1. Injection molding Injection molding is similar to casting in that
Cavity
Runner
Sprue
Parting line
Making a cavity for injecting the melt VS
Making a cavity for casting

2. Principle of the process
Structure/Configuration
Process modeling
Defects/quality control
Design For Manufacturing (DFM)
Process variation

3.
Video for general introduction to injection molding that includes the extrusion process

4. Shaping Processes For Plastics – Injection molding

5. The mold system The key is to make mold which has cavity.
The complexity of cavity determines the complexity of molding.
The mold system
Functional analysis:
FR1: to form a closed cavity.
FR2: to get the molded part out of the cavity.
FR3: to pour the melt into the cavity.
FR4: to separate the runner and sprue from the molded part
Constraint analysis:
CR1: uniformity
CR2: full fill
CR3: molten status

6. DP1 (two separate parts to form a mold cavity)
Functional analysis:
FR1: to form a closed cavity.
FR2: to get the molded part out of the cavity.
FR3: to pour the melt into the cavity.
FR4: to separate the runner and sprue from the molded part
Constraint analysis:
CR1: uniformity
CR2: full fill
CR3: molten status
DP2 (ejector system with one plate)
DP3 (runner and sprue with one plate)
DP4 (extra plate)
Two plate: <DP1, DP2, DP3, DP4>1: first design option
Three plate: <DP1, DP2, DP3’, DP4’>1: second design option
DP3’: sprue with one plate; DP4’: runner with one plate
Hot runner: <DP1, DP2, DP3’, DP4’>1: third design option
DP3’’: runner with heater; DP4’’: sprue with heather

7. DP1 (two separate parts to form a mold cavity)
Functional analysis:
FR1: to form a closed cavity.
FR2: to get the molded part out of the cavity.
FR3: to pour the melt into the cavity.
FR4: to separate the runner and sprue from the molded part
Constraint analysis:
CR1: uniformity
CR2: full fill
CR3: molten status
DP2 (ejector system)
DP3 (runner and sprue)
DP4: heat up the runner and sprue so that they keep the same temperature as the mold.