The Hindu Business Line : Some pencil truths

Technology plays a rather interesting part, but first back to the pencil. As we all know, children have a habit of sharpening pencils too often. They either have fun using a sharpener to adjust the tip or do it because of the lead breaking constantly as they sharpen the tip. Parents invariably take their children to task for using up pencil after pencil in a snap. But could it be that there are defects in the pencil which make the tip break, making frequent sharpening necessary? As a matter of fact, it could be so.

Pencil leads, as we all know, are sandwiched between two wooden pieces referred to as `slats'. The long wooden lead-stacked stick is then cut to size by a sawing process.

During this process, a number of defects such as missing leads, lead offset and slat mismatch could creep in. Apart from this, a chip off or hole could affect the pencil functionally.

Defects such as lead offset can cause the pencil lead to break during the sharpening process. It is, therefore, very important to rectify these defects at this stage before moving on to the finishing process.

Now, picture two million pencils being sorted for such defects manually, everyday. Apart from this being a laborious task, in manual tracing of defects, the precision levels may not be high. Take the lead offset defect, for instance. It could be virtually impossible to inspect minute defects with the naked eye.

And this is where technology comes in. Pencil manufacturers have little choice but look for a fully automated system to perform this critical function of quality checks.

Ganesh Devaraj, Managing Director and CEO of Soliton, describes how his company uses the line scan digital cameras and image processing hardware and software from National Instruments for sorting pencils.

"Two high-resolution, high-speed monochrome line scan cameras focus on the two opposite sides of the pencil. Motorised filter wheels enable an automatic filter change depending on the pencil lead colour. The cameras are connected to two separate digital frame grabber cards. The cameras are positioned in such a way that the pencil axis is in line with the camera axis as they travel on the conveyor. The control unit of the conveyor is interfaced to a Data Acquisition/Control Card and a 2.5 GHz PC with high-speed RAM is provided to perform the image acquisition and processing. The application software running on the PC processes the data captured from both the cameras. Based on the defect definitions, images are classified as either good or bad," Ganesh explains.

He points out that the crucial part of the development cycle is the image-processing algorithm. "It has to be sophisticated enough to detect the different defect types under varying conditions and at the same time perform within the shortest available period."

Since pencils are supplied to different categories of customers with different quality expectations, Devaraj believes that a flexible system that can accommodate the kinds of pencils that could be introduced in the future should also be taken into account.

"National Instruments' Vision Builder, with its performance meter, has proved to be an indispensable tool for accomplishing the task," says Ganesh. Soliton has used this tool to complete a high-demanding sorting application within a period of 16 weeks for a top producer of wooden pencils.

If all the wooden pencils in the market were sorted and defect-free, we probably will remember our first pencil as well, even if we are not able to hold it!

Picture by Sampath Kumar G.P.

lnr@thehindu.co.in

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