TTS Systems was recently asked by a customer to solve the following problem: measure the tension in a 25mm-wide tape as it is wound onto a specially shaped production mandrel; in addition, the tension must be varied as the component is wound.
In approaching this application, TTS called on its many years of experience and went back to basics:
- First, measure the tension in the tape as close to the production part as possible
- Keep the transducer's roller diameter large enough that it will not damage the tape
- Use a high-speed analogue load cell amplifier to give real-time feedback to the control system
Custom tension measurement system
The final system involved a custom-designed roller with a standard transducer element and housing. The roller is 50mm wide, with a 38mm diameter at the outside edges and 37mm in the centre; this naturally pushes the tape to the middle of the roller. The design capacity was 25kg force. Using foil strain gauges in a full Wheatstone bridge configuration, a nominal output of 0-20mV with a 10V DC excitation can be achieved.
The output signal is processed using the DCA-10 load cell amplifier; while this is a dual-channel unit, it works just as well with only one measurement input. DIN rail-mounted and operating from a 24V DC power supply, the DCA-10 provides two independent 0-10V DC analogue outputs that can be used by the control system and a local digital display.
Speedy set-up and calibration is always important, so the DCA-10 has two pushbuttons and eight information LEDs. Zero calibration is done with no load on the transducer, with the push of a button; a known load is then applied to the transducer using a flexible load tape to suspend a 25kg weight, which completes the span calibration. There is also an option to set the calibration data via the RS485 communications port; however, in practice most engineers use the pushbuttons.
The calibrated high-level signal from the measurement system can now be used in one of two ways: with a dedicated tension controller designed to provide a simple local machine control option or a PLC to offer greater programming and control capabilities. In this case the customer has a very good PLC engineer who understands both the product's construction and how to run the machine.
So, after a short commissioning period, the customer's machine is now winding tape 15 per cent faster than before and, with the improved tension profile control during production, the quality of the end product has improved.
TTS Systems has been designing tension transducers, load cells, instrumentation and controllers since 1998. Manufacturing takes place in the UK and custom-engineered, bespoke systems can be created to meet exacting application needs.
Typically TTS Systems' products are used with paper, foil, film, tape, plastics or rubber. In fact any material on a roll or reel that is processed through an automated machine can have its tension measured and controlled using TTS Systems' products.
When used in a closed-loop control system, the measured signals can be used to regulate the speed of the drive, brake or clutch, thereby ensuring constant material tension throughout the process.
Learn more about TTS Systems at www.tts-systems.com.