Kennametal
Kennametal

Combined chuck jaw and lathe chuck quick change provide maximum flexibility in turning applications

DMG MORI
Combined chuck jaw and lathe chuck quick change provide maximum flexibility in turning applications

SCHUNK Intec Ltd.

Lantek Sheet Metal Solutions

Combined chuck jaw and lathe chuck quick change provide maximum flexibility in turning applications

Productivity can quickly plummet without the freedom of alternately machining workpieces with large and small diameters on lathes. Tool specialist LMT Fette based in Schwarzenbek, Germany, has tackled this challenge by converting a universal lathe into a solution that drastically reduces set-up times. The solution combines SCHUNK chuck jaw and chuck quick-change technologies so skillfully that even rush orders from other business units can be incorporated during ongoing production without an impact on the company's overall performance.

 

When Thomas Frankenberger, machine operator at LMT Fette Werkzeugtechnik GmbH & Co. KG, recalls the strength it took to change lathe chucks in the past, you can still see the stress on his face: "Exact positioning was always an art when you had a 500 mm lathe chuck of 220 kg." Even with two people, it was a challenge to screw the lathe chuck onto the fine-threaded draw tube. "If you were off by as little as a half a millimeter, it wouldn't work," says the experienced operator. Forcing the screw would ruin the thread, and that would spell big trouble. In extreme cases, the draw tube would have to be elaborately re-machined with the thread restorer. "In the past, every time you changed the chuck it would require time, manpower, instinct, experience, and physical strength. Now that we're using the SCHUNK chuck quick-change system, I can easily change the lathe chuck by myself with much less effort and far less risk of accidents. "It used to take 45 to 60 minutes, sometimes with two colleagues, and now it takes just 15 minutes to do a complete chuck change with only one operator, including all secondary tasks such as cleaning, oiling, and storing the second lathe chuck.

 

Patented flex cone automatically centers large lathe chucks

 

Instead of using multiple fastening screws, the patented chuck quick-change system SCHUNK ROTA FSW is process reliably released and locked with a single clamping screw. Using a flexible adapter, the draw tube of the lathe can be automatically connected to the lathe chuck and centered with great precision due to a patented flexible taper. A patented dual stroke system ensures enormous pull-down forces, an optimum flat work surface, and maximum rigidity in the connection. Locking is done form-fit and in a self-retaining way. To eliminate the possibility of operating errors, a display continuously informs the operator of the current locking status. "Exchanging the lathe chuck has become much easier with the quick-change system," says Thomas Frankenberger. "Once I've positioned the lathe chuck, I tighten the screw with the torque wrench. The chuck aligns itself, is automatically centered, and then reliably clamped. "It hardly takes any strength," says Frankenberger. Moreover, a high repeat accuracy is also ensured. "In the early stages, we kept a careful watch on things and determined that everything worked perfectly every time," says Thies Mann, who is in charge of CNC programming for gear cutting tools at LMT Fette, and supervised the quick-change project. "Since then, we no longer check the accuracy of chuck changes because we know it works." There is also a much lower cleaning effort involved compared to a conventional chuck change, he says. "The system is easy to access, easy to keep clean, and easy to maintain," says Mann. Inspection and service of the quick-change system and lathe chucks are done at regular intervals by a qualified SCHUNK service technician, and ensures maximum process reliability, especially for heavy parts and long projection lengths.

 

The chuck quick -change system proves extremely helpful when it comes to large lathe chucks weighing over 200 kg. Large lathe chucks frequently oscillate during the complex assembly process, striking the spindle nose, and causing damage in this area. The design of the convenient SCHUNK system minimizes this risk. Moreover, the ROTA FSW reduces the need for cleaning and the risk of overlooked chips or dirt particles. The chuck quick-change system is available in three sizes for lathe chuck diameters up to 260 mm, 315 to 400 mm, or 400 to 630 mm. It can be used for retrofitting almost every lathe. No matter, if it is a manual and power lathe chuck. Their actuating force and maximum RPM remain fully preserved. Due to the low height, there are also only few restrictions in terms of installation space. Due to its large through-hole, modern turning centers can also be equipped with the SCHUNK ROTA FSW. Already existing clamping devices can be adapted to the system with little effort, and can be used repeatedly.

 

Workpieces weighing over 500 kg with a projection length of more than 500 mm, can be clamped on the fly

 

LMT Fette faced a common problem. At first, they tried to get by with a ROTA THW 500 on the new universal lathe, but they soon realized that with smaller components, the limits of RPM were reached quickly. Therefore, they decided to combine the existing ROTA THW 500 power lathe chuck and the ROTA FSW chuck quick-change system with a smaller ROTA THW plus 260. The 260 mm lathe chuck is connectable to the quick-change system using a special mounting flange. Now workpieces with diameters from 60 mm to 550 mm can be machined on one machine. The chuck quick-change system makes a considerable difference. For example, components for LMT segment mills with a length of up to 520 mm and a weight of more than 500 kg are quickly clamped to the power chucks for the facing cut and centering. Only when roughing the outer contour a tailstock tip is added for extra stability. The final bore hole is also drilled on the fly.

 

LMT Fette also takes advantages of the high-precision jaw quick-change option in order to realize different clamping diameters as efficiently as possible without changing chucks. Both power lathe chucks are standard features of the system, and are particularly designed for the production of small and medium-sized batches. The key advantage: Once machined, the chuck jaw sets can be used again and again, due to the high jaw change repeat accuracy of < 0.02 mm with the ROTA THW plus 260, or < 0.03 mm with the ROTA THW 500. In addition, chuck jaws can be exchanged in no time at all, which has significant ergonomic advantages given that chuck jaws can weigh up to 8 kg. "I simply slide the chuck jaw into position, lock it, and I am done," says Thomas Frankenberger enthusiastically. "I don't have to measure anything and I know immediately if a position is incorrect." To eliminate the possibility of operator errors, an integrated ball mechanism ensures that the actuation key cannot be pulled out, until the wedge bar has snapped into the base jaw. A sophisticated lubrication system ensures that the most important guiding areas are permanently greased. "The average run-out accuracy of our turned parts is 0.03 mm or better. We can achieve that level of accuracy with ease”, says Thies Mann. "In addition, we need the longest possible stroke because we have to clamp up to 10 mm”. LMT Fette uses customized SCHUNK claw jaws ensuring that oversized discs with diameters of up to 600 mm can be clamped on the 500-series lathe chucks.

 

Extreme flexibility for rush orders

 

LMT Fette was able to organize the production of the gearing tools much more freely by combining the fast lathe chuck change with the chuck jaw change. "We change the jaws four to five times a day and the lathe chucks three to four times a week," explains Thomas Frankenberger. For example, the standard batch size for segment mills is usually 16. Usually, large workpieces are manufactured as single items. Due to the high degree of flexibility, the team has taken over the manufacturing of taps in batches of between 6 and 12 units for another business unit. Thread sizes can range of up to M52 with a workpiece length of 500 mm. The machine can also accommodate unscheduled rush jobs from other departments. According to Thies Mann, the investment has fully met the company's need for added flexibility. He says that production at the Schwarzenbek plant is so precisely synchronized that if one machine is down for several hours, the impact is quickly felt. "That's why flexibility is a key function," says the programmer. "It's about being able to react quickly and intervene when there's a problem. A quick-changer like our machine is ideal for boosting production and speed."

 

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