Basic Process Improvements

Background:

The wear characteristics of the rivet less chain has been an ongoing issue throughout the years. The producing of the components is to a point that a very small amount of cost is involved in the production. These units are a very basic design and along with this are a very simple manufacturing method. For the most part these pins are drop forged and use a tumble deburring method. The links utilize essentially the same process but with a few additional steps for punching cross holes and the like. Improving the manufacturing is a very difficult proposition.

Basic improvements:

Utilizing newer and lower cost manufacturing processes can dramatically increase the life of the pins and links. Increasing the hardness is only one item in the attempt to increase the life. This has been done by Tsubaki Corp and several other companies already. As shown in the figure above, the part is case hardened which leaves a tough core. This can increase the life of the pin but may cause detrimental damage to the link.

Component function:

Understanding the interaction between the components and looking at ways to improve the function of these can lead to a process improvement which may be of interest to the industry as a whole. Life expectancy of a chain is controlled by several factors. Reducing or eliminating the basic issues with the connection between the two parts can greatly increase the life of the chain to a point that it may not be the “weakest link” anymore. As with any improvement, the root cause of the problem needs to be addressed. Inspection of the basic components can drive some of the life reducing issues. The other important factor is the function of the connection. How it works and what it needs to do to work.

Greatest improvements:

As in the design of ball bearings and the introduction of high speed bearings, the aspect of finishing the inner and outer races just before the second world war seemed an addition that generated an extreme life improvement. During long distance shipping, the axle bearings were damaged by the ball bearings being embedded into the raceways. Cross country shipping on railway cars had a constant jarring effect on the vehicle as it was traveling. As Chrysler found out, the finishing of these races did two things. First it removed the soft outer skin of metal (the amorphous layer) generated by the grinding process. This eliminated the initial problems with the bearing balls embedding themselves into the races on the long trip by rail to California. The noise generated was not a sound the customer wanted to hear, but after a relatively short time the bearing balls smoothed out the rest of the races and the noise subsided. The second unrealized improvement to finishing the races was the friction was reduced and the running surface hardness was increased because the finishing essentially pre-ran the bearing in. The new finishing process also improved the roundness of the bearings but most importantly, it improved the consistency. Having a hard surface is one thing but reducing the friction and improving the interaction by improving the consistency of the form between two surfaces greatly improves the way these part can interact. This is what will increase the life of these chain components.

Basic issues:

Reducing and eliminating the high spots (effectively the flash or parting line) as a result of the forging, reduces the point wear and point loading on the surfaces. This will even the wear and generate a smoother motion between the joints. This smoother action will also greatly reduce the friction and with this the frictional wear. In the chain system, one of the most detrimental problems is chain friction. Known as chain pull, this force can increase and decrease through out the system as the chain twists and turns around every corner. By reducing the friction at these turns, the pull can be reduced significantly and this effect can lower the coefficient of friction used in the chain pull equation. This can generate additional cost reductions like smaller more efficient motors, the elimination of a secondary drive on long systems and the reduction of wear on the units used to guide the chain. Friction can be one of the most costly effects on any system. Adding oilers and lubrication systems, hardening the components, adding cleaners and even changing material is only have the battle.

Current manufacturing processes:

The use of abrasive belts in the metal finishing process has been prevalent since the early ‘80s. They have become an inexpensive grinding alternative that can utilize a very cost effective method of not only reducing the roughness of this surface and markedly improving the geometric shape but to generate a more consistent quality. Abrasive belt finishing is a process that is extremely time conscience and consistent. Even imparting improved forms into the workpiece can be accomplished by using a pre-shaped roller behind the abrasive belt. These forms can greatly improve the function of the parts. Secondary oscillation motions are not needed when using an abrasive belt as with the traditional grinding or other finishing methods. This reduces the complexity and cost of the equipment.

Improved process development in this field can add even greater component improvement at a substantially lower cost than initial conceived.

Low tooling and abrasive costs:

The typical 1” wide x 30” long grinding belt for an application like this would be much less than $10 and would likely last from several hundred parts to close to 1000 parts.

Conclusion:

Understanding the design of the elements, how they interact and what a small manufacturing addition can bring into the function of the components can lead to a completely different outlook of the process. This can generate more efficient, more cost effective, improvements in life and reduction in the running cost of a large system.

As always said, its small improvements that can provide the most change.