Selecting a Hydraulic Work Support
The basic selection of a work support for a fixture depends on two factors: determination of the support force required, and then from that, the size of support cylinder required.
Determine support force needed
A work support is required if a portion of a part would be moved or deformed by forces due to clamping or machining. See Chapter 6 for a discussion of how clamping force is calculated and the next paragraph regarding machining forces.
Determine work support size
As a rule of thumb, the capacity of a work support cylinder at the hydraulic pressure to be supplied to it should be at least twice the clamping force to be applied. (By “capacity” we mean the amount of opposing force the support cylinder is designed to withstand when in its locked state.) For many applications a 2:1 margin of support cylinder capacity over clamping force is sufficient to also absorb machining forces. In cases of extreme vibration or interrupted cuts, the margin of support cylinder capacity should be increased to 4:1.
The support cylinder selection process involves both the clamping and support cylinders, and four criteria that need to be satisfied: