Re: [rp-ml] Fab@Home

From: Ian Gibson (
Date: Mon Jan 15 2007 - 05:13:33 EET

Steve, Marshall

I read your comments with interest and have a (slightly) different view.

- To Marshall, I would say '"don't underestimate the benefits toys
have on other branches of technology". These days, many very useful
software tools have benefited from getting a good start in the
computer gaming industry. From my era, I'm convinced Jerry Anderson
influenced a whole generation of aerospace and automotive engineers.
Also, the toy industry is highly competitive and demanding and I'm
sure many cost-cutting manufacturing techniques have originated from
there. Furthermore, it is my experience that many users of toys are
in fact young children, who could grow up to be engineers given the right push.

- To Steve, your analogy is something of a Curate's Egg. In my view
the support structure is not a problem, if you have sufficient time.
You can always switch the material in the nozzle every time you
require supports. However, I realise this would be very tedious and
so there are usable limits when applying the Turing model. An
alternative is to use a low-density approach, using a support
structure that can be reasonably easy to remove. Very early FDM
machines and at least one low-cost clone from China use exactly this
approach. Also, it would be a very minor cost increase to include 2
nozzles on the machine like current FDM. Better still, switch to
multijet printer technology.

My problem with Fab@Home is the business model, not the technology.


At 01:07 15/01/2007, you wrote:
>Marshall Burns wrote:
>>The Altair was little more than a toy. Even the Apple I, compared to
>>business computers of the day, was little more than a toy.
>I don't think this is a fair analogy.
>There is a mathematical/computing theorem called 'The Church Turing
>Thesis' that says that any computer with a certain minimal level of
>functionality (which both of those machines had) is capable of doing
>anything that any other computer can do providing you have enough
>memory, and enough time.
>I owned (and in fact still own) an Altair 8800 (1975)- and it was
>capable of doing quite a lot - even when compared to business
>computers of the time. I know of several businesses that successfully
>used Altairs - (because I wrote quite a lot of software for them to
>help pay my way through college!). My first job (with Philips Research
>labs) was to write software to control a telephone exchange using an
>Intellec-8 which was almost identical to the Altair 8800.
>You can see the old Intellec 8 here:
>But the Fab@Home machine has a very fundamental limitation. Being
>unable to build objects with overhangs means that there is a large
>set of things that it just can't make - no matter how patient you
>That's a more fundamental difference than there was between
>business computers and those early personal computers in the mid
>1970's where the only real difference was in memory size and speed.
>I believe that the first truly ground-breaking 'home fabrication
>machine' will be one that can make any shape - albeit very slowly
>and with some fairly restrictive size and precision limitations.
>But we have to take baby steps - the Fab@Home machine is a reasonable
>first effort - but solving the problem of support materials and using
>dual nozzles is something that needs to be done to make a machine
>that's of significant practical use. After all, if you can only make
>objects with no overhangs then you can already make those things
>cheaply using subtractive techniques on existing low-end CNC

Dr. Ian Gibson
Associate Prof.
Dept. Mechanical Engineering
National University of Singapore

tel: +65 9277 7343

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