2 questions from a total noob

[curious aardvark]

right first off - get yourself openscad.
http://www.openscad.org/

I'm not a programmer, but i also can't draw. So for me openscad is brilliant.
You just tell it what you want and it makes it.

simple cylinder script:

$fn=100; //sets spherical and cylindrical facets to be 100 - basically makes things rounder
od=10; // cylinder outer diameter
id=6; // cylinder inner diameter
ch=30; // cylinder height

difference() {
cylinder(d=od, h=ch);
cylinder(d=id,h=ch);
} // end diff (I always comment on my scripts.)

openscad-cylinder.jpg

what I would probably do is set a variable for wall thickness instead of an inner diameter.

$fn=100;
od=10; // cylinder outer diameter
ch=30; // cylinder height
wt=2; // wall thickness
difference() {
cylinder(d=od, h=ch);
cylinder(d=od-(wt*2),h=ch);
} // end diff (I always comment on my scripts.)

If you want to taper the cylinder you can have different start and finish diameters.
extremely useful.
Beauty of openscad is you can do things any way you like.

As far as printer accuracy goes - yeah you should easily be able to get within a mm of the stated height on a 150mm print.
But also don't be afraid to get the sandpaper and files and drill out for a bit of post processing work.
I like to print things fast and rough.
10 minutes post processing versus another 5 hours print time. These days, For me it's a no brainer :-)

One of the things you will get with more expensive machines is better accuracy. That said - once you know how your particular machine works - you can adjust accordingly.
I generally get my prints within a few tenths of a mm to the parameters.

It's not just the machine that can effect this though. Different filaments have different expansion and shrinkage coefficients.
So abs - for example, is a real bastard, and best avoided :-) Up to 1% built in shrinkage.
Pla is much better and with decent pla the shrinkage is barely noticeable - it's one reason pla is generally preferred (plus it doesn't stink and generally makes stronger and more durable prints than abs).

Then you have the flexible filaments that don't shrink at all.
And I find that any of the inclusive filaments (wood, metal, stone etc) also have no measurably shrinkage.

3d printing is a delicate balance between getting the filament to adhere to the build plate while printing, and releasing from it after. Different brands and colours of filament will all behave individually. You then need to balance that with the extrusion speed and temperature and how fast it's cooled.

The larger the bead you extrude the faster you need to cool it before it slumps and deforms.

Consequently the most important piece of software is the slicer. The thing that takes your model and turns it into thin slices of gcode that printer and use.
I recommend simplify3d for about 99.9% of printers.
If you go for a replicator dual clone. Then I recommend flashprint (which is free) - just handles the makerbot clones much much better than anything else out there.

So that's that aspect.

As far as resin versus fdm.
Resin is messy, apparently smelly and needs post processig: washing, hardening under uv light etc.
Fdm is actually much better - generally a model comes out and that's it done. If you've used supports then you'll need to remove them. But generally if you design it yourself, you almost never need to use supports.
FDM is pretty clean, the filament is generally fairly cheap and material wise there is more choice than you can shake a forest of sticks at.
Also with a multi nozzle or a 2-3 into one nozzle, you can mix different colours and materials in a single print.

That said resin machines use much thinner layers than fdm and consequently can produce injection moulded quality prints.
It all depends what you are mostly going to print.
You can get resin machines from $100 (olo/ono) on up these days. So getting a cheap one for the odd print isn't out of the question.

For example my klic-n-print replicator clone is currently setup with flexible and rigid pla. So I can print objects with flexible hinges, built in seals, valves etc.
Having two seperate extruders does come with a bunch of issues but also lets you use 2 materials with completely different printing parameters.
Mixer nozzles require filaments that print at the same temperature - so bear that in mind.

So the important thing: what sort of budget are you looking for ?

As far as fdm machines go I'd say Build quality wise they tend to max out at around the $5-10,000 mark.
After that you're pretty much just buying print volume.
That doesn't mean you can't get a a really nice machine for under $1000. If you're prepared to bolt a few pieces together yourself - you definitely can.
You can also get a fairly serious print volume as well.
have a look at this: http://www.formbot3d.com/formbot-lar...ize_p0018.html
Gets round the dual extruder issue by having two independant extruders. IDEX.
This makes dual material prints soooo much easier. All the hi-end industrial fdm machines I saw at tct this year have adopted The Idex setup.

The t-rex is what we call an i3 style. Printheads go left to right and up and down while the printbed does back and forth.
You then have the cartesian printers where the print head goes left and right and back anf forth while the bed goes up and down.
Last setup is the delta, where the printhead does everything.
I'm currently running one of each :-)
The delta is my personal favourite. But the i3 setup has a lot going for it too.

Then there's things like bowden extruder (filament is pushed through a long tube) and direct drive where filament is pushed through a really short tube directly on top of the hotend.
Bowden setup is fine - but you don't want it on a large machine.
One of the advantages of the i3 setup (designed by joseph prusa) is that you can have direct drive extruders but print at faster speeds than a standard cartesian machine.

So have a look at openscad and give us a budget to work with.
No matter what the budget, there will be something in there we can recommend :-)