September
21, 1998 Design News
BREAKTIME
Robot is pharmacy's 'little helper'
Stacy Orr, Manager of Engineering
Ron Leonard, Manager of S/N ScriptoPro LLC
Mission, KS
The ScriptPro (SP) 200, a four-axis robot, is the first
fully automated prescription dispensing machine for
retail pharmacies. Running unattended from start to
finish, this technological marvel receives fill requests
into its queue from existing pharmacy computer systems
via a serial or network interface. It processes each
request automatically by selecting a vial of the proper
size and filling it directly from its universal medication
dispensing cells.
Getting to here from there was not without its challenges,
however. Our major hurdle was to make the system "fit"
in terms of affordability, size, and functionality.
Reliability was also a major concern. We felt the product
had to withstand a 1.5-million-cycle life test--the
equivalent of roughly 10 years of continuous use in
a high-volume retail pharmacy.
To meet this goal, ScriptPro went to the aircraft industry
for leads on quality components, such as reliable brushless
dc motors and highly flexible cabling. We selected Windows
NT as the operating system, but prior to that decision
our software engineers thoroughly tested it out.
We spent a fair amount of time in the research and
evaluation of motion control boards, which are the critical
link between hardware and software in a robotics system.
The board would need to work within the NT multitasking
environment and provide sufficient I/O to control all
of the SP 200 functions. Ultimately, we selected an
Acroloop MCB, working closely with the company's engineers
to develop the interface.
The universal dispensing cell is a feat of engineering
and design simplicity. Basically, it is an assembly
of six inexpensive polycarbonate, acetal, and low-density
polyethylene components. To test the cell prototypes,
we needed access to a wide spectrum of pharmaceutical
products, which we obtained through a special research
license from the Kansas State Board of Pharmacy. Thousands
of man-hours were spent perfecting the control surfaces,
which cause pills of varying sizes and shapes to flow
in a single file pattern past the optical counting sensor.
Our design incorporates cross-over conveyors to align
all vials, regardless of size, in front of a triangulated
mechanical ram and roller assembly. The ram, which is
dampened by a linear decelerator, presses the vial into
position, while an industrial quality thermal transfer
printer applies the label. The computer uses sensors,
timers, and buffer procedures to control the process,
ensuring that the correct label is applied to each prescription
vial. The unit runs on a standard 100V circuit and does
not require compressed air.
A comprehensive control procedure involving extensive
use of bar codes and graphics ensures dispensing accuracy.
Each cell is labeled with an identifying bar code and
the system database records the current drug assigned
to each cell. When a cell is refilled, the system requires
scanning of the stock bottle as well as scanning of
the corresponding cell. Pills will not be dispensed
from the cell without a successful match.
A scanner mounted on the robotic arm also verifies
that the cell is in its proper position before dispensing.
When the operator removes the labeled prescription from
the system, a bar-code label is scanned. In response,
the system displays prescription information, including
a color picture of the drug.
Were we successful? Our customers think so. "The
SP 200 makes it fun to be a pharmacist," notes
Dr. Elizabeth Allan-Flynn of the Auburn University School
of Pharmacy.
Solve an engineering challenge you'd like
to share with Design News? E-mail Karen Field at kfield@cahners.com
Design Objective:
Develop an automated prescription dispensing system
to meet cost, size, accuracy, and reliability goals.
Design Challenges:
Produce a dispensing system to:
Operate completely automatically
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