How does consistent drawbar pull-force translate to improved machining outcomes?
In the machining process, it can often be difficult for machinists to chase down the source of particular issues. Poor surface finish, rapid tool wear, taper corrosion, machine downtime, and tool breakage can each have multiple causes. However, there is one thing that can impact all of these: the pull-force of a spindle’s tool clamping system.
What is pull-force? And why does it matter?
The term “pull-force” refers to the amount of force that the tool clamping system is exerting to pull the tool holder into the taper of the spindle shaft. A tool clamping system consists of the gripper, pulling-head, rotary union, and often an unclamp unit.
The tool clamping system keeps the tool holder in place during the machining process. Over time, drawbar pull-force can degrade, causing a multitude of issues:
The term “pull-force” refers to the amount of force that the tool clamping system is exerting to pull the tool holder into the taper of the spindle shaft. A tool clamping system consists of the gripper, pulling-head, rotary union, and often an unclamp unit.
The tool clamping system keeps the tool holder in place during the machining process. Over time, drawbar pull-force can degrade, causing a multitude of issues:
- Poor surface finish
- Increased tool wear
- Fretting on spindle and tool holder taper surfaces
- Cutting tool breakage
- Unexpected release of the toolholde
These can result in increased part scrap, higher tool costs, and in the worst case, machine downtime and possible operator injury. Improving pull-force by design
The right tool retention system is critical for delivering the ideal pull-force for every application. Since 1985, AME has partnered with OTT-JAKOB, the undisputed leaders in tool retention technology.
The right tool retention system is critical for delivering the ideal pull-force for every application. Since 1985, AME has partnered with OTT-JAKOB, the undisputed leaders in tool retention technology.
Products like the OTT-JAKOB steep taper SK power drawbar are engineered to provide superior pull-force for optimized machining and peace of mind. These innovative systems feature a built-in force intensifying mechanism that increases the pull-force of the springs by a factor of approximately 3.2 times the original force.
What does the force intensifying mechanism do?
During the process of tool clamping, the force of the springs press axially on the clamping sleeve towards the back of the drawbar. This causes the precision steel balls to move radially outwards with three contact points, creating an amplified force of 3.2x the relaxed position, changing the axial spring force into a radial force at the clamping sleeve contact points.
During the process of tool clamping, the force of the springs press axially on the clamping sleeve towards the back of the drawbar. This causes the precision steel balls to move radially outwards with three contact points, creating an amplified force of 3.2x the relaxed position, changing the axial spring force into a radial force at the clamping sleeve contact points.
The radial force generated by this action is then translated to the clamping body to deliver an even greater pull-in force. The precision steel balls have a locking function when they are in the clamped position, so the tooling can never come out - even when helix-type cutting tools are used and the tool wants to pull itself out during a machining operation.
Advantages of the OTT-JAKOB power drawbar
The power drawbars deliver high pull-forces in compact dimensions. Based on the smaller rotating masses, the units are easier to balance.
Additionally, lower unclamping forces are needed, resulting in less bearing load and allowing the use of smaller unclamp units. The self-locking balls prevent both bell mouthing and fretting of the spindle taper.
The power drawbars deliver high pull-forces in compact dimensions. Based on the smaller rotating masses, the units are easier to balance.
Additionally, lower unclamping forces are needed, resulting in less bearing load and allowing the use of smaller unclamp units. The self-locking balls prevent both bell mouthing and fretting of the spindle taper.
One system upgrade, countless benefits
It’s rare in the machining process for one system to have so many benefits. But the right tool clamping systems can impact everything from surface finish to tool life to operator safety.
It’s rare in the machining process for one system to have so many benefits. But the right tool clamping systems can impact everything from surface finish to tool life to operator safety.
The impact of the OTT-JAKOB SK power drawbar shouldn’t be overlooked. This innovative system can either be incorporated into a spindle’s initial design, or spindle rebuilders can also retrofit the system in most cases.
At AME, we’re always here to help you improve machining outcomes and drive profitability. Contact us any time to get started.