brick houses / 19.08.2023

Do-it-yourself welding of band saws. Homemade band saw welding with your own hands Welding a band saw at home

Welding of band saws is a highly specialized widespread operation, the purpose of which is to prepare band saws for various purposes for operation. Welding is used to repair (torn) band saws in need of repair and to produce new saws from coils.

An apparatus for welding band saws is a device in which an electric current is passed through the ends of the saw joined in the clamps, melting and welding the edges of the ends of the saw blade. The current is supplied through the electrodes connected to the clamps of the saw.

The principle of welding band saws. Apparatus classification

The principle underlying band saw welding is a special case of resistance butt welding or flash welding. The proposed apparatus for welding band saws includes equipment designed for different scopes of welding work and profile of activity.

Conventionally, butt welding equipment for band saws can be divided into three groups:

Resistance welding machines

They are inexpensive compact welding equipment designed for repairing wood saws on their own at production sites for sawing wood. They are characterized by simple design and low productivity (several dozen welds per shift)

Flash welding machines

Welding equipment of the middle class, operating on the principle of continuous flashing, are designed for welding of all types of saws and knives (including bimetallic ones with soldering) when loading about a hundred welds per shift

Flash welding machines with welding cycle automation

Automated with the cycle "installation of the saw in the apparatus - removal of the welded blade with partial removal of the burr". The productivity of such equipment is several hundred welds per shift, and they are used mainly in service centers

In addition to welding, auxiliary equipment is offered for the preparation and control of the process:

Machine (guillotine) for band saws
Machine (device) for stripping
Pyrometers, etc.

Technological sequence of the band saw welding process

Saw cutting

The canvas is cut on special guillotine shears. If scissors are not available, a chisel or cutting machine can be used. If the fabric is welded in the place that was welded earlier, 5 mm should be cut off from the previous weld on each side. Blade cutting is done between the tops of the tooth. On each side, an allowance of about 1.5 mm is left. The cut line after the scissors should be straight and strictly at right angles to the back of the saw.

Cleaning of weld ends

The ends of the saw are cleaned of dirt, if necessary, degreased with alcohol or acetone. The edges of the joint are treated with an abrasive until there are no irregularities and burrs. It is convenient to use a grinding machine with a cleaning abrasive.

Installing the saw in the welding machine, selecting the welding mode

The prepared web is installed in the clamping mechanism so that the edges completely coincide and converge in the middle of the space between the clamps. Depending on the size of the saw, the force, draft stroke and welding mode are selected. The documentation for the devices includes tables with mode settings depending on the size of the saw. Thus, for a particular saw, the control handles are set to certain positions, which is the welding mode setting.

Welding

Turns on with the start button or by turning the handle. The current is supplied to the ends of the saw, and the metal is melted at the junction. The movable clamp is shifted to the fixed clamp by the amount of shrinkage with the formation of a welded bead at the seam.

An important characteristic is the time of the current pulse. The automatic mode of welding assumes giving of an impulse within 1-2 seconds, at manual control time is controlled by the operator. If the welding result is unsatisfactory, a suitable mode is selected, the settings are recorded and in the future they use their settings for welding saws with similar characteristics.

The electrode surfaces must be clean. Disruption of contact between the sheet and the electrodes increases the resistance and disrupts the welding mode.

Weld Annealing

Annealing is needed so that the web material, which has become hard and brittle during welding, returns to its original viscosity and ductility. It is produced in the same clamps, but without precipitation and in a different current mode. Heating up to the annealing temperature and slow cooling is controlled by the annealing current supply button. If the device does not include a pyrometer, the temperature is controlled by the color of the metal. At the optimum annealing temperature, the color should be cherry red. Do not allow the metal to heat up to orange or yellow, which is evidence of overheating. Gradual cooling can last 3-5 minutes. Some blades require two cycles of annealing.

Stripping the canvas

The influx of metal from the welding area is removed by stripping. The correct shape of the cavity between the teeth of the saw in the place of the weld must also be displayed. Cleaning can be done with any abrasive. The grinder fits perfectly. The movements of the abrasive wheel should be directed along the weld.

Some technological details of the band saw welding process

Specifics to consider when welding band saws:

The alloys from which band saws are made are difficult to weld.
The saw blade is a detail of a developed section in contact-arc welding
The welding seam during operation of the saw is subjected to extreme loads
The geometry of the saw tooth in the area of the weld affects the level of load during operation

Band Saw Welding Principles

There are two principles of welding - resistance and fusion.

1. Resistance welding

Welding equipment operating on this principle is structurally simpler and cheaper, but has serious limitations in use.

The features of the technology include the requirements:

High quality preparatory operations. When cutting the web, there should be no edge deformations and burrs, which is almost often unattainable. As a rule, worn guillotine knives do not change in time and the cut edge of the blade does not meet the necessary requirements.
High quality of the contact surface of the welding electrodes, clamping segments and adjustment of their position.
Ensuring the correct mode of butt welding. The material of the web, as a rule, is not disclosed by the manufacturer, so the setting of the welding mode is done on its own. In this case, the service life of the weld is often lower than the life of the cutting part until complete wear.

2. Flash welding

Principle features:

High demands on the preparation of cloths and the surface of the electrodes
Compliance with the correct step (tooth sequence) of the blade, taking into account the loss of metal during welding. For saws for wood with a standard tooth pitch of 22 mm, this is not difficult, but for saws for metal with a variable pitch, it has its own difficulties (removal of a non-multiple part and location of the seam in the place of the smallest tooth pitch is required)

The correctness of the selected welding mode can be determined by the following features:

The reflow process is smooth and continuous from start to upset
When visually inspecting the weld, the extruded melt and deformation of the underlying surface should be clearly visible.

Material of electrodes of band saw welding machines

The electrode material must be hard and have good electrical conductivity. Copper is too soft. Bronze is more suitable, but the iron of the sheet under conditions of high temperature and voltage begins to drift into the surface of the electrode, changing the properties of its conductivity and resistance. After 25-30 weldings, the initial mode begins to shift and becomes incorrect for further work.

Free-cut (lead) brass is often used as electrodes, but lead and zinc also pass from the surface of the electrodes, changing the resistance. Thus, the electrode of the device fails much faster than its physical wear.

Special bronzes containing chromium slow down the drift of metals and the setting of boundary surfaces. Such electrodes withstand up to 600 weldings, after which they are restored by grinding the surface. Grinding should not be a mirror to avoid slipping of the saw on the electrodes during upsetting. On the other hand, the electrode should not have rough marks. Optimum roughness processing can be obtained by using a milling machine.

Heat treatment (annealing) of the weld

For low-alloyed sheets for wood, the annealing temperature is 420-450 °C, for alloyed bimetallic sheets for metal - 630-650 °C and higher.

The annealing temperature is specified by the manufacturer for approximately the following reasons:

Annealing is not an independent process, but an integral part of the welding mode
The time for changing the structure of the metal depends on the temperature (higher temperature - less annealing time). To ensure uniform heating of the section, the mode at lower temperatures with a long process time is preferable.

Stepwise annealing is the most reliable: primary heating with holding and temperature equalization over the entire cross section and subsequent rapid heating with controlled cooling.

Setting the heat treatment mode is carried out only after debugging a welding mode that is stable in quality (visually, the welding seams must be correct and the same)

You should not rush to release the clamps of the web after welding, you need to give it time to cool on the electrodes. Haste for some of the canvases can lead to incorrect hardening of the seam zone. After welding, wait 5 seconds, then release the blade.

Do not remove the saw after welding to clean the electrode surfaces, because. the hardened area is very brittle and cracks can form.

After blowing the clamps and electrodes with compressed air, it is necessary to release the web, blow the electrodes a second time and fix the welded saw for annealing.

There is an opinion that the blowing of the electrodes and clamps leads to accelerated wear of the linear guides of the movable sponge. Please note that in good quality devices, the bearings are closed with seals, so the blowing operation does not affect the working life of the guides.

For the normal functioning of the band saw, it is subjected to welding. The method by which this process is performed is selected individually, in accordance with the characteristics of the operation of this material. About the equipment for welding band saws, we will consider further.

Band saw: device and principle of operation

There are a large number of different saws that have individual application features and a peculiar design. Some use a disc as a cutting tool, while others use a tape.

The installation of the saw band is carried out on the pulleys of the leading and driven directions. To pull it, great efforts should be made, only in this case, the cutting line will be uniform.

The main features of this design are separate blocks that are complemented and built up independently. On a simple device, the material for cutting into which is fed manually, additional mechanisms are installed, such as an electronic system for monitoring the device's performance, thanks to which it works without outside human intervention.

Among the main structural elements of a band saw, we note the presence of:

a frame on which there are guides with which the tape moves;
in order to tension the tape, a mechanism is used that has a spring, mechanical and hydraulic drive;
cutting tape holder;
screw-type lifting mechanism, which is installed near the tape;
belt-type transmission, on which the wedges are located;
an electric motor with a power of about fifteen kilowatts or a gasoline-based motor with the same power;
eccentrics with which the log is fixed on the frame;
a water tank and a tap that wets the part during the sawing process;
rail strip on which the structure moves.

Also, each saw features individual structural elements, such as guardrail covers, and thrust mechanisms, which increase safety. In order to regulate and adjust the work on the working surface there are strips on which markings are applied.

The principle of operation of the mechanism is based on laying a log between two guides and its rigid fixation. To determine the thickness of the board, it should be raised using a special mechanism.

Do-it-yourself welding of band saws with your own hands

In order to connect the two ends of the band saw, they must be welded. This process is carried out using special equipment for welding band saws. Resistance welding of a band saw consists in the fact that electricity passes through the two connected ends of the saw, which leads to their overheating and melting of the edges on the blade. For current supply, electrodes connected to the clamps are used.

There are a huge number of welding machines with which contact welding is performed. Some advanced options are capable of automating the welding and annealing cycle. Therefore, errors due to excessive welding or incorrect timing during which the impulse is transmitted are eliminated. In simpler machinery, feed control of annealing and welding is carried out by an operator.

Self-welding a band saw is possible only if you have experience with this kind of equipment. Among the main design features of the machine for welding band saws, we note the presence of:

body part;
welding type transformer;
clamping mechanisms on which there are electrodes and clamping levers;
start button;
clamps: movable and fixed.

The main function of the movable clamp is free play, with the help of which the draft is carried out. In the process of how the ends of the saw move towards each other, a welding bead is formed. In order for the ends of the saw to be pressed against each other, a special spring is used to create pressure.

Do-it-yourself welding of band saws consists of the following steps:

performing saw cutting;
cleaning of its end sections;
installation of the fabric in the design of the welding machine, determining the operating mode: stroke and shrinkage;
welding of cloths;
performing annealing;
seam cleaning.

The first stage - cutting, involves determining the size of the saw. Use a guillotine shear or cut-off wheel to cut off the desired section of the canvas. When using a canvas that has previously been welded, about five centimeters are cut off on each side.

In this situation, when performing cutting, a number of rules should be considered:

the place where the blades are connected to each other should be located between the upper parts of the teeth;
during the cutting process, a little allowance should be left to compensate for the shrinkage of the metal, the optimal allowance is one and a half millimeters on each side;
try to make the cut line as even as possible, the quality of further welding depends on it.

Only in this case, the canvases will have a straight line on the bend.

A fairly simple way to perform cutting is to lay the saw in a certain position, trim and strip each of the ends separately. In this case, even if there is a cut line that is not perpendicular, its end sections will still be joined. In this case, the fabric after welding will be distinguished by an even seam.

Further actions are related to the stripping of the web. These areas should be cleaned of dirt, degreased with acetone or alcohol. Use an abrasive to clean the edges. As a result, you should get perfectly even and smooth areas.

Next is the installation of the canvas on the surface of the device. The prepared saw should be installed inside the clamping mechanism. At the same time, one part of it remains mobile, and the second does not. In the central part, the saw edges are connected to each other. Edge alignment must be perfect.

Using the control knobs on the device, the force, stroke, shrinkage, and mode of operation of the device are regulated. These parameters for each saw are selected individually and depend on its size, steel thickness, operating features, etc. With an increase in the cross section of the saw, the current required for welding increases.

In order to more accurately determine these parameters, use the instructions for the device. It should contain a table according to which the operating mode of the equipment should be determined. In some devices, it is enough to select only the welding mode, without indicating the current strength and voltage for operation. In order to weld the saw, the lever must be set in a certain position.

Band saw welding is done by pressing a button or turning a lever. After that, the current is supplied to each clamp, and from them it is transmitted to the saw. Thus, the metal in the zone of joining of the two sections is melted and connected to each other.

The spring acts on the surface of the movable clamp, which is displaced towards the fixed clamp, on the draft. At the same time, in the butt zone, the formation of a welded bead occurs, with the help of which the saw is connected.

When determining the welding parameters, one should choose the time during which the current pulses are applied. Welding machines with an automatic mode of operation turn off the current after a few seconds from the moment they are applied. However, if this parameter on the welding machine is adjusted manually, then it is necessary to monitor it.

In the process of welding, certain difficulties arise associated with the material from which the saw is made. In accordance with this parameter, the operating mode of the welding machine is determined. In some cases, it is very difficult to determine this parameter without experience. If in the end welding did not satisfy you, then you should experiment, choosing the necessary mode on an unnecessary trim of the canvas. After selecting the optimal operating mode, write down its parameters in order to apply it in the future.

Please note that the electrodes that come into contact with the saw must be clean. Foreign matter or dirt on their surface adversely affects the welding quality of the saw.

Further actions are related to the implementation of annealing, which helps the metal, which has become brittle and rather hard during welding, to acquire strength, toughness and ductility. For annealing, the same clamps are used as in the welding process. However, a different mode of current supply is used for operation.

The optimum temperature at which annealing is performed is about six hundred degrees. At the same time, the cooling of the device should be maintained at a slow pace, for this the current supply button should be held, pressed and released at a certain time. In order for the metal to cool gradually, the annealing current button should be pressed periodically.

If there is no pyrometer on the welding machine, then the temperature is controlled by the external characteristics of the metal surface. During the firing process, the steel acquires a red-cherry hue. In no case do not heat the metal to orange or even more saturated red. The process of gradual cooling of the metal takes no more than five minutes. Some blades will require two cycles of annealing. In some cases, welding and annealing are performed in the same process. In this situation, the time for cooling the seams is increased by periodically supplying current to the metal.

After welding, the blades should be cleaned from the influx formed on the weld. Almost any tool with abrasive characteristics is suitable for cleaning seams. The main condition for high-quality cleaning is to obtain a flat and smooth surface.

We suggest that you familiarize yourself with the main errors that occur during the welding process:

1. Offset of welded edges - in this case, the sheets are in different planes. This problem occurs when there is insufficient current strength during the welding process or when there is a very large draft.

2. The melt on the web is observed in the process of supplying a very high current.

3. Wet spots are formed if the pressure supplied to the system is too low.

The minimum value of the protrusion of the seam on a well-welded plate is about one and a half millimeters.

To check the quality of annealing, the fabric is bent within a radius of twenty centimeters and inspected. If the arc resembles a standard circle and the seam remains intact, then the welding quality is at the proper level.

Welding band saws price and soldering features

The cost of welding band saws is determined primarily by their size, steel thickness and operating features. However, there is another way to connect the saw - this is soldering. This option is easier to do at home than welding.

First of all, the blade should be prepared; for this, the saw edges are cleaned of dirt and degreased. The ends of the web are connected in a butt position, however, the edges must be beveled.

In order to give the edges a bevel shape, use an abrasive wheel. The optimal bevel size is from eight to twelve centimeters. Beveled sections should be connected to each other as evenly as possible.

In order to solder the saw, you will need solders, the best option is silver pSR45 or pSR65. Solders with a lower silver content are not recommended.

As a flux, it is preferable to use a paste that is used in the process of soldering metal. This version of the flux is easy to use. In the absence of this substance, it is possible to make it yourself. For this, ammonium chloride is combined with borax in a ratio of one to ten. With the help of water, the consistency of the composition is regulated, which should become pasty.

A gas burner is used to heat the saw during the soldering process. The heating temperature is determined by the type of solder, the optimal value is from 650 to 600 degrees. Do not overheat the metal, so as not to disturb its structure. With the help of a special device, the ends of the saw are connected to each other. The soldering process is as follows. First of all, flux should be applied to the surface of the edges. Try to apply the paste only on beveled areas.

Further, the joints are heated to a certain temperature and the solder is fed to the junction of the ends of the saw. After that, a strip appears on the surface, indicating that the soldering is done correctly. Solder melting is performed not under the influence of a burner, but from a previously heated metal. After a few minutes, the metal cools down, only after that, the saw is removed from the mechanism. In the presence of small influxes, the seam is cleaned with any abrasive material.

Band saw welding video:

Band saws are used in many areas of production related to sawing wood. In fact, this is a flat cutting blade, on one edge of which there is a cutting edge with teeth. According to its technical purpose, this fabric is welded into a ring. The place of welding is the two extreme ends of the tool. A band saw welding machine is used to connect the butt edges. This is a special equipment, it is highly specialized, it is used only for welding band saws.

The method of welding band saws on the machine is not very complicated. But you need to know some of the nuances of the process. First of all, the saw must be prepared.

The saw ends to be welded must be cut so that the butt planes are parallel to each other and perpendicular to the cutting edge. Cutting can be done on a guillotine or with a chisel and hammer.
If the wood saw broke at the place of preliminary welding, then the joint must be removed, stepping back from its edge by 5 mm on each side.
The blade must be cut between the teeth.
The ends are treated with a solvent to remove contamination.
They are ground on a grinder to create a rough surface and remove burrs and uneven cuts.
After preparation, the saw is inserted into the machine, where it is welded.

Apparatus for welding

There are several types of band saw welding machines, which mainly differ from each other in performance. The simplest apparatus is a small machine, which includes a transformer, electrodes, clamps (one is fixed, the other is movable - it is supported by a spring at the back). The electrodes are connected to the clamps, so the current from the transformer is supplied directly to the place where the parts of the band saw are joined.

The mobility of one of the clamps creates the conditions for adjusting the gap between the ends of the web. It is very important that the end result of welding is a neat weld bead that is strong and reliable. After all, a band saw experiences multiple cyclic bending and tensile loads.

So, the band saw is installed in the welding machine. One of its ends is clamped into a fixed clamp, the second into a movable one. It is very important that the cut ends are tightly connected to each other. After that, with the help of special handles, the clamping force is set, that is, the movable clamp is shifted towards the stationary one. Be sure to set the value of the welding current. These two parameters - the upsetting force and the magnitude of the current, directly depend on the dimensions of the section of the web. The larger it is, the greater the current must be, the greater the clamping force must be applied.

It should be noted that manufacturers of welding machines made sure that consumers do not look for current and pressure parameters. In the instructions for each device, a table of the dependence of the section of the band saw on the parameters of current and precipitation is attached. So there should be no problems with the choice of welding modes.

Band saw welding process

If the band saw is installed, the welding mode is selected, it remains only to press the start button for the welding process. In this case, the current from the electrodes is supplied to the clamps, and through them, in turn, to the ends of the welded parts of the band saw. They begin to melt, that is, they become soft. In this case, a movable clamp supported by a spring pushes one of the edges of the web to the other. This forms a weld bead.

It should be noted that in addition to the correctly selected welding mode, there is one more parameter that affects the quality of the final result. It's welding time. In simple devices, it is controlled by a worker who welds band saws. If welding is carried out on automatic models, then the welding time takes 1-2 seconds.

By the way, the cleanliness of the electrodes also affects the quality of band saw welding. Therefore, the machine must be kept clean. Even the smallest contamination of the ends of the electrodes is the resistance to the passage of current through them, which reduces the rate of the latter. This means that the magnitude of the current at the ends of the welded sections of the saws also decreases.

It should be noted that welding band saws with your own hands is not the easiest process. The difficulty lies in the fact that you have to join canvases with different sections and with different materials from which they are made. That is, for each criterion, you need to correctly select the welding mode. Which is very difficult, and sometimes it is simply impossible to do. Therefore, often the first welding of an unknown saw leads to an unsatisfactory result. After that, the operator begins to select the welding mode using the “poke” method. It sets different modes in turn and looks at how well the welding happened, how much the joint meets the strength requirement. Experienced operators thus create a table for themselves so that they do not repeat their mistakes in the future.

Band saw annealing

During the welding process, the joint of the band saw becomes strong, but brittle. One blow with a hammer destroys the connection immediately. The thing is that under the influence of high current, the metal changes its structure. To return it to a state of plasticity and viscosity, it is necessary to carry out an annealing operation. This process is carried out all on the same welding machine, without removing the blade from the clamps. The current mode simply changes and the upsetting force is removed.

A large current is applied to the electrodes, and the joint itself is heated to a temperature of +600C. Many machines are equipped with a pyrometer that monitors the temperature in the welding zone. According to it, it will be necessary to control the annealing mode. After heating, the current is turned off, and the saw slowly cools down. If the ambient temperature is below zero, then during the cooling process it is necessary to periodically turn on the current supply so that the cooling proceeds more slowly. Typically, the temperature decrease takes place within 3-5 minutes.

Some canvases require double annealing, it all depends on the brand of metal. Some experienced operators combine welding and annealing. That is, the web is heated to the temperature at which welding is performed, then the tool is slowly cooled. Here it is important to increase the cooling time, for which the current supply to the electrodes is periodically turned on.

Cleanup

The main requirement for cleaning is the removal of the influx of metal and giving the correct geometry to the cavity between two adjacent teeth in the place where the blade is welded. Cleaning can be done with any abrasive tool. It is important that the canvas does not lose its evenness in the plane, and the metal of the joint is flush with adjacent sections. Therefore, it is recommended that stripping be carried out not across the junction of the saw blade, but along.

What to look out for

When welding band saws, various defects can occur.

The edges of the ends to be welded may be joined unevenly. This happens if the clamp pressure was very strong, which affected the displacement.
A large amount of metal on the surface of the weld. So, there was too much current.
Lack of penetration of the web is a low current and a small clamping force.

By the way, the quality of welding can be checked manually, you just need to fold the saw into a ring so that the joint is located at the very top. If the arc has the correct shape, and the joint has not cracked, then the welding process has been carried out correctly. If cracks appeared in the welding zone, it means that the cooling of the sheet took place quickly during the annealing process. If a curved shape in the form of the letter “V” appeared at the place of welding, then this means that the joint turned out to be too soft. This was affected by slow annealing.

In addition, we suggest you watch a video on how to properly weld a band saw.

About the equipment for welding band saws, we will consider further.

Band saw: device and principle of operation
Do-it-yourself welding of band saws with your own hands
Welding band saws price and soldering features

Band saw: device and principle of operation

There are a large number of different saws that have individual application features and a peculiar design. Some use a disc as a cutting tool, while others use a tape.

The installation of the saw band is carried out on the pulleys of the leading and driven directions. To pull it, great efforts should be made, only in this case, the cutting line will be uniform.

Among the main structural elements of a band saw, we note the presence of:

a frame on which there are guides with which the tape moves;
in order to tension the tape, a mechanism is used that has a spring, mechanical and hydraulic drive;
cutting tape holder;
screw-type lifting mechanism, which is installed near the tape;
belt-type transmission, on which the wedges are located;
an electric motor with a power of about fifteen kilowatts or a gasoline-based motor with the same power;
eccentrics with which the log is fixed on the frame;
a water tank and a tap that wets the part during the sawing process;
rail strip on which the structure moves.

The principle of operation of the mechanism is based on laying a log between two guides and its rigid fixation. To determine the thickness of the board, it should be raised using a special mechanism.

Do-it-yourself welding of band saws with your own hands

Self-welding a band saw is possible only if you have experience with this kind of equipment. Among the main design features of the machine for welding band saws, we note the presence of:

body part;
welding type transformer;
clamping mechanisms on which there are electrodes and clamping levers;
start button;
clamps: movable and fixed.

Do-it-yourself welding of band saws consists of the following steps:

performing saw cutting;
cleaning of its end sections;
installation of the fabric in the design of the welding machine, determining the operating mode: stroke and shrinkage;
welding of cloths;
performing annealing;
seam cleaning.

The first stage is cutting, which involves determining the size of the saw. Use a guillotine shear or cut-off wheel to cut off the desired section of the canvas. When using a canvas that has previously been welded, about five centimeters are cut off on each side.

In this situation, when performing cutting, a number of rules should be considered:

the place where the blades are connected to each other should be located between the upper parts of the teeth;
in the process of cutting, a little allowance should be left to compensate for the shrinkage of the metal, the optimal allowance is one and a half millimeters on each side;
try to make the cut line as even as possible, the quality of further welding depends on it.

Only in this case, the canvases will have a straight line on the bend.

Please note that the electrodes that come into contact with the saw must be clean. Foreign matter or dirt on their surface adversely affects the welding quality of the saw.

We suggest that you familiarize yourself with the main errors that occur during the welding process:

1. Offset of welded edges - in this case, the blades are in different planes. This problem occurs when there is insufficient current strength during the welding process or when there is a very large draft.

2. The melt on the web is observed in the process of supplying a very high current.

3. Wet spots are formed if the pressure supplied to the system is too low.

The minimum value of the protrusion of the seam on a well-welded plate is about one and a half millimeters.

Welding band saws price and soldering features

First of all, the blade should be prepared; for this, the saw edges are cleaned of dirt and degreased. The ends of the web are connected in a butt position, however, the edges must be beveled.

In order to give the edges a bevel shape, use an abrasive wheel. The optimal bevel size is from eight to twelve centimeters. Beveled sections should be connected to each other as evenly as possible.

In order to solder the saw, you will need solders, the best option is silver pSR45 or pSR65. Solders with a lower silver content are not recommended.

Band saw welding video:

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Band saws are widely used throughout the woodworking industry, carpentry, furniture industry, etc. They are used in various sawmills, band saws and band saws.

A feature of band saws is a continuous cutting surface, which is a ring of metal band with teeth. For the manufacture of band saws, a pre-prepared tape is welded into a ring. Welding is also used to repair broken saws. About the technology of welding band saws and will be discussed in the article.

Band saw welding technology

It is divided into several stages - preparation, sharpening, welding and setting the teeth of the resulting saw. Due diligence must be observed at all stages. Let's consider the technology in more detail.

Repair of band saws has its own characteristics

Machines for welding band saws

As a rule, the apparatus for welding band saws works like this: the ends of the saw are clamped in clamps, joined, and then a current is passed through them, which melts and welds the edges of the ends. The current is supplied through the electrodes, which are connected to the clamps.

Resistance welding machines

These devices are cheap, compact, not very high performance and are intended for small amounts of work - for example, for repairing saws in industrial sawmills.

Features of the technology require high quality of seam preparation, high quality of electrodes, good adjustment of clamps and correct setting of the mode.

Flash welding machines

Productivity is much higher, such devices can be classified as middle class. They work on the principle of continuous fusion and are intended for welding all types of fabrics, including bimetallic ones.

Features of the technology - high requirements for the surface of cloths and electrodes, the need to maintain the correct tooth pitch, taking into account metal losses. A properly selected mode is characterized by a good, even process of flashing throughout the welding.

Automated flash welding machines

The welding process is automated, the operator only needs to install the saws in the machine and remove the welded blades. Such devices have good performance and are used, as a rule, in service centers.

In addition to welding machines, when welding band saws, some auxiliary devices are required - blade guillotines, stripping machines, pyrometers, and so on.

Band saw welding process

Consider welding technology. As mentioned above, it is divided into several stages, which will be considered in order.

Web preparation

Before welding the canvas, it must be prepared. The preparation of the saw consists of several steps.

Web cutting

The fabric is cut with special guillotine shears. If there are none, you can cut the canvas with a chisel or cutting machine. If welding is supposed to be carried out in the area that was welded before, then 5 millimeters must be cut off from the last seam on each side.

The blade is cut between the tops of the teeth. On each side leave an allowance of about one and a half millimeters. The cutting line must be strictly perpendicular to the back of the saw.

Band saw, very flexible but fragile tool

Trimming the ends

The prepared canvas must be cleaned. To do this, they are cleaned of contaminants, if necessary, cleaned with acetone or alcohol. The edges are treated with abrasive material, removing burrs and irregularities - this is convenient to do on a grinding machine.

After that comes the welding of the canvas. The prepared sheet is fixed in the machine and welded.

Installing the saw in the machine

The prepared blade is mounted in the clamping mechanism of the apparatus for welding band saws so that the edges of the blade completely coincide and are in the middle of the space between the clamps. The force, the upset mode and the course of the upset are selected depending on the blade - the documentation for the devices contains tables with information on the modes for various blades. The selected mode is set by turning the control knobs.

Fabric welding

The machine is started by turning the knife switch or pressing the button. In this case, the current begins to flow to the electrodes and melts the metal at the junction. The movable clamp goes to the fixed one and forms a welded bead in place of the seam.

An important parameter is the time of current supply. As a rule, with automatic welding it is one or two seconds, with manual welding it is controlled by the operator.

If the welding was unsatisfactory, suitable settings are selected and recorded; in the future, they are used for welding similar canvases.

The electrodes must be clean. Poor contact between the electrodes and the sheet increases the resistance and disrupts the welding process.

To connect the saws, a special installation is required

Saw processing after welding

Immediately after welding, the saw is not suitable for use. In order to bring it into proper condition, several operations are carried out.

Seam annealing

When welding, the web material hardens and becomes brittle. Annealing allows it to regain ductility and toughness. The saw is not removed from the machine, the draft is set to zero, another current mode is selected. By pressing the button for applying current to the annealing, the seam is heated, and then slowly cooled. If there is no pyrometer, the temperature is controlled visually. The optimum color for the heat of the metal is cherry red. Orange or yellow indicates overheating.

Cooling lasts three to five minutes. Some canvases require two cycles.

Stripping the canvas

When stripping the blade from the welded area, the influx of metal is removed, and the correct shape of the cavity between the teeth of the blade is also removed. Any abrasive is suitable for stripping, best of all - a grinding machine.

Technological features

It is worth considering that:

The alloys from which saw blades are made are difficult to weld;
When working on the welding seam, limit loads fall;
The geometry of the teeth in the weld area affects the loads during operation.

Conclusion

From what you read above, you learned how band saw welding is carried out, what equipment exists for welding band saws, and what features this process has. We hope that the information provided will be useful to you.

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