Measurement technologies step up to production machining needs

Advancements in manufacturing equipment such as Swiss screw machines and high speed CNC-milling systems have revolutionised precision part production. Some Swiss screw machines lathes have guide ways which hold bar stock at lengths of up to 12 feet (300mm) of steel, polymer materials, and composites. Part features are generated simultaneously by moving the bar stock and the cutting tool to create the component. This capability has introduced considerable speed advantages and optimised cutting of shapes to create with higher throughput than ever before. Part accuracy is superb (+/- .00002 in) and part-to-part consistency is greatly improved.

With the evolution of this machinery and their related processes, manufacturers of high-to-medium volume turned parts are facing increased inspection requirements in terms of frequency, feature measurement, and production statistics, as well as rising accuracy specifications. Manufacturers are seeking advancements in measurement technology, such as the speed of measurement cycles, the ability to check parts with greater accuracy, and the ability to precisely measure geometric features and free-flowing forms.

Metrology technology has come a long way in the last five years, and there are tools available to meet such exacting inspection requirements. The right solution of course, depends on the particular needs of the end user. We are going to explore three different, but effective, approaches to accurate measurement of turned parts in the medium-to-high volume production environment.

Non-contact turned part meas-uring centers

The dental implant industry is a compelling example of an industry making use of opto-electronic non-contact measuring systems. Manufacturers are producing many size and shape variations of the main 'core' components of a dental implant via turning/thread cutting as performed using CNC turning technology in a high volume production environment. The implants, also known as prosthetics, are human spare parts, and therefore quality is of utmost importance; all functional dimensions must be inspected on a 100% basis.

The components are very small, typically less than 4mm in diameter, with many dimensions that are very difficult and time-consuming to measure using traditional gauging methods like optical projectors, toolmaker’s microscopes or hand-held tools like micrometers. With increased levels of production and quality demands, and the variety and volume of components produced with increasing measurement criteria, non-contact measuring systems were the next frontier in metrology for this industry.

Today, a single non-contact automatic rotary profile measurement device such as a TESASCAN 25 can be dedicated to a cell of 2 or 3 CNC lathes producing one product type. The object to be measured is fixed in a rotary mandrel and turns (if required) while a light projects the profile onto a collection sensor array, which digitises the image. The software then measures the pre-programmed features using the digitised image as a guide. Typical cycle time for 12 dimensions on a part is 28 seconds. Often, production engineers are responsible for part programming, which is performed on and off-line, while the operators use the measurement system to automatically inspect the components. CNC operators can check all critical external dimensions with a single piece of equipment. Profile devices such as the TESASCAN offer advantages over laser systems both in terms of overall accuracy, speed and the types of features that can be measured.

Once each component is measured, the results can be displayed numerically and graphically together, with the facility to analyse measurement data statistically in the form of histograms, control charts, and capability reports. This capability, previously impossible with manual methods of inspection, has provided a statistical base for determining process treAir Max 90 Ultra 2.0 Essenti