| Background
A roller finger follower is a device that raises and lowers the intake and exhaust valves of an overhead cam
engine. It is located near the rotating cams of the engine (most common in overhead cam engines) and serves
as a direct connection between the cams and the intake and exhaust valves. The finger follower was designed to
look similar to a finger oscillating over a pivot point. With one end of the finger follower fixed to the head of the
engine, the rotating cam pushes up on the center of the finger follower allowing it to rise and fall allowing the valve to open and close.
A roller finger follower consists of four main components. At the center of the finger follower is an axle.
This axle is a solid cylinder which is polished to a very smooth finish and serves as the center, or point of rotation,
for the bearing. Around the axle are many cylindrical needles. Similar to polishing the axle at the center, the needles
further reduce the friction by allowing a role slide affect between the needles and the outer wall. This outer wall, or race, keep the needles in place while simultaneously providing the contact between the engine and finger follower. Finally the
components are assembled inside the finger follower body. The finger follower body is solid so that the cam can push up
on the race with no bending or deformation.
The manufacturing process for the roller finger follower is a series of checks and stations that both monitor failing
items as it is moved through each of the processes. The first station for the roller finger follower checks for the
hardness of the body. After hardness has been confirmed station two checks to make sure the dimensions of the body
are correct. Station three uses a camera system to confirm that the hole for the axle has been machined and that it
is in the right place. After this, station four cleans the underside of the roller finger follower. After all of the
dimensions have been deemed suitable the machine begins to assemble the entire part. A bearing is dropped into the center
of the body followed by an axle. After this, the machine again passes through a inspection check to make sure the
axle and bearing are in the right place and when all is confirmed the axle is staked into place. The last few steps include
checking that the bearing rotates properly and finally if any finger follower has been deemed “bad” they are ejected during
the last station before being put in crates.
 
The finger follower staking process is a unique system which uses a linkage system and therefore mechanical
advantage to accomplish the high pressures required to deform the ends of the axle. To ensure that the axle is in
the proper place this station also aligns the axle from above and below using pneumatic cylinders. The tools used for
the staking process are made from a carbide material and are removable and can either be reordered or machined back to
the proper dimensions. The indentation from these carbide tips is visible on the axle in figure A. This process requires
a lot of moving parts and is quite large.
This cumbersome, linkage-heavy staking process is also not safe for operators who work in close proximity to the
production line. The quick, deliberate motion currently seen on these roller finger follower machines can be a danger
if someone inadvertently gets to close. Accidents are known to happen at production facilities all the time. Anything
that can be done to improve the work environment as well as worker safety is a definite goal for this new design.
Environmental issues are always a major factor when considering a new design. This linkage heavy design requires a lot
of lubricants and grease to ensure proper function. If these chemicals are not properly handled or disposed of, they can create an environmental hazard
These roller finger followers are one of GT’s signature products. The process for assembling and testing this component,
as well as its function in the engine, has been previously described. GT currently has 9 different production
lines that assemble roller finger followers for a variety of automotive companies and their different engines.
Even though GT’s current assembly processes work, there are problems that arise in certain areas of the finger
follower assembly system. One the GT’s regular problems with the roller finger follower machines, is with the staking
stations. After the axle is inserted into the roller finger follower bearing, the part is moved to the staking station.
At that time, the ends of the axle are staked to insure the axle does not fall out. The center portion of each axle is
heat treated hardened steel, and the ends are left soft to allow for staking. The staking tool applies pressure to the
ends of the axle and causes the soft ends to expand, securing the axle in place.
GT currently uses carbide tipped staking tools for all roller finger follower axles. The carbide tips are expensive
and have a low reliability. When the tips break or become unusable they have to be machined and reworked before the
assembly line can be restarted. After being machined the tips are refit to the machine and production continues. The
down time GT suffers while these current tips are machined and refitted is a great loss on the company. When a serious
problem with a staking tip happens, that particular machine could be down for over a day.
Another problem with the current staking process of the Bodine machines is the complexity of the mechanism used
to stake the axle. As can be seen in Figure E and F above; the mechanism is heavily dependant on linkages and
pneumatic cylinders. It also requires a large assortment of different shafts and bushings to support the operation.
When any of these parts fail it causes serious down time and back ups, which in turns means loss of revenue. That is
why GT is eager to obtain a new design that can improve the company’s productivity as well as product quality.
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