WORK SAFE - FOLLOW ALL MANUFACTURER RECOMMENDATIONS
ON SAFETY AND PROCEDURES
Tie Bar Stretch
If you are using dial indicators, I recommend using one on each tie bar.
They need to mounted so the "die height platen" movement does not
interfere with the reading
Typically they will be fixed to the base of the press. And perpendicular to the
tie bar.
If you have a standard stetch gauge mount it on each tie bar according to
directions.
Usually on a clean oiled area of the tie bar.
Use a square mold.
Take the slack out of the toggle by just kissing the mold halves with no
pressure to remove "slack" from the linkage.
Hydraulic Presses are typically locked in at a preset length and if they vary
from bar to bar indicate an off center ram, uneven mold, broken or cracked tie
bar ect.
Set guages to zero, and apply tonnage or lock over. Use the amount of stretch
indicated as the Delta L.
The Measuring Length is the part of the tie bar that will actually be stretched
during the test.
The terms we will be talking about are :
CF = Clamping force
L = Measuring Length
Delta L = Tie Bar Stretch
E = The elasticity of
steel (30,000,000)
A = cross sectionof one
tie bar = R x R x 3.142
The formula for how much clamp force you have
after taking a reading can be derived by:
Delta L x E x A x 4
------------------------- = CF
L
IF;
Delta L = .060"
E
= 30,000,000
A
= 56.75 (Tie bar at 8.5")
4 tiebars sharing
the load
L =
180"
.060 x 30,000,000 x 56.75 x 4
-------------------------------------- = 2,270,000 / 2000
(lbs per ton)
180"
1135 Tons of clamp
The Amount of stretch you should have can be
derived by:
CF x L
----------- = Delta L
E x A x 4
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