One strategy that was implemented was to use an environmentally
friendly cooling agent that couldn’t endanger the environment and make it less
likely for workers to injure themselves on wet excess metal with sharp edges.
This would mean that there is less waste disposal due to the fact that the
cooling agent must be used to a minimum to ensure that you don’t have any
unneeded wastage when it comes to coolant or energy.

Gear Rolling
Diagram
Diagram
originally from Reference (8)

The second scheme was to use advanced manufacturing processes for the
gears, the process used for this was called gear rolling, otherwise known as
flat rolling. The gears are rolled at a cold temperature (the temperature at
which the metal is below its recrystallization temperature) that move in
opposite directions of each other allowing for the rolling dies to make the
teeth using compressive forces. This would consequently increase its compressive
strength thus making finishing processes such as heat treatment, forming
processes, and additive processes to be unnecessary allowing energy to be saved.
Another factor is that tool bits are used less frequently meaning they do not
need to be repaired/ replaced as often.  

Wire Electric
Discharge Machining
Diagram Originally
from Reference (9)

A machining method was introduced to reduce the amount of energy used
to pump coolant as well as multiple machining methods. It was called Wire
Electric Discharge Machining and the process works by using a wire that feeds
through the gears and cuts the material so accurately that it makes processes
such as milling and extrusion unnecessary due to it being so precise. Instead
of coolant being pumped into the system, deionised water is used as a
dielectric to protect the metal from being damaged showing that it’s an
efficient/economical. Since it can be reused easily, the process can make the
gears on a mass scale whilst giving it a nice surface finish helping reduce the
overall amount of methods required to give the gears a professional high
quality required for it to be sold.  

Finally, the hob tool that is used in dry hobbing (the
process that is responsible for gear cutting and creating the teeth) undergoes surface
treatment in the form of coating in order to extend its use. The hob tool is
coated ina Titanium doped Aluminium-Chromium-Nitrate  improving the tool tremendously as it will
not wear out easily making it last a long time before being replaced. Despite
being more expensive, the hob tool (5) performs better as it can be recoated if
it begins to wear making it cheaper than replacing the tool itself.  The tool then becomes more reliable to use as
the coating can cut material at a low rpm making it more efficient as other hob
tools that will not undergo this treatment will break quicker.  Also less energy is used to coat in comparison
to new hob tools being produced.

Justification

(10) Using environmental cooling agents such as propylene
glycol are much more sustainable than other cooling agents such as ethylene
glycol and can be used in the manufacture of gears. This agent is not as toxic
as ethylene glycol making it a safer alternative and is more useful for the
environment as there is less wastage. The fact that it can be produced from
recycled materials demonstrates that it is easier to reuse. There are other agents
such as recycled ethylene glycol that ensure production is environmental friendly
but both these cooling agents are expensive to produce making it less cost
effective to the whole process. Despite that the cooling agents would leave
less wastage due to it being used to a minimum, reducing the cost for coolant.

(11) Gear Rolling is a method that is very effective for
sustainable manufacturing; it is a cold rolling process meaning that heat energy
does not need to be produced to cut the metal saving a lot of energy when gears
are being mass produced. Another factor is that it can produce gears with a
tolerance of +/- 0.002mm, proving it is an accurate process as it negates the
need for finishing processes to get the correct dimensions which will save
energy and money. The added benefit of gear rolling is improved performance, compressive
strength is increased meaning that they are less likely to wear after being
used for a while. This reduces the amount of gears needed to be made as they
will last longer in machines and will not need to be maintained as regularly. Less
energy will be used to power the machines and will not need other processes
like heat treatment.