We can shortly define layer manufacturing (or more commonly known rapid prototyping) as a group of technologies which are able to:
- build a part directly from 3D data
- within hours
- without using a mould or a specific tool
Due to their high costs, these technologies are rather used for prototypes, though they are slowly entering the low volume production parts market.
Whereas 10 years ago this technologies were still in an early development stage, nowadays we have a wide range of established machines in the market. Each system has its own characteristics and the available materials go from plastic and resins to even metal.
The question for most of us designers is: how should I have my model built to have a good result? which of these technologies meets my requirements?
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picture from rootoftwo
In the web we can find plenty of comparison charts and information sheets, but the ones I found are mostly focused on technical aspects and not in the result that comes out of the machine.
Here is my attempt to synthesise the basic factors in a check-list:
Material: The available colours and textures for plastics and resins are limited, and technology dependent, so this is one of the issues you should first look into if optics is your priority. To build your model in metal will cost in layer manufacturing in average 10 times more as other materials. I would recommend for medium – big sized metal parts to use CNC milling.
Size: this is a decisive point; layer manufacturing processes are additive, and this means the bigger your part the more expensive it is, and in a rather exponential factor. Each machine has also its maximum buildable volume, so if your model were bigger you’d have to build it in several parts, adding a good bit of work to the model.
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picture from Wizard23
Part stability: if you need a functional model, you should go for a material with good mechanical properties. all materials look similar but you bet their properties are very different from one another.
Part geometry, detail resolution and accuracy: layer manufacturing processes work till some extent like printers; when they have a rough definition it is not possible to draw fine details in the model. You can also have a machine that can draw very fine details but that is not accurate and has a big tolerance. You should check the minimal feature size a machine can build and how accurate it can be. These factors are important if your model is part of an assembly and needs to fit into other parts.
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picture from superrune
Surface finish: each machine and material provide their own surface. In all layer manufactured parts you will be able to recognise the layer structure, either like steps or as a non uniform roughness. If this is an issue for you it is always possible to apply a finishing to the part but this could turn into the most expensive and time consuming factor of all, so look carefully into the finishing before building your model.
You have to put all these issues on a balance, set your priorities and have a look at as many parts as you can, to get a feeling how yours is going to look like.
