Features of the "Ohma® Cylinder"
The OHMA weld cylinder has several unique
features that distinguish it from both
conventional pneumatic weld cylinders and other
types of air over oil intensifier cylinders.
Ratio
All OHMA weld cylinders are designed to produce
a specific force ratio. The ratio represents the
factor by which air pressure is internally
multiplied to produce the weld force. For
example, a 22:1 ratio OHMA weld cylinder will
produce 22 lb. of force for every 1 PSI
introduced to the Intensifier Port (EE3). In
other words, sequencing 60 PSI of regulated
pressure to EE3 will result in the cylinder
developing (60 PSI x 22) 1320 lb. of weld force.
Power Stroke and Advance Stroke
The power stroke represents the stroke the
cylinder produces during the high pressure
portion of the sequence of operation. The power
stroke is limited to, and is a function of, the
cylinder's physical configuration. For example,
a 32:1 ratio cylinder with a 3" overall stroke
and .20 power stroke operating at 45 PSI will
initially make contact with the work as if it
were an air cylinder. In this particular
example, the advance force would be equal to the
cylinder bore area multiplied by the air
pressure (3.1416 x 45 PSI); this would equal 141
lb.. Upon initiation of the power stroke stage,
the force would be boosted by the ratio to 1440
lb.. (32 x 45 PSI). The maximum distance that
the cylinder will travel at this force will be
.20". Although the power stroke may appear to be
short, a vast majority of spot welding
applications will require a stroke length well
within this range.
It is important to note that the power stroke
can be initiated anywhere within the advance
stroke range. This is defined as the overall
stroke minus the power stroke. In our example
the advance stroke range would be: 3" - .20" =
2.80". Effectively, this means that the OHMA
cylinder can develop the power stroke anywhere
from 0" to 2.80". Where the power stroke is
initiated within the advance stroke range will
have no effect on the ratio or the power stroke
length. In order to further illustrate this
important concept please consider the following
example:
An OHMA weld cylinder with a 2" bore, 22:1
ratio, 5" stroke, .26 power stroke operating at
50 PSI will:
have an initial advance force of 157 lb (3.1416 {area of 2" bore} x 50 PSI)
develop 1,100 lb of weld force (22 {ratio} x 50 PSI)
will have the ability to stroke for a distance of .26" at the rated weld force
will be able to develop the power stroke anywhere from 0" to 4.74" (5" - 0.26")
Centerline (Windsor) Ltd