Tyre testing with laser precision

In Business Profile, January 20196 MinutesBy NZ Trucking magazineJanuary 20, 2020

A new standard in retread testing is on the block. And you have Hamilton-based Michelin Recamic retreading operation Tyreline to thank for it.

Seven-point-three-eight millimetres. That‘s the exact height of a string of staples. How do we know this? We recently taped some to the side of an old truck tyre and demoed the only tyre testing machine of its kind (so far) to use lasers for inspecting tyre casings for damage. Pressure testing machines are nothing new in the tyre retreading industry. They‘ve been around for 20 years or so, and Matteuzzi, the Italian company that made this G100 SLS (sheet laser system), is one of the best in the game. However, it was with a bit of Kiwi influence that this new machine came to be. Kevin Sigston, retreading technical consultant to Tyreline, explains that the concept has its roots at the Tyrexpo Asia 2017 trade show where he had a conversation with the director of Matteuzzi.

“While looking at their pressure testing machine, I asked for something that could do more than destroy tyres. I wanted to be able to measure whether a tyre is true, has bulges, and any movement as pressure increased,” Sigston says. “It‘s the first machine of its type in the world. We‘ve turned the old school into something that takes away a lot of the guesswork. It lets us know that a tyre will work.” How does the machine work? Taking the concept of the usual, destructive testing machines, the G100 SLS adds a bank of 2500 laser points either side of the tyre from bead to crown shoulder. These measure the changes to the surface of the tyre as the pressure is increased from two bar (29 psi) to the general truck tyre inflation point of six bar (87 psi) and then to the accepted burst pressure of eight bar (116 psi).

A bulge of 1.9mm on the lefthand side of the tyre. The G100 SLS had to be enlarged to accommodate the lasers. It weighs six tonnes.
The magic (deadly) eight bar. A sneaky view inside as the tyre spins through its scan.

“First at two bar the tyre rotates through the sheet lasers measuring, checking, calculating and storing the information. At six bar, the process repeats itself and any growth or movement in the tyre casing will be picked up. Again, at eight bar, any distortions caused by impact damage or movement from old age, for example, will show,” Sigston says. If the machine identifies any defect (as small as 1.7mm) at any stage, the process will automatically stop and it will display a description of the defect on the control panel, while highlighting it on the tyre with a laser pointer. It‘s probably fair to say that our staple experiment was the most obvious ‘defect‘ it‘s yet had to point out.

In the three months that Tyreline has been using the machine, five casings have destructed during testing. However, Sigston points out that these are the exception which only a pressure test could find, as there was no casing movement before destruction. Once a tyre has been through the machine, it receives an individual record that allows for it to be compared should it need to be retested. The machine has been set up to check all incoming tyres for 19.5, 20 and 22.5” rims, although the machine‘s range starts at 16”. Tyre widths up to super singles can be tested. “The machine gives us the ability to test the tyre after the retreading process as well, say if we have to make a major repair to a tyre, or if a tyre goes through final inspection and there‘s something we‘re not happy with. “We‘re really impressed with this machine. It‘s the next generation of what started off as the basic tyre-casing pressure tester concept. All the highly technical types of non-destructive inspection machines that are in the market are good, but this machine is something that is practical and gives both the retreader and the customer greater confidence in the end product. It adds a new practical side to casing inspection,” says Sigston.