Re: Looking for a micro/mini lathe & milling machine

Bill Lugg

That's impressive, nice work.  I took a look at Open SCAD, but couldn't
seem to wrap my head around it.  I use FreeCAD to do my 3D modeling.  I
find it much easier to visualize things in a graphical environment.  It
works on the concept of parametric "sketches", followed by performing
pads, pockets, rotations, lofts, etc.  Your dome example would be
constructed with a rotation to construct the basic dome and a pocket to
remove to boiler void - two sketches and two solid operations.  Just two
different way of accomplishing the same goal.

You're absolutely right about Shapeways' brass casting capabilities. 
The price is a little steep, but the results are beautiful.  Another
source for 3D prints is All3DP (CraftCloud). I've found them to be much
more reasonably priced in many cases. Just recently, I submitted a model
to Shapeways for printing in their high detail resin and they were going
charge me $30 plus shipping for one of them (i needed two), CraftCloud
came up with a printer that would do it for a little over $11 for the
pair in the same material.  I'm supposed to see the results Saturday. 
All of my past orders through them have been outstanding.

By the way, what printer did you buy?  I'm in the market for one and am
interested in what others are choosing.

Bill Lugg

On 2/16/22 08:49, Glenn Butcher wrote:
For a long time I've wanted to do brass scratchbuilding. Recently, I
set out to do just that, and came to the conclusion that a $2-3000US
investment in machine tools just wasn't practical.  I guess I want to
build the model just a little more than I want to learn machining...  :D

I just bought a resin 3D printer, and I'm going to try a
"print-if-possible" approach, similar to what Jeff Kraker did for his
On3 Shay, described here: Some
things you just can't get away from metal, e.g., drivers. Nigel
mentioned domes, and that's the thing that really got me thinking
about printing.  I researched how folk were cutting domes on a lathe,
watched a video of a fellow cutting the curved base with a fly cutter
on a lathe, then turned to a simple script in OpenSCAD which did the
same thing by subtracting a cylinder from the base, easy-peasy.  Well,
maybe not so easy if you've never done such, but the tools to do it
take up so much less space.

I know this is going to look complicated, but like most things
computer, it's pretty simple once you understand what's going on. This
is a screenshot of my DRG #168 steam dome model, and a piece of the
script that defines it.  The highlighted line, #41, is the cylinder
that's subtracted from the base with the difference() command at line
#33 to make the curved base to fit the boiler:

This is in OpenSCAD, a script-based CAD tool that lets you define
stuff in a script, rather than drawing it on the screen.  I find it
easier to express specific dimensions such as this dome-boiler
interface in text commands that can be edited more easily than mousing
around on the screen.  The whole steam dome is described in 92 lines,
and I've since found a simpler way to do the base than you see here

If metal is really what  you want to do, Shapeways offers a cast-brass
option, a bit pricey, but the results are sure pretty...

I've described all this because I've found that, while there's a bunch
of HOn3 parts out there for printing, the selection is based on the
interests of specific modelers, so chances of finding your specific
thing is rather small.  Me, I couldn't find Baldwin T-12 domes, so I
had to script my own.  It's not that hard once you learn the ropes,
but it's a barrier to using 3D printing as a machining alternative...

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