I have seen a lot of
questions on some industry forums lately about small holes, and the kind of
machines needed to produce them. Here are some things to think about if you
find yourself in a position to produce these holes, or to consider a piece of
equipment capable of producing them.
The hole
specifications will usually define the hole drill machine requirements. If you
need to blast a simple WEDM start hole through some hardened tool steel, any
cheap, fast “hole popper” will suffice. These machines can be manual, ZNC, or
full CNC, and range in price, accordingly, from around $15,000 to $35,000. Even
if they have ZNC/CNC controls for positioning and drilling, the generators are
relatively crude, they have little if any regard for accuracy of any kind and
surface finish is not a concern. These are used almost exclusively for drilling
WEDM start holes as fast as possible, using regular water as a dielectric.
The
next level of EDM hole drills, that are commonly referred to as “fast hole
drills” are more sophisticated, touting more advanced generators, tilting drill
heads, ability to integrate A/B tables, breakthrough technology, and use
deionized water as a dielectric. This breakthrough technology allows the
machine to drill holes through one wall of a part without violating an internal
wall or structure, such as in blades and vanes for turbine engines. Accuracy
requirements for these applications will usually be tighter than those of the
simple WEDM start holes. Where hole poppers are meant to be nothing more than
support equipment for WEDMs, the more advanced fast hole drills are usually used
as the main process center for drilling more accurately sized and shaped holes
in a production application. These machines will typically range in price from
just under $100,000 to upwards of $300,000, depending on size, options, and
configuration.
The third level of EDM hole drilling machines are known as fine
hole drills. These machines have advanced generators, highly adaptive spark gap
control, full CNC operation, and a variety of burn condition settings to cover a
wide range of applications. EDM fine hole drills will also use oil as the
dielectric, which allows finer spark gap monitoring and control, and superior
finishes. These machines may be capable of achieving L:D ratios of up to 100:1,
with typical hole sizes of 0.003” – 0.020”. The big difference with these
machines is that the holes they produce will be very accurate in shape, location
of entry to exit, cylindricity, size, and position. EDM fine hole machines are
used for manufacturing parts for medical, aerospace, and electronics
applications, as well as drilling WEDM start holes where size of hole is
limited, and location is critical, such as some small stamping dies. These
machines may also be able to perform as standard sinkers, being able to burn
cavities for molds, or details on small parts, punches, or mold inserts. You
can expect to pay between $180,000 and $500,000 for one of these machines,
depending on size and options. Options can include automatic part/tool
changers, A/B tables, electrode dressing devices, and robotic automation
components.
For more information
on EDM hole drilling, check out some of the other entries in this blog on the
topic, or visit Makino.com and look for information about the EDGE2 Fine Hole
EDM.