The MTXL retread was developed in response to an enquiry from a customer in Finland seeking a retread solution for OE tires fitted on its mining slag pot carriers, according to Ayhan Haliloglou, OTR tire area manager at Marangoni.
"These new premium tires of the size 29.5R29 had a newly designed casing, with higher load capacity and a completely new tread design," Haliloglou said.
"This tire size of 29.5R29 had never been retreaded by Marangoni, so the initial analysis was critical," Haliloglou said. "Our operators checked the different parts of the tires to ensure that the quality and casing integrity was acceptable for the retreading process."
The next step was to remove the old tire material by buffing to precise dimensions until the minimum required amount of base rubber remained.
The tires were used in very demanding and arduous conditions and several small damaged areas were detected. However, added Marangoni, due to it experience in tire repairing this posed no threat to the retreadability.
After studying the application and machine schematics, Marangoni's engineering and production departments proposed a tread depth, a pattern design and a tread compound that would fit this specific operation and be suitable to produce on this casing model.
Once the exact specifications were determined, the production process continued.
"Some people assume that a pre-cured tread is applied to the casing, but this is definitely not the case," Haliloglou said. "In fact, the OTR tire is rebuilt from the casing on as if it was a new tire. The casing is mounted on the building machine and starts to spin, while an extruder arm applies three different layers of compound—base, intermediate and tread—evenly from shoulder to shoulder.
During the inspection/measurement phase of the casing, it became apparent that this specific type of casing was not within the dimensional parameters of an L4 casing, Marangoni said.
As it wasn't feasible to process the casing in a conventional hot-cure mold, Marangoni opted to cure the built tire in the autoclave facilities at its factory in Rovereto. There, the company's grooved the tread patterns using it Recaflex system supported by software programmed with a design optimized to meet the end user's requirements.
"After the computer programming, the tire was mounted on the Recaflex machine and the equipment grooved the tire accordingly. The final inspection procedure included the use of shearography to examine the inner structure of the tire.
"Marangoni is one of the few retreaders in Europe who use a shearography device for OTR tires," Haliloglou said. "Due to this machine, we are able to commit to the highest quality demands, which are always required in heavy-duty mining and industrial operations."
According to Marangoni, the tires have been recently shipped back to Finland, where they have been further inspected and mounted on one of the Valtasiirto's slag pot carriers.