Pine Bandsaw Divorce
- When receiving a saw, check the compliance of its parameters with the state (dry, wet, frozen) and wood species.
- After 3 years of operation of the power-saw bench, check the bombing (convexity) of the running pulleys for their compliance with the design parameters. The bombing triggered leads to cracks in the saw, so the pulleys in this case are given for resurfacing.
- It is imperative that both running pulleys are precisely aligned. This can be checked using a plumb line. An error in installing the running wheels (pulleys) on the same line by only a few mm leads to runout of the saw and the occurrence of cracks. It is very important that the base of the saw tooth protrudes 3-5 mm above the pulleys.
- A large run of the saw from the pulleys leads to a stretching of the trailing edge, and as a result, the saw becomes unstable in the cut. It is also necessary to avoid the influx of saws on the rear guide. In this case, there is a danger of cracking from the back.
- The bearings of the machine must be in perfect condition, otherwise they will be sources of vibration and thereby cause the appearance of cracks on the saw.
- It is important that the saw is guided by the guide, and not be clamped in it. Foreign bodies, deposits of tar or wood dust must be carefully removed. If visible bands have formed on the saw, this is a sign of friction in the guide, as a result of which heating of the saw will lead to a runout in the final result.
It is necessary to check the correct installation of the rollers with the help of an adjustment ruler. The rollers should not have any traces of working out on the working surface leading to vibration of the saw blade. There should not be deep grooves on the sides of the rollers if the rollers do not rotate when the saw moves.
To ensure that the rollers are pressed evenly on the saw while moving the movable roller from one extreme position to another, the guide of the movable roller should move in a plane parallel to the plane of the support table. Failure to perform this adjustment or its incorrect implementation “provokes” the occurrence of a “wave”. It is necessary to check the play in the drive unit of the guide of the movable roller. even slight play is unacceptable here.
Timely replacement and adjustment of bed rollers is necessary. After adjusting the perpendicularity of the vertical guides to the bed, it is necessary to check the fit of the rollers to the corresponding guides.
- Most often, a “wave” occurs when sawing with blunt saws. If the wiring is insufficient, the sawing speed decreases sharply. In addition, the saw, even if it is sharp enough, warms up during operation and its tension has to be constantly restored.
- The uneven density of the wood also affects the formation of the "wave". In most cases, the density and hardness of the central part of the trunk is much lower than the density of the sapwood part (see Table 1, “Rules for Operating Band Saws”). Therefore, the number of sawdust when sawing the central part of the trunk is greater. Encountering sections on its way, the saw can no longer cope with the removal of sawdust. As a result, its back is heated and increases in size. The saw bends at the cut, and we see the appearance of a “wave." This applies to sawing such rocks as acacia, hornbeam, ash. In oak and birch, on the contrary: the central part is harder than the periphery. In alder, pine, aspen, poplar, linden, this difference is not significant: 2. 6%; in spruce, the hardness of the central and sapwood parts of the trunk is the same, but the presence of a large number of knots suggests the possibility of a "wave". In this case, it is necessary to saw carefully, as well as when sawing frozen wood (i.e. slightly frozen or partially frozen logs), it is necessary to gradually reduce or gradually increase the feed rate, while sawing completely frozen wood does not cause any problems.
- Sawing of resinous pine wood (spruce contains less resin, fir does not contain at all) also causes problems: the adhesion of sawdust and resin increases the thickness of the blade with a constant cut thickness, as a result of which the saw begins to rub against the walls of the cut, heats up and, as a result, the tension drops. The result is a “wave." It is necessary to use a washing liquid, wipe the outside of the saw from time to time. The installation of a squeegee soaked in crude oil, kerosene, diesel fuel can significantly help in this. When sawing the rest of the species, except spruce, use coolant. When sawing wet, frozen wood, it is not necessary to use coolant.
- The harder the wood, the lower the cutting speed (saw movement). However, the machine provides one, constant, cutting speed of 30 m \ s. in this regard, it is necessary to change the feed rate.
- The feed rate depends on the type of wood, more precisely its hardness, diameter of the log, the width of the sawn timber, the composition of the steel, its processing, the quality of sharpening, i.e. from many factors.
Therefore, the following rule should be used: the feed exceeded the optimum value if the saw began to run out, if wood dust appeared instead of sawdust. this is a clear sign that the feed speed and cutting speed do not correspond to each other.
- When using PLP-ASTRA-Mu, use the passport, description and instruction manual.
GENERAL INFORMATION ON BAND SAW PARAMETERS,
Видео: Pine Bandsaw Divorce
APPLICABLE FOR CUTTING LOGS AND BARS.
Remember that the performance of the band saw is largely dependent on the saw itself. It can make successful or fail all sawing operations and therefore requires special attention from the sawcutter.
To ensure reliable and productive work of the saw is tight, the teeth of band saws should be prepared according to the appropriate technological conditions. This is possible if you have the necessary knowledge of the parameters of the band saw for the saw blade and in compliance with the rules for preparing the saws for work.
C. rake angle
It plays a very important role in the sawing process, it can have a decisive influence on the productivity and resource of the saw as a whole. This angle is selected depending on the type of wood, the speed of the saw, the feedrate and the shape of the teeth. For saws up to 50 mm wide, it ranges from 8-17.5 0 for hard dry rocks, and within 25-30 0 for soft rocks.
A. rear corner
The slope should start right from the top of the tooth and should be at least 5. 7 0 so that the blade can move freely. When sawing softwood, it is necessary to increase the back angle to 12. 15 0. If the back corner is insufficient, the back side of the tooth near the top will rub against the log, which will lead to overheating and damage to the saw. When sharpening a saw, it is necessary to completely grind the back of the tooth in order to maintain the original posterior angle. Otherwise, the saw will heat up quickly, lose hardness and become dull.
In. the angle of sharpening
The point angle is the difference between 90 0 and the sum of the front and rear angles. Since the sharpening angle is determined by the strength of the tooth, it should be sufficiently large, at least 40 0. For hardwood, it should be close to 50 0, and for softwood it can be reduced to 35 0. If this angle is greater than the optimum for this breed wood, the saw sinks (gets stuck), and if it is insufficient, the sawing speed decreases.
h. tooth height
High teeth mean deep indentations with a large area. The tooth should not be too high, because it will vibrate and the cut will be oblique. Tooth stability depends on the ratio of tooth height to pitch. The best ratio is 1: 3 (the height of the tooth is 1 \ 3 steps). If the pitch is more than 30 mm, the ratio should be equal to 1 \ 5, in no case should the tooth height exceed the thickness of the saw by more than 8-10 times. Slight deviations of 1. 2 mm are allowed; for hard rock in the direction of decreasing the height of the tooth in order to ensure its stability, for soft breeds. in the direction of increasing to obtain a larger area for chip output.
t. tooth pitch
The pitch of the saw tooth is selected depending on the type of wood, the speed of the saw (cutting speed), feed speed. If the saw pitch is chosen too large, this will lead to a rapid blunting of the saw and the formation of sawdust with a loose consistency. A small step gives a smooth surface and is convenient when the saw is located vertically, when the sawdust is easily removed, when placed horizontally, significant recesses between the teeth (tooth axils) are necessary to place and remove the sawdust from the sawing area. With a saw width of 50. 70 mm, a tooth pitch of 15 mm is recommended. a saw whose tooth pitch or tooth height changes during the transition from tooth to tooth will be cut in jerks and with significant vibration.
We must not forget about the damage caused by unopened barbs. In addition to increasing the risk of rupture of the saw, the presence of barbs leads to inhibition of the saw in the cut, its heating, and, consequently, to the emergence of a "wave".
R is the radius of the recess
During sawing, stress is concentrated in the recess. The radius of the recess should be large enough so that the stress on a limited area is not too large. Scratches and heterogeneities cause microcracks and can significantly reduce the life of the saw, so the recesses should be rounded and sanded to a high surface finish.
b. saw thickness
The thickness of the saw should be 1 \ 1000 of the diameter of the pulley. If you take a thinner saw in order to reduce waste, then it will give a wavy cut. Remember, the thinner the saw, the lower the feed. For sawing logs and beams, saws with a thickness of 1.4 are recommended; 1.6, while the minimum allowable pulley diameters should be respectively 700 and 800 mm.
S. tooth divorce
The tooth bite on the side should not exceed 0.5 thickness of the saw. With an increase in divorce, the purity of the cut decreases, and the loss of wood in sawdust increases. In addition, increased effort spent on sawing and loads on the side faces of the teeth. The magnitude of the divorce of all the teeth of one saw should be the same. Otherwise, less bent teeth will not participate in sawing, and more bent teeth will work with overload and therefore quickly fail. The magnitude of the divorce depends on the hardness of the wood and its moisture: the higher the hardness, the less is the separation of the teeth; the higher the humidity, the greater the divorce.