Real-time clamping force measurement

Röhm’s new iJaw clamping jaw for the first time allows the clamping force to be measured in real time during machining. The company has therefore solved a problem for which there was no accepted industrial solution up to now: the clamping force is usually set by the operator of the machine tool and is a matter of experience. Errors during machining due to incorrect clamping force or workpiece loss are therefore pre-programmed. The iJaw integrates sensor technology for clamping force measurement as well as wireless data transmission in a full-fledged clamping jaw. The measurement takes place directly at the clamping point to the workpiece; the data transmission to a gateway makes use of the upcoming industry standard IO-Link Wireless. The gateway can be connected to the machine control system via the integrated Profinet interface and/or sends the data to a cloud via the integrated LAN interface.

Even on the most modern machine tools, workpieces are clamped today in the same way as they were 100 years ago: the operator clamps "by feeling". Due to the lack of sensors, the machine tool can only support the operator to a limited extent. And to ensure that workpieces are really “securely” clamped – no one wants to risk ejection – the clamping force is often set too high. Especially with thin-walled components or sensitive surfaces, this quickly leads to deformation and crushing.

The iJaw is a clamping jaw with integrated sensor technology for measuring the clamping force directly at the clamping point. There is simply a clamping insert that is only a few millimetres thick between the sensor and the workpiece. Röhm thus eliminates almost all falsifying influencing factors and the iJaw can provide information about the actual clamping force applied to the workpiece. The new tool transmits the measured data wirelessly to a gateway via the robust IO-Link wireless protocol with a high sampling rate of 100Hz. This means the tool measures in real time during machining. To this end, it has a suitably robust hardened steel and waterproof (IP 68) design. The transmitting antenna has a cover made of high-temperature plastic to protect against glowing chips. The iJaw can be mounted and used on all lathe chucks with a suitable (standard) jaw interface like any other clamping jaw.

For the market launch, the product is available as a stepped jaw for lathe chucks with straight or helical toothing in sizes 215, 260, and 315. Suitable lathe chucks from Röhm are the Duro-A RC, Duro-NCSE, and Duro-NC power chucks with the jaws quick-change system, as well as the counterpart from the conventional range, the Duro-T. To adapt the jaws to different workpiece geometries, there are various exchangeable hard and soft clamping inserts that are locked onto the jaw with screws.

Gateway as data hub

The gateway with the IO-Link Wireless receiver is used to receive the data and forward it. The gateway offers a Profinet interface for connection to the machine. Via this interface, the data is available at the machine control system and can be displayed on the HMI of the machine tool and/or further processed by the machine control system. The iJaw can be connected to the Internet via a LAN interface on the gateway, making it a true IoT solution. The data can be sent via this to a cloud where it can be archived and further processed.