Engineers at Trelleborg Sealing Solutions have come up with an alternative to the traditional method of sealing the pistons of car shock absorbers. In this innovative process, a flat disc of Turcon® PTFE based material is pulled over the piston. To do this a special assembly machine was engineered and developed by the company.
A car’s shock absorber includes a hydraulic piston, which moves within the absorber housing and damps the vibration from the road. The piston needs a seal to enable the shock absorber to perform. Traditionally a band of PTFE based sealing material was wrapped around the piston manually. The disadvantage of this method is that it tends to be time consuming and it is difficult to achieve high volume throughput, which is something the carmakers demand.
Trelleborg Sealing Solutions designs banded seals for hydraulic pistons in car shock absorbers, along with the innovative machines to fit them
“The manufacturers of shock absorbers really liked the new concept from Trelleborg Sealing Solutions, which gave a banding of consistent quality in high volumes,” says Michael Andersen, General Manager of the Trelleborg Sealing Solutions manufacturing unit in Helsingør, Denmark. “The automated assembly machine technology was ours and the first thought was that we should do the assembly of the bands onto the pistons at our production facility. That though did not make sense from a manufacturing flow point of view. The most efficient point to do this was at the piston manufacturer, after they were sintered. So we proposed we specify and commission the assembly machines, then sell them to the piston manufacturer for use in their production line.”
Innovative piston banding machines engineered by Trelleborg Sealing Solutions are supplied to piston manufacturers
A significant installed base of piston banding machines is now successfully supplying banded pistons to major shock absorber manufacturers and demand continues to rise with more assembly machines commissioned during 2007 than ever before.
The global capabilities of Trelleborg Sealing Solutions allowed it to support its customers as they have expanded their production globally from Europe into the US, Russia and Asia. Assembly machines are currently being supplied to China and rather than ship discs all the way there, the technology for disc production has been transferred to the Trelleborg Sealing Solutions facility in Shanghai.
Details on the shock absorber piston seal and banding process
In the Trelleborg Sealing Solutions automated process for banding shock absorber pistons a precisely machined thin disc of Turcon® is pulled over the piston in an assembly machine. It is engineered to incorporate a lip, providing enhanced friction characteristics. This improves the resistance to wear and overall performance of the shock absorber.
The advanced bronze-filled Turcon® material can operate in temperatures from -40°C/-40°F to above 120°C/248°F at peak pressures of 8 MPa/ 1160 psi with a linear movement of up to 3 m/sec/10 ft/sec. This provides long seal life, contributing to shock absorbers that can meet the demands from car manufacturers of one hundred thousand kilometers (sixty two thousand miles) before replacement.