Why the band saw gives a wave. Features of setting up a band sawmill. Band sawmill "Atlant"

Many sawmakers are familiar with this problem: sawing produces an uneven board surface, a "wave". The problem is really serious, but with the right approach, it is quite solvable. Let's take a step-by-step analysis of all the factors affecting the sawing process. There are only four of them: operator, machine, saw, wood.

Operator
The first item on our list can sometimes be the last. After all, it is the operator who determines the correct setting of the machine, the choice of cutting speed and the selection of the saw depending on the type of wood.
The sawing speed should be as close as possible to the maximum for the type of wood. If the cutting speed is not sufficient, the surface will look like a washboard. If the speed, on the other hand, is too high, the saw no longer has time to make a cut and, as a result, a "wave" appears.

Particular attention is paid to setting up the machine. Often, even experienced operators do not pay enough attention to the condition of the machine, citing the fact that adjustments take a lot of time. And the maintenance of the machine is carried out once a week, or even less often. Indeed, adjustments and repairs of the machine in this case is a rather lengthy process: after all, a lot of problems are accumulated in a week that have not been reached before. Our recommendation: check the setting of the machine every day, and always after possible contact of the saw support rollers with a log. Checking is not about regulating, and it takes little time.

The operator is also responsible for the control over the selection and condition of the saws, which I will discuss later.

Machine
Let's consider what parts and assemblies of the machine can provoke the appearance of a "wave" when sawing.

Saw guide rollers. They determine the position of the saw in relation to the machine support table. The correctness of the installation of the rollers is controlled using the adjusting ruler included in the machine kit. This ruler should be kept separate from other instruments to avoid damage to it. In case of loss or damage to the ruler, we recommend purchasing a new one, and not trying to make it yourself.

So, first we inspect the rollers. They should not have traces of wear on the working surface, leading to vibration of the saw blade. On the sides of the rollers, there should be no deep scratches formed in the event that the rollers did not rotate when the saw was moving.

In addition, the condition of the bearings is checked. Only a very slight backlash is allowed. In the event that the bearings are being replaced, it is necessary to check how they fit in the roller housing. If the bore holes are broken, you will most likely not be able to eliminate the backlash by replacing the bearings, and the newly installed bearings will quickly fail.

Next, the fastening of the roller axis (pin) in the housing is checked. If any backlash is detected (all pins securing the axle are tightened), the body is replaced. Often during operation, the place of attachment of the roller body to the carriage guide is damaged, therefore it is not possible to correctly adjust the position of the rollers (there is no adjustment margin). You can try to straighten the bend by first removing the roller housing. True, this can damage the weld spot, so it is better to replace the defective body with a new one.

It is better to immediately replace broken adjusting pins and rolled locknuts with new ones, and in the future, in order to prevent their premature failure, we recommend using only a high-quality adjusting tool (14 spanner wrench and 3/16 hexagon ‘’). After replacing defective units and parts, the saw rollers are completely adjusted according to the factory instructions. To ensure uniform pressure of the rollers on the saw when moving the movable roller from one extreme position to another, the guide of the movable roller must move in a plane parallel to the plane of the support table. This adjustment is often overlooked or incorrectly performed. As a result, when adjusting the kerf, the stiffness of the saw blade changes, and this provokes a "wave". Also check that there is no play in the idler roller drive assembly. Even a slight backlash is unacceptable here.

Bed rollers. There is no point in explaining the need to replace the rollers that are out of order. Let's focus on the correctness of their adjustment. After adjusting the perpendicularity of the vertical guides to the bed, it is necessary to check the fit of the upper and lower rollers to the corresponding guides. The lower pressure rollers (if any) are also adjusted if necessary.

Adjustment of the saw position on the working pulleys. The long 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. In this case, the defect does not appear immediately, sometimes after the second or third sharpening, and the operator, of course, suspects that the blade is of poor quality. But even the new saw, after several sharpenings, cuts in the same way as its predecessors. The conclusion, I think, you will make yourself.

Machine installation. This is especially important in cases where the supporting legs of the machine are not fixed with anchor bolts, as recommended in the machine's operating instructions. All supporting feet must touch the floor without any gaps. If a gap is found, it must be eliminated by placing a metal plate of the appropriate thickness under the supporting leg. On machines that were produced before 2000, there are no additional support legs, which are installed instead of the chassis and prevent the bed from bending when moving the saw head. If your machine model does not have these legs, we strongly recommend installing them by making your own or purchasing from Wood-Mizer.

Saw
After making sure that all machine settings are in accordance with the recommendations, we turn to the main culprit of the "wave". This is, of course, a saw. First of all, it must be remembered that the key to success in sawing is strict adherence to the instructions for sharpening band saws.

Most often, the "wave" occurs when sawing with blunt saws.

If the setting is insufficient, the cutting speed decreases sharply. In addition, the saw, even if it is sharp enough, heats up during operation and its tension has to be constantly restored.

The sharpening angle also affects the same. If this angle is more than optimal for the given type of wood, the saw is overloaded (bogged down), and if it is insufficient, the cutting speed decreases.

The uneven layout deserves a separate consideration. If the layout is different from tooth to tooth, the "wave" will have a random character, and depend mainly on the unevenness of the density of the wood. If the setting is different for different sides of the saw blade, the “wave” will depend on the prevalence of the setting (in one direction or the other) and occur when the cutting speed changes. Indirectly, the presence of such a defect is evidenced by the fact that after entering the wood the saw dives down or rises up.

A saw that has a tooth pitch or tooth height that changes from tooth to tooth will cut with jerks and a lot of vibration. We must not forget about the harm caused by unremoved hangnails. In addition to increasing the risk of the saw breaking, the presence of burrs leads to the slowing down of the saw in the cut, its heating, and, consequently, to the appearance of a "wave".

Often the saw is damaged by jumping off the pulleys or by improperly freeing it from a jam. They usually edit such a saw and try to cut it further, but you cannot achieve a high-quality cut from this saw.

Wood
Consider those characteristics of wood that affect the formation of a "wave". First of all, it is the uneven density of the layers. In most cases, the density of the core of the log is significantly less than the density of the outer layers. Therefore, the amount of sawdust when sawing the core is greater. The saw, meeting such areas on its way, can no longer cope with the removal of sawdust. As a result, its rear part heats up and increases in size. The saw bends in the cut and we see a "wave" occur. It is difficult to adjust the parameters of the saw so that it can cut equally well both hard outer and soft inner layers at the same time. We recommend changing the cutting pattern or leveling the surface after receiving the timber.

Most operators are familiar with the "wave" that occurs when cutting frozen wood. And if sawing completely frozen wood does not cause any special problems, then sawing slightly frozen or partially frozen logs is a very, very difficult task. The sawing technique here is the same as when sawing wood with different density.

When sawing wood with a large number of knots, the risk of a "wave" increases many times. In this case, it is necessary to cut very carefully and smoothly reduce, and then just as smoothly increase the feed rate when passing each knot.

Sawing highly resinous wood is particularly problematic. The fact is that the adhesion of sawdust and resin to the saw blade is tantamount to an increase in its thickness. And since the thickness of the cut does not change, the saw begins to rub against the walls of the cut, heat up and, as a result, the tension drops. The "wave" will appear immediately.

Use a cleaning fluid (although this does not always help, as fluid is usually only fed to one side of the saw and the resin sticks to both sides). Wood Mizer has developed the LubeMizer system for the simultaneous supply of washer fluid to both saw planes. We recommend purchasing this system and installing it on the machine.

Andrey Fedorov
Mechanic, JSC "Wood-Mizer East", St. Petersburg

Sometimes, when sawing, an uneven, wavy surface of the board appears, which naturally reduces the quality of the product.

• correct adjustment of the band sawmill
• cutting speed
• saw quality
• wood quality

Setting up the band sawmill.

The setting of the band sawmill should be checked daily, and always after possible contacts of the saw support rollers with the log. Saw guide rollers determine the position of the saw relative to the machine support table. The correctness of their installation is controlled using an adjustment ruler. The rollers themselves should not have traces of wear on the working surface - this leads to vibration of the saw. There should be no deep marks on the sides of the rollers (they are obtained if the rollers did not rotate when the saw was moving). The condition of the bearings is also checked. If the bearings are being replaced, it is necessary to check the condition of the bore holes in the roller housing - they must not be broken. In this case, replace the roller assembly.

Next, the fastening of the roller axis (pin) in the housing is checked. If any backlash is detected (all pins securing the axle are tightened), the body is replaced. Often during operation, the place of attachment of the roller body to the carriage guide is damaged, therefore it is not possible to correctly adjust the position of the rollers (there is no adjustment margin). You can try to straighten the bend by first removing the roller housing. True, this can damage the weld spot, so it is better to replace the defective body with a new one. Broken adjusting pins and rolled locknuts are best replaced with new ones immediately.

After replacing defective units and parts, the saw rollers are completely adjusted. To ensure uniform pressure of the rollers on the saw when moving the movable roller from one extreme position to another, the guide of the movable roller must move in a plane parallel to the plane of the support table. Without this adjustment, when the kerf width is changed, the stiffness of the saw blade changes, and this provokes a "wave".

Please note: there should not be even a slight backlash in the drive unit of the guide roller.

Bed rollers.

After adjusting the perpendicularity of the vertical guides to the bed, it is necessary to check the fit of the upper and lower rollers to the corresponding guides. The lower pressure rollers (if any) are also adjusted if necessary.

Adjustment of the saw position on the working pulleys.

The long 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. In this case, the defect does not appear immediately, sometimes after the second or third sharpening.

Installation of a band sawmill.

This is especially important in cases where the support legs of the sawmill are not secured with anchor bolts, as recommended in the machine's operating instructions. All supporting feet must touch the floor without any gaps. If a gap is found, it must be eliminated.

Sawing speed.

The sawing speed should be as close as possible to the maximum for the type of wood. If the cutting speed is insufficient or, on the contrary, too high, there is a chance of getting a "wave". Saw quality. The cutting speed is directly related to the quality of the saw. Often a "wave" occurs when the saw is dull or the cut is insufficient, all of which reduces the cutting speed. The sharpening angle also affects the same. If this angle is more than optimal for the given type of wood, the saw is overloaded (bogged down), and if it is insufficient, the cutting speed decreases.

The uneven layout deserves a separate consideration. If the layout is different from tooth to tooth, the "wave" will have a random character, and mainly depend on the unevenness of the density of the wood. If the setting is different for different sides of the saw blade, the “wave” will depend on the prevalence of the setting (in one direction or the other) and occur when the cutting speed changes. It is possible to assume the presence of such a defect if, after entering the wood, the saw dives down or rises up.

A saw whose tooth pitch or tooth height changes from tooth to tooth will cut with jerks and with significant vibration - and as a result, with a "wave". If the saw has intact burrs, it will heat up the saw and therefore create a “wave”.

If the saw has been damaged, then, as a rule, even after straightening, it cannot provide a high-quality cut.

Wood quality.

In the occurrence of a wave, wood is "to blame". Basically, this is due to the uneven density of different layers of the log, which is due to either the type of wood, the presence of knots, or the degree of "frostbite". It is difficult to deal with this: it is almost impossible to choose the parameters of the saw in such a way that it can cut equally well both hard outer and soft inner layers at the same time. We recommend changing the cutting pattern or leveling the surface after receiving the timber.

When cutting knotty wood, the risk of a “wave” increases. Carefulness is needed here: you will have to smoothly reduce, and then just as smoothly increase the feed rate when passing the knot.

If the wood is very resinous, the adhesion of sawdust and resin to the saw blade significantly increases its thickness, the saw heats up and, as a result, the tension drops and a "wave" appears. Cleaning liquid should be used.

To obtain high-quality wood blanks for use in construction or furniture production, it is important to make the correct setting of the band sawmill.

The need to adjust the band sawmill

If the adjustment rules are not followed, a surface in the form of a "wave" appears during the sawing process, which leads to a decrease in the quality characteristics of the material. Adjustment of band sawmills must be carried out daily and after the rollers of the sawmill come into contact with the wood blank. A thorough check and inspection of the machine components is carried out and, if necessary, adjustments are made.

Stages of setting up a band sawmill

The sequence of adjusting the units of the band saw machine requires special skills and knowledge, but is not particularly difficult.

With the help of adjusting bolts, wheels and a plumb line, the pulleys are aligned in a vertical plane.

Aligning the pulleys horizontally. This is done with a stretched tape with a special thread running along the sawmill. After the wheels are installed in the horizontal plane, the “driving” wheel is fixed, which is not involved in further adjustment.

The establishment of the backlash between the front edge of the "driven" pulley and the interdental gap of the blade is carried out with a tensioned belt by swinging the "driven" pulley horizontally.

The gap is set between the interdental gap of the tape and the leading edge of the "driving" pulley of the sawmill by swinging the "driven" wheel vertically.

Wave defect prevention

There is such a problem as the appearance of irregularities on the surface of the board being sawn, called "wave". Several factors affect the appearance of a defect:

• inexperience or inattention of the machine operator;
• incorrect adjustment (or lack thereof) of band sawmills;
• tape quality;
• type of wood.

Worker (operator)

The correctness of the band sawmill setting, the choice of sawing speed and band in accordance with the type of timber depends on his professionalism.

At low speed - the board turns out to be "ribbed", if it exceeds the allowable speed - there are not sawn sections in the form of a "wave".

Adjustment plays an important role in the smooth and quality operation of the machine.

Machine. The working units of the band sawmill affect the quality of the processing of logs, the wear of one of them or a failure in the setting will lead to a “wave” defect.

Guide rollers

With their help, the position of the saw relative to the support table of the machine is set. The accuracy of the position of the rollers is verified with an adjusting ruler, which is included in the set of the band sawmill. The working surface is monitored for wear, leading to vibration of the saw blade, deep risks are not allowed.

Worn studs and locknuts must also be replaced.

After the damaged parts have been replaced, the saw rollers are fully adjusted. Check the idler roller drive assembly for play.

Bed rollers. When worn, these parts are replaced and adjusted. Vertical guides are set perpendicular to the bed, control the correct fit of the rollers (upper and lower) to the guides.

Machine installation

During installation, it is important to ensure that the position is still, especially if it is not bolted to the floor, as indicated in the operating certificate. No gaps allowed. If backlash is established, a steel plate of the required thickness is placed under the legs of the machine. Some sawmill models have additional support legs to prevent the frame from bending.

Wood

Certain characteristics of the timber affect the quality of the cut, in particular the appearance of the "wave".

Different wood density. In the middle, the log is less dense than in the upper layers, so more chips are formed when sawing the central part. When cutting these zones, the saw cannot cope with the removal of sawdust, it begins to warm up and bend, resulting in a "wave".

It is difficult to choose the parameters of the band sawmill so that the hard outer and soft inner layers are cut well at the same time. It is necessary to redo the sawing pattern or carry out an additional operation to level the timber.

"Wave" is formed when processing frozen wood. If the timber is frozen in the same way, then this problem does not arise, but if you have to saw partially frozen logs, then a “wave” defect will arise, as when processing wood of different densities.

When sawing logs with a large number of knots, there is a risk of a “wave”. It is necessary to gradually reduce and then increase the cutting speed when processing them.

When processing the resinous surface of a log, sawdust sticks to the sawmill, which leads to its thickening, it heats up, the tension weakens, and a "wave" is obtained.

Inspection of mechanism parts

Before starting work, it is necessary to inspect the units of the sawmill.

The hoist mechanism moves the frame "up and down" using a transmission driven by an electric motor. The control panel is located in an electrical cabinet built into the upper crosspiece of the bed, an earthing connection is required. The frame consists of two beams connected to each other. The saw pulleys are located at the ends:

• "Leading" - fixed motionless;
• "Slave" - \u200b\u200bmoves longitudinally.

The sawmill is equipped with a saw tensioning device containing a spring-screw mechanism.

On the casing of the sawmill saw pulleys there is a tank with a cooling lubricant.

Checking and adjusting the saw band

The correct saw blade tension is a fundamental factor affecting the quality of the wood and the service life of the saw. The belt tension is carried out in accordance with the selected type of saw blade, the parameters are specified in technical documentation manufacturer. The saw band is pushed onto the pulleys, tensioned slightly, bolted, then tensioned to the desired value.

The saw stroke is checked on guides and pulleys. Make sure the saw band is correctly positioned on the guides. Then turn on the electric drive for a few seconds, turn it off. Open the covers and see the position of the blade on the pulleys. If the gap between the protrusion of the wheels and the trailing edge of the tape is from 1 to 2 mm, then the setting is correct.

If it exceeds this range, or the blade moves along the shoulder of the wheel, then the blade stroke is adjusted. When the screw is turned to the right, the blade will move to the protrusion of the tension wheel, if to the left, it will move away from the protrusion. Close the covers. Check the operation of the sawmill again.

Installation and adjustment of the guides "cubes"

The fastening screws of the guides are loosened and pressed against the upper edge of the blade. You need to make sure that the "cube" will not press into the tape and ruin it. Then they are tightened again, and if the "cube" has the correct adjustment, its upper edge and the adjustment ruler will be parallel.

Brush installation The brush has an effect on the efficiency and accuracy of sawing, the service life of the band, working pulleys, support rollers. When installing, make sure that the bristles do not touch the bottom of the saw teeth.

The first: what keeps the saw from going up and down while cutting? After all, it is because of this that a wave forms on the lumber. In many sawmills on the Russian market, squeeze rollers are used, which do not allow the saw to rise above them, because there is a stop, but nothing limits the saw when moving below. And when the saw is incorrectly sharpened, set apart and stands on the machine, in which the wrong geometry of the rollers, pulleys, it begins to look for a place for itself, goes down, breaking away from the rollers. As soon as it reaches a critical point, when it breaks further, the course of the sawmill becomes difficult. The operator senses this and reduces the movement, the saw slowly rises up, reaches the stops, cuts some distance straight, and dives down again. The result is a wave on the board, and not only on the top, but also on the bottom board.

On our first sawmills, we also used squeeze rollers (PLG-1E), but then we abandoned them. On the sawmill PLG 2M "Bobrenok" there are cheeks (slotted guides) in which the saw is held from above and below. In this case, the condition is met: when installing these cheeks between them and the saw, a piece of paper should pass in the upper position, and the same in the lower position. It turns out that when sawing, even if the saw is incorrectly sharpened and set, there will be a slight wave formation: 1-2 mm.

Second a very important point is the track. For example, when creating the Taiga and Kedr sawmills, well-known in Novosibirsk, rail tracks from a welded channel without any thin surfaces are used. It turns out that the roller is flat and rolls on a shelf 5-6 cm wide. If the roller rolls along the channel, even when installing scrapers that remove the sawdust formed during the sawing process, what has already rolled cannot be removed. It turns out that sawdust rolled in one place, and not in another. As a result, in this place the machine rises, even by 0.5 mm. On the saw, these are 0.5 mm. turn into 1.5 mm. The saw immediately makes a jump, goes down and returns to its original position, at best, only after a meter, or it can simply start “looking for a place for itself” and make 2-3 waves on a meter of lumber. At the same time, many manufacturers design 3 rail tracks, between which there are 2 joints. These joints make it difficult to catch the difference between the tracks, and this will constantly reflect on the lumber. In order not to get into such an unpleasant situation after buying a sawmill, we recommend visiting the production where the sawmill, which you are going to purchase, works, and measure the lumber with a vernier caliper at the place where the junction between the rail tracks occurred. Thus, you will immediately understand whether you can earn the money you plan on using such lumber.