Plastic Forming Processes

Question 1

What are some forming processes?

Answer 1

• Line bending
• thermoforming
• vacuum forming

Question 2

Can thermosetting plastic used in forming processes, if so name the processes?

Answer 2

No, thermosetting plastic can be used in forming processes

Question 3

What is thermoforming (thermoplastic) ?

Answer 3

A sheet material is heated just above its softening point and then held securely in a frame between two mould halves. The mould halves close and at a vacuum is applied through the lower mould. The upper mould ensures required detail.

Question 4

What are the advantages and disadvantages of thermoforming?

Answer 4

Advantages:
-low cost
-good for smooth shapes with additional detail
Disadvantages:
-deep moulds result in a thinning of the wall where it has been stretched
-simple designs
-trimming is usually needed

Question 5

What is vacuum forming (thermoplastic)?

Answer 5

Vacuum forming is the same as thermoforming accept apart from instead of an upper mould pushing the mould into shape a vacuum is used to pull the thermoplastic onto the mould.

Question 6

What are the advantages and disadvantages of vacuum forming?

Answer 6

The advantages and disadvantages are the same as thermoforming.

Advantages:
-low cost
-good for smooth shapes with additional detail
Disadvantages:
-deep moulds result in a thinning of the wall where it has been stretched
-simple designs
-trimming is usually needed

Question 7

What is line (or strip) bending?

Answer 7

Used to form straight lines and small curved bends in thermoplastic sheets.
- A strip heaters used for this. The sheet is clapped down on to heater and so the heater heats required part that needs bending. When soft enough the plastic is bent into shape.

Question 8

What are the advantages and disadvantages of line bending?

Answer 8

Advantages:
-low cost
-simple process 
Disadvantages:
-may be burnt if not monitored correctly 
-only simple shapes can be formed
-restriction to number of bends
-stress bends occur