Enhancing Material Handling Applications
On the battlefield,
is crucial to success.
In the manufacturing
process, moving materials
is just as important.
Moving product from
one production step to the
next must be smooth and
efficient, other wise bottlenecks
can form and create
issues down the line. Loss
of time, production capacity, increased labor, energy and raw
material costs as the expenditure of labor to correct these issues
can all arise. If allowed to continue for a prolonged period
of time, the higher price to produce erodes earnings and puts
the company in a competitive disadvantage. Appropriate and
reliable material handling addresses these specific issues and
cast nylon plays a key role.
There are several aspects to consider when selecting the
right material for the job. A short list of those include the
weight to be moved, its size,
speed of movement, cost and
preferred motion method (sliding,
rolling, driving, coasting,
etc). The operating environment
must also be considered. At what
temperature will the moving
take place? Will there be any exposure
to chemicals or explosive
materials? The items being
moved must also be considered.
For example, a fragile load will
need to be handled with more
care than a robust one.
The vast range of cast nylon
shapes and sizes allows for unique and specific solutions to
the varied manufacturing processes. Rollers are a commonly
found in shops. Cast nylon tubes are readily available from
1 ½” up to 24" outer diameter. The tubular shape alone, reduces
weight and material costs. Wall thickness typically
range from 1/4" up to 6". This allows for the right sized roller
to be paired with the load that needs to be carried with minimal
machine time and material waste. The nature of the
casting process also allows these tubes to be produced in various
lengths. Nylon tubes are produced from 1' to 10' long
which offers flexibility to roller design.
Several characteristics inherent in cast nylon make it useful
for a variety of applications. Being corrosion resistant, nylon
does not degrade or rust in wet or humid environments. It also
holds up well with common wash-down protocols. Elevated
acidic or caustic chemicals will degrade nylon under prolonged
exposure. FDA compliant formulations of cast nylon are readily
available for use in direct food contact. Depending on the application
and end user preference, there are 3 common FDA
approved nylon colors to choose from, off-white, blue and
black. Often, a color that contrasts to the product being produced
is preferred for ease of visual inspection.
For roller applications, the Hertzian model for contact
stress provides an accurate way to determine the working
loads. A roller on a flat, relatively hard surface deforms
slightly under load. This deformation does a couple of things.
It increases the contact
area thereby distributing
its weight over a larger
area. It also puts strain at
the rim of a plastic roller.
The amount of load a
roller can carry is not
only directly proportional
to its outer diameter and
length, but also its modulus
of elasticity. Generally
speaking, the higher
the tensile modulus of elasticity of a material the more weight
the roller can withstand. Compared to other common industrial
thermoplastics, unfilled cast nylon's tensile modulus of
elasticity is relatively high and allows for increased roller load.
Sometimes, sliding the part from A to B is the solution.
These parts are found in the material handling industry as
sliding pads, wear pads and guide blocks. While typically
simpler in design, the movement is usually slower as it is impeded
by friction. The amount of frictional force is determined
by the weight of the
moving object, multiplied by the
coefficient of friction between
the moving and stationery object.
This coefficient is comprised
of a number of features
such as finish, and hardness.
Typical material values on manufacturing
data sheets show a
coefficient of friction for a given
material on smooth finished
steel. The two types of coefficients
normally listed are dynamic
and static. Dynamic
frictional force is measured as
an opposing force for an object in motion, sliding on a flat
surface. Static frictional force is the force that opposes motion
when a force is applied (object remains stationary relative
to the surface on which it rests).
For most materials, the static coefficient is higher than the
dynamic coefficient of friction. Lubricated grades of cast
nylon are commonly produced. These grades reduce both the
static and dynamic coefficients of friction which reduces frictional
opposing forces. Some lubricants reduce the gap between
the static and dynamic coefficients. In high weight,
fast moving situations it is important to consider the ability
of the sliding pad to disperse frictional heat. This can be done
by calculating the Pressure Velocity and comparing this to
the manufacturer's specifications. Pressure Velocity is simply
calculated by the weight of the load divided by the contact
area. This is then multiplied by the surface speed of the
weight across the pad.
Getting product through the manufacturing process
quickly and safely is complicated. Getting the right piece to
the next step, on time is money.
Written by Nylatech, Inc. manufacturers of cast nylon 6 and 6/12
as rod, sheet and tubular bar as well as finished or semi-finished
custom cast components. Nylatech also provides premium copolymer
acetal rod, sheet, slab and strip available in natural and black
in a variety of sizes from stock.