Laser sensors keep tile maker Redland on top of quality issues

Leighton Buzzard, UK - Monier Redland has installed new laser sensor technology from SICK UK to improve production efficiency on the roofing tile line at its Leighton Buzzard plant. The factory produces around 67,000 tiles in a 12 hour shift: each tile made from two concrete layers, a fine grade upper layer and a stronger lower layer.

Mixes for the layers are automatically fed into separate hoppers and extruded together onto a conveyor as one tile. The compaction of each layer is governed by the level of material in the hopper, so keeping the level of mix within tight upper and lower limits is essential. Having too much or too little compaction could reduce product quality, waste material or even result in product being scrapped.

We had constant problems with the photo-electric sensors we were using previously, according to shift electrician Simon Jackson. Every time we changed products and colours, we had to recalibrate the sensors to monitor the level accurately. It took several iterations before we got it right, and could result in a lot of waste; although checking sensor operation used to take time, we always had to make sure it was correct to give us peace of mind.

"“By contrast the SICK DT50s maintain their detection accuracy, despite changes to the product colour. We can now ensure consistent quality in our tile ranges, while reducing the cost of waste and rejects," said Jackson. ”The SICK DT50 laser sensors are able to detect accurately and consistently the upper and lower fill levels, and signal the feeder to start or stop supply. The laser sensor signal is not affected by the mix colour or the dirty environment.

“We now have such faith in their reliability and accuracy that we now switch straight from one tile colour batch to another without any concerns. Redland has always had a high reputation for quality, and the new sensors give us added confidence that the consistency is being maintained.”

The DT50’s temperature-stable light spot and negligible black/white shift difference are said to enable "complete confidence" in measurement precision no matter what the colour of the surface. Initially designed as a low-cost distance measurement device with a range of up to 10m and repeatability of 2.5mm, the device is often used in place of photo-electric proximity switches due to its long range and colour independence.