Infinite focus for precision geometry of cutting tools

Geometry of a tool is a crucial factor for tool life-span and proper machining results. Production and quality assurance are also very important to continuously manufacture a defined geometry.

To judge the quality of cutting tools it is necessary to measure their geometry and wear during their use. This allows to take steps to improve the quality and durability of the tools as well as increase the machining speed. In the following article we demonstrate how the 3D metrology device InfiniteFocus can be used for such complex geometry and wear measurements. Due to the special technology it is able to measure very steep surface slopes and delivers highly accurate 3D data with perfectly registered colour information.

The three-dimensional measurement of cutting tools, drill bits and milling cutters is an important aspect of quality control in the industrial process, since the form and wear of cutting edges have a significant influence on the quality of machined parts. Among others the edge geometry influences the possible cutting speed as well as the lifetime of the tools. Since these tools often have a very complex geometry including steep flanks and undercuts, their 3D measurement is a big challenge for optical 3D metrology devices. The evaluation of 2D images is possible for simple measurements where no occlusions occur, however it is not possible for measurements where real 3D information is necessary.

In the last years optical 3D measurement methods have become more and more popular in various fields. The 3D measurement of drill bits and cutting tools however is often hardly possible with optical devices due to their complex geometry and their steep surface flanks. White light interferometers e.g. only allow the measurement of flank angles up to about 30°, which typically is not enough for the evaluation of cutting tool radii.

An optical measurement technology which is suitable for the measurement of steep edges is Focus-Variation [ISO 25178-6. This device fulfils on the one hand the requirement to measure steep flanks up to 87° and on the other hand it allows the measurement of quite large areas with high vertical resolution.

Geometry and wear measurement of cutting tools

Profile Based Roughness

The optical 3D measurement device based on Focus-Variation, is InfiniteFocus by Alicona. In order to perform 3D measurements the device vertically scans the specimen by the sensor while continuously acquiring data. By analyzing the variation of focus during the scanning process for each measurement a complete 3D model is obtained. In addition to the 3D data, the measurement device also delivers true colour information for each measurement position, which is perfectly registered to the height data. This colour information often enables the user to classify regions that have not been used, and those where wear has occurred. Additionally a repeatability measure is analytically estimated for each measurement point. This repeatability measure is an estimation of the standard deviation of the z-coordinate of the measurement point as it would occur in a measurement series. This measure can be used for different investigations such as the estimation of the quality of the measurement points, the filtering of measurement points with bad repeatability, the detection of vibrations or other exterior influences during the measurement.

In order to analyze the geometry of a cutting edge, a special software module is available that analyzes cutting edges on a surface profile based basis.

Surface roughness can be can be either calculated according to the draft of the ISO standard 25178 [ISO 25178-2 in an area-based matter or on a profile based basis according to [ISO 4287, ISO 4288]. The knowledge of the surface roughness has a significant influence on the production since it influences among others how well the material can be chipped. Volume measurement is also important parameter to know the worn of the manufactured tools and used tools.

To perform cost efficient quality assurance, crucial parameters such as radii and angles have to be measured production integrated. Measurements need to be quick, easy and in a high resolution. Usually, tools are measured with a number of different measurement devices during different stages of production.

With InfiniteFocus, a non destructive, high resolution 3D measurement is offered that covers the measurement of all necessary parameters. Clamping and overall usability of the systems is extremely user friendly whereas measurements are achieved very quickly. Process reliability and consequently the overall quality are raised significantly. In a further step, measurements can be performed directly in the grinding machine which shows its inline capability.

The use of InfiniteFocus enables fast and easy handling of production steps which leads to a more cost efficient production with continuous quality at fewer rejections.

With our 3D measurement device InfiniteFocus you measure form and roughness of drills, mills, etc. with only one system.

In R&D, InfiniteFocus is the only system that can measure the full geometry of a tool automatically and therefore most efficient. Meaningful surface analysis for maximizing surface state and consequently tool life-time can be performed with a highly accurate, simple to use and very cost efficient measurement device.