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Origins, introduction to and my perspective of the FreeForm™ modelling system. Written in 2002
Context - Realization
RP additive systems
Adding material - Self supporting - Additional support
Subtracting Material
CNC Machining
Established manufacturing engineering based process where a digital file provides the geometry that will control a milling machine, which has a rotating cutter that will systematically remove excess
material from a block.
This process can be used to produce very large and very small work. Accuracy and surface detail is excellent. A very wide range of materials can be used ranging from foam to steel. The positive model,
patterns or tools used for volume manufacturing processes can be produced using this process.
There are variations to the way machines themselves are designed to make this process possible. For example the rotating head can move around the work, or the work can move around the head. The size of
work usually dictates the practical method used.
A large cutting tool is used to rough out the model and remove large quantities of unwanted material from the work. Subsequently tools of smaller diameter and end profile follow this, until the work is
near completion. Finally a small tool is used to finish the surface to the required standard. Various size and shape cutters are used according to the materials and how fast they can be worked. Foam is
much faster to work than steel for example. Some machines can automatically interchange tools as the work progresses.
The number of axis available can determine a machines capability.
3 axis machines give the basic movements for 3D geometry x, y and z. Usually the revolving cutter moves up and down (y axis) and the work is clamped to a moving bed that travels from right to left
(x axis) and from forward to back (z axis).
4 axis machines allow the cutter to revolve around the x-axis, this option can be fitted to a 3-axis machine usually requiring in the work being clamped into a controlled revolving jig.
5 axis machines allows for the work to be simultaneously revolved around the z-axis. This broadens the potential further enabling work to be made that has undercuts.
Machine path verification
The more complicated the work, the machine and the machining needs, the more necessary it is to have verification software, that can predict and ensure that the form can be manufactured without damaging
the work, or the machine. When you commission work to be made this way, a company will automatically test your files to make sure the work is able to be manufactured.
Manufacture of Multiple Copies
Using the Rapid Prototyping and machining processes above enables you to make multiple copies, by creating moulds and tools. Choosing the process depends on many factors. The final material and function
of a product will usually be pre determined and designed into the process. This can be verified through simulation and rapid prototyping, before costly investment is used, on creating the tools and
moulds for mass production.
There are many possible outcomes and methods available to produce short, or long runs. In general a positive form can be used to create a case mould, can be vacuum formed, or used as a lost wax former.
Negative moulds can be cast from, or used to vacuum form, create formers for plastic injection, or form any other material whose properties change and solidify through processing.
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