Vacuum Forming Lab

In this lab we studied the process of vacuum forming and the effects upon the thermoplastic material. The thermoplastic material was in sheets that were 12" x 12". On these sheets were placed a 1" grid so that the amount of deformation could be seen after the vacuum forming was finished.

The procedure used to study the vacuum forming process required a heating oven in which the sheets of plastic were placed. The sheets were clamped between to square frames that held the sheets tight while they were heated. Once the sheets had been in the oven the designated amount of time and temperature they were pulled out of the oven and placed over top of the mold. The mold was then pushed up into the hot plastic and the vacuum pump was turned on. The vacuum pump ran a programmed amount of time and then the mold was automatically was lowered. The finish part was then removed from the clamped frames.

The temperature and time for each part was recorded and can be seen below.

Face #……………..Temp………………Time in Oven………………..Remarks

1……………………290……………….19 sec…………………………Abort-heated to long

2……………………295……………….20 sec…………………………good part

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 measurements were taken on selected parts. All dimensions are in inches.

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

The vacuum forming process was simple to do and worked well once the optimal operating temperature and time were found.

From the data that was taken it could be seen that the best operating temperature was between 267F and 295F. The time was kept the same to eliminate a variable while the best operating temperature was found.

Thermoset Casting

The thermoset casing part of the lab was shortened to just a demonstration of the process.

Two different mold conditions were studied to view the affect on the part that was being produced.

……..#1 Chill mold before mixture of compounds are poured into mold.

……..#2 Heat up mold before mixture of compounds are poured into mold.

A difference was seen in how the compounds cured. The compounds cured from the outside first in the mold that was heated up. The compound cured from the inside out in the mold that was cold. The curing was also faster in the mold that was heated up.