably mounted at one end of the tool holder.

The tool holder 12 comprises a connection point for connecting the tool module 10 to a tool assembly. Such a tool assembly is found on the machine tool, e.g. the mill or the lathe. In this embodiment, an external surface of the tool holder 12 provides the connection point, e.g. for use with a grip or clamp on the tool assembly. However, alternative forms of connectors are possible and they may be electrical or mechanical types in nature.

The tool holder 12 is generally rectangular cuboidal in shape. In this particular embodiment, the tool holder 12 is approximately 10 cm in length, 2 cm in depth and 3 cm in width. It is made from a grade of steel, although other suitable materials may be used instead.

The tool holder 12 comprises an elongate body portion 12a and a head portion 12b at one end thereof. The cutting tool 14 is mounted in the head portion 12b. The head portion 12b is best seen in Figure 7. The head portion 12b extends from the body portion 12a at an acute angle that is offset from a longitudinal extent of the body portion 12a. In this embodiment, the position of the head portion 12b is fixed relative to the body portion 12a, but it is envisaged that it could be adjustable instead.

The head portion 12a comprises a reception zone 16 (best seen in Figure 7) into which a cutting tool 14 is receivable. The reception zone 16 is located at one upper corner of the head portion 12b. Essentially, the reception zone 16 is a missing corner of the head portion 12b. In this embodiment, the cutting tool 14 is cuboidal in shape and the reception zone 16 is correspondingly cuboidal too. This means that the cutting tool 14locates in the reception zone 16 with minimal overhang. In principle, the configuration of the reception zone 16 matches that of the cutting tool 14 such that the cutting tool 14 is wholly receivable within the reception zone 16 with a cooperating arrangement.

The tool holder 12 houses a control unit (not shown) for the acquisition and processing of signals made by the integrated sensing element into data, and also a communication unit (not shown) for transmitting data relating to the condition of the cutting tool 14 from the control unit.

The communication unit is configured to transmit data from the control unit to a data management platform using wireless communication technology such as Bluetooth®, Wi-Fi® or RFID (radio-frequency identification).

The tool holder 12 comprises a chamber 18 defining a cavity into which the control unit and communication unit are received. A space saving slidable cover 20 conceals and reveals the chamber 18 within. The chamber 18 comprises first and second sub-chambers 18a, 18b connected via an intermediate third sub-chamber 18c. The first sub-chamber 18a is located at a distal end of the tool holder 12, remote from the cutting tool 14. The second sub-chamber 18b is located proximate to the reception zone 16 and the cutting tool 14. The first and third sub-chambers 18a, 18c are rectangular in plan view. The second subchamber 18b is generally L-shaped in plan view.

The chamber 18 is machined from a single block of material, such as steel, to varying depths and only to the extent required to accommodate the various components. In other words, the internal configuration is tailored to accommodate the necessary components and bespoke to the shape and size. In this way, the internal configuration of the tool holder 12 is optimised. The depth of the first sub-chamber 18a is greater than the depth of the second and third sub-chambers 18b, 18c.

The first and third sub-chambers 18a, 18c largely correspond to the portion of the chamber 18 situated in the body portion 18a of the tool holder 12, and the second sub-chamber 18b largely corresponds to the portion of the chamber 18 situated in the head portion 18b of the tool holder 12. The control unit and communication unit may be located in either the body portion 18a or the head portion 18b or both. In this embodiment, the first sub-chamber 18a houses both the control unit and the communication unit, hence why the greater depth is required.

Turning now to the cutting tool 14, the bulk material of the cutting tool 14 is polycrystalline diamond (PCD). Alternatively, it could be polycrystalline cubic boron nitride (PCBN) materials. PCD is a brittle material and wear or chipping can occur. For this reason, the working life of a cutting tool 14 is based on recommended maintenance intervals, at which point the cutting tool 14 is changed. However, a cutting tool 14 may, after this predetermined time, still have many potential hours of use. By using sensors or sensing elements to monitor conditions of the cutting tool 14, the tool 14 life can be more accurately monitored and the cutting tool 14 replaced shortly before an unacceptable amount of wear has occurred. This greatly increases the working life of cutting tools 14. For this reason, the cutting tool 14 also comprises an integrated sensing element 22 embedded into an upper surface 24 of the cutting tool 14, as shown in Figures 4 and 5. For monitoring cutting tool 14 health, it is important to have the sensing element 22 close to the cutting tip. However, attaching a sensing element 22 close to the tip often results in adhesion problems. Printing a sensing element 22 on top of the tool often results in damage due to flowing metal chips and higher temperatures. Embedding the sensing element 22 significantly reduces the risk of these problems.

In one embodiment, a recess 26 and two tracks 28 are provided into the surface 24 for receiving the sensing element 22 and associated electrical wiring 30 such that the sensing element 22 and wires 30 are generally flush with the surface 24 of the cutting tool 14. Laser ablation is used to create the recess 26 and tracks 28. The integrated sensing element 22 is a thin film platinum type resistance temperature device or detector (RTD). An RTD is an electrical sensor used to measure temperature. It is typically a wire made of a pure material, and it has an accurate resistance/temperature relationship, which is used to provide an indication of temperature. Platinum and platinum alloys show a linear increase in temperature when heated. During machining, the temperature increases and the resistance of the platinum increases. One degree Celsius increase in temperature changes the resistance in platinum by 0.385 Ohm. Wires 30 connect the sensing element 22 to the control unit and capture the analogue signal.

A heat resistant ceramic coating covers the RTD and any wiring for protection during machining. The RTD is secured in place in the recess using a heat resistant alumina glue.

In another embodiment, as shown in Figure 6, a pair of contacts 32 is provided on the reverse side of the cutting tool 14 in communication with the sensing element 22. The contacts 32 are embedded into a lower surface 34 of the cutting tool 14. Through holes extend from the sensing element on the upper surface 24 of the cutting tool 14 to the contacts 32 on the lower surface 34. This is an alternative arrangement to passing wires externally over the tool surfaces 24, 34. The arrangement advantageously minimises the risk of leads/wires interacting with swarf or external coolant pouring over the cutting tool 14, and consequently short circuiting and/or disconnecting. This is achieved by feeding the leads/wires internally within the cutting tool 14.

The contacts 32 are arranged to abut against a pair of connection pins 36 when a cutting tool 14 is loaded into the tool holder 12. As shown in Figure 7, the pair of connection pins 36 is arranged adjacent to the reception zone 16 of the tool holder 12. The connection pins 36 are in communication with the communication unit. The communication pins 36 are used to pass signals from the sensing element 22 to the communication unit. The communication pins 36 are spring loaded to ensure good electrical contact.

A clamp member 38 is moveably mounted to the head portion 12b about a pin 40 which extends outwardly therefrom. Preferably, the clamp members 38 slides about the pin 40 between a lowered position, in which the cutting tool 14 is clamped in place against the connection pins 36, and a raised position, in which the cutting tool 14 may be removed from the tool holder 12. The pin 40 and clamp member 38 may alternatively be co-operatively threaded and the clamp member 38 screwed into position. If the contacts 32 are not used and externally passing wires 30 used instead, then the clamp member 38 may clamp against a platform (not shown) adjacent to the reception zone 16.

Spacers 42 may be used in or adjacent to the reception zone 16 to accommodate cutting tools of varying depths.

The clamp member 38 and reception zone 16 form part of a tool retention system to selectively retain the tool in place on the tool holder 12. The clamp member 38 is operable to secure the cutting tool 14 in the reception zone 16.

A further sensing element 44 is located within the second sub-chamber 18b, as shown in Figure 9. Preferably, this further sensing element 44 is a vibration sensor. Its close proximity to the cutting tool 14 during machining is paramount since this reduces the noise in the signal being sent to the control unit.

The further sensing element 44 may be an acoustic sensor such as a microphone. A plurality of further sensing elements 44 are envisaged.

In use, a cutting tool 14 having an integrated sensor 22 is coupled with the tool holder 12 and secured in place using the tool retention system 16, 38, 40. During machining, signals relating to the condition of the tool 14 are passed from the sensing element 22 to the control unit for processing into data. The communication unit then wirelessly transmits data from the control unit to a data management platform. Data analytics are then performed and feedback is provided to the user in real time, with instructions and/or guidance as to what adjustments to machining parameters need to be made whilst machining is still in progress, for example the feed rate reduced.

The data management platform may be cloud based and preferably provided in a mobile phone app. Alternatively, the data management platform may be provided in the tool assembly.

In brief, the inventors have found that developed a self-contained tool condition monitoring system that allows easy retrofitting to existing tool machines.

While this invention has been particularly shown and described with reference to embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as defined by the appended claims.

Certain terms and concepts as used herein will be briefly explained.

As used herein, super-hard or ultra-hard material has Vickers hardness of at least 25 GPa. Synthetic and natural diamond, polycrystalline diamond (PCD), cubic boron nitride (CBN) and polycrystalline CBN (PCBN) material are examples of super-hard materials. Synthetic diamond, which may also be called man-made diamond, is diamond material that has been manufactured. A PCD structure comprises or consists of PCD material. Other examples of super-hard materials include certain composite materials comprising diamond or CBN grains held together by a matrix comprising ceramic material, such as silicon carbide (SiC), or by cemented carbide material such as Co-bonded WC material. For example, certain SiC-bonded diamond materials may comprise at least about 30 volume per cent diamond grains dispersed in a SiC matrix (which may contain a minor amount of Si in a form other than SiC).

In general and as used herein, catalyst material for super-hard material is capable of promoting the sintering of polycrystalline material comprising grains of the super-hard material, at least at a pressure and temperature at which the super-hard material is thermodynamically stable. The catalyst material may be capable of promoting the direct inter-growth of grains of the super-hard material and or more generally the sintering of the grains of the super-hard material to form the polycrystalline material. In some examples, the catalyst material may function as a binder material capable of forming a sintered matrix, on its own or in combination with other suitable material, within which the super-hard grains may be dispersed and not necessarily directly inter-bonded with each other. For example, catalyst material for synthetic diamond is capable of promoting the growth of synthetic diamond grains and or the direct inter-growth of synthetic or natural diamond grains at a temperature and pressure at which synthetic or natural diamond is thermodynamically more stable than graphite. Examples of catalyst materials for diamond are Fe, Ni, Co and Mn, and certain alloys including these. Catalyst or binder material for PCBN material may comprising a Ti-containing compound, such as titanium carbide, titanium nitride, titanium carbonitride and or an Al-containing compound, such as aluminium nitride, and or compounds containing metal such as Co and or W, for example.

As used herein, polycrystalline diamond (PCD) material comprises a mass (an aggregation of a plurality) of diamond grains, a substantial portion of which are directly inter-bonded with each other and in which the content of diamond is at least about 80 volume per cent of the material. Interstices between the diamond grains may be at least partly filled with a binder material comprising a catalyst material for synthetic diamond, or they may be substantially empty. Bodies comprising PCD material may comprise at least a region from which catalyst material has been removed from the interstices, leaving interstitial voids between the diamond grains.

A machine tool is a powered mechanical device, which may be used to manufacture components comprising materials such as metal, composite materials, wood or polymers by machining, which is the selective removal of material from a body, called a work-piece. A machine tool may comprise a cutter insert (or simply “insert”) comprising a cutter structure, and the insert may be indexable and or replaceable.

When a machine tool is in use machining a work-piece, pieces of the workpiece will likely be removed and these pieces are referred to as “chips”. Chips are the pieces of a body removed from the work surface of the body by a machine tool in use. Controlling chip formation and directing chip flow are important aspects of tools for high productivity machining and or high surface finish machining of advanced alloys of aluminium, titanium and Nickel. The geometry of chip-breaker features may be selected according to various machining factors, such as the work piece material, cutting speed, cutting operation and surface finish required.

Claims

1. A tool module for real-time tool condition monitoring during machining, the tool module comprising a tool holder and a replaceable cutting tool detachably mounted to the tool holder, the cutting tool comprising an integrated sensing element, the tool holder housing a control unit for the acquisition and processing of signals generated by the integrated sensing element into data, and a communication unit for transmitting data relating to a condition of the cutting tool from the control unit.

2. A tool module as claimed in claim 1, wherein the tool holder comprises a connection point for connecting the tool module to a tool assembly.

3. A tool module as claimed in claim 1 or 2, wherein the communication unit is configured to transmit data from the control unit to a data management platform using wireless communication technology.

4. A tool module as claimed in any one of the preceding claims, further comprising a tool retention system to selectively retain the cutting tool in place on the tool holder.

5. A tool module as claimed in claim 4, wherein the tool retention system comprises a releasable clamp and a reception zone for receiving the cutting tool, the clamp being operable to secure the cutting tool in the reception zone.

6. A tool module as claimed in claim 5, wherein the configuration of the reception zone matches the configuration of the cutting tool such that the cutting tool is wholly receivable within the reception zone with a cooperating arrangement.

7. A tool module as claimed in claim 5 or 6, wherein the reception zone is oriented an angle that is offset from a longitudinal extent of the tool holder.

8. A tool module as claimed in claim 7, wherein an angular position of the reception zone relative to the longitudinal extent of the tool holder is adjustable.

9. A tool module as claimed in any one of claims 5 to 8, wherein the tool retention system comprises one or more connection pins adjacent to the reception zone, the or each connection pin being in communication with the control unit.

10. A tool module as claimed in claim 9, wherein the or each connection pin is spring loaded.

11 .A tool module as claimed in any one of the preceding claims, the cutting tool further comprising one or more integral contacts in communication with the sensing element.

12. A tool module as claimed in claim 11, when dependent on claims 9 or 10, wherein the contacts on the cutting tool are arranged to make contact with the or each connection pin when the cutting tool is loaded into the tool holder.

13. A tool module as claimed in any one of the preceding claims, wherein the cutting tool comprises polycrystalline diamond (PCD) or polycrystalline cubic boron nitride (PCBN) materials.

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14. A real-time tool condition monitoring system comprising a tool module as claimed in any one of the preceding claims and a data management platform for receiving and analysing data received from the control unit.

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Application No: GB1814840.3