Taha Selman Cakir
030070023
11th week

Vacuum thermoforming (15:36) :

Vacuum forming is a thermoforming process that forms thermoplastic sheets into three-domentional shapes through the application of heat and vacuum. During the vacuum thermoforming process, plastic material is heated (170° C to 200° C) until it becomes pliable, and then is placed over a mould of the requisite shape and drawn in by a vacuum until it takes on the desired shape. The application of a vacuum draws out the air between the mould and the sheet so that the plastic conformsto the mould exactly. This is accomplished through venting holes in the mould that are joined to vacuum lines. The mould also has an integrated water-cooling system that brings the temperature of the plastic to the set temperature needed. Once the curing temperature is reached after the part is formed, air flows back into the mould and seperates the new part from the mould.

(Rao, Manufacturing Technology Volume 1, Ed. 3rd, p. 474)


Pressure thermoforming (15:54) :

An alternative to vacuum forming involves positive pressure to force the heated plastic into the mold cavity. This called pressure thermoforming or blow forming: its advantage over vacuum forming is that higher pressures can be developed because the latter is limited to a theoretical maximum of 1 atm. Pressure forming pressures of 3 to 4 atm are common. The process sequence is similar to the previous, the difference being that the sheet is pressurized from above into the mold cavity.

(Groover M. P., Fundamentals of modern manufacturing: materials, process, and systems, Ed. 4th, p.363)


Part-shaping processes (18:20) :

Part-shaping operations apply mechanical force and/or heat or other forms and combination of energy to change the geometry of the work material. There are various ways to classify these processes. The classification used here is based on the state of the starting material. There are four categories.

1. Solidification processes
2. Particulate processing
3. Deformation processing
4. Material removal processes

Groover M. P., Automation, production systems, and computer-integrated manufacturing, Ed. 3rd, p. 32)

Property-enhancing operations (18:29):

Property-enhancing operations are designed to improve mechanical or physical properties of the work material. The most important property-enhancing operations involve heat treatments, which include various temperature-induced strengthening and/or toughening processes for metals and glasses. Sintering of powdered metals and ceramics is also a heat treatment, which strengthens a pressed powder workpart. Property-enhancing operations do not alter part shape, except unintentionally in some cases, for example, warping of a metal part during heat treatment or shrinkage of a ceramic part during sintering.

Groover M. P., Automation, production systems, and computer-integrated manufacturing, Ed. 3rd, p. 32)