Accuracy is measured using ISO. The goal is why concentricity is such a significant challenge in the inspection process within the industry when using CMM as well as traditional measurements. Let's see if we can improve the reproducibility of measurements and the correlation of the results by following these steps in this demonstration.

The animation provides a clear demonstration of the correct application of the term "concentricity."The positions of all the center points and central axes of the circle are saved in the database whenever the actual tolerance feature is a cylinder or the number of circles. When the cylinder is measured around the datum axis, the diameter tolerance zone that must be met in order to be within the diameter tolerance zone is created. Given the circumstances, it is clear that the positions of the datum cylinder and the tolerance cylinder are only a few millimeters apart from one another. There is no separation distance between the parts that are being manufactured given the conditions that are currently in place.

Because the actual axis is like this, which is slightly inclined to the nominal axis, and the measurement of the tolerance cylinder is the same as it was under the previous conditions, the actual datum cylinder has shape error such as cylindricity or straightness error, as shown in the figure. This is due to the fact that the actual axis is like this. Now it is assumed that the tolerance cylinder is not immediately connected to the datum cylinder, but rather that it is very far away from it. This indicates that there is a separation distance between the datum cylinder and the tolerance cylinder, and that all other actual shape and location conditions remain unchanged. In addition to the separation distance that can be seen by calculating the concentricity, the datum axis extends to the tolerance cylinder, which is something that can be understood quite easily at this point. A fixed angle will be applied to either the projection or tilt of the datum axis. In this scenario, the same tolerance zone for the cylinder will be determined, and the calculated concentricity will be higher than the value allowed for tolerance. The explanation is still very straightforward. This distance is where the tolerance cylinder will be positioned, and the mathematical calculation that will follow will produce additional rules for proportional error.

This slide will assist us in arriving at some conclusions, one of which is that there is a direct connection between the datum cylinder Lane and the spacing cmm inspection services that exists between the datum and tolerance cylinders.

For instance, if the length of the datum cylinder is L mm and the spacing cmm inspection services is three times, or 3 L, then the tilt error at the datum cylinder will also spread three times. This is because the spacing cmm services is three times the length of the datum cylinder. As a result, we are able to say that the feature makes the measurement more inaccurate and that it also makes the ratio of the feature  to the datum length more disproportionate. The writer himself, Mr. The following illustration provides a clear demonstration of the issue of having short datum features on long parts. The length L2 that separates the datum cylinder and the tolerance cylinder is significantly greater than the present length, which is denoted by the numeral L1. In accordance with the rule of scale, the relative size of the smaller divisions of the datum cylinder grows noticeably as one moves up in cylinder. Therefore, in order to improve the reliability of measurement, the author suggests a new method to verify the validity of coaxiality tolerance verification if the ratio is not less than 3. This method is only applicable if the ratio is not less than 3. Athens National University of Technology in Greece produced a research report, which was published by the department that deals with mechanical design and control.

On the internet you can find a full research paper that was done by the School of Mechanical Engineering. Please use the following link as a point of reference. Verifying the coaxiality deviation of cylindrical features is one of the most difficult tasks that can be performed with a coordinate measuring machine (CMM). In order to guarantee the reliability of the coaxiality tolerance verification process, a set of standards that are derived from the most recent gdnt standards and the best practices in industrial engineering has been developed.

An cmm services example will be used to illustrate how this method should be used. Figure B presents the results of the research as a conclusion. In order to determine the coaxiality tolerance of the two cylinders, measure the coaxiality of the left cylinder first, and then measure the coaxiality of the right cylinder. The content of the reference slides was taken from a cookbook produced by a reputable CMM manufacturer. The link to the public domain version of this manual can be found on the internet, and it is also provided here for your convenience. In addition, the group recommended using the same method of coaxiality measurement that was covered in the slides that came before it. As an illustration, let's take a look at a real-life case study of coaxiality measurement. We are able to display the results of the measurements in real time because we use both traditional methods and CMM methods. The measured value of the tolerance cylinder is - 32 microns for 2 microns of the reference shaft taper. Now, these two conditions are collectively referred to as the first condition. If we remove the common error of 5 microns, the measured value of the tolerance cylinder is as follows:At the reference cylinder, the first condition has an error that is 10 micrometers.

After some time has passed, when the error at the reference cylinder has been reduced to 2  m, the concentricity that has been measured is +80  m. The observed degree of concentricity at that time was 32 microns. The analysis of the data shows that if the error at the benchmark is decreased by 8 micrometers, the concentricity error will change from +80 micrometers to -32 micrometers, cmm inspection services and the observed absolute change will be -112 micrometers. This demonstrates how sensitivity is reflected in the measurement of concentricity as a data when very short lane cylinders are being processed. The tolerance cylinder is situated at a great distance from the starting point. So, what exactly is the ultimate answer?

When selecting datum features according to their functional relationship with tolerance features and requirements, the corresponding interface features of matching parts shall be selected as datum features. However, the datum features on the parts shall be accessible and have sufficient dimensions to allow them to use the best industrial practices. In the event that the ratio is greater than three, the circular features of the datum and the tolerance must be measured as a single cylinder. Alternatively, the circular features of the datum and the tolerance must be measured more than once.