Hi!: somebody wrote here about a Chinese press machine he owned, being
able to
provide several tons of pressure.
The question is: would this machine be able to produce parts such as
body panels and
other steel, or aliminium, body parts of a car?
Wit the current 3D copiers, having one copier and a press of sufficient
size would allow
making, part by part, a replica of any old car you may wish, just the
time and the money
to make the casts or matrix would be needed, and an original or a blue
print to be used as
pattern.
Any comment on this?
Thank you, best regards. Salut †
Jose Gros-Aymerich
Madrid, Spain

Pressing steel fenders takes many tons of force.

3D printing in steel or aluminum takes a long time and the machine to do
it is
expensive. For one off parts use an English wheel.

Paul Lamar

Hi Paul: thanks for your response. My idea was not directly printing the
parts
in a 3D copier, but using the copier as a first step in preparing a cast
to be used
with the chinese press to make body parts from sheet steel or aluminum,
in the 60's,
a machine for preparing casts, by grinding in an Iron block, that
followed the contour
of anything used as pattern, costed here around 9'000 Euros, when an
inside town bus
ticket was 10 cents of an Euro.
Regards. Salut †

 Jose Gros-Aymerich
Spain

Jose, the economics of various fabrication strategies depends on the
dimensions of your desired parts, and the quantities needed.
It is pretty unlikely that anything in the home built aircraft situation
(short of going into the business like Vans or Zenith) will justify the
costs associated with 3D printing. For flat profile parts IE ribs and
such, a good wood shop router, bits, and band saw on MDF material are
plenty for making dies.
There was an article in EAA Experimenter outlining a pseudo hydroforming
technique for forming flat profile parts, using a high powered press and
strips of rubber in a die box, but the big caveat there was that as the
part area got larger so too does the force required to form the part and
also the die box to contain the forces of the compressing rubber. The
weight of the containment box for a 20"x 12" wing rib I calculated to be
around 250 lbs.
Conventional sheet metal forming methods are cheaper, quicker to get
right, and proven over many years. Perhaps a CNC router to make an MDF
blank, which could then either be used directly for a limited run of rib
like structures, or as a casting blank for an aluminum die for a longer
die life? There are some CNC routers out there for about $1000 or so
that could do a rib size piece in MDF.
Parts with great depth like cowls and such use good old fashioned
English wheel and other old world craftsman sheet fabrication techniques.
As Paul said the, forces involved in stamping metal (even Aluminum) are
quite large, and the die material must therefore withstand the many
thousands of pounds per square inch of pressure to achieve fully
developed stamping details. In the article, for the pseudo-hydroforming,
I think the baseline was in the order of 1200 lbs per sq in of part
surface area.
Have you gotten any quotes for 3D printing services, and what materials
can they print?

C. Smith


Craig, where he used the word "cast" I think he meant  stamping die.
IMHO He suggest making stamping dies with metal "printing".

Basically 3D printing in aluminum, Ti or steel  is wire feed welding on
a 2D plotter
with a 3rd vertical axis added. One weld bead on top of the last weld
bead. Probably in
an argon temperature controlled atmosphere.  One tiny piece of metal at
a time.

This is why it takes days to make something useful. An easy and
relatively cheap machine to make with a PC computer control. Finish is
an issue and it would probably be hand sanded for a stamping die.

The step file format from 3D programs like Rhino and Solid works is probably
what is used to control the stepper servos.


Paul Lamar

BTW any old NC mill would make a good 3D printer when combined
with a MIG welder. The spindle does not need to turn.