This week saw EUSPEN’s annual conference take place in Copenhagen. If you’re not already familiar with that organization, EUSPEN is a community of influencers drawn from industrialists, researchers, and other authorities. It aims to advance the arts, sciences and technology in ways related to precision engineering, micro-engineering and nanotechnology.
The conference focused on a variety of themes including Measuring Instruments and Machine Tools: Design and Performance, Mechanical Manufacturing Processes, Applications of Precision Engineering in Biomedical Sciences, and many others.
Conoptica’s CU2 Tool was included in a research project led by the Technical University of Denmark, exploring the topic of “A comparison of the performance of tool pre-setting optical systems: On- and off-machine tool assessment”.
For those who weren’t able to attend EUSPEN (probably most of our readers from around the world! J), this blog will outline the presentation but first, let’s provide some context by outlining the basics of tool geometry.
Tool geometry primer
As a starting point, it’s worth stating that there are seven basic types of machine tool, defined by their function. These perform one of the following: Turning, Milling, Grinding, Broaching, Shaping, Planing, or Drilling. The tools share five basic elements, providing further definition: chuck, blade, drill bits, socket, spindle, and motor. These are all important and work together to provide the basic functionality that the machine itself needs to perform a specific task.
Moving on to tool geometry, this relates to the shape and angle of tool face and cutting edge. Geometry depends on the nature of the tool, the work material, and the conditions in which it performs, for instance in the case of cutting took, feed depth, speed of cut, etc.
To some extent, tool geometry is standardized albeit not by a single, universal body. Examples include, for single point cutting tools, the American Standards Association which defines seven elements of geometry: back rake angle, side rake angle, end relief angle, side relief angle, end cutting edge angle, side cutting edge angle, and nose radius.
In contrast the International (or Orthogonal Rake System) standard also uses seven parameters to describe a tool, but (of course!) slightly different ones. Theirs are: angle of inclination, normal rake angle, side relief angle, end relief angle, end cutting edge angle, approach angle, and nose radius. Other standard systems include DIN (German) and British versions (from the BSI).
Why is tool geometry important? Essentially, because its effect is known to be an essential component in the mechanics of turning, which is integral to milling. Tool geometry has a significant influence on chip formation, heat generation, tool wear, surface finish and surface integrity during the working process.
It’s also important because geometry affects tool life. That’s the case as the inclination angle of the tool is a major factor affecting the wear and the surface roughness in hard turning. With an increase in negative rake and inclination angles, tool wear decreases, and the surface roughness increases. And, obviously, the tool affects the quality of the workpiece and the resulting products.
Determining tool geometry
At EUSPEN the underlying subject of the presentation was tool geometry. It addressed how one way this is determined is using tool pre-setters and how it can be accomplished either off- or on-machine. The latter (on-machine) process is particularly challenging. Pre-setting systems are an important part of successful outcomes to the machining process, in this case defined as reliable and accurate tool measurements and attaining the desired accuracies in operations.
Our friends from the Technical University presented research in this area, broadly as follows. In the lab, a reference artefact with a square cross-section was designed from a cylindrical gauge pin (Ø6 mm ± 1 μm) and machined into a square end by wire EDM. The reference artefact was mounted on a tool holder and calibrated using a coordinate measuring machine by repeating measurements twenty times during which the task-specific uncertainty was determined.
The calibrated artefact was later employed to evaluate the performance of the tool pre-setting optical systems for both on- and off-machine instances. Experiments showed the implication of the developed approach for the characterization of tool pre-setting optical systems for tool geometry assessment.
Performance validation
The goal of the research lay in validating the performance of on- and off-machine tool pre-setting optical systems based on a comparator approach. This involved utilizing the ISO 15530 part-3 which provides a method of uncertainty evaluation using calibration artefacts and measurement standards.
Outcomes
The research concluded that the validation of two camera-based tool pre-setting optical systems was accomplished by utilizing ISO 15530 part-3, for both on- and off-machine tool scenarios. The results did show an expanded uncertainty (within 95% CI) of 5.3 μm and 2.1 μm in the measured artefact’s effective radius and the runout, respectively, for on-machine while 2.4 μm and 3.6 μm for the off-machine tool pre-setting system.
This is consistent with the expectation stated earlier. Additionally, we discovered the larger bias in the on-machine tool pre-setter is due to systematic error. At Conoptica, an investigation is underway to determine how to alleviate the bias – but as you can see, participating in this kind of research is essential to our team, so we can deliver the products you need – and drive further enhancements in precision manufacturing.
About Conoptica
Conoptica is the market leader for measurement equipment in the wire & cable industry and has been providing high tech camera-based measurement solutions for the metal working industry since the 1993. We make sure that the metal working industry has access to key quantitative data about their products and tools.