Modernisation makes materials testing machines fit for the future again

Materials testing machines represent a substantial capital investment, particularly where high load capacities are involved. After many years of testing materials and components they inevitably begin to show their age.

Depending on their function, components of materials testing machines age through material fatigue, wear or due to various environmental influences. Their technology ages because it no longer reflects the state of the art and present-day requirements, cannot be combined with newer components, or can no longer be maintained due to non-availability of spare parts. Mechanical components such as load frames age very slowly and can generally remain in use for several decades. By contrast, electrical, electronic and IT components age relatively quickly due to the rapid pace of development in this field of technology, limiting their useful life to around ten years.

Competently executed modernizations allow testing machines with a load frame and existing accessories still of considerable value to be brought up to state of the art. A number of important factors should be borne in mind when selecting a suitable modernisation programme: in addition to updated measurement and control electronics and testing software, a modernized electromechanical testing machine also requires a new, maintenance-free AC servo drive. Additional components such as load cells, extensometers and other accessories can continue in use following minor adjustments and adaptations.

Measurement and control electronics
The deciding factor for modernization is invariably the measurement and control electronics. New, digital electronics offer high levels of flexibility and modularity; for reliable test results, synchronized module slots are used to ensure all measurement signals are evaluated within the correct time-frame, while high resolution is guaranteed for the entire measurement range by means of a real-time operating system. For example, Zwick’s testControl  electronics allow load-cell measurement ranges to be expanded down to 0.1% of load cell capacity, eliminating the need for several different load cells and associated changeovers. Test data acquisition rate is up to 500 Hz, enabling detailed analysis of results. During component testing, specimen deformation is often recorded via the machine crosshead position, rather than directly on the specimen via an extensometer. It is therefore essential for the modernized machine to possess the highest possible travel measurement and positional accuracy via the crosshead encoder and for machine and load cell deflection to be compensated for in real time via machine compliance correction.

Even if many machines which are to be modernized do not require CE certification, it is nevertheless essential that current accident prevention regulations are observed. For example, all testing system elements must be integrated into the Emergency Stop circuit, and electronic and software-based test-area monitoring must offer the maximum possible protection for user and test instrument.

Ensuring that modern, highly sensitive electronics comply with electromagnetic compatibility requirements means that they will neither transmit interference signals nor encounter them from pacemakers, mobile phones, overhead cranes or other devices.

The testing machine drive
Modern drives for testing machines – particularly higher performance drives – are no longer based on DC motors, but employ synchronous AC motors. Notable benefits of these include greatly improved resolution and freedom from maintenance due to the elimination of brushes and commutators, while their design enables faster, more dynamic control reactions with greater precision. These highly robust and resilient AC drives also offer considerably reduced energy consumption, while the elimination of intermediate gearing allows accurate, high-speed positioning, reducing test sequence times.

Testing software
A very large number of tests used in industry are regulated via clearly defined standards. These standards are covered by modern testing software, allowing a user with no programming knowledge to start the test directly after inputting the parameters which can be varied according to the standard. Complex, non-standardized test sequences are also possible, of course, these being essential for use in areas such as research.

Standardized interfaces with MS Office application programs or popular  database systems assist in providing reliable data transfer, with customized software and database solutions implemented by highly experienced professional providers.

Software operation should exclude operator error and manipulation by means of suitable plausibility checks. The accuracy of the calculation routines should naturally also be verifiable.

Reliability
Deciding which company should carry out the modernization naturally depends on the scope of the work and the firm’s ability to perform it, but the level of after-sales service available is also an important consideration.
It is vital that testing machine modernization is performed by a reliable, competent company which will provide customer support through the machine’s entire period of operation. Customers need access to a fast, user-friendly hotline, with expert advice facilitated by databases containing the customer’s machine configurations. A comprehensive service network should be available to ensure faults are eliminated swiftly. In this respect it is important that the modernized machine incorporates standard production technology to enable all technicians to perform a repair in the shortest possible time.

Some suppliers guarantee spare part availability for the entire system, rather than just for the components involved in the modernization, for a minimum of ten years. Zwick even offers this for fully modernized machines from brands such as Frank, Schenck-Trebel, Roell & Korthaus, UTS and many other manufacturers.

Summary
A professionally modernized materials testing machine is operationally equal to a new machine and at a significantly lower cost, allowing the user to upgrade the machine even further in the future. This could include testing-software expansions – for new test methods – or retrofitting items such as new digital extensometers. As an example, Zwick offers solutions using appropriate testing software, sensors and test fixtures for twenty different industries, in particular the metals, plastics and automotive industries, as well as for  academic institutes.