I changed the subject line here because this is shop talk and a little off
topic but is in response to LJ’s question and something I am still passionate
I don’t believe a run of the mill (FDM) 3D printer that squirts molten
plastic out of a heated nozzle can work for this. The features on the couplers
are very small and they have to be produced accurately. Think about the diameter
of the little hinge pin that the knuckle swings on. Its diameter is 0.0130
inches. My original 3D wax printer acquired in 2009 (for about $17k and probably
never actually paid for itself) had a drop size of 0.0010” meaning it could
squirt a single drop of wax 0.0010” in diameter. That was good enough to form an
HO scale coupler than would work. My current printer acquired in 2013 (for about
$24k that paid for itself in 3 years) has a “voxel size” of 0.0016”. That works
too. My newest not yet in service printer acquired just this week (for less than
$1000) has a voxel size of 0.0019” which I think will be fine as well. What’s
the smallest drop of plastic a typical 3D printer can squirt out? About 0.01
inches in diameter which just doesn’t cut it. Its not the right tool for the
I put the pay off times in there for anybody that is thinking about jumping
in. Those are based on profit from items sold that were 3D printed. They don’t
take into account the fact that I sell many more diecast couplers just because I
can offer the specialty couplers. You can see that my new printer will pay for
itself in less than 2 months at the same rate.
For this work you need a printer targeted at the jewelry and dental
markets. There have been some major advances that have occurred here recently
that has allowed the price of these very high resolution printers to drop like a
rock. Older designs use a UV laser or projector (like the one in a conference
room) to selectively solidify liquid resin one layer at time to create a 3D
object. The laser hardens one pixel at a time and is slower because the laser
has to “draw” each layer. The projector projects the complete image for the
layer at once, so its faster. Newer designs are actually much simpler. Rip the
LCD display off your fancy new phone and put a few UV LED’s behind it. Now the
pattern of UV light image that gets through the LCD can be directed at some UV
sensitive resin. Add a computer to control the image on the LCD and some
mechanics to advance the 3D object a little after each layer hardens and you
have the world’s cheapest 3D printer. Fancy phones with fancy super high
resolution screens have enabled this technology leap in 3D printers. As long as
what you need to print is smaller than the display on typical phone, your all
set. Imagine what happens if you have a 11” 4K LCD for a tablet computer. Hmmm.
Most HO locomotives and rolling stock many structures are small enough to fit in
that area. Trackwork components could fit in that area too if you don’t mind
plastic track (Unprototypical shiny nickel silver railheads on passing tracks
and sidings irk me anyway – why is that acceptable – dead rail is coming). See
where this is all going. These are exciting times in the model railroading world
and things are about to get crazy.
Also regarding 3D CAD. Check out Fusion 360. Free for a year for hobbyist
and small businesses. I have historically used Solidworks, but Fusion 360 is
about to eat its lunch. Fusion 360 plus a new ~$500 printer and a website can
make you a model railroad entrepreneur. You still need to be able to turn those
plastic parts into metal to make couplers, but maybe you have other ideas.
Finally in my opinion, the plastic parts created by any of these fancy new
printers I’ve described is hard and too brittle for items that will take
constant abuse like a coupler.
Sent: Wednesday, July 11, 2018 2:33 PM
Subject: Re: [Sergent Engineering] Sergent Engineering
interesting question regarding the 3d printing. what is
the problem so far with people printing in 3d? tolerance, or
material strength. I know there are some metal filaments
available with different metal types in 'suspension' with the PLA or
whatever. Has that been tried? perhaps that has no more
inherent strength than straight PLA or whatever. I also doubt it
allows any finer tolerances. Just wondering aloud.
I have a mostly put together home 3d printer, but haven't learned any CAD
yet. I would assume that a typical home 3d printer has insufficient
precision to allow the tolerances needed amongst the parts, but would love to
hear what you(Mr Sergent) has to say on the issue.
who is still only a dabbler as the railroad is not running yet.