02/23/2008 • Automation • Image processing / Optical metrology • Sensor Technology

Optimum measurement of wet wood

Wood is a great challenge for laser measuring technology as the different optical properties fluctuate frequently.

Measurement technology company Micro-Epsilon offers its lowcost optoNCDT1401 laser sensor for use in saw mill trimming systems specifically for this material.
The sensors are directly integrated at the manufacturer’s plant in the systems that separate the planks from the wane. Depending on the position of the plank in the original tree trunk, the wane is flatter or steeper and the plank is broader or narrower. Therefore, for maximum yield, the exact width of the yet to be trimmed plank must be determined before the trimming system is set up.

The cutting width of the trimming system vary because the manufacturer wants to obtain the maximum usable width from each plank.

The exact determination of the wane is a difficult task, particularly when the wood is wet, when it has a slippery, shiny surface that cannot easily be measured optically. Due to the changing reflection characteristics of the surface, the laser power and exposure time of the sensors have to be constantly regulated. Therefore, the optoNCDT 1401 sensors from Micro-Epsilon are used for trimming systems. The planks arrive width ways to the side of the trimming system and are measured. A sensor with a measuring range of 200mm measures the profile of the cross-fed plank. These sensors are positioned every 30 to 50cm. As standard, the measurement is made from above. If required, the side trimming system can also be fitted with optical sensors on the top and underside. In this way, any position of the planks – wane at the top or bottom – is possible.

The signals reach the controller unit directly via an A/D converter card. The maximum cutting width is calculated by using specially developed software. The automated solution ensures the maximum yield from every tree trunk.

The optoNCDT 1401 laser sensors use a CMOS array as the position-sensitive measuring element. The sensor housing contains all the electronics. With their high IP67 protection class and aluminium casing, the sensors are ideally suited for harsh industrial applications.
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Micro-Epsilon Messtechnik GmbH & Co. KG

Königbacher Straße 15
94496 Ortenburg

Phone: +49 8542 168-0
Fax: +49 8542 168-90

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