Injection mold makers everywhere are always looking
for ways to improve their operations. Any way you can shorten your
delivery date and improve your quality should be seriously investigated.
Jig-grinding
is almost always overlooked as a meaningful machine tool for injection
mold making. Yet, from my experience, it is a very valuable machine
that gets the job done quickly and very accurately.
Why is the jig-grinder overlooked?
It
is overlooked partly because most toolmakers view it as an out of date
machine that is only good for round holes or time consuming contours
that should be done on a CNC milling machine. It is true, it is not
very common, it is primarily used for round holes, and it does excel at
contours such as you might find in a gauge for inspection.
This
is why it is a secret weapon for building a plastic mold. Because it is
so overlooked, so efficient and so accurate, you should take a second
look at this tool of the not so distant past. Some shops run their jig
grinder all day long, doing a variety of tasks.
How can the jig grinder save me time and money?
Some good examples of the time consuming tasks it can do well:
-
Blind
hole floors. These are always a pain to do; either you mill them extra
deep before heat treat and grind to fit, or you leave stock for post
heat treatment machining. Either way, it is a bother to get the depths
right in a timely manner. With the jig grinder, you leave them shallow
before heat treat, and simply use a CBN wheel to very quickly grind the
depth perfectly. This is much faster and easier than hard milling or
guessing at the depths when grinding.
-
Bosses and similar details. Why EDM them when you can do it in a fraction of the time?
-
Adding
relief to cores and core pins. You can either use a Ded-Tru machine, or
a spin fixture on a surface grinder, or hard turn your cores. Or you
can do much of the work on a jig grinder.
-
Ejector
and core pin holes. While almost all knock out holes are WEDMd these
days, there are still applications when it makes sense to jig grind
them.
-
Pockets, whether round, square or
rectangular. It is hard to beat a jig ground pocket. This is a great
application for locators in the core and cavity blocks. This way you
are assured of perfect alignment.
How can you get started?
I
have never investigated, but I suspect that there are many used jig
grinders not being used. You might be able to pick one up at a bargain
price. You might have some trouble finding a qualified operator though!
Experience is what makes this a valuable addition to the modern injection mold making
shop. The basic operation is rather simple and straight forward, but
the almost endless list of uses is a direct reflection of the skill of
the jig grinder machinist.
"You know Dad, I've been thinkin', one is a lot more than zero!" my son, Thomas, age 5.
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