|Eppinger developed its new lathe toolholding system with live-tooling in mind. |
Eppinger GmbH is one shop that cashed in on the advanced capabilities of today’s turning machines. The tooling company began hardturning on lathes and not only eliminated secondary grinding operations but also gained the ability to finish parts in single fixturings. Prior to this, it pre-machined on generalprecision lathes, heat treated parts, then moved them on to finish grinding.
Hardturning requires extremely precise machine axis movement, and Eppinger uses Quest turning machines from Hardinge.
“If we need a finish dimension within microns, we can do it on the Quest,” said Ewe Eppinger, president of Eppinger in Denkendorf, Germany. “When the operator plugs in one micron of axis movement, the machine does it. With some other lathes, if you plug in that amount, either the machine can’t read the instruction or it moves five microns or more, which is not precise enough for our finish work.”
Coincidently, Eppinger uses its Quest turning machines to produce a new toolholding system for Hardinge’s VR Series of high-precision lathes. The system includes the ESA top plate, tooling and PreciFlex adaptors, and Eppinger uses it on its Quest lathes to reduce operating and set-up time by 80 percent.
“We make highprecision spindles and eliminate nine work steps per spindle, meaning nine other machines, by using one specially equipped Hardinge Quest. So, you can imagine what this means to set-up costs and precision by clamping parts only once. In fact, we are not really setting the machines up any more. We leave the twelve tool holders on the machine and change just the adaptors, which takes about one minute,” explained Eppinger.
With the system, shops know where tools are sitting because toolholders don’t change, so there’s no inaccuracy in the system. Operators change only system adaptors, and those are preset to within microns outside the machine tool.
Live tooling, by far, has had the biggest impact on turning machine capability as far as eliminating secondaryoperation equipment is concerned. However, Eppinger pointed out that the commonly used VDI toolholding system, developed in the 1960s, just wasn’t made for live-tooling applications, which is why his company developed the new system with live tooling in mind.
Machined tool pockets do not dictate positions of toolholders in Eppinger’s new system. Instead, patented keys and keyway systems do. Each top plate holds twelve ground keys that can be individually adjusted in the Y axis, allowing shops to adjust each key to zero on spindle centerline.
Keyways in the toolholders position them with the keys in the top plates for a backlash-free system. “Without any adjustment, we simply bolt each tool holder under the top plate, and it sits there within microns, station-to-station, to the centerline of the spindle,” commented Eppinger. Also with the system, tool holders are bolted to top plates with five to six times the force common in a VDI system.
In most instances, shops clamp live tooling, such as mills and drills, using collets. And while they have their advantages, collets can experience runout inaccuracies. Eppinger’s PreciFlex modular tooling reduces runout error to extend tool life and improve machining accuracy.
PreciFlex spindle collet seats incorporate ground spindle noses with four threads, and against these spindle noses, Eppinger attaches adaptors that have cone face contacts. These cones have the same shape as an ER collet, but in the tool holder, either ER collets or adaptors can be used. Adaptors bolt down under spindles and sit in ER seats, so they contact the ground spindle noses for extremely rigid connections between adapters and spindles.
Eppinger said that the big advantage is that it can leave a tool holder on the top plate and change only the adapter, which is preset outside the machine tool.