Posted on Nov. 4th, 2019, | By WayKen
The Modern Industry is characterized by the precision of the manufactured elements. It is already evaluated in the tenths of microns and continues to grow incessantly. Actually, the precision of the machine tools that are stated by the manufacturer has grown so much that it becomes harder and harder to measure the actual deviation of the manufactured part. So, new ways of control and metrology equipment are being constantly developed and improved. One of the flexible, fast and precise equipment units for estimating part precision is the Coordinate Measuring Machine.
The Multipurpose Application Of CMM in Contemporary Manufacturing
CMM is the most advanced modern means of automated and manual measurement, it has found a multitude of possible uses in the industry. A lot of different types of CMM make it possible for the tool to be used both on the large (gantry type CMM) and the smallest ( cantilever type CMM machines). A variety of probe types ( mechanical, optical, laser or white light) ensures that you can measure even the surfaces that must not be touched by a probe or any other object. A high degree of CMM automation makes it possible to both use it manually by a machinist and to cut labor by automating it for repeated operations where large production volumes are concerned.
How to use a CMM Machine will depend upon the aims you want to achieve. The level of its flexibility and precision gives the manufacturers a lot of opportunities. You can use CMM after machining or measure the existing parts to redesign them, or you can use it as a part of an automated manufacturing chain. Here are many options and a number of them is listed in the following paragraphs.
What You Have to Do Before Using CMM
CMM machines the most precise instruments to take measurements.They can estimate faults in the parts that are smaller than microns. However, for them to be as precise as they have been made to be, the machinist must thoroughly prepare the equipment to perform measurements. The level of preparation depends on the precision of the measured part. If we talk about the parts with the highest precision (the ones that have a tolerance of IT6 or even smaller) you will have to prepare both the CMM and the area where you are going to carry out the measurements. It must have a specific percentage of humidity and a temperature within the optimum, and must be extremely clean since, at that precision, even tiny specks of dust affect the outcome of the operation.
The CMM itself is usually calibrated by using an extremely precise metal sphere. Its size and form deviation are known to the highest degree. The position of the sphere on the granite working table is known as well ( usually there is a special fixture for it right in the center of the table). The probe must touch the sphere in a number of spots and determine the diameter and the form deviation of it. The measurements are then adjusted depending on their deviation and the sphere is measured again to ensure the correct setups have been saved.
CMM for Linear Surfaces Measurement
The simplest measurements include the tolerances of linear or cylindrical surfaces. In the majority of cases, those are measured by the machinist using a simple micrometer or a gauge right after he has finished machining. So, What is the point of using CM if a simpler tool can be successfully used for this kind of job?
The answer to that question is automation of all the processes. All the modern industry concepts including the futuristic Industry 4.0 include a high degree of manufacturing processes automation where even the additional movements and tasks are done without the machinist. A good example of such a task is quality control. You can program the CMM to perform identical actions on any number of parts in a batch. However, you will need an automated fixture and an additional robot to load and unload the parts before and after the control.
CMM for Complex Surface Measurements
Coordinate Measuring machines' main purpose is to measure complex surfaces. That is why when they are used for such parts as turbine blades, airplane wings, pump impellers and other components with unusual surfaces, the CMM works to their full potential. The automation of such jobs is possible as well if you are making a large batch of the identical parts and they are so precise that you must have every and each one of them checked. However, in the majority of cases, such parts are measured manually by the machinist.
In order to measure a complex surface, the machinist will move the probe along the three axes manually with a remote control until the probe touches the part where the machinist needs it to. Then, after a lot of measurements taken, the points are analyzed and the profiles of the part are connected as splines. Then, the measurements are compared to a 3D-model of the part ( including the acceptable deviations) or to some other data where the required sizes are shown.
CMM for Relationship and Form Deviations
The majority of the high-quality parts are not only characterized by the error of their dimensions but by the precision of their surface forms and their position in relation to each other. Those deviations are especially important for revolving parts to decrease vibration and to ensure the smoothness of movement. CMM measuring for such deviations is not too different from the measurement of complex surfaces. All the form and relationship deviations have a base surface they are compared to. So, in order to achieve the precision requirements, you would have to clamp the part on the base surface and measure the required one. If we are talking about the relationship between two surfaces, just design the fixture to clamp the first surface and measure the second one.
CMM Measuring of Surface Finish
A profiler is the most widespread instrument for surface finish measuring. However, CMM machines can measure the surface finishes of the part as well because of their outstanding precision. However, you would have to change the probe to a special needle. The needle will then move along a surface and determine any kind of microscopic unevenness that the surface finish is formed from.
How WayKen Can Help You
At Wayken, we operate a quality system that has been certified by ISO 9001:2015 standards. If you want to get machined parts with more accurate sizes and shapes, please free feel to contact us in advance to discuss your parts measurement requirements. Learn more, you can upload CAD file and request a quote here.