Computer screen cuts at timber

Press, 19 October 1987, Page 34

Computer screen cuts at timber

Humpty Dumpty sat on a wall, Humpty Dumpty had a great fall. All the king’s horses and all the king’s men Couldn’t put Humpty Dumpty together again. Unless, that is, Humpty Dumpty happens to be a sawlog, in which case there are scientists at the Ministry of Forestry’s research centre at Whakarewarewa, Rotorua, who can definitely put Humpty together again — on a computer screen. “Operation Seesaw,” a computer program developed at the centre, is described by Jim Park, a specialist in exotic-forest management, as a research tool that enables its users to reconstruct a sawn-up log and slice it up again in different ways. The program has a variety of applications, both scientific and commercial. Among other things, it should enable its users to predict very accurately the timber yields of specific stands of trees and, perhaps more importantly, exactly what particular sawmills will be able to extract from particular logs. "Seesaw” is not a hypothetical model. It is based on data from real logs. , The scientists reconstructed a gampie of logs in the computer from sawing data and at the Ml ne time .used the data to determine the .< shapes of the original logs and to measure and maptheir internal features, such as the size of the.cores, branch stubs and toots, and the percentage;>pf -—-K—•—

The program enables the computer operator to "cut up” the reconstructed log in different ways and to assess the variations in yield and quality of the resulting “timber.” Allowance is made for important mill variables, and the operator has the opportunity to make a decision at every point at which decisions on sawing would have to be made in a real mill. "Seesaw” features a graphic display that enables the operator to see the “log” in cross-section or in longitudinal profile. Press a button and flitches drop off like bits of cake. The log may be rolled or flipped, and a second visual display may be summoned to give a full-length profile of each flitch, knots and all, as it — 'fe”

falls off the “saw.” Each board is automatically classified in one of six grades of quality. A touch of another button instantly puts everything together again. Each “log” may be repeatedly sawn to as many different patterns as the operator can devise. “Seesaw’s” immediate objective is to identify types of pruned logs and to extend knowledge of the effects on timber yields of different sawmill practices and sawing patterns. The present program is based on measurements of pruned logs, but a version is planned to include representations of branches, so that the sawing of unpruned logs may be simulated. Milling companies both at home and in the United States have shown an interest in it. Interest has been shown, too, in the development of "Seesaw” as a training tool for sawmill staff. This will probably require a version different from that developed for research use. In the longer term, faster, nongraphic sawing simulations will be developed. Further in the future, new techniques for internal scanning of sawlogs may enable sawmillers, before they make the first cut, to build a clear picture of what lies inside a log — the size and shape of the core, the knots if any, branch stubs, and so on. If this becomes a commercial reality, “Seesaw,”

or a program developed from it, may clear the way for computercontrolled sawmilling with maximum timber yield and minimum WBSt6. Also in the pipeline at Rotorua is a means of converting Plnus radiata into "real” plastic wood. This seemingly self-contradictory objective stems from the fact that, while radiata is one of the world’s most versatile timbers, its range of uses could be much extended if ways could be found to make it harder, or more flexible, or both. Researchers are well on the way to doing just that by impregnating the wood, in vacuum conditions, with chemicals that can later be converted into tough polymers. The aims are to increase the water repellency, bending strength, and stiffness of the wood, to harden it, and even to alter its surface texture and colour, so that it can be used, in furniture or decking for example, as an economical substitute for Increasingly scarce and expensive hardwoods. In other respects, the “naturalness” of the pine is not affected because although the impregnation process fills the spaces between the wood cells the chemicals have little or no reaction with the cell walls. Chemical modification of wood to harden its surface or improve its quality as a veneer is not a

new development — back in the eary 1940 s a process was developed, through war-time research in the United States, to harden veneers by impregnating them with water-dispersed resins which were heat-cured to form a composite. But this process was restricted to very thin sections of wood. In the 1960 s a technique was developed to impregnate wood with vinyl monomers which could be, converted, with catalysts, into solid polymers. The Americans experimented with the use of gamma radiation to induce polymerisation. A project group at Rotorua has been experimenting with a much cheaper and environmentally clean system that uses tempera-ture-sensitive catalysts that work at relatively low temperatures. The catalysts are simply mixed with, the vinyl monomers before impregnation and will initiate the desired reaction at a temperature of 60 deg. C. Curing may be completed in a few hours. Among the most effective compounds tested to date is one called methyl methacrylate, the chemical used to make perspex. Pine polymerised with this chemical has a surface hardness up to eight times greater than that of untreated wood. Dyes can be included with the monomer to change the appearance of the finished product;

pine flooring, for example, can be made to look just like teak. The research with different chemicals is continuing, with the aim of determining the most suitable and economical hardening treatment. Such a product, if successfully developed, could be the “wonderwood’’ of the future. Cheap and readily obtainable, it would have an almost unlimited range of uses in construction, in furniture, and in kitchen benches, floors, cupboards, bathrooms, and other domestic and industrial products. The Rotorua campus where this research is based is huge and the variety and scope of the science going on there is more than any person — with the possible exceptions of Einstein and Leonardo — could absorb. The recently opened Papro plant, in a flash new building set among old trees, is now the research focus for the pulp and paper industry. An older, rambling complex houses a variety of equipment and laboratories for research into the milling, curing, preserving, and durability of wood — with a strong emphasis on radiata pine. Other research groups are studying such topics as agroforestry, shelter, alternative timber species, silviculture, forest management, weed control, tree establishment, and har-

vesting methods. A large experimental nursery raises thousands of seedlings for planting in trial areas throughout the country and has successfully developed techniques for mass production of open-grown eucalypts and native species from seed, and pines from cuttings. An arboretum attached to the nursery contains a range of examples of important economic trees, including a most unusual fastigiate radiata pine whose relatively slow, dense, and erect growth is ideally suited to hedging. Unfortunately, because bf the antidothistroma regulations, plants of this cannot be sent to Canterbury. The emphasis is on productivity, and some of the research now has private sponsors, with an accompanying commercial requirement for secrecy, a situation which many scientists, used to open exchange of information, accept reluctantly. Not all the research is directly related to forestry. One of the more offbeat — but regionally important — problems recently investigated by scientists from the centre is the question of how to dispose safely of Rotorua’s sewage effluent, now rapidly polluting Lake Rotorua with phosphorus and nitrogen. The researchers have come up wth a proposal to dispose of the effluent by spray-irrigating part

of Whakarewarewa State forest with it. The forest and its associated ecosystems will filter out the nutrients, and pure water will enter the lake. Trials of a pilot scheme were successful, and the main scheme has been approved in principle. Construction seems likely to go ahead at a cost of $2l million. “Pure” science has not been abandoned altogether — yet — and a wealth of information and expertise has been assembled at Rotorua on the biology, ecology, and management of indigenous forests and their fauna. Sometimes the Rotorua expertise finds unexpected outlets. Among the diversity of agencies to seek help recently was the United States space agency, NASA NASA’s problem was that its perimeter at Vandenburg Air Base was being invaded — not by protesters or Russian spies, but by pampas grass, the same pampas grass that is a major problem weed in the forests and kiwifruit orchards of New Zealand’s north. (The fluffy windborne seeds stick to the hairy kiwifruit and reduce their export value.) The request from NASA was relayed to Rotorua by Florida University, and scientists at the centre, who have learned quite a lot about how to control pampas grass, were happy to oblige with the necessary information. Pre l sumably they also sent their recently published brochure on suitable New Zealand native species for replacing pampas in low shelter and amenity plantings.