Wednesday, February 16, 2011

Elegant and cost-effective monitoring of roller gap separation

Measuring the gap between rollers, or checking parallelism to close tolerances is an essential requirement in a number of precision manufacturing processes. A measurement task that can be achieved using an RDP E725 digital indicator in combination with a pair of LVDTs.

Thanks to the E725’s capability to accept inputs from two separate transducers, in this case LVDTs of the same type and range, the indicator can be set to display individual readings, the average of both, or to check the difference to determine how parallel the rollers are. In some situations there can be an analysis requirement to switch between these different sets of readings, which is achievable thanks to the E725’s RS232 serial communication interface. Alternatively individual E725 amplifiers and LVDTs can measure gaps on either side of the roller and use the device’s 4 – 20mA signal as input to a PLC programmed to act in response to the gaps measured. It is normally unacceptable for rollers to be driven in contact with each other so a spacer is inserted between them for the purpose of zeroing. The E725 can be programmed to take account of the spacer size and return a reading that is corrected for the spacer size.

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