Retreading is a process through which we can use our old tyres. In this method, a worn casing of a tyre that has a good structural quality is taken off and put through a process in which it gets a completely renewed tread and sidewall rubber. After that, the revamped tyre is taken forward for a curing process in which the new rubber is vulcanized to the original casing and hence, the tyre gets a newly made tread pattern. Over the years, a lot of development has taken place in the tyre manufacturing industry across the world. High standard tyres are being manufactured using premium technologies, so that they could perform flawlessly not only in their ‘first life’, but also in their second and even sometimes third life. So, along with that, the retreaded tyre industry is also growing, as stronger tyre casings, enhanced re-manufacturing techniques and high quality rubber compounds are being used.
A retreaded tyre commences its life as a worn out tyre. There is a need for retreading when you find out that the tread is down to 2-3 mm or if it has been re-grooved earlier, or if your tyre has puntures and needs a repair. In these cases, you need to take your tyre to an experienced technician who will check and inspect the tyre to see whether it is in a condition to get retreaded. If the expert finds it alright, then you can go for a retreading of your tyre.
Advantages of Retreading of tyre:
There are several advanges of retreading such as:
- Retreads are quite safe and are being used in all kind of vehicles nowadays. May it be taxis or trucks, school buses or military vehicles, retreading is being used in all of them.
- Retreading is highly environment friendly. When the existing tyres are made ready for further use, the manufactures save landfill space. Also, it reduces carbon dioxide emmission and saves millions of gallons of oil which is required to manufacture new tyres. Therefore, when you get your old tyre retreaded instead of buying a new one, you play a major role in saving the precious natural resources.
- There are many economical benefits of retreading as the retreaded tyres are less pricey in comparision with the new ones. This definitely helps you save a considerable amount of money. You can retread your old tyre at least twice or thrice and this helps you save upto 40% of your money every time because if you go for a new set of tyres it will cost you almost double of the price of a retread one.
- Retread process is not responsible for spreading large chunks of rubber on the roads and highways. According to recent studies, it happens due to abuses like tyre failure, caused by road hazards, tyre blasts and overloading to both new tyres and retread ones.
However, instead of all these benefits of retreads, they could not really take off so well as most of the consumers have negative impression about the retreaded tyres.
Disadvantages of retreaded tyres:
- Retreaded tyres are generally a lot less expensive than the new ones, however, after the budget tyres have come into play, the scenario has changed to a large extent. Now, it seems that budget tyres are even less expensive than the retreaded ones and as they are freshly made tyres, they obviously have better quality than the retreaded tyres. Hence, a customer is more likely to prefer budget tyres to the retreaded ones.
- In retreading, a new lease of rubber is put on the casing of a worn out tyre without changing the cords of infrastructure. Hence, the quality of the retreaded tyres always stays a lot down than that of the new tyres. No matter how well it works after retreading, there has to be some issue with a retreaded tyre.
Tyre Retreading Process
1. Collection of Casings
Worn tyres are collected to select suitable casings for tyre retread.
2. Initial Inspection
Each tyre received in a retread plant is subjected to a rigorous visual inspection. Inspectors are assisted by the use of non-destructive sophisticated inspection equipment like the 540/2 Spectra or Newera inspection machine.
3. Buffing After inspection
The tyre’s old tread is mechanically removed on high speed buffers. Today’s buffers are extremely accurate and will remove the proper amount of old rubber while turning the tyre to an exact specified diameter and radius. Collaboration with international leaders like MATTEUZZI enables Newera to build computerized world class equipment under license for Asia.
4. Section Repairs & Skiving
With advances in state-of-the-art repair materials and repair methods, many of these tyres can be routinely repaired and in most cases can be retreaded when the original tread is worn off. The repair station is where any surface injury is treated using effective material and tools for grinding and patching.
5. Cementing and Filling
Even in small injuries it is critical that the injury is cleaned and filled. If this is not done, severe rust, separation and steel cable looseness could take tyre out of service. The injury should be inspected, and then cleaned out with a carbide cutter. After cementing the injury, a vulcanizing rubber stem should be applied to “fill” the injury. This would create a permanent repair that maximizes tyre life.
With Newera designed-and-built spray booth, your cementing operation can be executed in a clean, efficient & environmentally responsible manner.
6. Building – Tread Rubber
In the pre-cure system, the tread rubber has already been vulcanized with the new tread pattern design. The buffed tyre needs a thin layer of cushion gum to be wrapped around its crown area. The pre-cured tread rubber is then applied with the building machine. This is called the building process.
a) Enveloping & Rim Mounting or
The built tyres are then mounted with envelops and rims to prepare them for curing.
b) Double Envelope System
For enveloping, tyres are first fitted an outer envelope at the envelope-mounting table before the inner envelope is fitted into them. The enveloped tyres are then vacuumed out for preparation prior to curing. Modern plants have their casings hoisted by monorail systems. With professional planning from Newera engineers, you can be assured of workstations designed to maximize output and ease workflow.
8. Curing by Chamber
The tyre is then placed in a curing chamber and the pre-cured tread becomes adhered to the tyre through a vulcanizing process.
Our wide engineering capabilities and experience enable Newera to build chambers to suit our clients’ different preferences for size, steam heated, electric heated, or double heating system, semi-automatic and automatic chambers.
The monorail & hook system increases productivity by cutting down on chances of casings contamination and allows for faster loading and unloading of tyres. This increases your work place safety and productivity.
9. Final Inspection & Painting
The retreaded tyre is subjected to a final inspection. This inspection insures that only tyres that meet industry quality standards are allowed to leave the retread plant. All retreaded tyres are encouraged to be returned with the sidewalls painted using a light coat of black tyre paint.
Hot retreading involves the vulcanisation of a tyre in a mould at a temperature of around 150 °C. The tread and the sidewall veneer of the tyre are made up of non-vulcanised rubber compounds. The shape and tread of the tyre are created in the heating press.
Arguments in favour of hot retreading:
- Suitable for all tyre applications, including car and aircraft tyres.
- Material costs are lower than the more complex products required for precure retreading.
- Hot retreading also allows extensive repairs to be carried out on the tyre carcass (e.g. belt replacement).
- Even bias-ply carcasses can undergo hot retreading without any problems.
Points to note:
- A separate mould is required for each tread and size. This requires a high level of investment in a range of moulds, which will be needed to be regularly updated.
- The production process needs to be designed for large numbers of tyres. This calls for a central production workshop, an extended customer area and therefore brings with it relatively high logistics costs.
Precure or “cold” retreading involves vulcanisation without a mould at a temperature of between 95 °C and 110 °C. The tyre is put together using a pre-vulcanised tread liner (= new tread) and a non-vulcanised bonding gum layer. The bond between the carcass, the bondung gum and the precured tread is created in an autoclave. Precure retreading has become fully established in the truck tyres sector since the introduction of radial tyres in the mid-1960s.
Arguments in favour of precure retreading:
- Less investment is required on the part of the retreading plant (no expensive moulds) and lower follow-up costs, since it is the material supplier who updates the range of moulds.
- A wide range of tread types are available, allowing the optimum tread to be selected for the tyre application.
- The comparatively low investment costs involved mean that decentralised, smaller production units can be operated. This means lower logistics costs and makes the operator more flexible and closer to his customers.
- The precure retreading process is kind to the carcass, since vulcanisation temperatures are lower and put less strain on the rubber-metal bonds in the carcass. Heat build-up in the tyre, rolling resistance and other tyre properties are often easier to assess than with hot retreading.
- With comparable tread geometries, the running performance of a precured retread is often better than a hot retread and the same as an equivalent new tyre.
Points to note:
- Precure retreading requires high-quality carcasses.
- Material costs are higher than hot retreading material, since the precured tread is already vulcanised and is therefore a more heavily-processed product.
- Labour costs per retread are higher than for hot-retread truck and bus tyres.
RAJ 8 June 2020, 1:44 pm
RAJ 8 June 2020, 1:44 pm