Need an account? Click here to sign up. Download Free PDF. Cutting tool wear measurement by using active contour model based image processing Villalovos avila. A short summary of this paper. Download Download PDF. Translate PDF. Tool wear needs to be measured in order to evaluate if the tool reaches its design life and should be replaced. In this paper, a new tool wear measurement technology using geometric active contour model based computer image processing is represented.
This developed technology accurately and rapidly extracts the boundaries of the wear region in the captured image. The active contour model theory is applied to develop an image processing algorithm. Many a Flank wear cutting tests were conducted to obtain the tool wear and wear images with these tools were acquired by use of a computer vision system.
The effectiveness of the developed technology is verified. Keywords: Tool wear measurement; geometric active contour model; image processing; cutting tools I. Tool wear affects the outcomes of machining processes such as machined surface quality and b Crater Wear required cutting power for machines.
When tool wear becomes excessive, the tool needs to be replaced. Tool wear is normally Fig. One of the important problems facing the unmanned operation of CNC with the workpiece as it moves past during and after chip machining tool systems is how to monitor tool wear and timely formation. It is crucial to calculate and Crater wear shown in Fig.
KT is replace them. In some cases the KB dimension should be recorded according to its existing location and wear patterns. The crater is formed when tool material is removed illustrates two most commonly seen wear types: Flank wear from the chip face either by the hard particle grinding action or and Crater wear. Flank wear shown in Fig. Flank wear mainly is caused from minimal affinity between materials minimize the tendency for the abrasive wear mechanism.
The ISO standard [5] crater wear. Excessive crater wear changes the geometry of the defines the main tool life criteria. According to the standard, a edge and can deteriorate chip formation, change cutting force tool is considered to have reached its life if the maximum directions and also weaken the edge.
Crater wear is evaluated width of flank wear land VB max is 0. If the flank wear land is regularly area. In this research, the wear region will be measured.
The clearance side, i. The energy function is designed for the snake to converge toward the boundary of the target. It behaves similar to a rubber band placed outside of the object and shirks to reach the boundary of the target. This active contour model can be classified as parametric active contour models, which are represented explicitly as parameterized curves in a Lagrangian framework [11].
This method widely used in Fig. Geometric active contours are first introduced in image processing and computer The measurements of flank and crater wear in cutting tools vision independently by Caselles et al. The model uses level set method to indirect methods [8]. Direct methods usually employ machine represent snake, basic idea is: curve or contour in a plane vision or optical microscope to measure the wear area directly.
Using cross-Section between current. These methods can be used for on-line measurement, two 2-dimensional surfaces has several advantages over the but the accuracy of these methods depends on the sensitivity of traditional parametric active contours. First of all, the contours the measured cutting variable to the tool wear development, represented by the level set function can split into several small and is often unsatisfactory.
Among tool wear monitoring curves or merge naturally into a singular curve during the methods, the computer vision technique with image processing evolution naturally, this topological changes are impossible for has many advantages including the measurement accuracy and a continuously parametric curve. Second, the level set function easiness of implementation. Liu, K. Yamazaki, etc. By applying a In level set formulation of moving fronts or active contours , threshold value based on the histogram of the image, the tool the fronts, denoted by C, are represented by the zero level set wear region is extracted from the original image.
A new accurate and rapid method is required for tool wear measurement. The mathematical tool of active contour model based image which is called level set equation [14]. The function F is called processing has been widely applied to various engineering the speed function.
It is often referred to as the lead angle. It is the angle that prevents interference as the tool enters the work material. It is the angle that allows the tool to cut without rubbing on the workpiece. It is the angle which measures the slope of the face of the tool from the nose toward the rear. If the slope is downward toward the nose, it is negative back rake; and if the slope is downward from the nose, it is positive back rake.
The back-rake angle is zero if there is no slope. It is the angle that measures the slope of the tool face from the cutting edge. If the slope is toward the cutting edge, it is negative side rake; and if the slope is away from the cutting edge, it is positive side rake. If there is no slope the side-rake angle is zero. A convenient way to specify tool angles is by use of a standardized abbreviated system called tool signature sometimes referred to as tool character.
A typical tool signature will always appear in a definite order. The order used is back rate, side rake, end relief, end clearance, end cutting edge, side cutting edge, and nose radius. End clearance and side clearance are omitted unless clearance is used below the relief angles.
Parentheses are placed around these values when they are included in the tool signature. In all three methods, a pocket is machined in the shank material to fit the shape of the carbide insert. The carbide has a lower coefficient of thermal expansion, while the steel has higher. This approach to tooling completely eliminates tool grinding and resharpening.
All edges of the square and triangular inserts can be used, and with negative rake inserts, both top and bottom edges are to be used.
Thus, with a negative triangular insert, there are six cutting edges per insert. Positive rake tools are indexable on one side only see Fig. The tool is assumed to be loaded as a cantilever by tool forces at the cutting edge as shown in fig. The main design criterion for shank size is rigidity. The deflection at the cutting edge is limited to a certain value depending on the size of the machine, cutting conditions and tool overhung. The tool overhung Le is related also to the shank size as well as to end fixity conditions.
Fixed holders are used in work-rotating machines such as lathes, and rotating holders are used in tool-rotating machines, such as boring machines. The simplest form of a boring tool-holder is the boring bar with the boring bit held in a cross hole as shown in Fig 2.
The boring tool bit can be of high speed steel, solid or brazed carbide. These boring bars can also be preset away from the machine on a presetting device. Boring bars are also built with cartridges which hold throwaway type inserts Fig 2. These cartridges are adjustable in both axial and radial direction by means of set-screws.
Boring bars built with more number of cartridges are used for multi-point cutting Fig 2. Boring bars made of steel can be advantageously used for boring holes of length five times the diameter.
But quite often the ratio of bore length to diameter is more. In such cases, the use of conventional boring bars of steel may result in poor surface finish and lower accuracy of the bore. There are number of methods of overcoming this problem. One of the most successful ways is to use a solid carbide boring bar. The modulus of elasticity of carbide is about 2.
Other methods involve brazing a carbide shank to the steel boring bar Fig 2. Principles of some of the damped bars in use are diagrammatically shown in Fig 2.
They can be made to accommodate fly cutters, tool blocks, cartridges, etc. Some line boring bars are also provided with presetting arrangements. It has the means for precisely adjusting the boring tool. Also, there is a provision to place the boring tool in several radial positions to suit various bore sizes. Boring heads are available with either integral shanks or interchangeable shanks. These are also available with two cutting edges at to give a balanced cutting action.
Other applications of the boring and facing head are machining of taper bores and internal recesses. In a recent development, a small built-in stepper motor provides the drive for the tool slide in the boring and facing head. The advantage of such a tool is that it is possible to bore and face a number of steps and also to machine tapers or contours by suitably programming the sequence of operation.
The object of all cutters of this type is to secure rigidity and accuracy of cutter setting in the simplest manner possible. A similar type is used on jig-boring machines, vertical milling machines, and radial drill presses. It is often referred to as a boring head or wobble head. The adjustment for the bore diameter is made by turning the lead screw see Fig. Figure 2. A single screw is used if adjustment of the tool within the bar is not necessary, and two screws are used when such an adjustment is desirable.
One screw is to adjust and back up the cutter, and the second is to lock the cutter into position. The locking screw can be placed on the side of the bar or at the end, whichever is most convenient. However, if the cuts are heavy, it may be better to broach the square hole to a blind stop and drill a round hole much smaller in diameter than the cutter cross section. This avoids weakening the bar in the outside fibres that resist the bending action.
The cutter is located by means of shoulders and is held firmly in place by wedge. This cutter has the advantage of having two cutting edges. Its disadvantage of having no adjustment is largely offset by the fact that this type of cutter blade can be inexpensively made from flat stock.
When commercial boring tools were not available, there was no other solution, but now commercial tools are easily purchased. Standard bars and cutters will do a variety of boring operations, and boring-bar components are standard items for the constructions of special bars.
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