HYDRAULIC UNSCREWING DEVICE Calculations/Specifications
HYDRAULIC UNSCREWING DEVICE Calculations/Specifications
B. Control Cam Calculation
Thread Lead = 1/(Threads per inch) = 1/Pitch = Inches/Thread Thread Length = Length of threads to be removed from the cap A. Stroke (Inches) NOTE: Limit switches should be used if possible to limit full cylinder travel. This will extend the seal life inside the hydraulic cylinder.
a) Required revolutions (thread core) Thread Length =
+ Safety (.5 revolutions minimum)
Thread Lead b) 1. Required stroke – Inches = Gear Pitch Diameter x π x Required Revolutions If required stroke is too long, a cogwheel transmission should be used. 2. Length of Rack b 2 = x + y + b 1 c) Stripper stroke (Inches) = Cylinder Stroke – Required Rack Stroke
FULL OPEN POSITION ANTI-ROTATIONAL STRIPPER PLATE "OR BUMP" MOVES UP AT A FASTER
OPEN
O.D. OF THREADS (MAJOR THREAD DIA OF THE CORE) THREAD LEAD
RATE DUE TO ANGLE BETA AND SEPARATES FROM THE MAIN STRIPPER PLATE MOVING AT RATE DUE TO ANGLE ALPHA
CLOSED POSITION BOTH STRIPPER PLATES MOVE UP TOGETHER AT THE SAME RATE DUE TO ANGLE ALPHA
THREAD HT.
CLOSED
ANTI-ROTATIONAL STRIPPER PLATE MAIN STRIPPER PLATE STRIPPER PLATES
BUMP LIFT
ANTI-ROTATIONAL STRIPPER PLATE
ß BETA
ALPHA
PUSHED UP BY CAM ANGLES THREADS GET ROTATED
CAM
MAIN STRIPPER PLATE
ATTACHED TO MOLD
CAM
MOVING HYDRAULIC CYLINDER PUSHES CAM AND RACK
STATIONARY HYDRAULIC CYLINDER
SPUR GEAR
MOVES MAIN STRIPPER PLATE
B
BUMP
PITCH DIA.
STATIONARY HYDRAULIC CYLINDER BODY
RACK
A
MOVING RACK
STROKE
C. Unscrewing Force These figures should only be used as a guideline, as many other factors will affect the calculation (material, variation of dimensions, material shrinkage, core surface area, temperature, lubricants, friction, etc.). f) Residual Pressure (PSI) = 1/100 of maximum injection pressure g) Effective core surface area (Square Inches or in 2 , Outer Core Cylinder Shell) Flat end of threaded core neglected, x 2 value for 45° triangle thread shape = major thread dia. of the core x π x thread height x 2 h) Unscrewing torque (in-lb f ) = Residual Pressure x Effective core surface area x major thread radius of core i) Unscrewing force rack (lb f ) Unscrewing Torque X number of cavities = Gear pitch radius k) Hydraulic force (lb f ) NOTE: x 1.5 is 50% Safety Factor, if x 1.0 there would be no safety factor. = Unscrewing Force x 1.5
BACK VIEW, THREADED CORES EXTEND FROM OTHER SIDE OF THE SPUR GEAR
PITCH CIRCLE – PITCH DIA. x PI SPUR GEAR
Y = MAXIMUM PRODUCT SPACING (MULTIPLE CAVITIES CAN BE LOCATED BETWEEN)
> PITCH DIA. PERIMETER x REVOLUTIONS b 1
X
REQUIRED STROKE TO UNSCREW CAPS
UNUSABLE SPACE
b 2
84
85
U.S. 800-626-6653 ■ Canada 800-387-6600 ■ dme@milacron.com ■ www.dme.net ■ store.dme.net
U.S. 800-626-6653 ■ Canada 800-387-6600 ■ www.dme.net ■ store.dme.net
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