Laser technology in tooling inspections
Figure 5: (FIGURE COURTESY OF THE AUTHOR)
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Laser technology allows tooling to be inspected without the inspector touching the tip of the punch. Relatively low-cost laser
measurement devices may be incorporated for a noncontact inspection. In a noncontact inspection, various tool dimensions are
measured without a gauge probe ever physically touching the surface of the punch tip. This technique eliminates the potential
for scratching the sensitive tip face of the punch. Typically, a punch tip with a deep cup, bisect, or embossing requires
a relatively sharp gauge tip to access the deepest point of the cup. Measuring the deepest point of the cup is necessary to
obtain the working length of the punch accurately (see Figure 5). Unfortunately, the sharper gauge tip has a greater risk
of scratching the face of the punch tip. Noncontact laser measurements eliminate the risk of tip-face damage and will speed
up the process because this method typically requires few moving parts. A button is pressed to activate the laser for a measurement,
and the value is collected and recorded instantly. Electrically powered laser measuring devices further reduce overall maintenance
costs and the requirement for supporting systems such as compressed air.
Alternative methods for monitoring tool wear
There are other ways to monitor tool wear besides tool inspections. One method is to track the number of tablets produced
with a set of tools and to use the historical data for forecasting. For example, if history indicates that a set of tools
has typically produced 1 million tablets on average per tool and 800,000 tablets were produced, the tool wear is 80%. A database
designed to record tool use and compare it with an estimated total yield makes monitoring tool wear relatively easy. This
information can also provide a notice to prepare a backup set of tooling or signal a warning that the tooling should be monitored
more closely. Properly forecasting tool-replacement needs allows tablet manufacturers to contact tool suppliers in a timely
manner to improve lead times for procuring needed equipment.
Other tool control-related information is useful to maintain in a tooling database. For example, storing drawing files electronically
is much more efficient than keeping track of hardcopy drawings. Using a database to track tool-related activities such as
maintenance or issues found during visual inspection provides many opportunities for trend analysis to justify changes in
approach to tool-care procedures.
Inspections of multi-tip tooling
Multi-tip tooling is a relatively new phenomenon in the tablet industry and presents its own set of challenges to the inspection
process. With multi-tip punches, a tool has a separate cup, working length, and overall length for each tip on a single punch.
The software that tracks this information must differentiate between each tip on a punch. For example, a punch with three
tips will typically be numbered as Tool Number 1 with Tips A, B, and C, then Tool Number 2 with Tips A, B, and C, and so forth.
The preferred method for tool-matching with multi-tip punches is to measure the working length of each tip, then average
the values for the combined working length for the punch assembly. The average working length of each upper punch then is
matched with the corresponding average working length of the lower punches during the tool-matching process. Although it is
still possible to match each tip of an upper punch with each tip of a lower punch according to individual working lengths,
this approach would be very time-consuming.
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