[chbot] 3D printer kit recommendations, and quick start help

[Mark Atherton]

Hi all,

A mate of mine is about to embark on building a 3D printer and is 
looking for suggestions.

Main objective is low cost and maximum education, with a capability 
of printing (something like) a 30mm cube

He has strong mechanical skills, and has a background of configuring 
and programming light industrial equipment (programming within this 
context means creation of sequences of events rather than writing software).

Below is a first-cut list of pieces-of-the-puzzle which he will need 
to get to grips with. I may have left stuff out, or just got stuff 
wrong, so please feel free to correct me and to make relevant other comments.

Many thanks,

Mark

===============

 From my understanding of the process:

1) Get or create a design.

1a) Assume that the starting point is to print a simple object from 
http://www.thingiverse.com/ - learning to design items can be left as 
a later activity.

2) Convert to some kind of motion vectors

2a) What is the most common intermediate format, is it G code - if 
not, then what ?

2b) What are the recommendations for the best free/open source 
solutions to convert from design to printing motion activities ?

3) Convert the output of 2) into a format that can be carried to the 
hardware controller.

3a) Presumably there is a name for the physical link, and payload, 
again, name please.

3b) What are the recommendations for the best free/open source 
solution, or does 2) also drive the interface ?

3c) What is the currently most popular physical interface (USB, LPT, etc.)

4) Controller interface to hardware

4a) Plugs into 3c).. What are the names of popular, low cost, readily 
available controllers, and suppliers ?

4b) I think older interfaces used a pretty dumb motor controller 
using an LPT port. Are smarter controllers now used ?

4c) What not to buy, and suppliers to avoid ?

5) Hardware interface

5a) A collection of stepper motors are attach to 4a). Which stepper 
motor type is more popular, bipolar of unipolar ?

5b) recommendations for typical stepper motor size, NMEA type etc.

5c) Any special features for the stepper motors (voltage, dual shafts etc)

6) Mechanical frame

6a) From first hand experience, recommendations and warnings about 
current designs.

7) Omissions, corrections

7a) Anything I have forgotten

7b) Things I have got wrong ?

7c) Pointers to a web site, quick start guide document, or book that 
may cover these questions in more detail ?