The roller chain is an essential part of power transmission and it is essential that it runs smoothly. Over time, as the roller chain hardens, the chain links and sprockets will experience undue stress. It is recommended that any chain stiffness issues be resolved quickly to avoid permanent damage. When troubleshooting a chain drive, it is best to start with the most common causes. Reviewing proper installation techniques and checking lubrication are the right places to start. Many problems can be behind roller chain stiffening, so let's look at them one by one.
Was the chain installed correctly?
The most common installation issue we see is misalignment. Even the smallest alignment problem can create big problems. Sprockets and axles are the most common culprits. When installing the roller chain, make sure these components are aligned by testing in several locations.
The secret is to check the angular alignment of the shafts and the axial alignment of the sprockets in several areas. Being as accurate as possible with these measurements and dimensions is essential.
Is your chain well lubricated?
Proper lubrication is essential for roller chain maintenance. Without adequate lubrication, the unit will deteriorate, fail, and in some cases even become unusable. Roller chain stiffening is a certainty without adequate lubrication.
Frozen, stuck or stiff chains are often the result of corrosion. Any corrosion or rust will make the moving parts of the roller chain resistant to movement. In these cases, efficiency goes out the window and premature wear occurs on all chain components. Fortunately, you can mitigate corrosion by keeping a transmission well lubricated.
When was your chain last serviced?
Nothing lasts without regular maintenance. The roller chain may stiffen if foreign materials accumulate on the chain. With so many moving parts, it is easy to move the roller chain. Sawdust, plastic shavings, metal dust and dirt are frequent culprits.
Lubricants can mitigate contaminant build-up, but lubrication will not solve all problems. Regular cleaning of scale is part of a good maintenance routine.
When the chain becomes clogged with material and does not need to be replaced, a thorough cleaning with kerosene followed by relubrication will return the roller chain to working order. It's also important to remember that fat will make the problem worse, not better. Always use oil.
In roller chain applications, grease seals critical surfaces from required lubrication. Additionally, grease acts as a magnet for contamination buildup.
As with anything, an ounce of prevention (or in this case, cleaning) is worth a pound of cure. Current protectors are not strictly for safety; they can also keep out contaminants. Maintaining a clean operating environment whenever possible can also go a long way in preventing problems.
How fast is too fast?
High speeds put the chain at risk of excessive wear, especially if the lubrication system is not up to the task. But that's not the only risk: a chain can block if the transmission speed is too high.
When a roller chain is moving, there are several points of movement. The pin and bushing, bushing and roller are all in constant contact. When the unit moves too fast, one or more of these intersections may no longer function as intended.
Each chain has specific speed values, depending on several factors. When the chain speed is high and the selected lubrication method cannot meet the demands, it will cause increased friction, creating roller chain fatigue.
When one component increases friction against another, the effect precipitates, making it difficult for the roller chain to rotate around the sprocket. The transmission will lose chain tension and the voltage will increase. Over time, this problem will worsen and affect more drives.
What about excessive load?
Similar to excessive speed, excessive load can cause chain stiffness. Its roller chain has maximum load capacity. When the transmission system exceeds this value, the chain quickly becomes tired and can even bend.
The image below shows an example of an extreme load exerting pressure on a chain. You will notice that the pieces are deformed and no longer articulate or function properly. The roller link is pulling the pin link so hard that instead of allowing rotation, the parts stick.
The pins, rollers, and bushings push and pull against each other, causing a cascading problem. This causes stiffness in the roller chain and eventually the chain will fail.
This problem is most easily avoided during system design. Make sure your roller chain is rated for the speed and capacity of your main motor. Your chain can only do what it can. Pushing it beyond its specifications will lead to problems and potentially costly downtime.
Although rigid chain is not typical of roller chain applications, as always, proper installation and good lubrication go a long way in preventing most problems. Occasionally it may be necessary to clean the chain as well. Finally, make sure the drive is within speed and load limits.
