VMI-AZ builds new extrusion system for giant OTR tires

On September 18-19, 2008, guests from around the globe visited the OTR-Retreading Conference held at VMI in Epe, Netherlands, which was organized by the VMI Group and Kraiburg from Austria.

The highlight of the conference was the presentation and demonstration of new extrusion systems that were developed by the extrusion division of the VMI Group in Runding/Germany for the retreading of giant OTR tires. The system consist of the VMI-AZ BASE CONSTRUCTOR and the STRIP BUILDER.

Base constructor

The BASE CONSTRUCTOR consists of three PIN-type Extruders attached to a special retread extrusion head that supplies base rubber to the tire carcass. This set-up smears rubber onto the tire carcass while the carcass is rotating. Simultaneously skive holes are filled and the shoulder is automatically built at the same time. The so-called cushion-to-casing technology is already well known from VMI-AZ retread machinery for truck tires.

Strip builder

Once the Base Constructor’s job is done, the carcass is moved to the STRIP BUILDER. The strip builder provides a hot extruded rubber strip that is supplied to the tire carcass to build up the new tread according to a menu controlled pattern and shape. The strip is directly applied and compacted onto the carcass, avoiding any air entrapment. To use of a Shark® extruder gear pump system ensures a high dimensional precision of the extruded strip, as well as output consistency.

The OTR base constructor and strip builder are designed to retread tyres up to 63” rim size, 4000mm outer diameter and 1200mm width.

In both innovative machines unique technologies have been applied which offer great advantages over other retreading systems – in quality as well as capacity – and thus costs. The systems are also suitable for the building of new OTR tires.

If you would like to get more information about this brand new process, please contact VMI-AZ Extrusion GmbH Runding/Germany rrothaug [at] vmi-az [dot] com