Extruders - Non Plastic

Extruders - Non Plastic: Machinery used for the process of extrusion, which is the act or process of shaping by forcing through a die. 

Extrusion is a process used to create objects of a fixed cross-sectional profile.  A material is pushed or drawn through a die of the desired cross-section.  The two main advantages of this process ovver other manufacturing processes is its ability to create very complex  cross-sections and work materials that are brittle, because the material only encounters compressive and shear stresses.  It also forms finished parts with an excellent surface finish. 

Extrusion may be continous (theoretically producing indefinitely long material) or semi-continuous (producing many pieces).  The extrusion process can be done with the material hot or cold.  Commonly extruded materials include metals, polmers, ceramincs, and footstuffs. 

There are many different variations of extrusion equipment.  They vary by four major characteristics;

1. Movement of the extrusion with relation to the ram. If the die is held sationary and the ram moves towards it then its called "direct extrusion".  If the ram is held stationary and the die moves towards the ram its called "indirect extrusion".

2. The position of the press, either vertical or horizontal

3. The type of drive, either hydraulic or mechanical

4. The type of load applied, either conventional (variable) or hydrostatic.

A single or twin screw auger, powered by an electric motor, or a ram, driven by hydraulic pressure (for steel alloys and titanium alloys for example), oil pressure (for aluminum), or in other specialised processes such as rollers inside a perforated drum for the production of many simultaneous streams of material.

There are several methods for forming internal cavities in extrusions.  One way if to have the mandel intergrated into the ram.  If a solid billet is used as the feed material then it must first be pierced by the mandrel before extruding through the die.  A special press is used in order to control the mandrel independently from the ram.  Another method is using whats known as a "spider die, porthole die and bridge die".  During extrusion, the metal divides and flows around the supports for the internal mandrel.