We are in a time where investment casters need to improve their
competitiveness against other processes. The area where the greatest savings,
both financially and time, can be made is in the finishing area. This is due to the
simple fact that to date very little automation or engineering has been developed
in this area. Savings in the order of 70% are readily achievable. This can be
compared to savings in the wax, dipping, and casting area of between 5-10%.
This is due to the fact, that these areas have had considerable development in
automation and engineering over many years. This paper discusses several
innovative ideas that have been designed to address the automation of the
finishing area
Investment Casting, like most modern manufacturing techniques, is facing
new competition from new technologies and improved older ones. As investment
casters, we need to look at ways to improve our process so that we can improve
our throughput while incurring less cost. Equipment builders are working to
come up with better designs that cut overall time or consumables to make us
more efficient and therefore increase our profit. Paste wax injection, for example,
has made great strides in reducing injection cycle time and reducing the need for
chills in larger parts. The use of robots in the shell area has increased
throughput while reducing the dependency on human labour to dip our shells.
The latest induction furnaces allow us faster melt rates and precise control of the
melting process. These are the areas in which we spend our capital investment
dollar, but are they the right areas?
Let us look at the after-cast area. Most foundries treat the after-cast area
as a necessary evil. We throw money and people at it out of necessity to get our
castings out. These areas are noisy, dirty, and frankly, we all wish it would go
away. Many foundries still have equipment in these areas that was designed, or
is, from the early days of investment casting. The modernization process stops
at the melt area. Unfortunately, the after-cast area is not going to go away. It is
part of our process and it needs to be addressed just like any other area.
The good news is that the after-cast area is one of the easiest places to get
a return on capital investment. There has been much advancement in
technology in the after-cast area that makes the whole process less painful. We
will explore advances in ingate removal. There are other developments such as
automated cut-off, which we will cover in the future.
There are three main methods for automated ingate removal, plunge type
grinders with a rise/fall table, reciprocating bed grinders, and rotary bed grinders.
Each type fits different applications as will be explained here.
PLUNGE TYPE GRINDER with Rise/Fall Table (Figure No. 1)
The plunge type grinder is ideal for castings up to a few kilograms with
monthly production runs of less than 5000 per month. It is the most versatile
type of grinder. That makes it ideal for ingate removal in a commercial "job shop"
foundry. It can handle both straight flat ingates as well as curved ingates by use
of manual rotary fixtures or by adding a powered head. The powered head
causes a rotational motion instead of a rise/ fall motion when the table is driven
into the grind position (Figure No.2). Usually this easily attached plate fits on top
of the existing table, and uses the machines hydraulic system for the rotational
motion (Figure No.3). Fixtures are easily changed using either method and
typically, setup from job to job is less than five minutes. There are also after
market "quick change" mechanisms available. The rise/fall motion is required to
remove the curvature that would be ground into the part using a straight plunge.
The rise/fall motion sweeps the parts past the contact wheel to render a flat
surface. This type of grinder can also grind larger ingates using less horsepower.
With this style of machine, we take advantage of something known as the
"flywheel effect". The combined mass of the contact wheel, drive shaft, and
motor store the rotational energy, which is dissipated when the part comes into
contact with the abrasive belt. When this energy is used up, the power of the
drive motor takes over. This stored energy can be as high as three times the
kilowatt rating of motor, but lasts for such a small time period that it basically
doubles the effective area that can be ground efficiently. Abrasive belts can be
easily changed and to change a belt should take no more than two minutes


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