Harvester: how a forest is cut today
Let's start with the glossary. The stress in the word harvester falls on the second syllable, no matter how strange it may sound to connoisseurs of the English language (in English harvester, "reaper", stressed syllable first). Consider it professional, like a compass for sailors. To understand what the harvester does, a small educational program is needed in the field of logging. A tree consists of several parts. The lower, it is butt, part contains a minimum of knots. From it, expensive material is obtained, the fancage from which plywood is made.
The middle, more knotted part goes to the boards and is called a sawlog. The top of the tree is suitable only for firewood or paper and is called balance. Each part of the tree, intended for a specific industrial application, is called an assortment. And the process of cutting a tree into assortments is a bucking.
There are two methods of logging: whiplash and assortment. With a whiplash, the first machine (feller buncher) fells tree trunks, forming bundles, the second (skidder) moves them to the upper warehouse, where the third machine (processor) unloads them in accordance with the requirements of the customer.
The assortment method involves the use of a harvester, which not only cuts the tree under the root, but also immediately cuts it to the most valuable assortments for the customer, simultaneously clearing the knots. The second machine, the forwarder, collects the finished assortments and takes them to the logging site in large quantities (up to 20 tons at a time).
The assortment method helps to save a lot of time. And this is due not so much to the complex construction of the harvester as to its intelligent software.
The main working tool of the machine is a harvester head. Using the manipulator, the operator brings the harvester head to the tree. The delimbing knives capture the trunk, while their position is fixed by sensors to determine the thickness of the tree. Also, the barrel is wrapped in rollers. Their tines reliably cut into the bark, but do not damage the precious wood. At the command of the operator, the sawing mechanism cuts the tree under the root.
After the cut, the harvester head automatically rotates, placing the tree horizontally. Rotating, the rollers stretch the barrel to the desired length (a measuring sprocket serves to accurately determine the length), while the knots are cut with knives. In a matter of seconds, rollers, knives and a saw turn a tree into a set of strictly defined assortments.
The secret of the phenomenal speed of the harvester lies in the complete automation of the sorting process. Before starting work, the operator or technician creates a file called “bucking instruction” using the personal computer in the cockpit. The file contains information about which particular assortments are needed by the customer. It is interesting that for each assortment its value is indicated.
For example, today orders were received for a two-meter fancier (birch), a three-meter sawlog and a more expensive four-meter sawlog (pine). They also order a balance, but its cost is low.
When the harvester head captures the trunk, the operator is only required to indicate the tree species. Based on the data on the thickness of the barrel, the computer predicts its length and calculates which assortments will be obtained from it. The machine tries to choose the most expensive combinations of assortments, but if the tree is not so large, it also procures cheap ones.
Thanks to computer control, the rollers stretch the barrel exactly to the length of the necessary assortments. Theoretically, bucking can take place in a fully automatic mode, but in practice the decision on sawing is made by the operator. Only a person can notice that the tree is rotten or excessively knotty.
Old new harvester
By design, the harvester resembles modern industrial robots. His brain is six programmable controllers and a TimberMatic H-12 control system. Five of the six controllers are the same and interchangeable. These are the controllers of the frame, cab, transmission, manipulator, harvester head. A specialized controller controls the engine.
Controllers receive information from controls and numerous sensors, make calculations and generate an output signal for the actuators of the machine (hydraulic motors, manipulator cylinders and interframe joints, etc.).
With each TimberMatic software update, new firmware is released for the controllers, which teach them new functions. Among these functions, self-diagnosis comes first. Thanks to it, the operator in some cases can fix the machine himself (for example, if the fuse is blown), and in the rest - send detailed information about the malfunction to the service center so that the technician arrives with the necessary tools and spare parts. The issue of operational diagnostics and repair is very important for the harvester: the machine works in corners very far from civilization, and its simple cost is very expensive.
With TimberMatic, a person can customize the machine for themselves. It is more convenient for novice operators to work with smoother responses to the deviation of the handles, while an experienced worker prefers quick reactions to the exact actions of trained hands. In addition, the computer constantly monitors safety: for example, it deactivates the harvester head if the cab door is open, or blocks the rotation of the cab when driving on the road.
View manual John Deere 1270E HarvesterThe article “The Lumberjack” was published in the magazine Popular Mechanics (No. 12, December 2013). I wonder how a nuclear reactor works and can robots build a house?
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