Check-list for finding the right rapid prototyping technology

Posted on June 8, 2009 by Nora González Dwyer

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?

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.

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.

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.

Design case: Tata’s Nano

Posted on April 20, 2009 by Nora González Dwyer

Tata Motors has launched the cheapest car in the world with the purpose of providing a car with the minimum standards and affordable for many Indians.

Strategy:

It is an extreme case of design reduced to what is strictly essential; we have seen this in notebooks and other electronics already. Having a look at the features it includes, helps us picture the scene:

On the cheapest version the driver’s seat is the only seat which can be adjusted.

There is no power steering and various “luxuries”, such as air conditioning, fog lamps, front power windows or central locking are only available on pricier models. I don’t know about you, but I could do without front power windows if that would mean reducing the price of the car. For us, the ones that see the car as a big tool that helps us get from A to B, there is a big difference in the value of real functionality, such as power steering, and commodities that allow you to get lazy such as central locking.

It is a nice example of targeted design: rather than competing directly with the next cheapest car, it aims to substitute scooters and small motorbikes, with a price of Rs. 100,000 (around $2000).

Safety on the road – the Nano has a point here. Image from Joe Athialy

To meet all economical and quality requirements a good bit of innovation has been required. It is estimated that at least 35 patents associated with the vehicle have been registered.

Environmental issues:

This is one of hottest aspects of the Nano; on the one hand it is a car and it pumps out twice the CO2 as a scooter. On the other hand it has a 4-stroke engine and a crude catalytic converter which appears to reduce most pollutants by about 80 percent and which scooters lack of.

It also meets Euro-IV and Bharat Stage-III compliant, European emissions standards.

From my point of view, the problem here is not the Nano. Of course it will have a terrible effect on the already highly polluted cities in India, when the 50 million orders already placed for the car are delivered. But this is just the consequence of a barely existing public transport system in cities.

Now 50 million can… Image from Jaaziel

Indian cities are extensive and saturated with traffic, and on top of it most of the families can’t afford their own vehicle. This is cry for a well planed and far reaching public transport. If there are no measures taking in this direction, India will probably soon assume the car centred transport system, similar to the US, and then it will be really difficult to change things.

3 key aspects to green design

Posted on March 30, 2009 by Nora González Dwyer

It is tricky to design environmentally friendly products in an ever complex industrial world, but at the same time there is still plenty of room for improvement in today’s products. Here are some keys to help you identify the potential.

One: reduce waste by not designing it.

my contribution to paper waste

This week I came across a very nice piece of crafts made out of the core of toilet paper rolls. Then I stopped to think about it and realised that we can found very often coreless paper rolls in public places. I suggest, let’s not take things for granted and question why are they the way they are. Paper rolls were initially conceived with a core, because at the time the technology wasn’t able to do it otherwise.

Marriott Hotels are introducing coreless paper rolls by the end of 2009, they have a brief comment about it on their website.

Two: design reusable rather than disposable.

A significant fraction of our domestic waste is just disposable products. Reusable products minimize waste an costs. A good example for this is my last acquisition: the menstrual cup, a gem. It is a silicone device that substitutes sanitary towels an tampons. Since I have it I have saved money and literally stopped creating waste.