APPLICATION
1: EXTRUDER SYSTEM
A manufacturer of candy is retrofitting an extruding machine. The
machine presently uses a hydraulic ram attached to a plunger to
push a thick candy mixture through a dispensing tube into a mold.
The manufacturer is concerned with contamination from leaking hydraulics
and would like more consistency in the dispensing rate and volume.
SPECIFICATIONS:
- Force to push the candy is 7500 pounds (no load on retraction)
- Force is vertical and will put the jack lift shaft in compression
- Minimum speed is 1 inch per second
- Actuation cycle: 50 times/hour, 8 hours/day, 200 days/year
- Desired design life is two years
- Mechanism must be mounted overhead
- Maximum stroke is 15 inches
- Food processing plant requires cleanliness
APPLICATION
1 ANALYSIS:
Configuration: Speed, duty
cycle and orientation of the operation dictates the use of an inverted
ball screw jack. The plunger mechanism will be attached to the travel
nut of a rotating jack.
Column Strength: Using the
application data with the column strength chart shows that the a
five ton or larger jack will handle the compressive load.
7500 pound load, 15 inch travel with an “L”
dimension of 21 inches, assume mounting condition “A”
Speed and Horsepower: The
0.473 inch lead lift shaft in a 5 ton ball screw jack will provide
the proper speed:
1 inch per second X 60 seconds per minute x 12.66
“turns of worm for 1" raise” = 760 input rpm.
Horsepower required Use a speed control with
a motor rated for at least 1.65 horsepower at 760 rpm for this application.
Torque to raise 1 lb. X Load (lbs.) X Worm Speed
(rpm)/63025 =
(.0183 X 7500 pounds X 760) /63025 = 1.65 Horsepower
1.65 Horsepower is below the three horsepower limit for this jack.
Life: The life, based on
the Ball Screw Life Expectancy chart, is at least 2,406,000 inches
of travel for a standard inverted rotating 5 ton jack with a 7500
lbs load.
Calculated life is 15 loaded inches per cycle X
50 cycles per hour X 8 hours per day X 200 days per year =
1,200,000 inches per year or two years of life.
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APPLICATION
1 SELECTION:
Reference Number: Put together
a reference number for the following: 5 ton ball screw jack, inverted
rotating configuration, 6:1 worm gear ratio, motor mount with 2
Hp 3 phase motor and motor mount on the input shaft, standard extensions
for the output shaft, flange base, travel nut orientation “A”,
“L” dimension of 21" for a 15" travel. Lastly
the jack will be modified to include food grade grease and epoxy
paint.
5-BSJ-IR 6:1/203-1/SSE-2/FA/21/M
M= food grade grease and epoxy paint.
APPLICATION
2: MACHINE TOOL FIXTURE LOADER
A manufacturer is building a system to position a machine
tool table horizontally inside the machine.
SPECIFICATIONS:
- The table is well guided and weighs 4,000 pounds
- The fixture needs accurate and repeatable positioning
- The table moves only a few times per shift.
- Stroke length is 30 inches maximum
- Desired design life is two years
- Thrust can only be applied at two corners
- No specific speed requirements
APPLICATION 2 ANALYSIS:
Configuration: Infrequent
operation suggests a machine screw jack. Application arrangement,
available clearance and good guidance allow the use of upright translating
jacks. The jacks must have an adjustable anti-backlash feature to
assure accurate bidirectional positioning. Two manually operated
jacks will be used, connected with a common driveshaft.
Column Strength: Even though
the unit is horizontal, column strength must still be considered.
Using the application data with the column strength chart shows
that a 2 ton upright jack with 1" diameter screw will handle
the potential compressive load of 2000 lb. per jack.
4000 pound load, 30 inch travel, assume mounting
condition “C”
Input Torque: This is a horizontal,
manually operated system. The force required to move the load is
the actual load times the coefficient of friction of the guide system.
For example, if linear bearings were used, the force required to
move the load would be equal to 4000 pounds times .002 or 8 pounds.
The torque required to move 8 pounds with a 6:1 ratio jack is 0.0250
times 8 or .2 in-lbs. This could easily be supplied by an operator
turning a handwheel.
APPLICATION 2 SELECTION:
Reference Number: From page 289, put together
a reference number for the following: 2 ton anti-backlash machine
screw jack, upright translating configuration, 6:1 worm gear ratio,
standard shaft extensions for the worm shaft input and output, Flange
base, clevis end on the lift shaft with 30" travel. An interconnecting
shaft will be installed between the jacks at assembly to drive the
jacks from a common handwheel.
2AB-MSJ-U 6:1/SSE-1/SSE-2/FC/30/S
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