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SATRA innovation on display

Reviewing some recent innovations that have resulted from a number of different SATRA research projects.

by David Smith

SATRA has been supporting its members with innovation and development in the footwear and leather industry for over 100 years. During this time, the organisation has been at the forefront of many technical advancements, including the development of nearly 450 test methods, which are regularly reviewed and address all aspects of testing footwear and leathergoods.

These methods are rightly regarded as industry standards, and have been widely adopted by footwear manufacturers all over the world. SATRA test methods form the core content of many International footwear standards.

SATRA continues to create new test methods, test equipment and performance guidelines to meet industry needs, as well as revising older methods to ensure that they fit the requirements of the 21st century footwear industry. Please see the article ‘SATRA test method development’ to learn about the effort that goes into the creation of a test method.

This article discusses the innovation and development capabilities within SATRA, giving some operational insight and examples of recent projects.

Types of innovation

The research activities of SATRA’s innovation and development department can be broadly divided into two subsets, which are described as ‘consulting innovation’ and ‘sponsored innovation’.

Consulting innovation takes the form of tailored testing and consultancy for a specific member. This is often conducted in order to help develop a new product, or to develop innovative new methods to appropriately verify its performance. In its simplest form, this could mean modifying existing test methods – for example, enhancing existing test equipment so that testing can be carried out at extreme temperatures.

However, consulting innovation often requires the development of completely new testing techniques and/or equipment to verify a product’s performance.

Consulting innovation for an individual member is completely confidential, as it frequently involves assessing products and ideas not yet on the market. SATRA has a standard ‘Non-Disclosure Agreement’ to cover all such potentially sensitive and confidential work.

Once the customer’s requirements have been defined, focused workshops can be held at SATRA’s facilities to progress the work. These can be tailored to suit the customer and the work, typically last between one and three days, and can be hosted by an appropriate team of SATRA’s consultants.

Members can visit SATRA to view tests being conducted and check results when they are ready, as well as collaborate on test method or prototype development. A range of facilities can be made available, including scanners and three-dimensional (3D) printers for prototyping work, in addition to comfortable and well-appointed meeting rooms with video conferencing facilities. Such workshops can often reduce the time it takes to bring a new product to market.

SATRA’s research projects

SATRA’s sponsored innovation covers projects with potential industry-wide benefits. A unique operating model has permitted the development of a comprehensive annual research programme for the benefit of our members. Some of the projects proposed and considered are completely new, while others are continuations of a previous year’s work. While project topics vary considerably, they blend experimental research with new and innovative thinking.

Some of the projects provide technical support to the international standards committees with which SATRA is involved. These include the European Technical Committee TC161 and International Standards Organisation Committee ISO/TC94/SC3, as well as a number of ASTM committees responsible for safety footwear standards.

SATRA conducts a large quantity of laboratory testing and research to ensure that current test methods and guidelines are still correct. This is especially important when an existing standard can no longer be used to assess a new technology, material or process.

Test methods are very carefully written to ensure that they are not design or material restrictive, nor restrict innovation. Without perfect foresight, however, this does occasionally happen and is therefore addressed.

Development of new tests

One example of the evolution of SATRA’s capabilities is in the area of water resistance testing. Feedback from SATRA members highlighted issues of particular interest, specifically: i) the use and testing of new ‘performance’ materials in sports footwear, ii) new lighter-weight designs, and iii) the customer’s expectation that this kind of footwear can be worn for all manner of extreme sports in challenging conditions and then simply washed clean.

Together with a demand for more severe testing for military and hiking footwear and the rise in popularity of off-road running events and obstacle courses, it was clear that a new test was needed.

As a result, SATRA TM446:2018 – ‘Resistance to waterborne abrasive particulates’ was developed, which subjects footwear to immersed flexing in a deep tank of water. Unlike existing water resistance tests that use clean or even deionised water, SATRA TM446 maximises contaminant-related wear by introducing aluminium oxide powder into the water. This extremely abrasive material is kept in suspension by compressed air bubbling up from the bottom of the tank to create a turbulent and dirty environment. Prolonged flexing in such an environment simulates use in a range of hostile environments, such as running through a muddy river or coastal shallows.

SSG Clifford Coy

With some footwear being worn for extreme sports, SATRA has developed a special test to test product durability

Test methods must change to allow footwear or components in new materials to be treated fairly and tested effectively. This is where SATRA’s empirical research comes in. The original research work is re-assessed and new perspectives are considered, based on modern technology, production techniques, design and materials. Further work may be initiated to confirm the validity of current guidelines and test methods, or, in the case of any discrepancies, to modify performance guidelines. It is important that evidence is gathered supporting any such modifications.

SATRA’s approach is unique, as we have access to all the original research that led to the creation of our own standards. These standards have, in turn, often been used in British or International standards, and are reviewed on a regular basis with fresh research.

Digital last assessment

Using our extensive Global Foot Dimensions survey data and responding to the need for digital-based services, SATRA has developed methods of fit assessing lasts in a digital format. Developed in the 1970s, last assessment is a traditional service which measures the last and compares its metrics with guidelines. The modern way is to measure a digital last. If a digital model is not available, we have the facilities to create one from the physical master to engineering tolerances. The metrics can be compared against global data to reveal population coverage and the last can be modified to ensure the best achievable coverage.

Measurement of slip

Slip measurement is another active area of footwear research. Recent SATRA gait analysis work using a variety of tools and techniques has furthered our understanding and knowledge of this subject. Using tri-axial force plates, underfoot pressure-mapping and high-speed videography, we have re-examined some of the principles of slip to confirm the validity of guidelines and techniques used in slip assessment.

This work and tests on materials permitted the guidelines for top-piece friction to be modified. Parallel developments in slip research have also included the development and verification of mud simulants, and the means to carry out realistic and standardised slip testing on such materials.

Studded sports footwear and aggressively cleated hiking footwear can now be tested on substrates that are appropriate for their intended use, yielding results that are particularly useful for product development.

Recent investigative work also explored the need for a method to measure torsional/rotational slip or grip of footwear on different surfaces, including artificial turf and polyvinyl chloride (PVC). This metric is of increasing interest, due to the prevalence of lower leg injuries that result from high torsional forces being transmitted up the leg during turning motions on footwear. A biomechanically correct test will allow for improved testing of footwear soling designs that permit a measure of free rotation while maximising linear slip resistance. This is especially important where the sports activity for which the footwear is intended involves sudden changes of direction and/or a swivelling motion.

In addition to developing a biomechanically correct test that simulates this motion – to assess the effectiveness of different rotation-control strategies on a variety of flooring surfaces – SATRA has also developed a patented rotating sole mechanism that maintains the wearer’s grip while permitting a degree of controlled rotation relative to the floor. Laboratory trials have shown this device to be capable of reducing and buffering potentially damaging torque build-up in the lower leg.

SATRA facilities available

Considerable SATRA investment into innovation and development in recent years is reflected in the impressive range of test equipment, workshops with machining capabilities and research tools used to progress SATRA projects. These tools are also available to assist with customer enquiries for consulting innovation, where they play a valuable role in product development. They also provide test data to validate marketing claims and fitness for purpose testing.

For example, SATRA has two high-speed cameras which are powerful assessment and measurement tools. These are used for extracting information from destructive tests or dynamic events, where the ability to record movement at high resolution and a high frame rate allow detailed scrutiny of a product’s performance.

SATRA has two high-speed cameras which are used for extracting information from destructive tests or dynamic events

SATRA also employs two thermal imaging cameras, which can record both infrared video footage and still images. The ability to visualise thermal comfort or the spread of heat across a garment or sample of footwear during testing provides an extra level of information, over and above that supplied by other temperature monitoring. Thermal imaging has also been used to predict early failure in furniture and footwear under dynamic test conditions.

SATRA’s optical microscopy facilities have just been upgraded with the acquisition of a new imaging system that provides high-resolution images with vertical stacking for increased depth of field.

Other facilities include a large walk-in climate chamber, controllable from -40°C to +50°C with variable humidity, two 3D printers, digital foot scanners and an extremely high-resolution handheld 3D scanner. Scanning to an accuracy of 0.03mm, this unit was particularly useful during a recent consulting innovation job, which required accurate measurement of the effects of simulated cumulative footfall on a sample of rock taken from a site of special scientific interest. This research involved scanning the sample before and after a period of wear on the SATRA STM 528 Pedatron test machine and then superimposing the two scans.

Another recent investment is an X-ray scanner with a conveyor belt feed and an inspection area large enough to admit boxed safety footwear. In addition to being able to detect the presence of all manner of small foreign objects in footwear or other goods, this system also displays the location of such contaminants, creating images that can be stored for use in technical reports.

Member engagement with innovation

Prioritising the subject areas for the innovation and development programme comes largely through engagement with and feedback from member companies. Members are encouraged to contribute ideas to these programmes, both while visiting SATRA’s facilities or attending our many technical seminars and events, where current work is disseminated.

Surprisingly, some of the best ideas come from quite casual conversations with members, where it becomes clear that there is a common problem to be solved. This is an important member benefit that may lead to a project being funded by SATRA to address the issue.

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Publishing Data

This article was originally published on page 44 of the June 2020 issue of SATRA Bulletin.

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