Injection Molding Flashcards
What is the objective of this lab?
The objective of this lab is to study the effects of key process parameters—temperature, pressure, and the number of gates—on the strength of injection-molded specimens. By performing regression analysis on data collected from tensile tests, the lab aims to identify relationships between these variables and evaluate how they influence the mechanical properties of the final products.
What is the procedure for this lab? Part 1
Preparation Phase:
1. Preheat the Machine:
Allow the injection molding machine to run until the hydraulic oil reaches its operating temperature.
Familiarize yourself with the machine’s operation.
- Inspect the Mold:
Set the initial mold temperature to 30°C.
Confirm the plastic flow path from the sprue to the tensile test specimen cavity.
Adjust mold valves to ensure plastic flows through a single gate for initial tests.
What is the procedure for this lab? Part 2
Specimen Production:
1. Initial Setup:
Set the initial injection pressure to 1000 psi, plasticizer to 45 mm, and nozzle temperature to 410°F.
Produce a single specimen in semi-automatic mode and inspect for defects.
Switch to automatic mode, discard the first five specimens, and collect the next six, marking them sequentially.
- Change Pressure:
Increase injection pressure to 2000 psi.
Discard the first five specimens produced under the new conditions, then collect and mark six sequential specimens.
3.Two-Gate Setup:
Adjust mold valves to allow plastic flow through two gates.
Set the plasticizer length to 50 mm and produce one test sample. If acceptable, continue.
Repeat the procedure for pressures of 1000 psi and 2000 psi, collecting six specimens for each pressure after discarding the first five.
- Adjust Mold Temperature:
Change the mold temperature to 35°C while keeping the two-gate configuration.
Repeat the procedure for pressures of 1000 psi and 2000 psi, collecting six specimens for each condition.
Change the mold temperature to 40°C and repeat the process as above.
What is the procedure for this lab? Part 3
Tensile Testing Phase:
1. Specimen Preparation:
Measure the cross-sectional area (A) of each specimen.
- Tensile Strength Test:
Turn on the INSTRON tensile testing machine and its hydraulic motor.
Place tensile test jaws and adjust their position for the specimens.
Zero the force and displacement displays.
Mount a specimen, ensuring it does not slip using sandpaper if necessary.
Gently load the specimen and note the maximum force (Fmax) before failure.
Return the jaws to the initial position and repeat for all specimens.
- Calculate Ultimate Tensile Strength (UTS):
UTS = Fmax / Area
Data Collection & Analysis:
Record all relevant parameters:
Number of gates.
Plasticized length.
Injection pressure.
Mold temperature.
Maximum force (Fmax).
Cross-sectional area (A).
Calculated UTS.
What is the lab conclusions?
This lab investigated how pressure, temperature, and gate configuration affect the tensile strength of polypropylene specimens made through injection molding. Key findings:
Pressure and Strength: Higher injection pressure significantly improved tensile strength.
Gate Configuration: Double gate designs yielded stronger specimens than single gates, as they improved material flow and distribution.
Temperature Control: Proper temperature management is essential to achieve desired material properties.
Sequence and Defects: Mold sequence affected defect occurrence, likely due to variations in machine settings over time, emphasizing the need for consistent process control and machine stability.
In summary, optimized pressure, gate design, and temperature, along with stable machine parameters, are crucial for producing high-quality polypropylene parts.
Specific Things to Remember!
d. Select the 1200 range on force. If the variation in the displayed value does not exceed 10 lbf in 10 minutes, it is warm enough to proceed.
