Lending A Hand To The Machining Center

This coolant-operated gripper loads in the spindle like a toolholder, allowing the machining center to lift and move its own workpieces.


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The coolant flow is, in a sense, a machine tool axis. After all, the flow can be turned on and off by the control. True, this may make it a rudimentary axis, but why not put this additional axis to work?

Using coolant, at least for its traditional roles of cooling and chip removal, seems increasingly to be questioned. Dry and semi-dry machining can help some shops eliminate coolant-related maintenance and disposal costs. On the other hand, the fact that through-spindle coolant is now a commonplace feature of machining centers has brought new possibilities to shops. The chance to gundrill on machining centers (see the next article) illustrates the point. In addition, developers of machining center accessories have found some clever ways to use the through-spindle coolant for mechanical actuation.

Benz (Charlotte, North Carolina) offers an example of such an accessory. The company’s Universal Parallel Gripper is a coolant-operated workhandling device that loads into the spindle like a toolholder. A spring closes the gripper, while the pressure of the through-spindle coolant forces the gripper open. With this device, the machining center spindle can grip and lift workpieces weighing as much as 8 kilograms with the standard fingers, or as much as 40 kilograms if the gripper’s fingers are form-fitted to the part.

Clearly, compared to other machining center workhandling systems, this gripper has an important limitation. It relies on the machine itself for movement, so it can’t travel beyond the machine’s work zone. Are there uses for work handling that applies only within the machine tool’s travels? Benz technical application specialist Mike Starnes says that in certain applications, this simple device can deliver a high rate of return.

One such application is the machining of hex dies, or other part types in which several workpieces are set up together for one machining cycle. When the coolant-operated gripper is coupled with vises that can automatically release the workpieces at the end of the cycle, the gripper can allow the machine itself to gather all of these pieces and place them in a bin. This reduces the amount of human labor involved in the process.

The gripper can also deliver value in precisely timed production operations in which the number of seconds the operator spends on loading and unloading can have a measurable effect on productivity. By lifting the finished part out of the fixture automatically, the machining center can place the part where it will be much easier for the operator to grab—shaving time off of the work the operator has to do as every cycle ends.