Blank for dental tool and method of manufacture thereof

Abstract

A pre-fluted blank 14 for a dental or medical tool includes a shank 22 and a stem 24 extending 5 coaxially from the shank 22, and an end that has not been formed into a cutting end. The stem includes,

Description

This invention relates to a method for use in the manufacture of a tool such as a milling tool for use in dental applications, and in particular for use in the milling of materials during the manufacture of a dental prosthesis such as a crown, bridge or denture. GB2573524 describes a milling tool for use in dental applications, the milling tool comprising a shank for receipt by the chuck of a milling machine, a fluted stem projecting coaxially from the shank, and a ball-nosed end region into which the flutes of the fluted stem project and defining a cutting face or profile which, in use, engages a block of material to be milled using the tool to grind, abrade or otherwise remove material from the block to form the block to a desired shape or profile. The milling tool is typically manufactured by taking a blank of uniform diameter, for example of tungsten carbide or another suitable material, and cutting it in such a manner as to result in the formation of a relatively large diameter shank region and a smaller diameter stem extending from the shank. Then, with such a shaped blank installed within a suitable grinding machine, or in several grinding machines in sequence, material is removed from the blank to form the rod to the shape outlined hereinbefore, forming the flutes upon the stem, and forming the ballnosed end region. Typically, the shaping or forming of the shaped blank to the required form requires the use of several machines, and is a time consuming, slow operation. Similar methods are used in the manufacture of tools with other end profiles such as bull-nosed tools. Whilst such a technique results in the formation of a tool of a desired shape, it is thought that the manufacturing method is inefficient and it is an object of the invention to provide a method for use in the manufacture of a tool in which at least some of the disadvantages associated with known manufacturing methods are overcome or are of reduced effect. According to a first aspect of the invention there is provided a method for manufacturing a tool the method comprising the steps of positioning a pre-fluted blank including a stem and a shank within a machine, using a probe to identify an orientation of the pre-fluted blank to ascertain the position or orientation of at least one flute of the pre-fluted blank, and using the machine to form a cutting end region at the end of the stem of the pre-fluted blank remote from the shank, the flute extending into the cutting end region, the machine being controlled to ensure that the cutting end region is correctly orientated relative to the flutes of the pre-fluted blank. The probe may comprise a physical probe which contacts the pre-fluted blank, in use, to identify the orientation thereof. Alternatively, it may comprise, for example, an optical probe which does not contact the pre-fluted blank. The probe may identify the position or orientation of a flute of the pre-flued blank directly, or alternatively may be operable to detect the position of an orientation indicator provided on the pre-fluted blank. The machine may be used to form other features on the pre-fluted blank. By way of example, it may involve shaping the flute to form a land and / or relief thereon. It will be appreciated that by using the method of the invention, the pre-fluted blank is formed as a separate operation to the formation of the cutting end region. If desired, it may be undertaken using a different machine to that used to form the cutting end region, although the same machine (or same type of machine) could be used to undertake both of these operation, and it could be undertaken at a different location, if desired. By way of example, a manufacturer specialising in the formation of cutting end regions and finishing of the tools may buy in prefluted blanks from another supplier, potentially leading to significant manufacturing efficiencies for the manufacturer. Where an orientation indicator is provided on the pre-fluted blank, by using the machine used to form the pre-fluted blank to also apply the orientation indicator to the pre-fluted blank, and subsequently using the orientation indicator when forming the cutting end region, it will be appreciated that it can be ensured that the machining of the cutting end region, and other features formed on the tool, is properly aligned with the flute or flutes formed on the pre-fluted blank. The orientation indicator may comprise, for example, a flat, groove, recess or upstand provided on the pre-fluted blank. By way of example, it may be provided upon the shank, conveniently adjacent the stem. However, the invention is not restricted in this regard, and the orientation indicator could be located elsewhere. The tool may be of the form described and illustrated in GB2573524. However, it will be appreciated that the tool need not be of precisely this form and that variations or modifications may be made thereto without departing from the scope of the invention as defined by the appended claims. Thus, the invention may be employed in the manufacture of, for example ball-nosed, bull-nosed or flat ended milling tools, drilling tools and the like, and may be employed in the fabrication of tools with any number of flutes. According to a second aspect of the invention, there is provided a method for manufacturing a tool the method comprising the steps of, in a first machine, forming a rod of material to a shape including a shank and a stem extending coaxially from the shank, the stem including, upon its outer surface, at least one generally helical flute, and thus forming a pre-fluted blank, and forming an orientation indicator upon the pre-fluted blank indicative of the orientation of the flutes thereon. The invention further relates to a pre-fluted blank comprising a shank and a stem extending coaxially from the shank, the stem including, upon its outer surface, at least one generally helical upstanding flute, and an orientation indicator formed on the shank or the stem. The invention further relates to a milling tool manufactured in accordance with the method set out hereinbefore. The invention will further be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic view illustrating steps in a method of manufacture of a dental tool, part of which constitutes an embodiment of the invention; Figure 2 is a diagrammatic view illustrating part of a pre-fluted blank; and Figure 3 is a view illustrating a finished milling tool. Referring to the accompanying drawings, a method for use in the manufacture of a milling tool 10 is illustrated. The method is undertaken in two main stages. In a first stage or operation, a rod 12 of a suitable material, for example tungsten carbide or another suitable hard, wear resistant material, is machined to form it into a pre-fluted blank 14. In the second stage or operation, the pre-fluted blank 14 is machined to form it into the shape of the final milling tool 10. The present invention relates primarily to the second of these stages or operations, as illustrated by the right hand part of Figure 1, making use of a pre-fluted blank 14 manufactured in the first stage as illustrated by the left hand side of Figure 1. As shown in Figure 1, in the first stage, the rod 12 is placed into a support 16 forming part of a first machine 18. A cutter in the form of a grinding wheel 20 or the like of the first machine 18 is then moved to a position in which it is able to bear against the surface of the rod 12, cutting or grinding material therefrom to form the rod 12 into the shape of the pre-fluted blank 14. Specifically, the cutter 20 forms the rod 12 to a shape including a relatively large diameter shank 22, and a smaller diameter stem 24 projecting co-axially from the shank 22, the manner in which the stem 24 is formed also resulting in the formation of at least one generally helical groove or flute 26 formed integrally with the stem 24, the flute 26 extending along a significant part of the length of the stem 24. The flute 26 may be formed, if desired, using a suitable cutting or grinding procedure, and the formation of the flute 26 results in the stem 24 being shaped to include one or more integral upstands or ribs 26a, formed integrally with the stem 24. In the arrangement illustrated, three flutes 26, and three upstands or ribs 26a, are provided. However, it will be appreciated that the invention is not restricted in this regard, and arrangements including fewer flutes, for example one or two flutes, or a greater number of flutes such a four flutes, are also possible without departing from the scope of the invention. In addition, whilst the rod 12 is fitted to the support 16, the first machine 18 is preferably operable to form an orientation indicator 28 onto the shank 22 (although in some arrangements, the formation of such an orientation indicator 28 may be omitted). The orientation indicator 28 conveniently takes the form of a flat or a groove or recess cut into the shank 22, for example on a part thereof spaced significantly from the stem 24. However, the axial position of the orientation indicator 28 is not of importance to the invention and it may be located elsewhere, for example on a part of the shank 22 adjacent the stem 24 (as illustrated), or on the stem 24 itself. Furthermore, rather than take the form of a flat, groove or recess, the orientation indicator 28 could take the form of a projection upstanding from the surface of the stem 24 or shank 22. The purpose of the orientation indicator 28 is to provide a datum indicative of the angular orientation or position of the flute or flutes 26 for use during subsequent stages in the manufacturing process. Whilst the description hereinbefore is of an arrangement in which the first operation is undertaken using a single first machine, as described hereinbefore it may be undertaken using several machines in sequence. For example, one machine may be used to form the stem, and another may be used to form the flute upon the stem. The term "first machine" as used herein is intended to cover both situations, and so may refer to more than one machine where the first operation is undertaken using a plurality of machines. Where two or more machines are used in performing the first operation, the orientation indicator (see below) is preferably formed using the same machine as that used to form the flute, so as to ensure that the orientation indicator is properly aligned or orientated relative to the flute. After manufacture of the pre-fluted blank 14, the blank 14 is removed from the first machine 18 and positioned within a second machine 30, supported by a support 32 thereof. In accordance with the invention, the second machine includes a sensor or probe that is operable to detect the orientation of the pre-fluted blank 14, and hence the positions of the flutes thereof. This may be achieved by identifying, using the probe, the orientation or location of the orientation indicator 28, where provided, or may be achieved by directly sensing the position and orientation of at least one of the flutes of the pre-fluted blank 14. The probe conveniently comprises a physical probe that contacts the pre-fluted blank 14 and outputs information that can be used to identify the orientation of the pre-fluted blank. Alternatively, it could comprise an optical probe, for example, that does not physically contact the pre-fluted blank 14. The position or orientation information derived through the use of the probe is supplied to control unit of the second machine 30 for use in controlling the operation thereof. The second machine 30 includes a cutter in the form of a grinding wheel 34 operable to cut or grind the end part of the stem 24 remote from the shank 22 to form a cutting end region 36 thereon, for example of ball-nosed, bull-nosed or flat ended form. The operation of the grinding wheel 34 involves removing parts of the ends of the upstands or ribs 26a to form the cutting end region 36. It will be appreciated that, as shown, the flutes 26 extend into the cutting end region 36. The grinding wheel 34 is further used to generate a required land width and relief along the upstands or ribs 26a. In order to achieve all of this, it is important for the control unit of the second machine to have knowledge of the orientation of the pre-fluted blank 14 and the positions or orientations of the flutes 26, hence the need use a sensor or probe to detect the position of the orientation indicator 28 as described hereinbefore, or to directly identify the orientation of the pre-fluted blank 14, and control the operation of the machine 30 accordingly. After machining of the tool 10 using the second machine 30, the tool 10 is removed from the second machine 30, and a hard material coating or the like may be applied thereto to enhance the wear resistance and extend the useful working life of the tool 10. It will be appreciated that the use of the invention is advantageous in that manufacturing efficiencies may be made, using machines or equipment specifically adapted for use in the steps of the process. The stages of the manufacturing process need not be conducted in the same location as one another, for example the first machine may be located at a first site, from where the pre-fluted blanks 14 are dispatched to a second site at which the second machine 30 is located. The most time consuming part of the manufacturing process is the completion of the first stage mentioned hereinbefore. It is envisaged that by having this stage completed elsewhere, a manufacturer specialising in the formation of the cutting end region and other 5 finishing processes may make significant time savings and efficiency enhancements through using pre-fluted blanks, using the method of the invention to ensure that machining thereof is undertaken correctly. By way of example, time savings in the region of 20% may be made, thus the invention can lead to significant manufacturing efficiencies. 10 Whilst a specific embodiment of the invention is described hereinbefore with reference to the accompanying drawings, it will be appreciated that a wide range of modifications and alterations may be made thereto without departing from the scope of the invention as defined by the appended claims. 06 12 24

Claims

1. A pre-fluted blank to be machined into a dental or medical tool, the pre-fluted blank comprising a shank and a stem having a smaller diameter than the shank and extending coaxially 5 from the shank, and having an end that has not been formed into a cutting end, the stem including, upon its outer surface, at least one generally helical flute, wherein the pre-fluted blank is removed, comprising said end that has not been formed into a cutting end, from the machine in which the pre-fluted blank was formed, the blank further comprising an orientation indicator formed to extend partway along the shank, the orientation indicator being for a probe 10 to identify an orientation of the at least one generally helical flute.

2. The pre-fluted blank according to claim 1, comprising one flute.

3. The pre-fluted blank according to claim 1, comprising a plurality of flutes.

154. The pre-fluted blank according to claim 3, comprising two flutes.

5. The pre-fluted blank according to claim 3, comprising three flutes.20 6. The pre-fluted blank according any one of the preceding claims, wherein the orientationindicator comprises a flat.

7. The pre-fluted blank according any one of the preceding claims, wherein the orientationindicator comprises a groove or recess.

258. The pre-fluted blank according any one of the preceding claims, wherein the orientationindicator comprises an upstand.06 12 249. The pre-fluted blank according any one of the preceding claims, formed from tungsten carbide material.5 10. A method of forming a pre-fluted blank having an end that has not been formed into acutting end, according to any one of the preceding claims, the blankto be machined into a dental or medical tool, the method comprising, in a first machine, forming a rod of material to a shape including a shank and a stem with a smaller diameter than the shank and extending coaxially from the shank, the stem including, upon its outer surface, at least one generally helical flute, 10 to thereby form a pre-fluted blank, and forming an orientation indicator extending partway along the shank, the orientation indicator indicative of the orientation of the flutes on the stem, wherein the method further comprises removing the pre-fluted blank, without an end that has been formed into a cutting end, from the first machine.15 11. The method according to claim 10, comprising forming one flute.

12. The method according to claim 10, comprising forming a plurality of flutes.

13. The method according to any one of claims 10 to 12, comprising forming the orientation 20 indicator with a flat.

14. The method according to any one of claims 10 to 12, comprising forming the orientation indicator with a groove or recess.25 15. The method according to any one of claims 10 to 12, comprising forming the orientationindicator with an upstand.

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