How Does Lube-Free Chain Really Work - And what are the Real Benefits?
With so many companies claiming expertise in manufacturing roller chain products that do not require any external lubricant throughout their lives, Tsubaki, the original creators of lube-free chain explain how it is done and detail some surprising real world benefits...
There are a number of ways of achieving non-lube performance of drive chains. These vary with the load capacity and life requirements of the transmission medium. Today engineering plastics, especially self-lubricating acetyl types, play a part but, in the main, these type of chains suit applications where corrosion resistance and weight saving are more important than load capacity. Where conventional externally lubricated steel roller chain is normally used power transmission capacity and wear life are the main criteria for selection and an all steel lube-free chain is required.
How do they work?
There are two main methods of achieving 'lubrication-free' steel roller chain and both involve internal lubrication between the load bearing surfaces, i.e. between the chain pin, internal bushing and the roller. As chain passes over a sprocket, particularly a driven one, it is these internal bearing surfaces that have to articulate under load. Given inadequate lubrication, these are the main areas of wear and the resulting chain elongation.
The first method for lubrication is to pack the rollers with a high viscosity grease lubricant that maintains internal lubrication, externally the chain is virtually dry to the touch and additional external lubrication is virtually impossible due to the inability to penetrate through the existing lubricant and is therefore generally not recommended. This type of lubrication does limit the temperature range of the chain and has a limited effective life span. Where there are any contaminants such as paper particles or general grit and dust present the lubricant can become contaminated or dry out and the wear rate of the chain is then significantly accelerated.
The second method of achieving internal lubrication of the chain is oil impregnation of the components during their manufacture known as sintering. The steel bushings are forged with lubricant actually included within the material structure of the steel. During operation, the lubricant forms a micro thin layer between the pin and internal roller surfaces. Meanwhile, the exterior of the chain is totally dry to the touch, a condition that stops it acting as a surface receptor for harmful contaminant particles.
An additional benefit of this process is that the motion of the lubricant within the rollers under load is from the centre outwards, the opposite direction to conventionally lubricated chains that draw lubricant in from the exterior. As a result of this, any debris from the atmosphere that does settle on the surface of the chain is mostly excluded from the load bearing surfaces of the rollers and deters the acceleration of wear.
The overall performance of a good lube-free chain is also enhanced by specially hardened pins and rollers. The durable rollers facilitate super smooth engagement on the sprocket for longer periods of time. This reduces sprocket wear significantly. Moreover, the smooth articulation of chain and sprocket reduces power transmission losses by a high order.
So what are the benefits?
There are some obvious initial benefits to using lube-free or (internally lubricated) chain. Food production environments that have traditionally used expensive food grade lubricants can now operate food production lines without the need for chain lubrication, even in some arduous washdown environments. Although only sintered chain is recommended in these environments. Other areas where the chain is proving extremely effective are the paper, packaging, electronics and white goods industries where any external lubrication of chain can lead to unacceptable product marking or quality failures.
Contamination of the final product from oil spillage or oil mist is a major reason for the lube free demand in these sectors, but not exclusively so. There are other important considerations, including the observance of Health and Safety regulations, the cost of the lubricants themselves and the down-the-line costs of their disposal. In addition, if lubrication can be avoided altogether then planned lubrication intervals are unnecessary and maintenance costs are reduced accordingly.
One of the less obvious benefits of 'lube-free' chain is in extending wear life. Most chain manufacturers issue lubrication recommendations for standard chain and most maintenance personnel understand the importance of lubrication. However, there is often a gap between what is understood and what is done. The thoroughness with which external lubrication is carried out is often open to human error and forgetfulness, especially so if the chain is hidden away or inaccessible, on an overhead conveyor for example.
A high proportion of chains in use are lubricated erratically and this can result in them not reaching their predicted life or require more frequent adjustment because of excessive wear. This problem is avoided by using chains that do not require external lubrication, but in the case of sintered lube-free chain, wear life can be extended to over thirty times that of standard chains in some applications, especially where contaminants are present.
It is in this instance that the real world benefits make even more sense when they can contribute towards a company's operating efficiency and profits. The best technology lube-free chain costs on average two and a half times more than good quality standard roller chain. Taking into account the lack of lubricant, maintenance adjustment and initial purchase cost - lube free chain can conservatively contribute over twelve times its initial purchase cost to a company's bottom line.
The demand for chains that operate without lubrication began with the food and IT manufacturing sectors, but has now spread to many more industry sectors where product cleanliness and environmental conditions have become far more important. The result is that lube-free chains are now in the mainstream of industrial manufacturing and can replace conventionally lubricated chains in the majority of applications, including a comprehensive array of attachment and conveyor types for replacement and OEM applications.