On reflection, Alphr Technology chooses Omron sensors

The Application

To develop and manufacture two machines: The first would heat metal compression limiters to 380°C within a few seconds by induction, and would then press them into the top of a plastic component. The second machine would inspect and leak test each component to ensure that the limiters protruded by the correct distance above its surface. Measurement accuracy of ±0.3 mm or better was needed. The inspection process needed to be automatic using a sensor system that would simultaneously check the top and bottom of the component.

The decision to use Omron

Initially the Alphr design engineers felt that optical sensors would be unsuitable, because the body of the plastic component is matt black and the compression limiters are highly reflective. The engineers then investigated the use of linear variable differential transformer (LVDT) transducers, but found that the speed of response, the potential physical damage and the high contact temperature could be potential issues. It was also decided that the use of vision systems would increase costs and would have been difficult to configure for this unusual application. At this point Alphr asked Omron, with whom they have an excellent relationship, for advice and suggestions. Omron proposed the use of its ZS family of laser measurement sensors, with a servo drive system to allow the sensors to scan the component being inspected.

The Solution

The ZS sensor range is specifically designed to deal with difficult surfaces and textures. It is capable of delivering dependable results not only with black plastics, as used in the present application, but also with foils and even glass. The built-in user interface makes it straightforward to match the sensor's operating characteristics to the application and the PC-based configuration tool, supplied as standard, allows settings to be fine tuned and the performance of the sensors to be monitored while they are in use.

Another benefit for Alphr was the fact that the ZS system has the ability to daisy-chain up to nine heads and controllers. In this application, four are used, two to inspect the bottom of the component, and two to inspect the top. ZS sensors also make measurements in as little as 110 μS, thereby easily satisfying the need for speed and, in the configuration used by Alphr, they deliver accurate and repeatable results to within ±0.01mm, thirty times better than is actually needed.

Paul Bridgewater of Alphr Technology said "Within just a few days of receiving our enquiry, Omron sent an engineer to our premises to demonstrate the equipment using samples of actual components that would be inspected by the machine. Not only that, having shown us convincingly that the ZS sensors were suitable for the job, the engineer took the product samples back to Omron for further tests. As a result, the Omron application team provided us with details of the optimum settings for the sensors in our application. That made commissioning very easy. In spite of the challenges of the application, the sensors worked first time, and they do exactly what they are supposed to."  

Omron also supplied the servo drive system needed to allow the sensors to scan across the component being inspected. Products from the XtraDrive range were chosen because of their compact size, high positional accuracy, near zero settling time and excellent value for money. Additionally the engineers at Alphr knew that the drives' integral auto-tune function would make them easy to set up. Like the sensors, the servo system worked first time and easily met the project's requirements. With the machine now in full service, both sensors and drives are continuing to work flawlessly and dependably, allowing the machine to meet and exceed the end user's demanding requirements for accuracy and throughput.

"Being able to use the same supplier for the two key items of equipment needed for this project was a major benefit," said Paul Bridgewater, "as was the superb support we received from Omron throughout the project. In addition the capabilities of the ZS sensors and XtraDrive servos have opened new doors for us in the design of future machines, and we'll certainly be using them again."