Injection Molding Flashcards
is the expensive manufacturing process of making plastic
injection molding
a manufacturing process capable of creating completely 3D plastic parts
injection molding
injection molding is most commonly used in manufacturing ____
closures and tubs
injection molding makes use of ____
thermoplastics
injection molding is the leading method used to produce
caps and lids
injection molding process is based on the ____ method
molten die casting
melt volume or _____ accumulates at an empty space at the end of the screw
shot
once the screw stops rotating, the melt is driven forward _____
mechanically or hydraulically
4 steps in injection molding process
filling cycle, cooling cycle, mold open, eject part
2 parts of injection molding machine
extruder section, clamp section
The _____ should be able to eject a precise amount, or shot, of polymer into the mold
extruder section
reciprocating screws are also called
ram-screw type
must be large enough to hold the mold and provide adequate space for the part to be readily removed when the mold opens
clamp section
are the reasons why injection molding has a high tooling cost
mold mass and complexity
there must be enough _____ to hold the mold close against the pressure of the material being injected
clamping force
would be prominent when there is too much injection force, and low clamping force
parting lines and flashes
is an excess material attached to a molded, forged, or cast product
flashes
if the injection force is too low and the shot size is too small, it will result to a _____
short shot problem
occurs when a material does not completely fill the mold cavity
short shot
clamping force is also called
tonnage
the size of the extruders are named according to their
L/D ratio
for injection molding, the size is dependent on the
injection capacity and clamping force
what does 400-ton injection machine means?
400 tons of clamping force
is a hollow form or matrix for giving a particular shape to sometheing
mold
hollow or female part of the mold
cavity
positive part or the male part of the mold
core
mounted to the machine in a stationary position
cavity half
2 main parts of the mold
cavity half, core half
mounted on a sliding frame so the mold can open and close
core half
use a melt-conveyance screw designed to provide reciprocal as well as rotary motion, combining the function of screw and piston
ram-screw-type (reciprocating screw)
have a separate chamber and piston for injecting the molten polymer, allowing for faster injection of the plastic into the mold
screw plunger or two-stage machines
wall thickness of the molded part is determined by the
space between the mold’s core and cavity
the small opening through which plastic melt enters the mold cavity
gate
is the main channel through which the melt enters the mold
sprue
are designed with material feed runners and gate systems that are insulated from the cooled mold cavity and core
runnerless or hot runner
are often incorporated into the runner system to ensure that the plastic is kept on a hot, fluid state
auxiliary heaters
is a channel that distributes molten plastic to various cavities in a multicavity mold
runners
cools the molten polymer so that it solidifies
cooling channel
cooling systems usually use
water or water-glycol mixture
helps in physically ejecting the molded part
knock out pins and ejector plate
might also be use in injection
compressed air
is a part feature that prevents a mold from opening in a normal back-and-forth motion unless other pieces of mold metal are first removed
undercut
these marks are mostly due to plastics’ high expansion coefficients
sink marks
occur where there is a substantial variation in the thickness of the plastic
sink marks
