1. Injection molding
Injection molding is similar to casting in that it also has the concepts of
Cavity
Runner
Sprue
Parting line
Making a cavity for injecting the melt =
Making a cavity for casting
Video to overview polymer melt injection molding

2.
Video for general introduction to injection molding that covers both cold runner and hot runner
Hot runner: sprue with runner is not a part of the mold; instead, it is a separate system

3. Shaping Processes For Plastics – Injection molding

4. The mold system (cold runner)
The key is to make mold which has cavity and the product can be got out from the mold afterwards.
The complexity of cavity determines the complexity of molding.
3-plate mold
2-plate mold
Functional analysis:
FR1: to form a closed cavity.
FR2: to pour the melt into the cavity.
FR3: to get the molded part out of the cavity.
Constraint analysis:
CR1: uniformity
CR2: full fill
CR3: molten status

5. Design of the mold system (cold runner)
Two plates: <DP1, DP2, DP3, DP4>: first design option
Design of the mold system (cold runner)
DP1 (two separate plates to form a mold cavity)
Functional analysis:
FR1: to form a closed cavity.
FR2: to pour the melt into the cavity.
FR3: to get the molded part out of the cavity.
Constraint analysis:
CR1: uniformity
CR2: full fill
CR3: molten status
DP2 (runner, sprue and molded part on one plate)
DP3 (ejector system on the moving plate of the mold)
DP4 (manual operation)
DP1 (two separate plates to form a mold cavity)
FR1: to form a closed cavity.
FR2: to pour the melt into the cavity.
FR3: to get the molded part out of the cavity.
DP2’ (runner, sprue on one plate)
DP3’ (ejector system on the moving plate of the mold)
Three plates: <DP1, DP2’, DP3’>: second design option

6. DP1 (two separate plates to form a mold cavity)
Design of the mold system (hot runner)
DP1 (two separate plates to form a mold cavity)
Functional analysis:
FR1: to form a closed cavity.
FR2: to pour the melt into the cavity.
FR3: to get the molded part out of the cavity.
Constraint analysis:
CR1: uniformity
CR2: full fill
CR3: molten status
DP2 (runner and sprue at stationary frame)
DP3: Heater for the sprue and runner
DP4 (ejector system on the moving plate of the mold)