Basic System Set-Up
The four essential steps
Building the right workholding system for a specifi c production tooling requirement is best achieved by observing the following basic steps – three steps deal with equipment selection, one with system connection.
Selecting the type of cylinders, determined by shape and size of workpiece and the machining process involved, is the critical factor in any workholding system. For that reason, Enerpac offers an exceptionally broad range of production tooling cylinders – in terms of type, stroke and force rating.
Positioning and push cylinders are designed to position the workpiece and to push-clamp it securely in that position.
Down-holding cylinders are designed to clamp the positioned workpiece firmly to the fixture or worktable. The range of Enerpac swing cylinders and edgeclamps meet virtually any downholding requirement.
Pull cylinders are used where the workpiece shape or fixture dictates clamping by pull forces, this type of cylinder with hydraulic or spring return can be selected to match particular needs.
Work support cylinders are designed to maintain the workpiece accurately on the prescribed plane throughout the machining operation. These support cylinders preclude both vibration and distortion problems.
Select cylinder force and stroke, and choose single- or double-acting operation. The choice of force and stroke is largely dependent on size and shape of the workpiece and machining operation involved. Another factor to be considered is working space or clearance around the job, fixture or worktable.
Where a machining operation requires positive hydraulic return action, doubleacting cylinders should be specified. Where spring-return action is sufficient, single-acting cylinders or a combination of the two can be used.
Select the power source. The power source for an automatic workholding system can accurately be matched to the requirements. Enerpac pumps span a wide range of sizes and capacities – in compressed air or electric-driven configurations.
Connect the system. Getting your workholding system together for operation means connecting the pump to the various control valves and cylinders through a circuit of hoses and/or piping, fittings, gauges and other accessories.
For example, two swing cylinders and work support cylinders working in sequence, powered by an electric-drive hydraulic pump unit would require the following components:
1. ZW Workholding pump
2. GA Gauge adaptor
3. G Pressure gauge
4. H Hoses
5. FZ Fittings
6. SU Swing cylinders
7. WFL Work aupport cylinders
8. WVP-5 Sequence valve
Select all these components from their respective catalog sections.
Swing cylinders and work supports
The combined use of clamping cylinders and work supports in fixturing has become indispensable.
Swing cylinders have become important clamping components for fixturing applications where unrestricted loading and unloading of the workpiece is required. Enerpac offers the most complete, comprehensively featured and compact swing cylinder line.
Work supports are widely used to support critical workpiece areas to prevent them from bending and/or vibrating during the machining process. This minimizes the deflection of the workpiece, improving its quality and assuring a high degree of repeatability.
The combination of swing cylinders and work supports provides substantial time savings and quality improvements in the machine tool industry.
When designing a fixture, several products features of swing cylinders and work supports have to be considered. The determination of the necessary support force and the size of the work support is very critical. In principle the work support has to overcome two forces:
- clamping forces
- machining forces (including forces that may be generated by vibrations)
In practice, as a rule of thumb, the clamping force applied to the work support should not exceed 50% of its capacity at a given operating pressure. For many applications this is sufficient to absorb additional forces like machining forces. This 2 to 1 safety factor may need to be increased to 4 to 1 if extreme vibration or an interrupted cut is used.
The pressure/force diagrams, provided in the product selection pages of this catalog, allow for quick selection of the right combination of swing cylinder and work support.
The recommended ratio between clamping force and support force can be achieved by selecting the right sizes of the clamping components and/or by operating the swing cylinder and the work support with different operating pressures, e.g. the work support will be operated at maximum pressure while the swing cylinder operates at a reduced pressure.
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