Page 394 - CarrLaneCatalog_2019ed-c.pdf

LOCATING AND CLAMPING PRINCIPLES

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Positioning the Clamps Alternatively, required clamping force can be calculated based
Position clamps to hold the part against the locators without on calculated cutting forces. A simplified example is shown in
deforming the workpiece. Look for the most rigid points of the Figure 6. The cutting force is entirely horizontal, and no workpiece
workpiece, where they will not interfere with the operation of locators are used, so frictional forces alone resist the cutting forces.
the machine tool, during either the cutting or return cycle. Most
clamps are positioned on or near the top surface of the workpiece.
The clamp must be large enough to properly and safely hold the
workpiece, but small enough to stay out of the way.

With most workholders, this means positioning the clamps directly
over the supporting elements in the baseplate of the workholder,
Figure 4, or against horizontal locators rather than the supports. In
either case, the clamping force must be absorbed by the locating
elements.

Figure 4. Clamps should always be positioned so the clamping force
is directed into the supports or locators. Figure 6. A simplified clamping-force calculation with the cutting
force entirely horizontal, and no workpiece stops (frictional force
resists all cutting forces).
Selecting Clamp Size and Force
Calculations require an approximation of the necessary clamping
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force. The table in Figure 5 shows the available clamping forces Another general area of concern is maintaining consistent
for a variety of different size manual clamp straps with a 2-to-1 clamping force. Manual clamping devices can vary in the force
clamping-force ratio. they apply to parts during a production run. Many factors account
for the variation, including clamp position on the workpiece, but
operator fatigue is the most common fault. A good way to control
clamping force is to replace manual clamps with power clamps.

The force generated by power clamps is not only constant but also
adjustable to suit workpiece conditions. Another benefit of power
clamps is their speed of operation: not only are individual power
clamps faster than manual clamps, every clamp is activated at the
same time.

Figure 5. Approximate clamping forces of different size manual
clamp straps with a 2-to-1 clamping force ratio.

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