Precise-Cast Prototyping
The Fraunhofer Institute in Germany is one of the world's biggest research organizations concerned with materials and manufacturing. One method of production that has recently been developed by the institute is precise-cast prototyping.
Precise-cast prototyping(or pcPRO") is a method for rapid prototyping that combines casting and
milling operations in a single machine. It is a two-stage process, with the first stage involving a milling machine (see p.20) cutting a mould into an aluminium block using information from a CAD
file. This mould is filled with a polymer resin. Once the resin has hardened, the same milling machine cuts it to a precise final shape. The essence of this process is that it allows for one side of a product (the mould side) to be replicated exactly each time the mould is filled, but the top (milled) side may be adapted according to the information contained in the CAD file.
A product prototype usually requires numerous adjustments before it is optimized, forcing the model maker to start from scratch each time. With precise-cast prototyping, however, changes are only ever made in the CAD data. The main advantage is that for components such as housings forvarious electrical products, which have one side where the shape needs to be fine-tuned, multiples can be cast using the mould, with only one side being altered with CAD files. being altered with CAD files.
Volumes of production
This is a CAD-driven process so it is suited to both one-off and batch production, though, obviously, the mould side remains constant, so one-offs' only differ on their milled side.
Unit price VS capital investment
The tooling (the mould, in this case) is made using the same machine that makes the component, which means precise-cast prototyping is highly cost effective.
Speed
Milling of the mould typically takes between half an hour and two hours, casting and curing of the resin and milling of each part takes a minimum of an hour, depending on the part's complexity.
Surface
The surface quality corresponds with the normal quality of milled surfaces.
Types/complexity of shape
The shape is limited only by the CAD drawing and the cutter (o cutters), though extremely complex shaped parts or undercuts in the inner contour can be made by five axes milling only (that is, one cutter moving along five trajectories) and undercuts in the outer contour require special mould inserts o silicone parts.
Scale
The scale of the parts made on a standard machine is 250 by 250 by 150 millimeters.
Tolerances
Depending on the machine's accuracy, commonly some 10 microns.
Relevant material
A two-component resin.
Typical products
Complex shaped parts with high-tolerance outer surfaces and low-tolerance inner surfaces The process is used for the rapid prototyping of bodies of mobile phones, cameras, car parts, and electric and computer accessories.
Similar methods
Conventional milling (p 20) and casting methods. Other prototyping techniques, including stereolithography (SLA).
Sustainability issues
Moulding, creating the form and machining the part in a single process allows for incredible energy efficiency on many levels. By reducing the machinery used, energy consumption is cut
dramatically, along with the emissions from transportation of parts between manufacturing locations. Alterations to the milled surface can be carried out immediately without the need for a whole new mould and test runs, significantly reducing material use.
