There are many plastic parts in use today. Most products in today’s market have some component that is made of plastic. This lab will focus on three manufacturing process used to form plastic parts: injection molding, vacuum forming and thermoplastic casting
Injection molding starts out by using granules of plastics. The granules of plastics are feed into a heated cylinder(barrel), where they are melted. The melt is then forced into a die through the machine nozzle via an air cylinder. Nozzle temperature, barrel temperature, barrel pressure and cycle time will be the parameter investigated.
ABS Recommended:-----Temp Barrel-475°F Temp Nozzle-500°F
All Temperatures are Nominal
#1 450 475 115 Unknown #2 450 500 115 2 #3 450 500 115 31 #4 450 500 115 30 #5 450 500 115 7 #6 450 500 115 11 #7 450 500 115 11 #8 450 500 115 11 #9 450 500 115 11 #10 450 500 115 2.8 #11 450 500 115 2.8 #12 450 500 115 30 #13 450 525 115 10 #14 475 500 115 10 #15 475 475 115 10 #16 475 500 100 10 #17 475 500 80 10 #18 475 525 115 10 #19 500 500 115 10
Set at nominal temperature and pressure, varying cycle time
Speciman---Temperature-°F---Pressure-psi---Time-sec.---Expected Outcomes
-------------Barrel--Nozzle
#9 450 500 115 11 Good Shot #10 450 500 115 2.8 Short Shot #11 450 500 115 2.8 Short Shot #12 450 500 115 30 Over Fill/Mold Seperation
Set cycle time and pressure, varying barrel temperature
#9 450 500 115 11 Short Shot
#14 475 500 115 10 Good Shot
#19 500 500 115 10 Over Fill/Mold Seperation or Burnt Set cycle time and pressure, varying nozzle temperature
#15 475 475 115 10 Short Shot #14 475 500 115 10 Good Shot #18 475 525 115 10 Over Fill/Mold Seperation or Burnt
Set cycle time and nominal temperature, varying pressure
#14 475 500 115 10 Short Shot #16 475 500 100 10 Good Shot #17 475 500 80 10 Over Fill/Mold Seperation
Varying Cycle Time
This leads to an over/under-filled shot
The material properties would not be effected, this only effects the amount of time the part is in the mold
Varying Barrel Temperature
Leads to an under-filled part if the temperate is lowered
Leads to an over-filled part if the temperature is to high
Leads to a week microstructure because of the high temperature of the barrel(burnt part)
Varying Nozzle Temperature
Leads to an under-filled part if the temperate is lowered
Leads to an over-filled part if the temperature is to high
Leads to a week microstructure because of the high temperature as the plastic passes the nozzle(burnt part)
Varying Pressure
This leads to an over/under-filled shot
The material properties would not be effected, this only effects the force at which the material is injected
All the ultimate load values have a high correlation. The high correlation
implies that varying the different parameter did not lead to a large change
in microstructure.
Sample # Ultimate Elongation at Failure Elongation at Initial Initial Injection
Load (lb.) Ultimate Load Load (lb.) Failure Load Thickness Width sample #
(in) (in) (in) (in)
7 275.5 0.48 122.73 5.01 0.1775 0.476 7
9 240.89 0.51 121.43 5.62 0.1445 0.479 9
12 325.11 0.52 143.62 8.05 0.203 0.4705 12
13 245 0.51 122 5.4 0.142 0.4785 13
14 242.85 0.57 112.94 3.89 0.1555 0.474 14
15 242.2 0.63 101.84 4.05 0.1485 0.479 15
16 253.3 0.54 116.86 2.1 0.151 0.478 16
19 265.05 0.39 101.9 1.12 0.179 0.4755 19
Vacuum forming is a series of process for forming thermoplastic sheets. The process starts by heating the sheet. The sheet is then placed over a mold with a pressure differential. The malleable plastic then forms to the mold, trimming is some times needed. The lab will focus on the heating temperature parameter.
Face# ............Temp(F) .............Time in Oven ...............Remarks
1 ........................290 .......................19 sec .............................abort
2 ........................295 .......................20 sec .............................OK
3 ........................286 .......................20 sec .............................bad part (operator error)
4 ........................283 .......................20 sec .............................good part
5 .......................276 ........................20 sec .............................bad part (cool around edges)
6 .......................269 ........................20 sec .............................good part
7 .......................262 ........................20 sec .............................bad part (not hot enough)
8 .......................258 ........................20 sec .............................bad part (not hot enough)
9 .......................253 ........................20 sec .............................bad part (not hot enough)
10 .....................258 ........................20 sec .............................bad part (not hot enough)
11 .....................267 ........................20 sec .............................good part
12 .....................275 ........................20 sec .............................good part
13 .....................276 ........................20 sec .............................good part
The Following Feature Measurements Were Taken (in):
Face # ....................Between the Eyebrows ............................Midway Down The Nose
2 .......................................1.177 ...........................................................1.525
4 .......................................1.20 ..............................................................1.48
6 .......................................1.28 ..............................................................1.53
11 .....................................1.29 ..............................................................1.55
7 .......................................1.36 ..............................................................1.43
8 .......................................1.29 ..............................................................1.25
Feature Measurments in Graphical Form, Figure 1
Face number two corresponds to the optimal forming temperature which is 295 DEG F. This can be seen in figure 1 by the face with the largest distance between features. This is the some thing as saying the face has formed to the mold details.
In thermoset casting two fluids are mixed and then pored into a mold. The chemical reaction takes place quickly in the mold and the polymer solidifies, in ambient air usually. Heat is generated in the reaction which helps speed up the reaction time. The molds can be flexible to help in part removal. Due to time constraints this portion of the lab was conducted for reference purposes only, with no data gathered.