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CANADIAN AUTOMOTIVE PLASTICS Capabilities
An Introduction to Plastic Injection Moulding
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CANADIAN AUTOMOTIVE RADIATOR and affiliate plants |
Canadian Automotive Radiator Plastics, an operating division of
CANADIAN AUTOMOTIVE RADIATOR, is a plastic injection
moulding facility located in Debert, Nova Scotia. This plant
is housed in a 20,000 square foot building, and has 15 injection
moulding machines in operation. These moulding machines range
from 28 tons (1 1/2 oz. / 43 gm.) to 800 tons (108 oz. / 3065 gm.),
and are rated by the maximum amount of clamping pressure that
can be applied during a portion of the injection moulding cycle.
This rating directly determines the amount of plastic that can
be "shot " in any one cycle by the machine. Several of these
machines are less than 3 years old, featuring the latest in "lights
out" microprocessor controls with SPC (statistical process control)
interface.
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Standing beside the controller of a 500 ton Mitsubishi plastic injection moulding machine. |
With its integrated affiliate CANADIAN AUTOMOTIVE Precision,
CANADIAN AUTOMOTIVE Plastics is supported by engineering,
tool design,mould manufacture,and repair and remanufacturing services.
Tool designs are now achieved using the latest version of the internationally
acclaimed Unigraphics CAD-CAM software package backed up with fully
equipped toolroom and machineshop facilities.
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An overhead view of CANADIAN Plastics plastic injection facilities. |
Plastic injection moulding is a highly specialized production
methodology. A moulding machine is actually two machines in one,
a plasticizing delivery mechanism, and a clamping mechanism. The
delivery mechanism takes pelleted plastic resin, melts this material
by means of pressure and heat, and delivers the desired amount of
plasticized resin to the mould. The clamping side of the machine
ensures that the mould base stays securely closed during the loading
of the mould with material. Every machine features temperature and
pressure sensors, as well as timers for each part of the moulding
cycle. There is also the need to control the temperature of the mould
which is achieved by a seperate temperature controller attached to
the mould base.
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Standing beside a 120 ton Mitsubishi plastic injection moulding machine. |
A primary factor that will determine the approach taken in the
development of a mould will be the desired quantity of parts to be
made from it. A second related factor is the market life expectancy
of the part moulded. Different approaches to mould development
could be taken, for example, if the customer desired 100,000 units
per month for one year only, in contrast to another customer who
requires 5000 units per year for 10 years. As part production
increases, the cost of developing more efficient tooling may be
offset by the increased production.In the development of a mould many factors will determine the
operational features that are built into its functionality. One
important factor considered is how much human involvement
is required during the part ejection phase of the shot cycle.
Moulding operations can be fully automated, involving little,
if any, human involvement, or they can be semi-automatic,
requiring plant personnel to operate.
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| The component parts of a plastic injection mould |
A second consideration would address the number of parts formed
per cycle. In the moulding industry, each part formed per shot cycle is
identified by a mould "cavity". When related parts are formed during
the same shot cycle they are known as a "family" of parts. To give
the reader an example of a family mould, we would refer to the plastic
model kit, where all the pieces that make the model are attached to
a tree-like runner.Though plastic injection moulding cycles are fundamentally the
same, there are factors that make each product run, or each mould
run unique. The characteristics of the material used to form the
parts, the temperature and pressure ratings, the amount of material
"shot";these and other related factors will determine the "cycle time"
for each run. Cycle times can vary from 2 seconds up to 5 minutes.
It is easy to see how cycle time is as important as "shot size" (the
amount of plastic used per cycle) in determining the cost per part.
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| Sometimes traditional methods don't cut it. |
Housed in the same building as CANADIAN Plastics is the CNC Metal
Fabrication Department. This department is responsible for the cutting
of flat stock metal, and other materials, into intricate and close
toleranced two dimensional pieces. The cutters used are a CNC laser,
and a Strippit high-speed nibbler / punch.The geometries of the pieces cut are developed on PC workstations
using CAD/CAM software. Unlike CANADIAN Precision Machining, this
department is involved in the cutting of production pieces, rather
than tooling.
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The Strippit machine is a computer-controlled device. CNC Met Fab use this machine to cut many of CANADIAN's sideplates and mounting brackets. |
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Combining laser cutting technology with CNC machine control allows for intricate cutting of very tight tolerances. |
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