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Photo processing printer system succeeds with rugged stepper motors |
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The Europa digital image printer
from Express Imaging Systems
(express-imaging.com) in Seattle
provides ultra high speed printing of digital
images from cameras
and cell phones.
The Europa must unwind heavy stock
photographic paper from large 1800-ft
rolls. Because of the nature of photo printing,
the system goes through frequent start and stop events.
According to Will Reed, senior design
engineer at Express Imaging, ěDuring the
imaging process the system must also
maintain a set web tension and be able to
position and hold the paper end to within
±0.010 in., which is no small task.î In
addition, the systemmust tolerate slack in
the paper at start upwithout stalling from
the large inertial impulseload, which occurs as
the paper is pulled tight.
Motor stalls were a huge problem with
older stepper motor system designs as they
caused the machines to shut down. The
older steppers werenít able to accelerate
the paper roll to operating speed in the
required time either. ěThe search was on
to find a better solution to the challenge,î
Reed said.
ěWe felt that the Alpha-Step series of
step motors and controllers from Oriental
Motor provided an ideal solution,î Will
said. Alpha-Step combines the precision
incremental positioning capabilities of a
stepper motor with the needed stall resistance
and high speed of a servomotor.
Two results occurred from the use of
the Alpha-Step. First of all the stalling
problem was completely cured. Secondly,
the Alpha-Step provided the system with
at least twice the speed of the older design.
The bonus benefit for Express Imaging
was that the Alpha-Step system allowed
them to use their existing software almost
unchanged. Overall results, according to
Reed, include more speed with a simpler,
more reliable system.
Express Imaging worked with Oriental
Motor as well as PacMation, a consulting
and supply service company located in
Redmond, WA, that serves B.C. and
Alberta. PacMation (pacmation.com) and
Oriental Motor sales engineers worked as a
team to calculate the size of the motor and
to arrange for a demo unit to be shipped to
Express Imaging. The two also visited
Express Imagingís manufacturing facility
several times to be sure that the design challenges
were understood and that the Alpha-
Step system worked correctly. Another concern
was to maintain the lowest cost system
that was possible to do the job.
System components finally chosen
included the Alpha-Step AS911AA and the
AXHM-5100KC brushless gear motor for
the take-up side of the Europa. Reed said,
ěThe major advantages of the components
we chose to use are that we gained the highest
possible performance while maintaining
stall-free technology and that we got servo
performance levels while acquiring stepper
motor ease-of-use.î Express Imaging only
took about an hour to set up and install the
Alpha-Step.
The Alpha-Step is a single-phase 115 Vac
step motor and driver with a permissible
speed range of 0 to 4000 rpm and maximum
holding torque of 35 lb in. The motor
is 3.35-in. square. The system has a closed
loop control with no loss of synchronism.
Also important for the Express Imaging
application is that the Alpha-Step provides
low vibration at low speed operations.
The end result required the system to
accelerate a 10 kg roll of paper to a web
speed of 38 ips within 1.2 s. Then it needed
to stop the paper trailing edge once the roll
ran out to the specified ±0.010 in. tolerance.
This article was provided by Oriental
Motor (orientalmotor.com).
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