I am not sure as to what is being referred to as “steel molds”.
Steel is very difficult to engrave and is usually reserved for
making stamping dies. There are softer metals for engraving molds
that I believe are more suitable. Free machining brass,
magnesium, aircraft aluminum, and low melting temperature mold
metal are used to make metal molds. For making graphic details to
reproduce in wax you might want to check out the Model Master
system in which a photopolymer is exposed to ultraviolet light
with a negative and the results are rubber molded and used in the
regular way that rubber molds are used. This system is reasonable
in price and will produce waxes that are acceptable for many
designs. For greater detail or higher volume metal molds are
desirable and more expensive to produce.
Traditionally metal molds have been engraved with 2 and 3
dimensional pantograph engraving machines. These machines use
templates that guide the rotating cutter to remove the metal
where it is desired. These machines use cutters called single lip
cutters and are probably the first form of rotating cutter ever
invented. Many pantographs can be setup to cut different ratios
of the master template to the mold. Some will work in ratios from
16:1 to 1:1.
More recently die and mold makers have started to use CAD/CAM
systems in which a computer controls the action of the cutter
instead of a template. The advantages are obvious as a detailed
template does not have to be made and also the operator does not
have to tediously tend to tracing the template as in a manual
system. Unfortunately, CAD/CAM systems are still quite expensive
but are becoming more reasonably priced every year.
Stamping dies are made in the same way as molds except they are
made with tool steel and the engraving is much slower as the tool
steel is much harder to engrave than the softer mold metals. Of
course the metal is annealed when engraved and then hardened when
finished. If one has access to an EDM machine then the engraving
can be done in soft graphite and then etched into the mold or
Once a die is made a hydraulic press is needed to imprint the
design into the metal. The pressure needed for such operations is
from 25 tons to 300 tons depending on the die.
For molding with metal molds the common thing to use is a air
powered plastic injector that has been engineered for the jewelry
industry. These inject with pressures from 3,000 to 6,000 psi. I
have seen engraved brass molds used with dental wax and a
hydraulic press to force the wax into the mold with good results.
Of course this would not do for high production situations.
Hope this helps and good luck in your endeavors.