Micro and Nano Metrology
The demands to manufacturing metrology are set by production, so metrology has to follow the trends of production engineering. Two of the most important trends in production engineering are miniaturization (e.g. implantable insulin pumps, cameras for mobile phones, etc.) and the incorporation of micro and nanotechnology into conventionally sized products, e.g. easy-to-clean surface modifications, embedded systems, etc. Modern manufacturing metrology has to support these developments and explore new dimensions. The new tasks are manifold and addressed by bottom-up and top-down approaches. Bottom-up is the modification of analytical tools from materials science or solid matter physics (e.g. scanning probe microscopy) for metrological purposes; top-down is the miniaturization of conventionally sized metrology devices, such as CMMs, for the measurement of micro features.
The need for metrology in nanotechnology
The continuous miniaturization in manufacturing technologies now allows fabrication of nano-sized samples as well as nanoscale precision and nanoscale features. This progress is achieved by a variety of techniques such as precision engineering, beam sputtering, and photolithography as well as molecular manipulation. Nano-technology products are now found in pharmaceutical industry, microelectronics, and in precision engineering.
Nano-technology is not only a simple continuation of micro technology. It marks the ultimate end of materials science, namely the dimensions where materials properties stop and molecular properties start. One can also say that nano-technology is where molecular features and materials meet. However, the relevance of molecular features is often implicitly. Whereas the study of DNA is obviously related to nano-technology, the “nano”-aspects of sheet metal for its paintability, and the “nano”- aspects of a honed car-engine cylinder easily escaped the uninitiated eye. Nevertheless the two latter examples have been projects within measurement and testing under previous framework programmes.
Below we have listed some areas where dimensional Metrology is widely applied:
1) A flexible, low cost robotic platform for the aerospace sector
A major Airbus research project to develop greater levels of accuracy in automated drilling and riveting has led to the formation of a consortium to build a robotic platform incorporating a Nikon Metrology K-series Optical CMM.
Since industrial robots do not meet Airbus process specifications; Airbus, Nikon Metrology, KUKA and Delmia have formed a consortium to build a new aerospace grade robotic platform.
Initially the system will be applied to two KUKA production robots that jointly pick up an unfinished large wing assembly, and present this part to a drilling/riveting station at a fixed location. Both the drilling/riveting machine and the part being manufactured (through its fixture) are tracked dynamically by means of infrared LEDs and the Nikon Metrology K-series Optical CMM station. As part of the control feedback loop, the position of the part with respect to the machine is systematically returned to the robot controller. This Nikon Metrology/KUKA robotic solution is responsible for positioning wing part holes and rivets at CAD-specified wing locations with accuracy levels 10 times higher than before.
2) Laser Scanner speeds up body geometry verification at Volvo Cars Gent
The innovative Nikon Metrology Cross Scanner is used at Volvo Cars Gent to further accelerate the design-through-manufacturing process for its brand new Volvo XC60 crossover vehicle. By digitizing physical sheet metal and plastic body parts and virtually assembling vehicle bodies in software, Volvo engineers completed pre-production geometry verification nearly twice as fast! 3D laser scanning technology, point cloud processing and virtual assembly shortened physical evaluation of prototypes and eliminates the need for costly specialized verification tooling.
Generally spoken, development in metrology always means to extend the degree of information that can be gathered about an object, or to reduce the costs per unit of measured information. This development can be seen today first of all in the following future trends and new applications: • holistic measurement (multi-sensor metrology, integral measurement with CT, 100% testing)
• Micro / Nano metrology
• cost reduction of standard measurements (quicker, cheaper, more robust and easier to use)
The today used tactile methods are to be complemented or partly replaced by optical 3D measurements depending on needed accuracy and surface properties since they offer the possibility to acquire more points in shorter time. These higher point densities will lead to shorter inspection times in association with increased reliability of the acquired information. Challenging is still to raise the robustness of optical metrology towards optical properties of the work piece and to improve the ease of use in a way that even unskilled personnel is able to achieve valid results with small uncertainty.
INITIAL PRODUCTION INSPECTION (IPI)
The Initial Production Inspection checks the materials or components stored by the manufacturer for the production of your order. It also inspects the initial production run.
This type of inspection identifies defective materials or components, as well as deviations from the customer’s specifications at an early stage, thereby minimizing the occurrence of non-conformities and allowing for timely corrections where necessary.
DURING PRODUCTION INSPECTION (DUPRO)
The During Production Inspection or DUPRO checks semi-finished or finished goods and takes place when a minimum 20% of your order has been produced.
A DUPRO improves your control over production, allows timely correction of defects and improvements to quality. It also allows you to verify that your order is produced according to schedule. Corrective action can be taken accordingly.
FINAL RANDOM INSPECTION (FRI)
The Final Random Inspection checks finished products when at least 80% of your order has been produced and export-packed.
Samples are selected at random, according to AQL sampling standards and procedures.
The FRI ensures that the production complies with your specifications and/or the terms of your purchase order or letter of credit.
Reference: – https://www.cotecna-inspection.com/Home/FinalRandomInspection
The rapid development of manufacturing technology during the first half of the nineteenth century was accompanied by, and in fact could hardly have taken place without, a corresponding development in the design and manufacture of measuring machines, standardization of screw threads and indeed such basic things as engineering flat surfaces and straight edges, all of which are essential for precision manufacturing on a large-scale. Among the famous names involved were Henry Maudsley, who made what is probably the first accurate measuring machine, which he called his Lord Chancellor (now in the Science Museum, London) and Joseph Whitworth, who was trained by Maudsley. Whitworth is credited with developing, while working for Maudsley, the technique of making a flat surface by successively scraping off the high spots from three flats one against each other. In due course, Whitworth was able to make steel plates sufficiently flat that they would stick together. He then went on to produce many measuring machines and introduced his system of standard screw threads. By the middle of the nineteenth century engineering metrology had reached a high level with widely available measuring machines that could measure to 0.0001 inch with corresponding flat surfaces and straight edges also at the disposal of engineering works. Added to these was the codification of the principles of engineering design that allowed rigid structures to be made with well-fitting components connected together so that linear and circular movements could be obtained. All of this comes under the name of kinematic design. In the 1840s, the principles of engineering design were even beginning to be taught at Cambridge University by Robert Willis who is thought to have been the person from whom James Clark Maxwell and William Thomson learnt their principles of mechanisms and engineering design.
The next major advance in engineering metrology was made by Carl Eduard Johansson, who in the last decade of the nineteenth century invented the techniques for making accurate gauge blocks by hand lapping using a domestic sewing machine. He made sets of 102 gauges each having an accuracy of 1 μm. Standards of length in the range from 1 to 201 mm with an accuracy better than 10 μm could be obtained by wringing together combinations of two or more individual gauges.
The stage was thus set for the development of modern metrology.
Reference: – http://rsta.royalsocietypublishing.org/content/363/1834/2307.full
Today two-point measures are still widely used. They are quick, easy and cheap to assess and are often sufficient to ensure the function of a product or to control a process. Especially in the shop floor two-point measures taken with simple devices like calipers or micrometer screws are still dominant, because of their efficiency and ease of use.
On the other hand it is very tedious or even impossible to check more complex attributes of a workpiece (e.g. volume of a complex shaped cylinder head, curvature of formed sheet metal parts) or to do reverse engineering with the help of independent two-point measurements.
With the propagation of affordable and powerful computers coordinate metrology became more and more important for industrial metrology. Coordinate metrology is the most universal measurement technology in mechanical manufacturing. Coordinate measuring machines (CMMs) acquire points on the surface of the workpiece rather than measuring features directly. From this set of points diverse geometric features may be calculated which are afterwards used to evaluate the compliance of the workpiece with the specification.
Today there exist many different types of coordinate measuring machines with differing sizes to measure small objects like housings of mobile phones as well as large objects like engine blocks for cargo ships or bearings for wind generators. Portable systems with position measurement based on triangulation (set-up e.g. with laser trackers) can be beneficially used for measuring extremely large objects, such as complete ships or aircrafts and miniaturized CMMs are able to measure micro parts with nanometer resolution. Special robust CMMs can be used to measure in the shop floor in harsh environment next to manufacturing machines.
9th INTERNATIONAL SYMPOSIUM ON MEASUREMENT AND QUALITY CONTROL (9th ISMQC)
November 21 – 24, 2007, IIT Madras
MANUFACTURING METROLOGY – STATE OF THE ART AND PROSPECTS
Weckenmann A., Kraemer P., Hoffmann J.