HOFFMANN ZeroClamp

Hoffmann recently introduced the ZeroClamp zero-point clamping system. Designed to significantly reduce set-up times and increase machining efficiency, the patent-registered new system provides an effective route to producing more components, quicker and at a lower cost. Some features set this reliable and robust work-holding solution apart from other competitor systems.

Using the face and taper HSK spindle tooling principle the ZeroClamp clamping pots can achieve a repeatability of +/- 2.5 microns, around ten times more accurate than existing systems. As the hollow, tapered-shank bolt is drawn into the clamping pot the elastic properties of the seating ring expand slightly, allowing the taper to locate positively and the faces of the pot and the pallet or raw material to engage and locate solidly. Subsequently, each fixing point has a break-out force of between 12.5kN and 60kN, depending on the clamping pot diameter.

This principle also removes any machining-induced vibration, minimises all thermal effects and compensates for hole misalignments of up to +/-0.1mm as the tapers always compensate towards the centre of the clamping position. The tapered bolts are produced from case-hardened 42CrMO2 steel and are very strong, allowing the workpiece or raw material to stand on them for storage. Only one design is used, avoiding the confusion caused by ‘fixed’ systems, which usually require three different bolt designs that are also known to magnify any thermal errors.

“Thanks to the highly accurate repeatability of the ZeroClamp system parts can be unloaded and reloaded with the minimum of fuss. So, moving components from one machine to another can be carried out without any accumulated errors, and important features can be measured part way through the machining sequence with the safe knowledge that the part can be reloaded accurately,” says Simon Kolakovic, head of clamping technology development, ZeroClamp GmbH.

Another advantage of the taper bolt design featured on the ZeroClamp design is the ability to tilt the pallet or workpiece during loading and unloading without fear of damage, making heavy and unbalanced workpieces easier to handle. It also means the units can be fitted at any angle, so they can be used in conjunction with tombstones or similar fixtures on horizontal machining centres. By contrast, fixed systems are often only used on vertical machining centres as they need to be lifted parallel or they can deform or lock together.

Fail-safe clamping is achieved on the ZeroClamp system by a stack of precision-manufactured segmented spring steel collars that, by design, lock the taper bolt in. These collars are opened by an expanding bellow inflated with compressed air at standard shopfloor pressure. The bellows are guaranteed for one million operational cycles.

The simple design uses just a few high-quality stainless or corrosion-resistant steel components so it is very robust and is unaffected by swarf or coolant ingress, the pots can be quickly cleaned out with a blast from a standard airline gun.

Avoiding all the disadvantages of a hydraulic system, the smart design of the Leader ZeroClamp system means that the units are around half the height of any alternative zero point fixtures, which allows the machine tool to keep more of its working envelope capacity.

“This is an important point as the fixturing is often fitted to the worktable and it therefore reduces the distance between the spindle nose and the workpiece. We have kept this to a minimum so that larger parts can still be loaded and machined,” explains Simon Kolakovic.

“The typical use of zero point fixturing involves manual pallets, which improve efficiency by allowing parts to be loaded and set up outside of the machine tool,” he added. “However, the full application and benefits of the Leader ZeroClamp system is only really limited to the imagination of the engineer considering its use.”

hoffmann-group.com/au/en/asia/

Australian distributor: suttonhps.com