|
|
|
TORQUE TALK
 |
|
< Back to Torque Talk
Torque Talk
Industry: Packaging
Application: Box Taper
In the packaging industry, applications for gearmotors can be found in equipment
used to automate the assembly, filling, and closing of cardboard boxes. One
of these applications is a machine used to automatically close the top
and tape it shut. Two Gearmotors drive opposing conveyor belts that pull
the carton through the machines closer and tape head assembly.
Issues to consider when specifying a gearmotor in this application include power
analysis, shaft loads (at the output shaft), lubrication and sealing system.
Power Analysis:
Boxes with varying sizes and weights generate a range of
torque loads. This torque data coupled with a range of belt speeds are
used to specify the geartrain and motor.
"Our application engineers use one of our calibrated
PMDC gearmotors and drives to assist in the power analysis."
With the calibrated unit running at proper speed, the range of loads are determined
by measuring the current at the gearmotor at the various load conditions.
PMDC motors have a linear relationship between current and torque, so
the supplied speed-torque current curve is quickly referenced for torque
loads.
Shaft Loads:
Radial loading on the output shaft and resulting life expectancy
of the bearings needs analysis. Typically three to five inch timing belts
are driven via pulley. These pulleys mount directly on the output shaft.
Radial loads come from belt tension, separation forces within the gear
case, and loads developed from the cardboard boxes as the belts pull the
box through the tape head.
Typically we use full compliment needle bearings for maximum life of the output
shaft bearings. Our output shafts are carburized in an inert atmosphere
to heat treat to a depth of 0.020". This maximizes operating life
of the needle bearings.
Lubrication:
Since these gearmotors are running continuously during packaging at customer
installations, hours accumulate rapidly. Assuming the motor, geartrain
and bearing system were sized properly, the life of the gearmotor depends
on the lubrication used and the sealing system to maintain the lubrication.
While our competitors typically specify grease lubrication for applications in this
equipment, we specify oil bath. Why? Because bearing and gear life depend
on it. Bearings keep our gearing right on pitch line, insuring maximum
reliability and quiet power transmission. Bison's entire catalog product
offering is oil bath lubricated.
Sealing System:
The secret in maintaining the oil within the gearcase is where Bison leads
the field. Input and output shafts are heat treated and ground in the
seal area. Seals are pressed in with custom assembly tooling to bores
that are concentric with the shaft. We even measure the roundness of our
ground seal areas to monitor the grinding process and prevent multi-lobed
problems that can lead to leaking problems.
|
