Precision metrology or dimensional metrology is a key aspect of science. It is the field of study of calibration of equipment. It uses measurement tools to quantify the length, angle, distance, and size of a given object. Some of the examples of dimensional metrology are in astronomy, dimensional measurement, where there is a need to have accurate telescopes with large mirrors and sub-micron accuracy. In physics, experiments on accelerators depend on tracking detectors with sensors at micron levels of 10’s of meters. The next-generation light sources will need accurate positioning of over 10’s of Kms. All these can be achieved with the help of precision metrology.
The Goal of Precision Technology
The main goal of this technology is competency in these measurement aspects:
- Accuracy: The real dimension of the part and degree of exactness that the measurement produces.
- Precision: The ability to reproduce the exact measurement every time it is checked.
- Reliability: The accurate results that have to be consistently reproduced by equipment every time it is measured over time.
- Traceability: Validations or checks that show the real dimension of the object and the actual measurements are similar.
What is the difference between Accuracy and Precision?
The data or the measurements that are captured by the equipment may not be perfect as the data accuracy depends on the equipment. It also depends on the conditions under which the measurements are taken. There is a difference between accuracy and precision, it is the difference in measurement between the true value and the measured value. A measurement is considered accurate when the error is small. So experimental errors with regards to measurement have to be accounted for.
Accuracy: It is the measure of how close the measurement is to the actual object. For example, a gauge block measured using a micrometer gives a result of 10.88 mm, then it is not accurate as the gauge block is considered as a standard. If the micrometer measures 10.02 mm then it is considered accurate as the error is negligible and in the range of the artifact.
Precision: It is a measurement that proves the consistency of the results. It refers to how close each measurement is to each other. It is independent of accuracy and it is possible to get precise measurements that are repeatable without scattering or noise. Instrument errors can lead to inaccuracy. For example, if the calibration is not right, the meter may show inaccurate but consistent results.
Tools used for Precision Metrology
In any manufacturing process, one of the most critical aspects is quality control. That ensures the final product is as per the specifications of the client. To perform these inspections, metrology equipment should be used. There are many such tools present in the market that caters to the various requirements of scales and accuracy. Some of the tools used are:
Coordinate Measuring Machine(CMMS)
A coordinate measuring machine is a tool that measures the geometry of objects. It uses a probe to sense the discrete points on the surface. These probes can be of various types including optical, laser, white light and mechanical. The horizontal arm CMMS is one of the types of common CMMS that provide great performance in speed, repeatability, and accuracy. There are a few UK designed and made precision measurement equipment that offers great stability when at high acceleration and velocity. It is used to make panels and full-body inspections, digitizing and reverse engineering in the inspection of large parts like castings, mold tools, etc.
The CMMS is made from various materials, but the most used are granite and aluminum. It is used because of its stiffness to weight ratio. The position of the probes can be controlled automatically or manually. Even the probe angles can be controlled so that the measurement of complex surfaces becomes reachable.
One of the major uses of this tool is that it overcomes the limitations of traditional handheld inspection tools. It can easily inspect complex parts accurately and overcomes the need to have skilled people inspecting the components.
Some of the other main benefits of this tool are:
- Accuracy and repeatability
- Low cycle time even high acceleration and velocities
- Multisensor platforms
The Adjustable Angle Plate
It is a device that holds the workpiece and its operation, which is similar to the universal vise. T-bolts and clamps are used to secure the workpiece to the angle plate. It can be adjusted to any angle so that the tapers and bevels are cut without using any cutters. These tools are made from high-quality cast iron, it is stabilized so that there is no movement.
Toolmakers Precision Vise
Vises are screws that were earlier used to hold the work by tightening the two jaws together. Though it works well in most applications it may not be helpful to use it when working with delicate parts that need finesse. The toolmaker vises are the preferred device for such occasions. These vises are designed so that the delicate parts are held precisely. It can also adjust the clamping pressure accurately so that you can orient the parts in any desired way.
These are precision tools that are useful in marking out steel parts. These blocks have electromagnets in them that emit a magnetic charge. That helps to hold the ferrous metal parts in place. The magnetic V blocks can hold the rectangular parts in such a way that the edges can get machined. They have hardened strips on the blocks for a resistance against wear and tear. These tools are used for drilling, an inspection of the square and round jobs, grinding and light milling.
Magnetic Sine Table
These are instruments that are perfect for a great finish in grinding operations. These tools are highly precise and hence they are useful for many measuring purposes. The design enhances the high precision for an extended period of time. It offers many features like best angle accuracy, firm chuck locking, single-piece precision base, no-slip gauge, etc.
There is a great demand for precision metrology so that the quality of products manufactured can improve. There is constant research being conducted in metrology as that can improve and maintain accuracy for a longer time.