Clamping force measurement in real-time

iJaw components
iJaw components

At the recent EMO exhibition in Milan, clamping technology specialist Röhm unveiled the iJaw clamping jaw for the first time.

The jaw allows the clamping force to be measured in real-time during machining – solving an age old problem where the clamping force is usually set by the machine operator and relies on experience. Often this is excessive as no-one wants to risk parts falling out of the chuck, unfortunately resulting in crushed or deformed components.

The iJaw integrates sensor technology for clamping force measurement and wireless data transmission. 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.

The iJaw uses a clamping insert just a few millimetres thick between the sensor and the workpiece, offering accurate information about the actual clamping force applied. Data is transmitted wirelessly to a gateway via the robust IO-Link Wireless protocol with a high 100Hz sampling rate. This means the iJaw measures in real time during machining.

The gateway receives data from the iJaw via the IO-Link Wireless protocol
The gateway receives data from the iJaw via the IO-Link Wireless protocol

It has a robust hardened steel and waterproof (IP 68) design. Additionally, the transmitting antenna features a cover made from high-temperature plastic to protect against 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 iJaw 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 quick-change jaw capability, as well as the Duro-T from its conventional range. 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.

The gateway with the IO-Link Wireless receiver is used to receive and send the data and offers a Profinet interface for connection to the machine. Via this interface, data is available to the machine control system and can be displayed on the machine tool’s HMI. 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 subsequently sent to the cloud where it can be archived and further processed.

“We have identified seven different scenarios in which the iJaw offers significant added value,” says Claus Faber, head of product management and marketing at Röhm. The first three situations are about the ‘feeling’ before and during machining. Before machining, the iJaw assists in feeding workpieces and setting up the clamping system. If errors occur, the measured clamping forces deviate from the target values and manual or automated compensation can be initiated.

“During machining, clamping forces that are too high and risk damaging the workpiece, or too low, resulting in workpiece ejection, can be detected. Three further scenarios offer solutions for the evaluation of series and serial measurements. Here, changing clamping forces can be used to detect trends at an early stage. This includes the early detection of upcoming maintenance to maintain the clamping force or tool wear to prevent rejects.

“In this scenario we can refer to historic documentation,” Mr Faber explains. “This is vital for critical components – such as in aerospace applications – but it can also be used effectively for process optimisation. If I want to know how a component was manufactured, I can research the historic manufacturing data via the cloud. The iJaw archives the manufacturing fingerprint so to speak.”

The iJaw on Rohm’s Duro-A RC power chuck with quick change jaw system
The iJaw on Rohm’s Duro-A RC power chuck with quick change jaw system

Since the end of 2020, Röhm has developed exclusive partnerships with machine tool manufacturers DMG Mori, WFL, and Emco who tested the iJaw on their machines in the final phase of development and accompanied Röhm in the series production stage. DMG Mori ran the iJaw on a CTX beta 1250 TC 4A at its pre-EMO showcase in Pfronten and also at the show itself on an M50-G.

Röhm sees the IO-Link Wireless protocol as the emerging standard in wireless communication in an industrial environment. Compared to Bluetooth, which is widely used today, IO-Link Wireless is significantly more robust and stable. Röhm has therefore secured exclusive use for applications in clamping technology from IO-Link Wireless specialist CoreTigo for the development period of the iJaw technology. CoreTigo is a development partner for the hardware components for wireless transmission.

The iJaw will be available from February 2022.




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