Patent Application
20140238119
Embodiments of the present invention relate to methods for obtaining edge prep profiles of cutting tools. Embodiments of the present invention specifically relate to automated methods for obtaining edge prep profiles of cutting tools with a point sensor, from which edge prep profiles on cutting tools may be measured.
Various types of cutting tools are known and are in use for machining parts. It is well-known that prepping (e.g., honing, chamfering) edges on high performance cutting tools increases tool life and enhances machined part quality, when applied correctly. Many cutting tool manufacturers established various edge prepping processes to get desired cutting edges, for different applications, though they did not have a good way of measuring the edge preps on cutting tools, specifically, complex cutting tools. Moreover, in some cases, when users could not get satisfactory performance from purchased cutting tools, they may hone in-coming cutting tools by themselves. These honed edges over time might become unmanageable.
However, some machined parts are very sensitive to the edge preps of the cutting tools. For example, airfoil thickness may be very sensitive to improper edge prep treatment. A cutting edge with a too heavy hone may cause oversize conditions on the airfoil, due to deflection, resulting in additional, and costly, benching or rework. One with an edge prep that is too light, or with no edge prep at all, could result in undersize conditions, excessive chatter, broken cutters, and possibly even scrap hardware. As the demands for more accurate and robust cutting tools become greater, for creating tight tolerances on machined parts, the edge prep profile is getting more important for it affects the tool life, part quality, especially for the machining process with tight tolerances.
Therefore, it is necessary to know exactly the actual size and shape of a cutting edge.
There are commercial 3D profile measurement systems that can be used to measure the edge prep. One commercial system uses white light interferometry methods to create a very high resolution slice of the edge region. Another commercial system uses focus variation based or confocal imaging methods to define narrow vertical slices of the edge. These technologies focus on how to get high density and accurate data. Both of these systems are microscope based, able to measure only a very small region, typically much less than a millimeter at a time. To cover larger areas requires stitching of data, and continuous repositioning of the cutting tool. The cutting tool setup and repositioning with these current methods requires the operator to position the cutting tool and make sure the target region is within sensor's working range. Usually this manual positioning process is tedious and time consuming, and very dependent upon operator skill to obtain good quality data due to the very limited range of angles and measurement range of these methods.
Accordingly, it would be desirable to develop an improved technique for obtaining edge prep profiles of cutting tools.
Embodiments of the invention provide an automated method for obtaining an edge prep profile of a cutting tool with a point sensor, from which edge prep profile parameters associated with the edge prep on the cutting tool, including but not limited to edge prep radii and chamfer width may be measured. The method comprises steps: (a) scanning edge points of the tool including a target edge point on a target edge using the point sensor, by rotating the tool around its axis, to generate a first point cloud, wherein the first point cloud includes location and orientation information of the target edge point; (b) repositioning the point sensor and tool relative to each other based on the location and orientation information of the target edge point, such that the sensor focus is at a region of interest containing the target edge point; and (c) scanning the region of interest using the point sensor to generate a second point cloud, wherein the second point cloud includes information for edge profile analysis.
Embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. In the subsequent description, well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” or “substantially”, is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value.
Any numerical values recited herein include all values from the lower value to the upper value in increments of one unit provided that there is a separation of at least 2 units between any lower value and any higher value. As an example, if it is stated that the amount of a component or a value of a process variable such as, for example, temperature, pressure, time and the like is, for example, from 1 to 90, preferably from 20 to 80, more preferably from 30 to 70, it is intended that values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc. are expressly enumerated in this specification. For values which are less than one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 as appropriate. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner.
In embodiments of the invention, edge profiles of different types of cutting tools, for example, rotary cutting tools, such as ball end mills, flat end mills, drills and reamers may be captured and measured.
Referring to
It should be noted that the invention is not limited to any particular type of cutting tool. Rather, the example depicted in
In one non-limiting example of the invention, the first stage 220 may move along the X-axis within a range of approximately zero millimeters to approximately fifty millimeters with a resolution of approximately 0.1 micrometers, and may move along the Y-axis within a range of approximately zero millimeters to approximately one hundred millimeters with a resolution of approximately 0.1 micrometers. In other embodiments, the first stage 220 may move along the X-axis and/or the Y-axis within other suitable ranges having any suitable resolution. Additionally, the rotatable element 225 may rotate approximately 360 degrees with a resolution of approximately 0.0001 degree. Alternatively, the rotatable element 225 may rotate within other suitable ranges with other suitable resolutions.
In the illustrated embodiment, the second stage 221 is fixed on the base 21 to movably hold the point sensor 23 and adjacent to the first stage 220. In one example, the point sensor 23 may move on the second stage 221 along the Z-axis. In more particular examples, the point sensor 23 may move along the Z-axis within a range of approximately zero millimeters to approximately 250 millimeters with a resolution of approximately 0.1 micrometers. In other embodiments, the point sensor 23 may move along the Z-axis within other suitable ranges and with other suitable resolutions.
In certain embodiments, the point sensor 23 may also move on the second stage 221 along the X-axis and Y-axis within a range and with a resolution substantially similar to these of first stage 220. In other embodiments, the second stage 221 may be movably disposed on the base 21. Accordingly, in embodiments of the invention, the controller 24 may control the first stage 220 and the second stage 221 to cooperate to position the point sensor 23 at variable distances from the rotary cutting tool 10 to measure the points on the rotary cutting tool 10.
In the illustrated embodiment, the controller 24 comprises at least one of a computer, a database, and/or a processor to control the movement of the stage 22 and the point sensor 23, and to store and analyze the measured data points from the point sensor 23. It should be noted that embodiments of the present invention are not limited to any particular computer, database or processor for performing the processing tasks of embodiments of the invention. The term “computer”, as that term is used herein, is intended to denote any machine capable of performing the calculations, or computations, necessary to perform the tasks of embodiments of the invention. The term “computer” is intended to denote any machine that is capable of accepting a structured input and of processing the input in accordance with prescribed rules to produce an output. The computer may be equipped with a combination of hardware and software for performing the tasks of embodiments of the invention, as will be understood by those skilled in the art. Additionally, the measurement system 10 may further comprise a monitor 25, such as a LCD to display data.
In one embodiment, each of the stages has accuracy better than 1 micron within 20 millimeters travel range. In one embodiment, the working range of the point sensor is about 0.2 millimeter and the point sensor has accuracy better than 1 micron and lateral resolution better than 4 micron.
Methods for obtaining an edge profile of a cutting tool using a measurement system comprising a point sensor, in accordance with embodiments of the present invention, will be described herein below with reference to
As used herein, edge points refer to points located on edges of the cutting tool, formed by a rake face and a primary relief surface or clearance surface.
In one embodiment, the region of the interest is a patch region with a center at the target edge point. In a specific embodiment, the region of interest refers to a region of about 4-millimeter-square with the center of the region of interest at the target edge point.
The step (a) of the method (may be referred to as “coarse scanning” herein below) may comprise: (i) specifying a target edge point on a target edge; (ii) positioning the point sensor and cutting tool relative to each other to allow the sensor beam to pass through the axis of the cutting tool within a given distance from the tip or axis of the cutting tool, wherein the given distance is related to the location of the target edge point on the cutting tool; and (iii) scanning edge points of the cutting tool, including the target edge point using the point sensor, by rotating the cutting tool around its axis to generate a point cloud from the scanning.
As illustrated in
As illustrated in
As illustrated in
Therefore, the sensor beam is able to pass through the target edge point at least one time during rotation of the cutting tool around its axis, for example 360 degrees. Thus, edge points including the target edge point are scanned and a point cloud, which includes location and orientation information of the target edge point, may be generated.
In some cases, the cutting tool may be too close to the point sensor or too far from the point sensor to get an effective point cloud which includes location and orientation information of the target edge point. Under such circumstances, repositioning the point sensor and cutting tool relative to each other and rescanning may be needed. Therefore, in one embodiment, step (a) may further comprise: (iv) filtering noise from the point cloud obtained from step (iii); (v) moving the point sensor and/or cutting tool along a beam direction toward each other and repeating steps (iii) and (iv) if insufficient points remain after filtering for generating a point cloud including location and orientation information of the target edge point, or moving the point sensor and/or cutting tool along a beam direction away from each other and repeating steps (iii) and (iiv) if readout of at least one point in the resulting filtered point cloud is close to a lower boundary of the sensor's working range; and (vi) repeating step (iv) until a point cloud which includes location and orientation information of the target edge point is generated.
In one embodiment, the step (b) of repositioning the point sensor and cutting tool relative to each other comprises: rotating the cutting tool around its axis with an angle, wherein the angle is determined from the location and orientation information of the target edge point. Referring to
When the target edge point is positioned at the planned view position, such that the sensor focus is at the region of interest, it may be started to use the sensor to scan the region of interest to generate a second point cloud, wherein the second point cloud includes information for edge profile analysis.
Under some circumstances, to ensure the region of interest is scanned along an appropriate and effective path, the step (c) of scanning the region of interest may comprise: trial scanning the region of interest to generate a line segment scan path over the region of interest; and rescanning the region of interest along a path generated from the line segment scan path.
Referring to
In some cases, the actual location of the target edge point may vary from the planned view position, and it is not able to get a correct line segment scan path with a single scanning. Under such circumstances, repositioning the point sensor and cutting tool relative to each other and rescanning may be needed. Therefore, in one embodiment, the step of trial scanning the region of interest to generate a line segment scan path over the region of interest comprises the following steps: (a′) scanning the region of interest along a line intersecting the target edge around the target edge point to generate a point cloud from the scanning; (b′) filtering noise from the point cloud obtained from step (a′); (c′) moving the point sensor and/or cutting tool along a beam direction toward each other and repeating steps (a′) and (b′) if insufficient points remain after filtering and insufficient points remain after filtering and readout of the points in the resulting filtered point cloud is close to an upper boundary of the sensor's working range, or moving the point sensor and/or cutting tool along a beam direction away from each other and repeating steps (a′) and (b′) if readout of at least one point in the resulting filtered point cloud is close to a lower boundary of the sensor's working range; and (d′) repeating step (c′) until a line segment scan path is generated.
The trial scanning enables the generation of a correct line segment scan path even when the actual location of the target edge point before trial scanning varies from the planned view position.
Referring to
In one embodiment, the step of rescanning the region of interest along a path generated from the line segment scan path comprises: trimming the line segment scan path; and scanning in a zigzagging pattern the trimmed line segment scan path along the edge direction of the target edge, to generate a second point cloud, wherein the second point cloud includes information for edge profile analysis, such as a point cloud 902 as shown in
Based on the second point cloud, parameters associated with the edge prep on the cutting tool, including, but not limited to, edge prep radii and chamfer width may be measured and calculated.
Embodiments of the invention provide a method capable of determining the shape of the cutting edge to optimize performance of the rotary cutting tool. It uses knowledge about the cutting tool, and location information obtained from a coarse scanning of the cutting tool to scan the cutting edge area to directly obtain measurement points using the point sensor. This method can significantly reduce the cutting tool setup time, and it also can align the local edge prep profile data with the macro cutting tool profile data, enabling visualization of the edge prep profile within the context of the overall cutting tool geometry. This ability to obtain more complete, integrated geometry information of the edge prep with the overall tool geometry permits significant analysis and optimization of cutting tool performance. Improved cutting tool performance can improve both tool life and critical part quality, and reduce machining times on critical parts such as aerospace components.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201110304920.9 | Sep 2011 | CN | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US12/52761 | 8/29/2012 | WO | 00 | 3/20/2014 |
