Method for grinding small cutting tools with a grinding machine

Abstract

A method for grinding small or complex shaped rotary cutting tools is provided. The present invention relates to a method for machining a rotary cutting tool (10) on a grinding machine, the method comprising: a) mounting a workpiece (10a) on a spindle (20) of a grinding machine; b) machining a calibration part (CP) of a workpiece (10a) by making one or more impressions (M1, M2, M3, M4) on the workpiece (10a) with one grinding wheel or with a plurality of grinding wheels (W1, W2, W3, W4) of different shapes corresponding to the workpiece (10a), Each trace or each trace (M1, M2, M3, M4) is a geometric feature (R1 W , R2 W , a1 w , a2 w , L w ) and at least one geometric feature (R1, R2, a1, a2, L) corresponding to In the XYZ coordinate system of the grinding machine, the 3D coordinates of the grinding wheel (D1 w , D2 w machining a calibration part (CP) of a workpiece having two position features (D1, D2) corresponding to the calibration part (CP); c) measuring said at least one geometric feature (R1, R2, a1, a2, L) and said two position features (D1, D2) of said trace or each trace (M1, M2, M3, M4) of said calibration part (CP); d) generating a set of instructions for grinding the workpiece (10a) into a final and desired shape of the cutting tool (10) based on the at least one geometric feature and the two position features of the or each trace measured under step c); e) controlling the 3D coordinates of the one or more grinding wheels (W1, W2, W3, W4) in the XYZ coordinate system during a plurality of grinding operations on the workpiece or another workpiece according to the set of instructions to obtain the cutting tool (10). It is equipped with:

Description

[Technical Field]

[0001] The present invention relates to a method for grinding small rotary cutting tools with very high precision. The cutting tools may have, for example, one or more spiral flutes (a type of flank) with an outer diameter of less than 3 mm, and may have a minimum outer diameter of 50 micrometers, or even as small as 30 micrometers. These cutting tools may be milling tools, such as end mill cutters, drills, or complex shaped cutting tools. The present invention also relates to a computer-readable storage medium having stored thereon instructions for causing a grinding machine to perform a calibration routine and thereafter grind the cutting tool according to the methods disclosed herein. [Background technology]

[0002] Trends in ultra-precision and micro-manufacturing are necessitating a rethinking of new machine and process technologies.

[0003] The traditional manufacturing process for cutting tools basically involves the following steps: i) setting parameters of the cutting tool to be manufactured in a preliminary programming and simulation software to generate the contour of the cutting tool to be ground; ii) the operator's selection and preparation of the various types of grinding wheels required to perform the various grinding operations that machine the cutting tool into its final desired shape; ii) the operator selecting and preparing a number of different types of abrasive wheels required to perform the various grinding operations that machine the cutting tool to its final desired shape; iii) measuring the geometry of the selected grinding wheel with a pre-configured optical measuring system; iv) performing a machine setup specific to the cutting tool being machined; v) performing repeated adjustments of the cutting tool geometry by successive cutting of several cylindrical workpieces; The steps include:

[0004] The smaller the dimensions of the cutting tool to be produced, the more iterations are required to obtain the final shape. The geometric deviation between the virtual tool programmed in the software and the initially manufactured tool is due to a number of factors, in particular the inherent accuracy of the preset optical measuring system that measures the shape of the grinding wheel, the inherent accuracy of the grinding machine (especially its calibration), the quality of the setup by the operator, the type of grinding process and the inherent shape of the cutting tool.

[0005] The most common method of correcting dimensional deviations from the desired shape is to measure the cutting tool after machining is complete and correct any inaccuracies, which is not only time-consuming as it requires multiple operations, but also inconvenient as it requires the use of multiple bar stock or cylindrical workpieces to manufacture one cutting tool, resulting in excessive material waste.

[0006] The biggest challenge is knowing, with as much precision as possible, the exact shape, dimensions and position of each wheel in the grinding environment, which is defined by the grinding machine's XYZ coordinate system.

[0007] Currently, calibration measuring devices external to the grinding machine, such as presetting devices or CNC machines with optical measurement capabilities, are used to measure the key geometric features and 3D coordinates of the grinding wheel and calibrate its position and shape within the grinding machine. The accuracy of these external measuring devices is in the order of 10 micrometers.

[0008] For grinding cutting tools with an outer diameter of more than 3 mm, an accuracy of around 10 micrometers is generally sufficient, however, to obtain cutting tools with smaller outer diameters, for example 50 micrometers or even 30 micrometers, the final geometry of the cutting tool must be fine-tuned by repeated trial and error. These inaccuracies lead to significant time loss and large amounts of scrap of rod-shaped or cylindrical workpieces in the production of cutting tools.

[0009] Patent Document 1 discloses a method for machining a workpiece with a desired spiral groove. The method includes grinding a calibration groove into the surface of the workpiece according to a predetermined spiral pattern of the desired spiral groove using a grinding wheel of a grinding machine. The calibration groove has a calibration length equal to or less than the predetermined length of the desired spiral groove and a calibration depth less than the predetermined depth of the desired spiral groove. The method includes determining the size and position of the grinding wheel by measuring the calibration depth, and grinding the desired spiral groove with the grinding wheel using the determined wheel size and position.

[0010] In this manner, no raw material is wasted and the time required to calibrate the machine is advantageously reduced, as the calibration procedure is carried out as an integral part of the machining of the workpiece.

[0011] However, machining the calibration groove requires that the workpiece have a predetermined diameter with the desired shape, which makes this solution unsuitable for calibrating small rotary cutting tool grinders, especially those grinding rotary cutting tools with outer diameters of less than 3 millimeters down to 50 micrometers or even 30 micrometers. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] International Publication No. 2019 / 197931 Summary of the Invention [Problem to be solved by the invention]

[0013] It is therefore an object of the present invention to provide a method for grinding rotary cutting tools such as milling cutters, drills or complex shaped tools having an outer diameter of less than 3 mm and which can be as small as 50 micrometers or 30 to 35 micrometers.

[0014] Another object of the present invention is to provide a method for grinding small rotary cutting tools that is easy to implement.

[0015] It is yet another object of the present invention to provide a method for grinding small rotary cutting tools that streamlines the manufacturing process for large numbers of cutting tools.

[0016] It is an additional object of the present invention to provide a computer readable storage medium storing instructions that, when executed by a processing unit of a grinding machine, perform the methods disclosed herein. [Means for solving the problem]

[0017] These objects are in particular achieved according to the invention by a method for machining a rotary cutting tool, preferably having an outer diameter of less than 3 mm, on a grinding machine, the method comprising: a) mounting a workpiece on a spindle of a grinding machine; b) machining a calibration portion of the workpiece by making one or more impressions on the workpiece with one grinding wheel or with a plurality of grinding wheels of different shapes corresponding to the workpiece, the or each trace having at least one geometric feature corresponding to a geometric feature of the grinding wheel on which the trace was ground; machining a calibration portion of a workpiece, the calibration portion comprising two position features corresponding to 3D coordinates of the grinding wheel in an XYZ coordinate system of the grinding machine; c) measuring the at least one geometric feature and the two position features of the or each trace of the calibration portion; d) generating a set of instructions for grinding the workpiece into a final and desired shape of a cutting tool based on the at least one geometric feature and the two position features of the or each trace measured under step c); e) controlling the 3D coordinates of the one or more grinding wheels in the XYZ coordinate system during grinding operations on the workpiece or another workpiece according to the set of instructions to obtain the cutting tool. It is equipped with:

[0018] In one embodiment, at least one geometric feature of the grinding wheel from which the trace is ground corresponds to an angle or edge radius of said grinding wheel.

[0019] In one embodiment, measurements of one or more geometric features and the two positional features of the or each trace are taken automatically by a laser imaging system integrated into the grinding machine upon completion of grinding of the calibration portion, for example, by performing a laser scan along the calibration portion of the workpiece.

[0020] In one embodiment, each of the plurality of traces is ground using one of a corresponding plurality of grinding wheels of different shapes required to grind the workpiece into the final desired shape of the cutting tool.

[0021] In one embodiment, under step b), the method further comprises a step of directly measuring a geometric characteristic of the grinding wheel or one or each of the grinding wheels using a preset device before machining the or each trace of the calibration part.

[0022] In one embodiment, the method further comprises the step of performing a measurement of the position of the workpiece along one axis of the grinding machine's XYZ coordinate system. Based on the measured position of the workpiece along the one axis and the two position features of the one or each trace of the calibration portion performed in step b), 3D coordinates of the one or each of the plurality of grinding wheels in the XYZ coordinate system of the grinding machine are determined.

[0023] In one embodiment, the multiple traces of the calibration portion are applied adjacent to each other on the workpiece along the longitudinal axis of the workpiece or along a transverse axis extending from one end of the calibration portion to the opposite end.

[0024] In one embodiment, the measurements of at least one geometrical feature and two positional features of each trace carried out in step c) are stored for each grinding wheel of said plurality of grinding wheels. These measurements are taken to perform at least two successive grinding operations on the workpiece to obtain the rotary cutting tool.

[0025] In one embodiment, a first position feature of the or each calibration portion trace defines a first position along a first of three coordinate axes of an XYZ coordinate system of the grinding machine, the first axis coinciding with the longitudinal axis of the workpiece.

[0026] In one embodiment, a second position characteristic of the or each trace of the calibration portion is used to determine a diameter of a corresponding grinding wheel used to perform the or each trace, and based on the diameter, second and third positions along second and third axes of the coordinate system, respectively, are determined to calculate 3D coordinates of the corresponding grinding wheel.

[0027] In one embodiment, the calibration portion is machined into a distal end portion of the workpiece.

[0028] In one embodiment, the rotary cutting tool is made from a workpiece that has been pre-machined to obtain said calibration portion.

[0029] In one embodiment, a rotary cutting tool includes a helical flute that is machined by controlling the 3D coordinate position of the flute wheel based at least in part on at least a first different geometric feature and a second different geometric feature of the flute wheel.

[0030] In one embodiment, the control of the 3D coordinate position of the flute wheel for machining the helical flutes is further based on one or more of three different geometric features of the flute wheel.

[0031] In one embodiment, the cutting tool is an end mill cutter having end flanks that are machined by controlling the 3D coordinates of the end flank wheel based in part on at least one geometric feature of the end flank wheel.

[0032] In one embodiment, an end mill cutter has an end gash that is machined by controlling the 3D coordinate position of the gassing wheel based in part on two distinctive geometric features of the gassing wheel.

[0033] In one embodiment, an end mill cutter includes an outer diameter relief land that is machined by controlling the 3D coordinate position of the outer diameter relief wheel based in part on three distinctive geometric features of the outer diameter relief wheel.

[0034] In one embodiment, the cutting tool comprises spiral flutes and the 3D coordinate position of each of a plurality of grinding wheels is continuously controlled to perform successive grinding operations that grind the workpiece into the desired shape of the cutting tool having an outer diameter of less than 3 mm.

[0035] Another aspect of the present invention relates to a computer readable storage medium having stored thereon a plurality of instructions that, when executed by a computer of a grinding machine, cause the machine to perform a calibration routine to grind a cutting tool. a) obtaining and storing a first set of measurements of geometric and positional features of a particular shape of one of a set of differently shaped grinding wheels or of each grinding wheel, the first set of measurements being obtained by a preset device; b) calculating a first sequence of instructions for machining one or more impressions into the workpiece based on the first set of measurements; c) obtaining and storing (sorting) a second set of measurements of at least one geometric and positional feature of one or more impressions made on the workpiece by the or each corresponding grinding wheel of the set of grinding wheels; The cutting tool comprises: d) calculating a second sequence of a plurality of indications based on the second set of measurements; and e) grinding the cutting tool by executing the second sequence of instructions; and is obtained by

[0036] In one embodiment, during the calibration routine, a first set of measurements is obtained under step a) for each of at least two grinding wheels (preferably at least three grinding wheels) in a set of grinding wheels of different shapes, and a sequence of instructions under step b) is calculated to grind at least two adjacent traces (preferably at least three traces), preferably along a distal portion of the workpiece.

[0037] The invention will be better understood with the aid of the description of several embodiments given as examples and illustrated in the following figures: [Brief explanation of the drawings]

[0038] [Figure 1] FIG. 1 shows a perspective view of a cutting tool in the form of an end mill cutter. [Figure 2] FIG. 2 shows an enlarged perspective view of the cutting tool in the form of an end mill cutter of FIG. [Figure 3] FIG. 3 shows a front view of the end mill cutter of FIG. [Figure 4] FIG. 4 shows a side view of a cylindrical workpiece mounted on the spindle of a grinding machine used for machining the end mill cutter of FIG. [Figure 5] FIG. 5 shows a side view of a stepped bar-shaped workpiece with a pre-machined cylindrical portion. [Figure 5a] FIG. 5a is an enlarged view of the pre-processed portion of FIG. [Figure 6] FIG. 6 shows the workpiece of FIG. 5 after grinding away the calibration portion of the distal end portion of the workpiece. [Figure 7]FIG. 7 shows an enlarged view of the calibration portion of FIG. 6 with several different impressions made by each grinding wheel of a set of different types of grinding wheels. [Figure 8] FIG. 8 is an enlarged view of one of the traces of FIG. 7 made with a first type of grinding wheel. [Figure 9] FIG. 9 is a side view of the first type of grinding wheel. [Figure 10] FIG. 10 is an enlarged view of another trace of FIG. 7 made using a second type of grinding wheel. [Figure 11] FIG. 11 is a side view of a second type of grinding wheel; [Figure 11a] FIG. 11a is a partial side view of an abrasive wheel designed to perform the same type of grinding operation as the abrasive wheel of FIG. [Figure 12] FIG. 12 is an enlarged view of another trace of FIG. 7 made with a third type of grinding wheel. [Figure 13] FIG. 13 is a side view of a third type of grinding wheel. [Figure 14] FIG. 14 is an enlarged view of another trace of FIG. 7 made with a fourth type of grinding wheel. [Figure 15] FIG. 15 is a side view of the fourth type of grinding wheel. [Figure 16a] FIG. 16a shows diagrammatically one sequence of operations (according to the first type) performed by the grinding wheels of the first to fourth types to obtain the calibration portion of FIG. [Figure 16b] FIG. 16b shows diagrammatically one sequence of operations (according to the second type) performed by the first to fourth types of grinding wheels to obtain the calibration portion of FIG. [Figure 16c] FIG. 16c shows diagrammatically one sequence of operations (according to the third type) performed by the grinding wheels of the first to fourth types to obtain the calibration portion of FIG. [Figure 16d] FIG. 16d shows diagrammatically one sequence of operations (according to the fourth type) performed by the grinding wheels of the first to fourth types to obtain the calibration portion of FIG. [Figure 17]FIG. 17 shows a diagram of a pre-calibration measurement of a grinding wheel with a preset device. [Figure 18] FIG. 18 shows diagrammatically the grinding operation of the spiral flutes of a cutting tool carried out by an abrasive wheel according to the prior art. [Figure 19] FIG. 19 shows a cross section of the cutting tool of FIG. [Figure 20] FIG. 20 shows another schematic diagram of the operation of grinding spiral flutes performed by the grinding wheel of FIG. 18 according to the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0039] There is a need to manufacture small rotary cutting tools, typically less than 3 mm in outer diameter, in a reliable and cost-effective manner, particularly milling cutters (milling tools) such as the end mill cutters (end mills) shown in Figures 1 to 3, or drills or tools with complex shapes. For machining cutting tools with such small diameters, conventional calibration mechanisms such as those described above are not suitable because they cannot determine the grinding wheel shape to a very high standard of precision.

[0040] The machining process disclosed herein is suitable for calibrating CNC grinding machines for grinding rotary cutting tools with outer diameters as small as 50 micrometers, or even 30 to 35 micrometers.

[0041] 4 to 7, an elongated workpiece, e.g., a cylindrical workpiece 10a, is mounted on a grinding machine spindle 20. The workpiece is first machined in the form of a stepped bar having a distal portion 10c, as shown in Figures 5 and 5a, whose diameter exceeds the outer diameter of the cutting tool to be ground, typically by between 5 and 20 micrometers. For example, the diameter of the cylindrical distal portion 10c is between 0.205 mm and 0.22 mm for a cutting tool with an outer diameter of 0.2 mm.

[0042] Next, as shown in particular in FIGS. 6 and 7, a calibration portion CP is ground on the distal end portion of portion 10c. This calibration portion CP not only allows the determination of specific geometric features for the set of differently shaped grinding wheels W1, W2, W3, and W4, but also the determination of the three-dimensional coordinates of each grinding wheel in the Cartesian coordinate system of the grinding machine. Furthermore, this is done with very high precision for both the geometric features of the grinding wheels and their three-dimensional coordinates. This precision may advantageously be less than 3 to 4 micrometers, and preferably on the order of 1 micrometer. The stepped bar may be machined directly on the grinding machine used to grind the calibration portion CP for grinding the grinding machine, or on a separate machine.

[0043] 7, the calibration part CP comprises different adjacent machined features M1, M2, M3, M4, which are aligned along the longitudinal axis Z of the cylindrical workpiece 10a or along a transverse axis A extending from one side of the pre-machined part 10c to the opposite side, as shown in FIG. T The number of traces and the specific geometric and positional characteristics of each trace depend on the desired final shape of the cutting tool 10. For cutting tools of simple shapes, one particular type of grinding wheel may be sufficient to machine the cutting tool into the desired shape. In that case, depending on the particular shape of the cutting tool, placing one trace on the calibration section may be sufficient, but in most cases, different characteristic traces M1, M2, M3, M4 are required to determine the different geometric features of the grinding wheel to grind the cutting tool into its final shape.

[0044] However, for most applications, a set of different grinding wheels, such as those illustrated in Figures 9, 11, 13, and 15, is required to grind the cutting tool to the desired shape. In one illustrated embodiment, the end mill of Figures 1-3 is ground using four grinding wheels of different shapes: a flute wheel W1 of Figure 9, an outer diameter flank wheel W2 (hereinafter referred to as the "OD flank wheel") of Figure 11, a gash wheel W3 of Figure 13, and an end flank wheel W4 of Figure 15.

[0045] In the context of the present invention, the term "flute grinding wheel" refers to a grinding wheel having a specific shape suitable for grinding the spiral flutes of the end mill cutter 10 shown in Figure 2. As shown in Figure 9, cutting wheel W1 is an example of a grinding wheel suitable for grinding spiral flutes. Similarly, the term "OD flank wheel" refers to a grinding wheel having a particular shape suitable for grinding the outer diameter flank 18 (peripheral flank) of the end mill cutter 10 of FIG. The grinding wheel W2 shown in FIG. 11 is an example of a grinding wheel adapted for grinding the outer diameter flank face. Similarly, the term "gassing wheel" shall mean any grinding wheel whose shape is specifically adapted for grinding the end gash 16 (end cutting gash) of the end mill cutter 10 of Figure 2. An example of the shape of the gassing wheel W3 is shown in Figure 13. Similarly, the term "end flank wheel" refers to a grinding wheel having a specific shape suitable for grinding the end flank 14 (end cutting edge flank) of the end mill cutter 10 shown in Figure 3. The cup wheel W4 shown in Figure 15 is an example of a grinding wheel suitable for grinding the flank(s) of the end mill cutter 10 of Figure 3.

[0046] Additionally, the term "grinding operation" (singular) shall be understood as one of multiple operations required to grind a cutting tool to its final desired shape. Grinding operations may include, for example, flute groove grinding, gash groove grinding, end flank grinding, outer diameter grinding, etc.

[0047] For example, grinding an end mill cutter 10 having an outer diameter of less than 3 mm requires, in one embodiment, sequential grinding operations using multiple grinding wheels, e.g., four different grinding wheels W1, W2, W3, and W4. In this case, a cylindrical workpiece or blunt distal end portion 10c is machined with four different traces M1, M2, M3, and M4 with the respective grinding wheels W1, W2, W3, and W4 to obtain a calibration portion CP. The general shape of the calibration portion CP shown in FIG. 7 is merely an example of other different shapes that can be characterized by the geometric and positional features of one or more grinding wheels of a particular shape.

[0048] Before a series of grinding operations are performed on the workpiece 10a, in which a calibration portion CP, the shape of which may depend on the final desired shape of the cutting tool to be ground, is ground, the geometric and positional characteristics of each grinding wheel of the set of grinding wheels W1, W2, W3, W4 required for grinding the cutting tool are measured by a preset measuring device. For this purpose, each grinding wheel is mounted, for example, on a stand whose dimensions correspond to the dimensions of the spindle of the grinding machine on which it is intended to be mounted. This allows the grinding wheel to be positioned in exactly the same position relative to the stand and the spindle when mounted. In this way, the 3D coordinates D1 of the grinding wheel in the coordinate system of the grinding machine are calculated. w , D2 w It becomes possible to measure.

[0049] The pre-calibration measurements of each grinding wheel shown in Figure 17 typically consist of measuring the profile of a continuous section of the grinding wheel. The values ​​of the main geometric characteristics of the grinding wheel, such as R1, R2, a1, a2, and the

number

[0050] This calibration portion CP is obtained in this example by performing successive grinding operations on the distal end portion 10b of the cylindrical workpiece 10a, as shown in Figures 16a to 16d: first grinding the first trace M3 with the gash wheel W3, then grinding the second trace M4 with the end flank wheel W4, then grinding the third trace M2 with the outer diameter flank wheel W2, and finally grinding the fourth trace M1 with the flute wheel W1.

[0051] As such, each of these traces M1, M2, M3, and M4 has geometric features R1, R2, a1, a2, and L, and location features D1 and D2, which are specific to the grinding wheel that ground it. The geometric features of this particular grinding wheel can be determined with very high accuracy by measuring the geometric features of the traces. In addition, an additional geometric feature of each trace, referred to here as the location feature, is the 3D coordinates D1 of the grinding wheel in the XYZ coordinate system of the grinding machine. w , D2 w It can be used to determine.

[0052] Various methods may be used to measure the geometric and positional characteristics of the different traces M1, M2, M3, and M4 of the calibration portion CP. In one advantageous embodiment, one or more geometric and two positional characteristics of each trace M1, M2, M3, and M4 are measured using a laser imaging system integrated into the grinding machine. This laser imaging system is already used to periodically measure the diameter and outer shape of cutting tools to ensure unattended, automated, and cyclical production of cutting tools, so that necessary corrections can be made automatically during grinding. This laser imaging system has an accuracy of 3 to 4 micrometers or less, preferably 1 micrometer, and can perform in-situ laser scanning along the longitudinal axis of the calibration portion CP, eliminating the need to remove the workpiece 10a from the spindle 20 for measurement. This allows the cutting tool 10 to be ground to its final desired shape immediately after the laser scanning, streamlining the manufacturing process. This is particularly important when producing cutting tools in large quantities, where once the cutting tool has been ground to its final shape it can be automatically replaced by the workpiece (machined) for production of the cutting tool without human intervention.

[0053] Alternatively, the geometrical and positional features of the different traces M1, M2, M3, M4 of the calibration part CP may be measured outside the grinding machine, for example using a microscope, with an accuracy of less than 5 micrometers (preferably of the order of 1 micrometer).

[0054] Thus, by measuring these different traces M1, M2, M3, M4, the geometrical features of each grinding wheel W1, W2, W3, W4 and their 3D coordinates in the Cartesian coordinate system of the grinding machine can be determined with high precision. This high precision calibration is essential, especially for machining small rotary cutting tools with an outer diameter of less than 3 mm, such as less than 100 micrometers, e.g., 50 micrometers or 30 to 35 micrometers.

[0055] Referring to Fig. 8, the trace M1 of the exemplary calibration portion CP of Fig. 7 was ground by the flute grinding wheel W1 shown in Fig. 9. This trace M1 has several characteristic geometric features specific to the flute grinding wheel, namely, radii R1 and R2, angles a1, a2, and length L, which correspond to the different geometric features R1 of the flute grinding wheel W1 shown in Fig. 9. w , R2 w , a1 w , a2 w , L w This trace additionally has two position features D1 and D2, and the 3D coordinates D1 of the grinding wheel W1 are w , D2 w can be used to determine the Cartesian coordinates (XYZ) of the grinding machine.

[0056] More specifically, the first position characteristic D1 is the z coordinate D1 of the grinding wheel W1. w , i.e., the position along the first axis Z of the horizontal plane of the Cartesian coordinate system. Meanwhile, the second position characteristic D2 is the x-coordinate D2 of the grinding wheel W1.w , i.e., to determine the position along the second axis X of the horizontal plane. Because D2 w corresponds to the diameter of the flute grinding wheel W1. The second position feature D2 is also used to determine the y-coordinate of the grinding wheel W1, i.e., its position in the Cartesian coordinate system along the third axis Y (vertical axis), since the diameter of W1 also corresponds to the third axis.

[0057] However, it is necessary to measure the position of the cylindrical workpiece 10a mounted on the grinding machine spindle 20 and have a reference to determine the exact location of the workpiece 10a along the first axis Z. This measurement can be done, for example, using an on-board laser imaging system to detect the distal end of the cylindrical workpiece 10a. Knowing the exact position of the workpiece 10a along the first axis Z and the first and second position features D1 and D2, the exact 3D coordinates D1 of the grinding wheel W1 can be determined. w , D2 w is determined.

[0058] The numerically controlled grinding machine then calculates a set of instructions (a sequence of instructions) using a known mathematical model of the grinding wheel's motion. The mathematical model is then modified to account for deviations between preset values ​​used in the mathematical model and the values ​​measured at the calibration section CP. These modifications are made to one or more geometric features and two positional features of each grinding wheel of the set of grinding wheels W1, W2, W3, W4 of different types and shapes required to perform different grinding operations to obtain the cutting tool. The sequence of instructions may be pre-programmed, for example, by software based on a predetermined numerical model of the desired shape of the cutting tool.

[0059] The 3D coordinates of the different grinding wheels are then controlled by a series of instructions that subject the workpiece to successive, preferably different, grinding operations to machine the cutting tool into the desired shape.

[0060] In one illustrated embodiment, flute grinding wheel W1 of Figure 9 is used to grind flutes 12 on end mill cutter 10 shown in Figure 2. With such small diameter dimensions, the 3D coordinates of flute grinding wheel W1 in the grinding machine's XZY reference frame must be as accurate as possible. This accuracy is important for successful machine setup and to avoid repeated grinding until the tool is within specifications and tolerances.

[0061] The 3D coordinates are the radius R1 of the flute grinding wheel W1, which is measured directly from the mark M1 on the calibration part CP of the workpiece shown in Figure 8. w and angle a1 w For a particular spiral profile, the calculation is based on the geometric characteristics including at least: R1 and a1, as well as the following geometric characteristics of the flute grinding wheel: width L w and chamfered part a2 w and the transition radius R2 w 。) can also be used in combination with one or more of the following:

[0062] The 3D coordinates of the flute grinding wheel W1 measured in advance by the above-mentioned preset device are the position D1 of the flute grinding wheel W1 in the Cartesian coordinate system of the grinding machine. w , D2 w The movement of the flute grinding wheel W1 in the flute grinding operation is calculated using a known mathematical model according to the geometric features described above and the 3D coordinates of the calibrated flute grinding wheel W1 in the Cartesian coordinate system of the grinding machine.

[0063] Referring to Figure 10, the trace M2 of the exemplary calibration portion CP of Figure 7 was ground by the OD flank grinding wheel W2 depicted in Figure 11. This trace M2 exhibits several characteristic geometric features specific to this grinding wheel, namely, the distinct geometric feature R1 of the OD flank grinding wheel W2 depicted in Figure 11. w , a1 w , a2 wAs for the trace M1 of the calibration part, the trace M2 is the 3D coordinate D1 of the OD relief wheel W2 in the Cartesian coordinate system of the grinding wheel, as previously described for the flute grinding wheel. w , D2 w The present invention provides two additional location features D1, D2 that can be used to determine the position of the object.

[0064] The motion of the OD relief wheel W2 for the OD grinding operation is calculated using a known mathematical model, based on the calibrated 3D coordinates D1 of the OD relief wheel W2 in the Cartesian coordinate system of the grinding machine. w , D2 w and geometric feature R1 w , a1 w , a2 w The OD grinding operation consists of grinding the outer diameter relief land 18 of the end mill cutter 10 shown in FIG.

[0065] 12, the trace M3 of the exemplary calibration portion CP of FIG. 7 was ground by the gashing wheel W3 depicted in FIG. 13. This trace M3 has at least two characteristic geometric features, namely, a radius R1 and an angle a1, which are similar to the corresponding geometric features R1 of the gashing wheel W3 depicted in FIG. w , a1 w As with the traces M1 and M2 of the calibration part, the trace M3 additionally comprises two position features D1, D2, which are the 3D coordinates D1 of the gash wheel W3 in the Cartesian coordinate system of the grinding wheel as described above for the flute wheel. w , D2 w can be used to determine

[0066] The movement of the gash grinding wheel W3 for the gash grinding operation is calculated by using a known mathematical model and considering the above two geometric features R1. w , a1 w and the three-dimensional coordinates D1 of the gashing wheel W3 w , D2 w The gash grinding operation consists of grinding the end gash 16 of the end mill cutter 10 as shown in FIG.

[0067] 14, the trace M4 of the exemplary calibration portion CP of FIG. 7 is ground by the end flank grinding wheel W4 shown in FIG. 15. This trace M4 is ground by the radius R1 of the end flank grinding wheel W4 as shown in FIG. w Similar to the traces M1, M2 and M3 of the calibration portion CP, the trace M4 has one geometric feature R1 corresponding to the three-dimensional coordinates D1 of the end flank grinding wheel, as described above. w , D2 w Two additional location features D1, D2 are provided that can be used to determine

[0068] The movement of the end relief wheel W4 for the end relief grinding operation is determined using known mathematical models and the end relief wheel W4 has at least the above-mentioned geometric characteristics R1. w and the three-dimensional coordinate D1 w , D2 w The end flank grinding consists of grinding the end flank 14 of the end mill cutter 10 shown in FIG.

[0069] The grinding wheel geometry may vary significantly for a particular type of grinding wheel, as a person skilled in the art will determine the desired wheel geometry based on his or her experience. For example, the OD flank wheel W2 shown in FIG. 11 may have different geometries, as shown in FIG. 11a, and may be varied to achieve the same grinding operation. In this case, the geometric feature R1 in FIG. 11 w and a1 w is the geometric feature R1 in Figure 11a. w ' and a1 w ' corresponds to '.

[0070] Therefore, the disclosed method for machining small rotary cutting tools may be used independently of the abrasive wheel geometry designed for a particular type of grinding operation.

[0071] For cutting tools of simple geometry, one or two grinding wheels may be sufficient to machine a cylindrical workpiece to its final shape. For cutting tools of simple geometry where only one wheel is required to perform all grinding operations, it may be necessary to make multiple impressions on a calibration portion of the workpiece during calibration of the grinding machine to determine the different and distinct geometric features of the wheel required to perform all grinding operations. However, in some cases, a single impression may be sufficient to characterize the geometric and positional features of the grinding wheel for grinding a particular cutting tool of simple geometry.

[0072] The disclosed method has the advantage that by grinding a calibration portion on a workpiece that will ultimately be machined by successive grinding operations of different types to obtain the cutting tool, all grinding wheels required to grind the cutting tool to its final desired shape are calibrated, thereby reducing raw material waste.

[0073] The grinding machine includes software with instructions that, when executed by a processing unit of the grinding machine, cause the grinding machine to perform the above-described method for machining a small rotary cutting tool 10 having a core less than 3 mm in diameter. The method performed by the software calibrates the geometric features and three-dimensional coordinates of each grinding wheel W, W2, W3, W4 with high precision, e.g., down to the micrometer.

[0074] In that respect, the software is configured to calculate the main geometric features and the contour of at least one grinding wheel obtained by the preset optical device.

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[0075] A first sequence of primitives is then calculated based on the first set of measurements to control the movement of each grinding wheel W1, W2, W3, W4 to perform (machining of) separate traces M1, M2, M3, M4 along the longitudinal axis of the distal portion of the workpiece. The software then extracts a second set of measurements of at least one geometric feature and two positional features of each trace M1, M2, M3, M4 made on the workpiece.

[0076] As previously mentioned, the locations and geometric characteristics of the distinct traces M1, M2, M3, M4 may be measured by a laser imaging device integrated into the grinding machine, which is mounted to perform a laser scan along the longitudinal axis of the distal portion of the workpiece to obtain a second set of measurements without having to remove the workpiece from the grinding machine spindle.

[0077] The second set of measurements typically has an accuracy of about 1 micrometer, which allows grinding of cutting tools with diameters of less than 3 mm with dimensional deviations remaining within acceptable limits, and can be as small as 50 micrometers, or 30 to 35 micrometers.

[0078] Alternatively, the geometric and positional characteristics of the different traces M1, M2, M3, M4 of the calibration portion CP may be measured external to the grinding machine with micrometer accuracy, for example using a microscope. In this case, the software may grind and acquire data from these measurements that are sent to the grinding machine's computer. Alternatively, the software may provide a user interface with fields for manually entering a second set of measurements.

[0079] A set of instructions for the movement of one or more grinding wheels is calculated based on known mathematical models and according to a second set of measurements for machining the cutting tool.

[0080] In one advantageous embodiment, during the manufacture of a cutting tool, a set of measurements corresponding to each grinding wheel in the set of multiple different grinding wheels can be stored and retrieved for grinding additional cutting tools requiring a given grinding wheel (in the set of multiple different grinding wheels) to grind a specific part.

[0081] In summary, the method disclosed thus far advantageously allows for the accurate preparation of a grinding machine based on different geometrical features of one or more grinding wheels W1, W2, W3, W4 obtained by measuring one or more corresponding traces M1, M2, M3, M4 ground into the workpiece by each grinding wheel, thereby advantageously allowing for the manufacture of rotary cutting tools, in particular cutting tools with spiral flutes, with outer diameters of less than 3 mm (and possibly even values ​​of 50 micrometers, or 30 to 35 micrometers).

[0082] On the other hand, the step of grinding calibration grooves into the surface of a workpiece according to a predetermined helical pattern of the desired helical flutes, as disclosed in Patent Document 1, does not allow for the grinding machine to be prepared as precisely as in the method disclosed therein. In fact, the predetermined helical pattern cannot be used to determine the geometric characteristics of the grinding wheel that grinds such a pattern. More specifically, when grinding helical flutes, the geometric shape of the grinding wheel is not reflected in the flutes. As shown in Figure 18, a grinding wheel W with a simple shape, with a sharp edge at the tip or an edge radius of a few micrometers, will produce a complex cross section of a cutting tool, as shown in Figure 19.

[0083] Regardless of the plane on which the tool cross section is created, it does not reflect the original shape of the grinding wheel W. In addition, in the case of a spiral flute, the inclination angle of the grinding wheel is always greater than the helix angle of the flute, as shown in Figure 20. Therefore, the method disclosed in Patent Document 1 cannot obtain the geometric characteristics of the grinding wheel that has ground the spiral flute, and the angle or edge radius of the grinding wheel cannot be obtained.

[0084] In Patent Document 1, direct measurement of the spiral flutes with a probe does not allow calculations to determine the grinding wheel's geometry, but it does provide an accurate indication of the positional error in the XYZ workspace. To achieve this, the geometry must first be input into the calculation software as accurately as possible. This method is only applicable to cutting tools large enough that the exact geometry of the grinding wheel can be known in advance. This geometry is measured using specific measuring equipment before the wheel is mounted on the machine.

[0085] In contrast, for micro-tools, the geometry of the wheel that generates the spiral flutes is only approximately known. The method disclosed therein allows the exact geometry of the wheel used to grind the spiral flutes to be determined, i.e., not only certain important geometric features, but also their exact location in the XYZ workspace.

[0086] Those skilled in the art will appreciate that the embodiments of the invention described herein, and modifications and variations thereof, can be made without departing from the scope of the invention as defined in the appended claims. For example, the above method can of course be adapted to other rotary cutting tools, e.g., other types of milling tools such as slab mills, face mills, straight fluid mills, etc., or different types of drills, such as multi-fluid drills, straight fluid drills, countersinking drills, etc. [Explanation of symbols]

[0087] Cutting tool 10 (e.g., end mill) Cylindrical workpiece 10a Distal end part 10c Spiral flute (secondary relief) 12 End relief (first end cutting edge relief) 14 End groove 16 Outer diameter relief land (relief surface, margin) 18 Spindle 20 Calibration part CP Evidence M1, M2, M3, M4 Geometric characteristics of traces R1, R2, a1, a2, L Trace location characteristics D1, D2 Grinding wheels W1, W2, W3, W4 Geometric characteristics of the grinding wheel R1 w , R2 w , a1 w , a2 w , L w Grinding wheel position feature D1 w , D2 w

Claims

1. A method for machining a rotary cutting tool (10) on a grinding machine, comprising: a) mounting a workpiece (10a) on a spindle (20) of a grinding machine; b) machining a calibration part (CP) of the workpiece (10a) by making one or more traces (M1, M2, M3, M4) on the workpiece (10a) with one grinding wheel or with a plurality of grinding wheels (W1, W2, W3, W4) of different shapes, Each trace (M1, M2, M3, M4) is a geometric feature (R1) of the grinding wheel that ground the trace (M1, M2, M3, M4). Ｗ , R2 Ｗ , a1 ｗ , a2 ｗ , L ｗ ) at least one geometric feature (R1, R2, a1, a2, L) corresponding to In the XYZ coordinate system of the grinding machine, the 3D coordinates of the grinding wheel (D1 ｗ , D2 ｗ machining a calibration part (CP) of a workpiece having two position features (D1, D2) corresponding to the calibration part (CP); c) measuring said at least one geometric feature (R1, R2, a1, a2, L) and said two position features (D1, D2) of said trace or each trace (M1, M2, M3, M4) of said calibration part (CP); d) generating a set of instructions for grinding the workpiece (10a) into a final and desired shape of the cutting tool (10) based on the at least one geometric feature and the two position features of the or each trace measured under step c); e) controlling the 3D coordinates of said one or more grinding wheels (W1, W2, W3, W4) in said X-Y-Z coordinate system during a plurality of grinding operations on a workpiece or another workpiece according to said set of instructions to obtain said cutting tool (10); A method for machining a rotary cutting tool (10) on a grinding machine, comprising:

2. At least one geometric feature (R1) of the grinding wheels (W1, W2, W3, W4) on which the traces have been ground Ｗ , R2 Ｗ , a1 ｗ , a2 ｗ , L ｗ 2. The method of claim 1, wherein the angle or edge radius of the grinding wheel corresponds to the angle or edge radius of the grinding wheel.

3. 3. The method according to claim 1 or 2, wherein the measurement of one or more geometric features (R1, R2, a1, a2, L) and the two position features (D1, D2) of the or each trace (M1, M2, M3, M4) is performed automatically by a laser imaging system integrated into the grinding machine, for example by performing a laser scan along a calibration portion (CP) of the workpiece (10a), once step b) is completed.

4. 4. The method according to claim 1, wherein each of the plurality of traces (M1, M2, M3, M4) is ground using one of a corresponding plurality of grinding wheels (W1, W2, W3, W4) of different shapes required to grind the workpiece (10a) into the final desired shape of the cutting tool (10).

5. 5. The method according to claim 1, further comprising the step of directly measuring, using a preset device, one or each geometrical feature of the grinding wheel or wheels (W1, W2, W3, W4) before machining the or each trace (M1, M2, M3, M4) of the calibration part (CP) under step b).

6. Further comprising the step of measuring the position of the workpiece along one axis (Z-axis) of an X-Y-Z coordinate system of the grinding machine; Based on the measured position of the workpiece along the one axis and the two position features (D1, D2) of the one or each trace (M1, M2, M3, M4) of the calibration portion performed in step b), the 3D coordinates (D1, D2) of the one or each of the plurality of grinding wheels (W1, W2, W3, W4) in the X-Y-Z coordinate system of the grinding machine are calculated. ｗ , D2 ｗ 6. The method according to claim 1, wherein the .times. ...

7. The plurality of traces (M1, M2, M3, M4) of the calibration portion (CP) are aligned along a longitudinal axis (Z) of the workpiece (10a) or along a transverse axis (A) extending from one end of the calibration portion to the opposite end. Ｔ 7. The method according to claim 1, wherein the first and second electrodes are applied adjacent to each other on the workpiece along the longitudinal axis of the workpiece.

8. The measurement results of at least one geometric feature (R1, R2, a1, a2, L) and two position features (D1, D2) of each trace (M1, M2, M3, M4) performed in step c) are saved for each grinding wheel of the plurality of grinding wheels (W1, W2, W3, W4); and 8. The method according to claim 1, wherein the measurements are taken for at least two consecutive grinding operations on the workpiece to obtain the rotary cutting tool.

9. 9. A method according to any one of claims 1 to 8, wherein a first position feature (D1) of the or each trace (M1, M2, M3, M4) of the calibration portion (CP) defines a first position along a first axis (Z-axis) of three coordinate axes of an X-Y-Z coordinate system of the grinding machine, the first axis coinciding with the longitudinal axis of the workpiece.

10. a second position characteristic of the or each trace (M1, M2, M3, M4) of the calibration portion (CP) is used to determine the diameter (D2) of the corresponding grinding wheel (W1, W2, W3, W4) used to perform the or each trace; 10. The method of claim 9, wherein second and third positions along second and third axes of the coordinate system are determined, respectively, to calculate the 3D coordinates of the corresponding grinding wheel based on the diameter.

11. 11. A method according to any one of claims 1 to 10, wherein the or each trace (M1, M2, M3, M4) of the calibration portion comprises at least one radius (R1, R2) determining at least one radius of a corresponding grinding wheel (W1, W2, W3, W4).

12. 12. The method according to any one of claims 1 to 11, wherein the calibration portion (CP) is machined on a distal end portion (10b) of a workpiece.

13. 13. The method according to any one of the preceding claims, wherein the rotary cutting tool is made from a workpiece (10a) that has been previously machined to obtain the calibration part (CP).

14. The rotary cutting tool has at least a first different geometric feature and a second different geometric feature (R1) of a flute grinding wheel (W1). ｗ , a1 ｗ 14. The method of claim 1, wherein the spiral flutes (12) are machined using 3D coordinate position control of the flute wheel based at least in part on the 3D coordinate position of the flute wheel.

15. The control of the 3D coordinate position of the flute grinding wheel (W1) for machining the spiral flutes is achieved by controlling three different geometric features of the flute grinding wheel (L ｗ , a2 ｗ , R2 ｗ 15. The method of claim 14, further based on one or more of:

16. 14. The method of any one of claims 1 to 13, wherein the cutting tool is an end mill cutter with an end flank that is machined by controlling 3D coordinates of the end flank wheel (W4) based at least in part on at least one geometric feature (R1') of the end flank wheel.

17. 17. The method of claim 16, wherein the end mill cutter comprises a plurality of end gashes machined by controlling the 3D coordinate position of the gashes (W3) based at least in part on two different geometric features of the gashes.

18. The end mill cutter has an outer diameter flank and three different geometric features of the outer diameter flank grinding wheel (R1 ｗ , a1 ｗ , a2 ｗ 18. The method of claim 16 or 17, wherein the outer diameter flank is machined by controlling the 3D coordinate position of an outer diameter flank wheel based at least in part on:

19. 1. A computer-readable storage medium storing a plurality of instructions that, when executed by a computer of a grinding machine, cause the machine to perform a calibration routine to grind a cutting tool, the calibration routine comprising: a) the geometrical characteristics (R1, R2, a1, a2) of the specific shape of one or each grinding wheel of a set of differently shaped grinding wheels (W1, W2, W3, W4); and [Equation 1] obtaining and storing a first set of measurements of the temperature of the object, wherein the first set of measurements is obtained by a preset device; b) calculating a first sequence of instructions for machining one or more traces (M1, M2, M3, M4) on the workpiece based on said first set of measurements; c) retrieving and sorting a second set of measurements of at least one geometric feature (R1, R2, a1, a2, L) and position feature (D1, D2) of one or more traces (M1, M2, M3, M4) made on the workpiece (10a) by the or each corresponding grinding wheel of the set of grinding wheels (W1, W2, W3, W4); d) calculating a second sequence of indications based on the second set of measurements; and e) grinding the cutting tool by executing the second sequence of instructions; and 1. A computer-readable storage medium comprising:

20. For each of at least two grinding wheels, preferably for each of at least three grinding wheels of said set of grinding wheels (W1, W2, W3, W4) of different shapes, a first set of measurements is obtained under step a); and Under step b), the first sequence of instructions is calculated for at least two traces (M1, M2, M3, M4), preferably at least three traces (M1, M2, M3, M4), adjacent along the distal portion of the workpiece, 20. The computer-readable storage medium of claim 19.

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