Thermoforming Flashcards
1
Q
Thermoforming heating methods
A
- radiant heating
- heating by conduction with hot plate
- two-sided contact heating
2
Q
Thermoforming methods
A
- vaccum or pressure
- match mould
- plug-assist vacuum forming
- plug-assist pressure
- Free blowing / billow forming
- Pressure reverse draw with plug-assist
3
Q
Thermoforming steps
A
- roll stock
- nip rollers
- electric eye
- forming station
- trimming station
- scrap wind
- part stacking
4
Q
Condition monitor
A
- sheet temperatures should be measured using infared thermocouples
- mould and coolant temperature should be monitored
- heater temperature should be closely monitored
- air pressure and vacuum pressure should be monitored
5
Q
Advantages
A
- low temperature and pressure
- only single surface mould required
- moulds inexpensive and easy to fabricate
- no need for plastic to flow
- large surface area to thickness ratios
6
Q
Disadvantages
A
- wall thickness variation
- waste of material
- sheets must be formed form pellets which are expensive
7
Q
Thermoforming steps
A
- sheet and mould alligned
- sheet is heated
- sheet is stretched over the cold mould, cooling it
- part i extracted from the mould
8
Q
Pultrusion
A
- fibres impregnated with pre-polymer
- exactly positioned with guides and pre heated
- pulled through a heated, tapering die where curing takes place
9
Q
Pultrusion advantages and disadvantages
A
- automated process with high production speed
- continuous reinforcement
- versatile cross-sectional shape production
- dies are expensive
- mainly used with thermoset polymers
10
Q
Free blowing
A
- pre-deformation step of heated sheet prior to forming step
- controlled by a photocell monitor
- pre-deformation contributes to a more uniform wall thickness variation
