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COMPANY NEWS
VMI - AZ Retrax Meets Evolving Quality Demand
In developed markets, including most of Europe and North America, high quality retreads are an integral part of most manufacturers’ strategic planning, and this is especially true of Bus and Truck businesses. In fact, it is now widely assumed that a single tyre carcass should be capable of reuse up to three times over: once using the
negative side-effects of their own. In particular use of water-based cement requires a longer period of vulcanisation in order to evaporate the water, while there is also a tendency for air bubbles to form in the cement layer, and this reduces the effectiveness of bonding.
AZ RETRAX technology: in detail
At the heart of the AZ RETRAX family of machines is the ability to extrude and smear cushion gum onto a buffed tyre body in a single, automated process. Here’s how it works:
• The body of the tyre is buffed to remove the previous tread, leaving
• Cushion gum can be extruded with precision to cover exactly the right amount of the tyre surface, including wings at the edges, where the tyre design makes this necessary.
Using VMI AZ RETRAX means that precisely the right amount of cushion gum is used, without wastage; skives or holes in the body of the tyre are filled automatically, as part of the process; hot extrusion makes the grip between tyre body and retread more secure; the length of time spent in vulcanising can be reduced and the quality of the tyres produced goes up.
Delivering the benefits
AZ RETRAX is proven to raise productivity, improve tyre quality performance, deliver higher levels of user safety and cut risks to manufacturing staff. Mature retread manufacturers can achieve performance benefits, all of them proven in action over the past decade. These include:
Lower material cost and waste. With the VMI hot extrusion approach there is no need to cut the more expensive calendered cushion gum strips to width and length, since the optimum quantities for each retreaded tyre are automatically applied, with only one type of extruder feed strip as input. That will normally lead to a saving of up to US$2.40 per tyre.
Lower labour costs. Manual skive filling can be largely cut out, and reducing human touch points raises productivity and cuts the man hours needed for making batches of retreads. 1 minute per tyre of human labour is saved in this, or up to 1.5 hours per day.
Lower inventory costs. Only one size of input cushion gum strip is required, so it is no longer necessary to store different sizes and widths.
Higher product quality. Automated extrusion smearing improves both tyre quality and consistency, thanks to improved adhesion of the bonding gum to the buffing pattern and avoidance of air entrapments. Better environmental performance. Using much less or even no VOCs and solvent-based cement sprays means fire hazard is reduced, the toxicity of the process is cut and wastage is controlled. This also saves at least 10 cents for each tyre.
Towards market maturity
Proven in action across the world, AZ RETRAX is now de facto industry best practice, and VMI believes that it will step by step become the “business as usual”
The AZ-Retrax type 6005 with MCTD-60 (60 mm) extruder, for up to 200 retreads per 8 hour shift
original tread and twice more using a retread. A combination of new technology and tighter regulations continue to drive these major changes in the retreading market. Traditional retread technology involves buffing the tyre carcass to remove all trace of the previous tread, and then spraying the surface of the tyre body with solvent-based cement, which includes Volatile Organic Compounds (VOCs). These compounds present numerous disadvantages. They require operators to wear protective clothing and work within an entirely enclosed space to prevent the toxic spray residue from escaping. These compounds will inevitably cause waste, which is highly damaging to the environment, while they are also very flammable, presenting constant fire hazards.
In many countries, notably the US and the EU, regulators have progressively restricted the use of VOCs and VOC cements to reduce risk to health and environmental damage. New concepts, including water-based cement in place of solvents have been trialled with some success, but these have
VMI’s AZ RETRAX: the key driver for change
As the world leader in tyre manufacturing solutions, VMI sees the retread market as increasingly being core business. We keep the potential for reuse top of mind in our research and development activities, helping bus and truck clients, in particular, to develop long-term strategies to integrate premium quality original tyres from VMI machines with high quality retreads, using the most advanced technology in the world: also from VMI.
VMI invested in its unique AZ RETRAX technology over a decade ago and since then most of the key changes in the market have been driven by VMI. These changes have been based on a number of patented advances, of which the most important is hot extrusion smearing of cushion gum to buffed tyre bodies. This approach, now thoroughly proven in the market, brings a high level of automation, reliability and speed to the retreading process.
just the smooth carcass ready for processing.
• Buffing will normally reveal a body that is not in perfect condition. There will be blemishes and holes (known as skives) in the body. In the conventional retread process each of these skives must be accurately filled and smoothed out by the operator, using a handheld extruder. AZ RETRAX technology reduces this task to a minimum, with only the deeper and most unusually shaped holes needing special treatment.
• Instead, AZ RETRAX machines have a highly advanced automated extrusion module, which uses a cushion gum feeding strip as input, plasticising and heating the cushion gum compound till it reaches the right condition. It is then fluid enough to be smeared directly onto the tyre carcass, while being tacky enough to achieve a very high adhesive level.
• The extrusion smearing process will normally fill in all skives, creating a flat surface that is strong and also ready for the new tread to be placed directly onto the tyre body.
46 Retreading Business