SDS Systemtechnik: “Better, safer and faster”

Retreaders – whether small or large, industrial scale operations – can use the best processes, machinery and materials, but if the used casing isn’t good, then the finished retread won’t be any good either. The failure of a retreaded tyre when fitted to a customer’s vehicle is a worst case scenario for retreaders. Therefore, experts such as Stefan Dengler recommend that efforts be made to ensure high-end and comprehensive casing entry control. Visually inspecting casings is of course beneficial, however the SDS Systemtechnik managing director notes that even the most experienced casing inspector cannot see within a tyre. The most important technical aid in this area is shearography, something that every retreader can and should invest in.

“The quality of a retreaded tyre is directly dependent on casing quality,” Stefan Dengler tells Tyres & Accessories. “Damage inside the casing structure is invisible even to very experienced inspectors. Supposedly bad casings – externally – are often defect-free. And optically ‘fantastic’ casings with uniform and clean wear patterns may have breaker edge looseness all round and fail in the next life.” Modern shearography systems are able to give a good view within the casing and identify defects concealed within that experienced inspectors would miss.

Even though the use of such systems in countries such as the United Kingdom, Germany and Austria is not yet 100 per cent, Dengler says it is in Southern Europe – including the large Italian retreading market – where most catching up is required; at present perhaps only every second retreader there works with a shearography system. No retreader, however, should use the cost of such a system, which depending on level of automation and potential casing throughput can lie between 100,000 and 150,000 euros, as a reason to decide against employing shearography in entry control. The process can save money; already damaged casings can be ruled out at an early stage before further costs are incurred during the retreading process by retreading the defective casing. “In this way major savings can be achieved through its use.”

Furthermore, the use of shearography systems need not slow the entry control process, Stefan Dengler adds. As a rule, the conventional visual inspection performed by an entry inspector can be considerably shortened when the inspector is able to ‘take a look’ at the shearography system’s monitor. “When paired with the relevant materials handling technology and barcode system, a marked improvement of throughput at entry control can, to an extent, be seen,” the SDS Systemtechnik managing director adds; with shearography, an experienced casing inspector is “better, safer and faster. This outcome is documented,” Dengler notes.

In this regard, the founder and head of the German company points to a further truth that should convince even smaller retreaders to invest in a shearography system: casings are scarce throughout Europe and prices are regularly rising. For this reason, the economic harm of working on defective casings that will fail later in production or when in use by the customer is even larger for retreaders these days. Therefore, in this present environment investment in a shearography system will be amortised sooner than during times when casings are freely available. Dengler stresses that today there is “in my view” no situation in which a retreader can speak against the acquisition of a shearography system. “That will continue to intensify due to the casing situation.”

Following the new technology’s introduction in the 1970s, German firms such as Gummi-Mayer and Vergölst took delivery of the first shearography systems in Europe – units that Dengler says virtually required the expertise of a physicist to operate; the requirements placed upon staff in relation to the inspection technology were particularly high. These first systems were very costly to maintain and operate. “I contend that I was the first to design and build systems in which the inspection technology was placed in the background. And today these inspection techniques can be applied on a small or large scale without the need to think about the physics involved and the excessive image processing in the background. This has admittedly led to some users these days lacking the necessary diligence when it comes to dealing with the technology and instead placing their faith in technology. This, however, brings us full circle – an experienced inspector and shearography are a strong team. This is, incidentally, a particularly large advantage for smaller retreaders,” Dengler adds.

The application of shearography remains varied throughout Europe and the path towards 100 per cent utilisation is progressing “only very slowly”, Dengler says. And in the retreading of truck tyres – as opposed to aircraft tyres – (exit) inspections are not mandatory, and therefore the demand for shearography systems for truck tyre retreading is not buoyed by legal requirements.

Stefan Dengler established SDS Systemtechnik in 1998; the company came into being as the “Engineering Bureau Dengler”. Today the company reports an annual turnover of three million euros and employs 17 permanent staff at its production site in Calw, Germany. It also runs a representative office in Shanghai. Dengler says he doesn’t define his firm’s business goals based upon growth in turnover. “We see ourselves as a flexible, customer oriented ‘centre of excellence’ in the field of tyre inspection. In addition to shearography, there are other inspection methods that are to an extent unique and facilitate previously unattainable test results and analysis possibilities. In this area, patents that protect our ideas and the resulting advances in technology play a particularly large role.”

With a touch of pride, Dengler mentions a number of key customers. “We are the company that supplies Michelin worldwide and that equips customers, for example Goodyear, with the latest large-scale equipment. And our systems are known and prized around the world for their outstanding image quality, ease of use and robust service. I view aircraft tyre retreading as the premier league and in this sector we supply Bridgestone, Michelin, Goodyear and numerous smaller companies – more than 25 systems globally. Following the supply of facilities used in the OTR new tyre industry, at the start of this year we delivered an entry control facility for the retreading of tyres up to 63-inches to China.”

SDS Systemtechnik’s products are divided according to size and application into three “ITT” series. While the “ITT-1” series is a modular and compact range with single sided manual loading and unloading, one to three measuring heads and automatic tyre turnover and conveyer technology, the speedy and efficient shearography offered by the “ITT-2” is typically applied by larger-scale retreaders and the new tyre manufacturing sector and offers dynamic servo drives plus rapid loading and unloading cycle times in order to optimise the number of tyres inspected each hour. The third range is the “ITT-OTR” series, which allows the inspection of a wide range of tyre sizes up to 63-inches and can be developed according to customer specifications.