I purchased a Felix 3D printer with the intention of printing scenery type stuff for my Sn3.5 in progress railway. My research suggested the resolution would not be adequate for printing the fine detail required by rolling stock. However I reasoned there was a fair change of success with stationery parts. My test part was a simple old style phone box - remember them?
The results were very disappointing. I struggled to get any reasonable result for MONTHS. A key issue is that the Skeinforge software used by Felix, RepRap and so on just has far too may variables to play with. Then I happened to se a UP printer being demonstrated, and to cut a long story short, the guy just took my STL phone box file and drag-and-drop printed it first go. So I traded the Felix on a UP and as advertised it worked 15 minutes out of the box. The key is its "Closed" software means there are few adjustments one can make, no G Code files and so on. One just draws the object (I use 3D CAD) and print it.
Phone box and the like - no problems. I then went for a Red/Green signal, printing the base, and ladder, with allowance to insert a 3mm brass tube for the post and top it with a head, target and shroud to which I fit a 3mm bi-level Dialight LED. It's about the right size for 1:64. After some experimentation I have success.
Keys to success are to oversize the pars so they will print and be robust enough to remove the thin support structure the UP inserts during printing. The result becomes what I call "Visual" or "Stand OFF" scale rather than exact fine scale. I challenge anyone to pick the difference at 2 metres.
The printable design has ladder sides 2mm x 0.6mm, as are the ladder steps. The safety ring is 1.2 x 3mm and for printing the thing has one edge of the base down and the ladder rotated so the safety ring is at the same Z level as the edge of the base. In this orientation the thin support structure is minimal about the fragile safety ring, and with a bit of practice all the support stuff can be removed without destroying the part we want.
So, at full size the ladder would be about 36 x 120mm, and the ring 38 x 180mm. Well oversize, but as I said, at 2 metres the difference to exact fine scale can only be detected by persons of overstimulated imaginations or those prone to extreme pedantry.
That said the signal as a test item show the limitations of 3d printing. The signal at proper scale id too fragile for any (home) 3D printer to make reliably. Even if successful the strength of the plastic is quite low. Big chamfers on the base of the ladder to stop breaking away from the base, for example. But unless pointed out, it still looks the part.
But, I conclude
* That a signal at 1:64 scale is about the limit of practical resolution and practical strength for 3D extrusion printing
* That strength and detail are not adequate for locomotives or rolling stock.
* The focus should be on scenery and building items. (I make doos and windows with the UP and building sides and door/window cut outs with 3mm MDF and a 3020 CNC router. Quite a productive combination.
My recommendation is go for a UP for its "Drag and drop" printing, forget about the bigger (you won't use the extra size) machines and treat Skeinforge et al as you would a vampire! Concentrate on using the machine, not finessing its operation I say.
Hope that helps. If anyone wants an example (eg the signal) I am happy to post you one.
Hope that helps