The first step which must
be taken before starting anything on CAD/CAM, is creating a working directory
as this is crucial for every single step in the process.
this, the creation of the model was properly created by using a combination of
the “Spline Tool” and the “Line Tool”, which allowed the user to create the
right curve that they desired, by dragging the orange circles on the workpiece.
The line tool was also important on this process as it allowed the author to
obtain the straight edges in the correct places.
next step when making the workpiece was to Sweep the generated lines together
and create a centre line for them to rotate around.
The Sweep tool is an amazing feature
which allows the user to create advanced shapes in a matter of seconds.
this feature, the author had to create a centreline, this is the first location
the sweep feature needed to know, so that it was set as its origin line.
By opening the References tab, you
can then click on each of the remaining lines which will automatically be named
as “Chain 1” and “Chain 2”.
Then clicking on the pen and
paper, you are now able to sketch a curve that your lines will follow,
As the author was given the task
to create a clam shell of an electric screwdriver, the next step to achieve
this objective after generating the solid workpiece, was to shell out the
When adding extra little
details to the workpiece, the author had to create new planes, by off-setting
the original plane to a certain distance.
After this, the author was able to sketch
the shape that they required and extrude it backwards into the workpiece to
remove the excess material that wasn’t needed.
This rectangular cross section was removed
from the workpiece to create a place for the pressure handle.
Chamfers were added to the edges
on the removed section
Upon further inspection, the base
of the model was found to have been curved. To fix this small problem, a simple
extrusion was the simplest solution. By starting a new sketch, the author took
references on the X-Plane to assure perfect level, followed by drawing a
rectangle underneath the model and extruding the shape the entire length of the
model. This small detail will help later on when creating a silhouette curve for
ideas for how to make this model look better were considered, but due to the
problems that would occur during the molding process, it was decided that it
would be best to leave it.
was an idea to have a trapezoid pattern around the top of the model that was to
be extruded down into the material, but not all the way through. This was
achieved by creating a layer within the model that you could select to cut down
to, if you were to extrude into it, but this idea failed as the author couldn’t
find a way to create a new origin for the pattern to correctly rotate around.
other plan was to have a small shelled half cylinder at the bottom of the model
to represent a charging port for the workpiece. But again, it would have
problems with the molding stage.
author was disappointed that he was unable to use these features as it would
have made the workpiece stand out more.
moving onto the next stage, PTC Creo allows the user to analyse their mold with
ease, to identify any problems that they could potentially run into when creating
their mold, so that they are able to develop designs, and improve the
manufacturability of their models.
plastic part designers, it grants reliable and easy-to-understand data to gain
insight to further improve their design. The Creo Mold Analysis allows the
quickly and accurately analyse and develop designs that are manufactured by
illustrate, as well as provide appropriate resolution to potential mold filling
problems, such as short shots, air traps, welds lines and other important
are the most common fault when using injection molding, this occurs when the
liquid material is unable to fully make its way into the corners of the model. There
are numerous ways to counter this problem which include:
Increasing the mold temperature to increase its
ability of flow.
Take the gas that could be created into account,
and make sure that the mold is vented so that the gas isn’t trapped in small
Use a less viscous material.
Increase the material feed rate in the molding
had decided at this point that they were happy with the outcome of the design
stage, and moved further onto the to the next stage of molding.
can tend to be the most difficult, as there is so much that could cause the
molding process to fail. When starting, it is important to clear your session
by activating the “Erased Not Displayed”, selecting the correct working
directory so that every part is saved to one place.
setting up the file correctly, it is important to reference the model by mating
the correct planes to each other, the model turns golden when successful. Following
this, the workpiece is to be created, the author found that the automatically
generated workpiece was quickest and most effective way for this step.
found that it was best to create a thin ‘skin’ over the open areas of the model
before carrying onto the next stage. Boundary blends were used to seal the ends
of the part and when considering the area for the pressure handle portion, the
author first tried to create the skin by using a second Sweep and restricting
its path to only cover the needed portion, instead of the whole model. This
plan worked, but never fully closed the gap needed. Because of this, the Shut
Off tool was attempted, and the results were incredible, full closure of the
pressure handle was achieved.
everything was ready, the next step to take was to create a Silhouette Curve,
by considering the chains you can change which lines and curves will connect to
a functioning mold you must have a parting surface. This was achieved by using
the Extended Curve feature which creates a surface to the edge of the
workpiece. For the pressure handle, the extended curve was used again and was
projected, by selection, to the workpiece face.
sections that were left, the author simply took references of where they needed
to be, and manually drew them in and used the project tool to check if they
were good enough.
To create one complete parting surface, it was
only a matter of joining all the previously made curves together. By utilising
the Merge feature, you can connect each quilt together, but this can only be
accomplished by layering them in a logical sense that works.
Now that the parting
surface is functioning, the user can then create a cavity insert, which in turn
will turn your workpiece into a solid block of material that houses both the
model and the parting surface. All that is left to do is mold the component, this
step finalises both the top half of the mold (female) and the bottom half
(male). The Runner should be added after so that it can rise from the bottom of
the mold to the top of the model.
There are many advantages to using CADCAM, the
time spent on making a project similar to this would be dramatically increased
if it weren’t to CAD programs, therefore money is saved on labour costs,
material costs as well as the fact that realistic simulations can be run on the
part to understand how it would handle under certain loads.
Although the parting surface took a large amount
of time to comprehend the working behind it, the author would’ve preferred to
try and make the whole thing flat, leaving no humps in the mold itself. If this
was successfully achieved, time spent on manufacturing would be decreased, as
milling out the bumps wouldn’t occur.
Moving on to the final stage of manufacturing the
molds that were previously made.
Both sections of the mold must be referenced as
well as have a workpiece generated around them. DUGARD mill machine is chosen
and configured to 3-Axis along with other important information, such as a new
coordinate system from which the milling machine will start, where it will
travel, the spindle speed and its horsepower.
CNC (Computer Numerical Control) milling machines
are machine tools that’re used when shaping metal and other solid materials.
They exist in two basic forms: horizontal and vertical. This takes reference to
the orientation of the cutting tool spindle. CNC refers to a computer
(“computer”) that stores then reads instructions. This numerical information
usually “G and M” codes, a type of programming language, is then utilised to
control and drive a machine tool, a powered mechanical device (“machining
centre”). This mechanical device which is powered is used to fabricate
components using cutting tools for material removal.
To create the finished part, the cutting process
can be started from a selection of parts, from either a solid block, a
pre-machined part, castings or forgings. For these scenarios, the skill
requires the CNC milling machinist to read and understand intricate technical
drawings and specifications and maintain a high degree of detail and precision;
to be skilled at meta work and understand how certain metals react to various
processes; to become a skilled computer operator so that you can use the
specific software in industry; to be highly adept machine operator.
A profile mill is selected, along with a large
diameter end mill tool bit to start the manufacturing process. This clears the
excess material from the outside edge of the workpiece. A Milling Window is
used for the 3-axis conventional surface milling NC (Numerical Control) sequence.
A combination of Volume and Surface milling is next used to fully define the
model to the fullest using 3-axis. Further detail was made by cooperating
Corner Finishing into the manufacture, this feature highlights the edges that
are present on the model.
An End mill with large diameter was used to remove
material around the perimeter of the molded workpiece. A volume mill was then
executed, with the aid of a mill window, to remove a large amount of material
that makes the model. The
workpiece was then trimmed down using the Finishing Tool, this allows the user
to create combinations of vertical and horizontal cutting tool paths to meet
your manufacturing goals within the constraints. This tool can also on occasion
flatten the top surface by scraping away excess material that exist.
Once the Tools
were setup and tested numerously with their milling operation, the next step to
take is creating a CL file, which allows the user to watch the output given
when all the operations that were singularly created work together and view the
outcome of the mold. This is useful for many engineers that create parts using
CADCAM as it cuts down material and numerous prototype costs. The CL file is
also a very useful tool, although in practice, it is near impossible to run the
entire operation at the one time as each process will need to be positioned and
clamped down differently.
Injection molding is a useful
process used to manufacture numerous things, such as; automotive parts and
components, mechanical parts (which include gears), and the majority of plastic
products that’re available in this day
and age. When taking plastic parts into consideration, injection molding is the
most commonly used method of manufacture as it is ideal when producing high
volumes on the same product.
The process itself simply involves
a liquid material being pushed into a mold cavity. It can be performed with a
variable amount of different materials including; glasses, metals (known as
die-casting), and the common types being thermoplastic and thermosetting
When taking the machine into
account, it functions under two main sections:
Injection Unit: Material
is fed into the hopper on the top, which is then heated to a liquid state by
the heaters around the barrel, and is transferred forward to the nozzle which
feeds into the actual mold. This occurs as the liquid material is spun around a
reciprocating screw thanks to the cylinder in the back which is powered by a
motor and gears for the screws rotation.
Clamping Unit: Connecting
the nozzle from the injection side to a stationary platen and moveable platen,
in between these platens lies the mold to which the liquid material will flow
into, cool down and take form of the given mold. The moveable platen is able to
change its distance from the stationary with the aid of the hydraulic cylinder
which connects to the Clamping cylinder resulting in sliding across the 4 Tie
After the product is designed, by
an engineer, molds are created from metal (usually steel or aluminium) by a mold
maker, and is precision machined to create features of the desired workpiece.
Injection molding is vastly used to manufacture a large number of parts, from
the tiniest components to complete body panels of cars.
When designing the parts, which
are to be injection molded, they must be very wary to facilitate the molding
process; the material that will be used for the part, the required shape and
features of the workpiece, the material that will be used for the mold itself,
and the properties of the molding machine must all be accounted for.
To reiterate and go further into
depth, the injection molding process uses a screw-type plunger which forces the
liquefied plastic material in a mold cavity, this then solidifies into the
shape that the mold is conformed to. Polymers that are Thermoplastic/thermosetting are the most commonly used
material for injection molding. Thermoplastics are known for their characteristics that
make them suitable for this process, such as: their ability to relax and flow
with ease upon heating, the fact that they’re biodegradable and their ability to adapt, which makes them widely
used for several applications.
Thermoplastics are somewhat better than thermosets as they’re partially safer, for example, if a thermosetting polymer is not shifted from the
injection nozzle in a marginal time frame, the injection molding machine could
potentially be damaged due to chemical crosslinking which can cause the screw
and check valves to seize.
process consists of raw material getting pushed through at high-pressure into a
mold which contorts the polymer into the required shape. Furthermore, the molds
themselves can either be of a single cavity or multiple cavities. More often
than not, molds are manufactured from tool steels, but aluminium and stainless
steels are suitable for certain applications. Aluminium molds aren’t typically the best for high volume production or components
with tapered tolerances, as they have terrible mechanical properties and have a
tendency to wear, deform and get damaged during the injection and clamping
cycles; however, molds that
are made from aluminium are cost effective in low volume manufacture, as the
time and mold fabrication costs would be reduced considerably. Many steel molds
are designed to withstand the process for more than a million parts during its
lifetime, these type of molds however, tend to cost hundreds of thousands of
pounds to fabricate.
As thermoplastics are molded, they typically use fresh material which
is placed into the hopper and falls down into the heated barrel and moved along
to the nozzle with the use of a reciprocating screw. Awaiting entrance to the
barrel, the heat increases and the forces that act against the flow of single
chains are weakened, this is due to the increased spacing between the molecules
at this higher thermal energy state. After this, the viscosity which enables
the polymer to flow with the force exerted by the injection unit. The
reciprocating screw delivery system pushes the raw material forward, combines
and homogenises the thermal and viscous distributions of the polymer, and
lowers the heating time needed by mechanically shearing the material and adding
a large amount of frictional heating to the polymer.
numerous defects that can occur during injection molding and, as previously
mentioned, a shot is one of these. A shot can be described as a location where
the liquid material isn’t able to fill a small area. This means that the liquid
material wasn’t able to reach and take shape of the mold cavity. As a result of
this, there is a portion where there is no plastic, this then leads on to the
finished product becoming deficient due to this blank space.
They can be caused for a number of
reasons, such as:
-failure to calibrate the plasticising
capacities can result in the material being inadequate to fill the cavities
within the mold.
– If the plastic material used for the
injection molding technique is too thick, there’s a possibility of a shot forming, as it may solidify before fully
occupying all the cavities within the mold.
But there are ways to fix this
problem, one technique to use, is trying to replace the previously mentioned
plastic material for one that is less viscous and higher flowability, which
will allow the new material to reach the hardest cavities. Another effective
way to fix this problem would be to increase the temperature of mold to also
increase its flowability.
thermosets, two separate chemical components tend to get injected into the
barrel. The components mentioned previously start to mix, and create an
irreversible chemical reaction which eventually crosslinks the material into a network
of molecules. As the chemical reaction undergoes, the two fluid components merge
into one permanent viscoelastic solid. As this new solid gets pushed
through the injection barrel and screw, it tends to solidify within these parts
and can turn out to be rather problematic, therefore by reducing the thermoset
curing within the barrel is crucial. This assumption is usually made that the
residence time and temperature of the chemical predecessor are reduced in the
injection unit. The time
within the barrel can be altered by reducing its volume capacity and by
maximising the cycle times. It was discovered that if the reacting
chemicals were injected from the barrel into a heated mold, that is isolated
from thermal energy. The outcome of this results in an increased rate of
reactions which decreases the time taken for the thermoset to solidify.
the component has solidified, valves close to isolate the injection system, the
process then repeats as the mold opens to eject the newly molded parts, then
close to repeat the operation all over again.
Finite Element Analysis
Finite Element Analysis (FEA) is
quick and easy way of simulating any given physical phenomenon by using a
numerical technique most commonly known by engineers as Finite Element Method
(FEM). It again gives great reason as to why CADCAM programs are the way
forward in modern day engineering, as it is used to decrease the total number
of physical prototypes and experiments and develop components in their design
stage to therefore optimize better products, at a higher, and faster, rate.
Mathematics are a necessity to
fully comprehend and quantify any physical phenomena, such as structural, fluid
behaviour, thermal transport, etc. These processes are known as Partial
Differential Equations; however, it has taken decades to develop numerical
techniques and the most recognisable one, today, is Finite Element Analysis.
Being able to grasp the immediate
stresses and deformations a part undergoes is critical to structural analysis,
therefore they, can be used to distinguish displacements, stresses and strains on
the model when an internal or external load is applied on a certain point, or
around the entirety of the model. Fatigue analysis grants visualisation of life
and damage during cyclic loading and can be useful when predicting where
failure may occur and hence, increase product durability. The geometry from
analysis is shown by the use of triangular (two-dimensional), tetrahedral