The frame is the basis of all silk screen printing, a lot depends on it when creating a stencil and performing high-quality printing. With a frame, mesh and squeegee available, you can already start printing. The rest of the screen printing equipment can be considered an addition, purchased as needed and taking into account financial possibilities.

wooden frames

Wooden frames are inexpensive and easy to manufacture, but have a number of disadvantages in operation. The tree easily swells in water and within a few hours can change its linear dimensions, as the frame is affected by changes in relative humidity and air temperature.

Frames are made from hard, well-dried straight-grained wood to avoid warping of finished frames. It is better not to use boards with knots and a pronounced oblique layer at all, since the frame can be deformed at the most inopportune moment, and making a re-stencil will require additional time. On small frames, defects of this kind are hardly noticeable, but with an increase in size, warpage can complicate all technological processes.

The frame bars are fastened at the corners into a spike with epoxy glue and additionally reinforced from above with metal corners. To protect against moisture, the finished frame is coated with waterproof varnish or paint. An excellent protection for these purposes is epoxy or polyurethane adhesive (paint).

The minimum section of the bar is 30 x 60 mm. The size is determined by the type of wood: the softer the wood, the thicker the bar is taken. On the underside of the frame, where the mesh will be attached, a slope is made around the entire perimeter, approximately 3-50.

metal frames

The most reliable and stable frames are made from aluminum and steel tubes, which have a square or rectangular section. To increase strength in the manufacture of large templates, a profile with thickened vertical walls is taken.

In practice, blanks are used not only with parallel, but also with beveled walls. triangular profile

used in textile printing. The bars are connected by welding, leaving no holes so that aggressive screen cleaning fluids cannot get inside the profile, cause corrosion from the inside and destroy the frame.

Finished frames must have right angles and be completely flat. They must be processed with an abrasive grinding tool, destroying all burrs and sharp corners.

Steel frames are galvanized chrome plated to prevent rust. Aluminum ones are not afraid of water, but actively react with alkali solutions, which degrease and regenerate meshes.

Table of parameters that are desirable to use in the manufacture of frames

DIN format		Protective	Interior	Aluminum	Aluminum profile with	steel profile,
			frame size,	profile and thickness	variable cross section
				wall width, cm	walls, mm

SIEVE TENSION Basic Requirements

The mesh is pulled onto the frame with a maximum force close to the yield value of the given material. If the fabric is not stretched enough, then the linear dimensions of the image may be distorted in printing and the contours of individual colors may not match when multi-color printing. This is especially important when making stencils for color raster printing, where changes in the size of the raster dot are unacceptable. Any deviations cause a change in the color gamut of the image.

Manual tension of the sieve

On wooden frames for simple work, the mesh can be stretched manually. The fabric is grasped with special tongs with wide jaws so as not to damage the fabric. To do this, the sponges are additionally glued with rubber. The canvas is fixed with staples, hammering them with a mechanical or electric stapler (stapler).

Usually in practice, manual and mechanical, and in mass production, pneumatic stretching devices are used to uniformly tension the sieve.

Stretching the mesh manually with a stapler

1. Fixing the braid with staples at the corners of the frame.

2. Stretching the mesh and fixing around the perimeter with staples.

3. Trimming excess fabric with a knife.

4. Checking the evenness of the mesh tension (shaking off dust and other debris).

If templates of the same format are used in a printing workshop, then the simplest device will be a wooden fixed frame, along the perimeter of which they are crammed in a checkerboard pattern.

a row of needles or small carnations without hats. The thickness of the fixture rails should be 5

mm less than working stencil frames. The device should be easy to put on the frame. On wooden frames, the fabric is attached with staples or two-component glue.

For small metal frames, it is convenient to use a large-format tensioner, in which several frames can be placed at once and the mesh can be fixed to them in one step. The fabric is pulled by hand on the needles with maximum effort. The frames are placed so as to optimally use the entire area of ​​​​the canvas.

To save expensive mesh fabric, a fairly simple method is used. The width and length of the stretched mesh is taken 4 cm less than the distance between opposite rows of needles. Then, along the perimeter, any thin, durable fabric 8-10 cm wide is sewn with an elastic zigzag seam. It is convenient to hold the sewn tape with your hands and prick it on needles for stretching. After fixing the mesh on the frame, the fabric is cut off and sewn to the next mesh.

Sliding fixture

With a large assortment of stencil frame formats, you can independently make a simple sliding device in the form of four bars with holes for pins or bolts.

comrade On each bar, needles are hammered along the entire length with an interval of 10-15 mm in two rows. The needles are placed in a checkerboard pattern, which allows you to more firmly hold the mesh in a stretched position. Instead of needles, thin carnations can be hammered in, and their caps can be removed with wire cutters. In order for the nails to be pointed, you need to bite them off at an acute angle.

To use such a device, only a flat table surface is required. Rearranging the mounting bolts allows you to create any necessary in the work, rectangular or square outlines of the frame. After finishing work, the device can be easily disassembled into bars and in a compact form takes up little space during storage.

If disposable mesh fabrics with a pre-applied photo layer are used for work, then for each new stencil, the process of stretching the mesh is repeated. Some photopolymer copy layers, fixed only with ultraviolet radiation, are also not subject to regeneration and are removed along with the grid.

Mechanical fixtures

Companies producing prepress equipment offer several standard sizes of such machines.

The mechanical tensioning devices are quite easy to handle and do not consume energy. The mesh along the edges is captured by needles arranged in several rows, as in a conventional hand-held device. With a strong tension in the fabric, the needles can cause the mesh to break.

More expensive models are equipped with special clips instead of needles, the planes of which have an anti-slip coating. The rough surface does not allow the fabric to stretch and keeps it in constant tension for a long time until the glue

will harden. Clamps are located around the perimeter close to each other. Each clamp captures 10-20 cm of tissue.

The fabric is fixed so that the threads are parallel to the edges of the tensioner. By rotating the handles of the screw transmission, the fabric is stretched first in the longitudinal and then in the transverse direction.

leniyah. An improperly positioned mesh will warp when stretched, which can change its print throughput.

The maximum frame size that can be placed in a mechanical tensioning device depends on the model and can be from 70x70 to 210x210 cm. Each model of the device allows you to transform to a smaller side and create the configuration required by the user. This is important in cases where frames of non-standard formats are used, as well as to save the mesh fabric.

Electromechanical devices

For triad printing, when it is necessary to have several large frames with the same mesh tension, a machine with an electromechanical drive is used. All the necessary frames are placed in the machine at once. The edges of the canvas are clamped with clamps. Such devices have a width of 180 cm and a length of 3 to 6 meters.

Pneumatic accessories

In mass production of stencils, the most convenient are pneumatic ones, consisting of a set of standard clamps independent of each other. Each clamp is equipped with a separate

pneumatic cylinder, which is connected to the compressor for the time of stretching the sieve. As the pressure in the cylinder increases, the clamping force of the web holders automatically increases. This allows you to firmly hold polyester, nylon and metallized fabric, as well as metal meshes, in a tense state. The width of the clamps is determined by the standard size and is 15 and 25 cm.

A stencil frame is placed on a flat table and, by combining the clamps, a device is required in size for this frame. To place the clips around the frame, the table must be 70 cm longer and wider than the largest frame.

An air line is fixed along the perimeter of the table, equipped with valves for connection and a pressure gauge for pressure control. Cylinders can be connected to each other in series, and connected to the line at one or two opposite points. The edges of the mesh fabric are fixed in the clamps and the pump is turned on. The same pressure in all pneumatic cylinders gives the mesh equal tension in the longitudinal and transverse directions. The table can be additionally equipped with a device for extracting solvent vapors, which is part of the adhesive.

By adjusting the pressure in the line on the pressure gauge, you can change the tension of the sieve. Stretched tissue tends to weaken over time. This is especially noticeable when using mesh fabrics made of twisted thread, commercially produced in the textile industry. Monofilament nets change their performance less, but thinner threads, and therefore higher fabric numbers, stretch 2 - 3% more than thick ones.

Constant air pressure in the line maintains the tension force of a given value and compensates for all changes that occur in the threads. It is recommended to glue the stretched mesh not immediately, but to wait for some time to stabilize, which depends on the material and category of the mesh fabric.

The internal tension of the tissue after a few hours decreases by 10-20% and then changes slightly. This important factor must be taken into account when determining the magnitude of the load during stretching of the fabric. The use of a tension gauge simplifies the control of this operation. A 10 - 20% increase in traction load compensates for future changes, and it is not necessary to wait several hours for the internal stresses in the tissue to stabilize. Metallized fabrics and fabrics containing carbon fibers are not very elastic, they stretch by 1–2%, and metal meshes are even more rigid, their coefficient of stretching is low and does not exceed 0.5%.

For work, they select a silent compressor with a receiver volume of at least 50 liters and a capacity of up to 6 atmospheres, or they purchase tables specially made for such purposes, equipped with the necessary devices.

SCREEN TENSION CONTROL

When talking about sieve tension, one cannot use the words “a little more” or “a little less”. Usually, all further problems in the technological cycle of stencil manufacturing begin with this, and as a result, most often, additional rejects are obtained during printing. Misalignment of colors and change in the linear dimensions of the pattern are the most characteristic signs that the meshes are stretched with different tensions.

Craftsmen who have been working in silk screen printing for a long time stretch the nets based on their experience, and this is enough for a certain level of quality. Smaller print shops use a limited number of mesh webs, and for non-separation jobs, manual and rough tension control is fine.

Firms with a wide range of orders are faced with the fact that the range of applied numbers and categories of nets is increasing. In such conditions, it is no longer possible to rely only on the intuition of the master. After all, the maximum force that must be applied to the mesh fabric during tension depends on the frequency of the threads and their thickness. That is, with the same mesh number for a light category, less effort is required than for a heavy category fabric made from thicker threads.

Machine screen printing is particularly demanding on the same tension of the nets on the frames.

The tension of the mesh can be controlled with a special measuring device showing the value in Newton/cm (N/cm).

Tensiometer

A device that measures strain distributions is called a strain gauge. Manufacturers of mesh fabric and screen printing equipment

cabins several modifications of strain gauges. For example, SST Tpa1 offers a mechanical instrument with a pointer indicator, and SVECIA offers an electronic measuring instrument with a digital liquid crystal display, which is powered by a built-in battery. Measuring range

from 0 to 60 N/cm

The strain gauge has two fixed supports, and between them is a retractable rod, which, depending on the tension of the mesh, bends its surface and transmits the obtained value to the dial through a system of levers. The device mounted on the glass should show the maximum value of the scale. A special calibration screw allows you to adjust deviations in the readings of the device.

The strain gauge is installed during the measurement on the grid, preferably in the middle, at the same distance

standing from the edges of the frame, and stretch the fabric to the values ​​that are recommended for a given mesh and type of print. To avoid distortion in the readings of the device, the frame is located in a horizontal position, and measurements are taken no closer than 10 cm to the edge of the frame.

Up to 6 - for printing on textiles and for manual printing; 10-12 - one-color or multi-color printing that does not require precise alignment of the contour

8-20 - for general graphic works; 15-25 - for high-precision printed publications (for example: printed circuits for radio

electronics, scales of measuring instruments, etc.), multicolor halftone printed matter

Since the stencil must retain some elasticity during the entire printing process, there is no need to stretch the fabric to the frame as much as possible. In practice, it has been proven that in graphic multi-color screen printing, registration accuracy can be achieved when the grids, for example, have a tension of 10 N/cm. Long-term printing and repeated regeneration of the sieve also lead to a decrease in tension.

It is important that all grids for one job show relatively the same values. The deviation may vary within 2 N/cm for each frame. The maximum mesh tension is required only for machine printing, where the squeegee pressure on the stencil is constant, equal to

dimensional, and there is no danger of accidentally pinching the limit of elasticity of the threads. Exceeding this limit leads to stretching of the mesh without restoring the original length.

Grid numbers, none						Permissible deviations
		tension, N/cm
(mono polyamide, capron, nylon)
(mono polyster - lavsan)
(mono polyster modified)
(mono polyster - metallized)
(monopolister - antistatic with carbon

In the manufacture of nets from No. 90 to No. 120 of the normal category, the Italian company Saati uses a thread of the same thickness (40 microns). Since fabric No. 120 contains one and a half times more threads, the strength increases accordingly. Therefore, the recommended tension for No. 90 will be 25-28 N/cm, and for No. 120 already 28-32 N/cm.

Since mesh fabric manufacturers conduct tests for their products, they offer their own tension indicators for each number and category, which may differ from those of other companies. Therefore, when purchasing nets, do not forget to obtain the necessary information.

For example, here is such a summary table of the tension values ​​​​of their screen meshes

lags the Swiss company Swiss Silk Boltina Cloth Mfg.Co.Ltd.Zurich.

Causes of Tension Loss

With insufficient rigidity of the frame, especially large sizes, the sides sag

To middle and the tension in the middle of the stencil drops. This applies to both wooden and metal frames.

The fabric is not properly secured in the clamps of the tensioner. The frame must be fixed in the tensioner at the same level relative to the clamps so that the fabric fits evenly around the entire perimeter during gluing.

If in the room where the sieve is stretched, there are high fluctuations in air temperature.

The holding time between the end of the sieve tension and the beginning of gluing is not observed.

FASTENING THE NET TO THE FRAME Mechanical fastening With staples

A simple and quick way to fasten a stretched mesh to a wooden frame is with a mechanical or electric stapler. There are two options.

In the first option, the mesh is held manually with the help of special tongs, stretched and the staples are immediately hammered. The fabric is cut out in such a way that the jaws of the forceps firmly grasp the edges. If it is necessary to save the mesh, strips of ordinary durable fabric, 5-10 cm wide, are additionally sewn along the edges, which are held with tongs, which also reduces the risk of breaks and distortions along the perimeter of the mesh.

The first four staples are hammered into the middle of the bars of the frame crosswise, pulling the canvas with maximum effort. The next attachment points are located at the corners, taking into account the tension of the fabric diagonally. It is necessary to ensure that the warp threads are without distortions and mutually perpendicular. Further fastening is carried out symmetrically from the middle of the bars to the corners of the frame.

In second option, which gives undoubtedly the best results, the fabric is pre-tensioned in any stretching device, and then slowly fixed. The interval between the staples to be driven in depends on the tension of the web and the complexity of the future pattern. Staples are hammered parallel to the edge of the frame, and with a strong tension of the mesh or frequent placement of staples - at an angle.

In the absence of a stapler, the mesh is fixed with small nails and wooden slats with a section of 5x10 mm.

Since the slats should not protrude above the plane of the stencil, the frame is pre-made with additional grooves around the entire perimeter. Groove depth 5.5 mm and width 11 mm.

The wood for the slats is selected soft so that it does not chip off with a frequent arrangement of nails. The planes of the frame bars are planed with a slight slope of 2 - 3 mm to the outer edge in order to compensate for the deformation of the tree inward under heavy loads. In addition, the mesh, tightly adhering to the inner perimeter of the frame, does not peel off when the squeegee presses on the stencil during printing and does not allow ink to leak there.

Before hammering the slats, the mesh is fixed with a slight effort in a stretching device. The load is not made maximum, since the rail, when driven into the grooves, additionally increases the tension. Nails are pre-hammered into slats, which are placed over the grooves. Gradually, hammering nails with hammer blows, immerse the slats into the grooves. The method allows you to evenly and with a sufficiently strong tension to fix the canvas on the frame. The mesh is held not only by nails, but also by the friction force when the fabric is bent in the grooves.

Self-tensioning frames

It is possible to fix and stretch the mesh onto the frame to the required size without a tensioning device using the frame itself. Such frames are equipped with additional devices that stretch the mesh after it is fixed. The mesh is mounted without the help of glue in special grooves, where flexible aluminum or double nylon rods tightly hold the web from displacement. During tension, the rods are displaced, rest against the walls of the groove, and due to this, the jamming factor increases proportionally.

Rotating frames are a product of corners and four massive pipes, which can only be rotated in one direction with a wrench. Each side of the frame rotates independently. All parts are made of aluminum and stainless steel. Depending on the model, pipes with a diameter of 2.5 to 5 cm are used, which makes it possible to manufacture frames ranging in size from 17 to 155 cm.

having additional stiffening ribs from metal corners, which do not allow the sides of the frame to sag.

The operation of stretching the mesh is quite simple. The frame is superimposed on the fabric, its edges are wrapped around the pipes and fixed in the grooves with rods. A tension meter is placed in the center of the grid and, alternately rotating the pipes inward with a key, they achieve the required indicators.

Frames with sliding tension bars have a simpler design. The sides of the frame have an aluminum alloy brace profile. Inside the profile there are metal strips that move when the bolts rotate. Washers and bolts are made of stainless steel and placed 3-4 pieces on each side. The slats have a corresponding shaped groove for fastening the fabric with aluminum strips with a section of 6x1.5 mm or nylon double rods. To simplify and facilitate the installation of the rods, a special tool is used in the form of a wide chisel made of aluminum with a thickness of 3-5 mm. The groove silhouette may vary, but the mesh clamping principle remains the same (Fig. 1, 2).

Frames of a small format are welded from a simple profile (Fig. A), over 150 cm - from profiles reinforced with an additional internal jumper (Fig. B).

In another version, the frames are assembled from metal corners and movable bars, also moved by bolts, but with recessed heads. The slot in the bar is machined in accordance with the selected method of clamping the fabric.

Adhesive mount

The mesh is fixed with glue to both metal and wooden frames. Before applying glue to the frame, the surface must be degreased. New frames, especially metal frames, are deburred, and all sharp corners are rounded off with an abrasive bar or circle. Recycled frames are thoroughly cleaned of ink residue and old glue. If the same type of adhesive is used repeatedly, it is not necessary to scrape off the old adhesive film, provided that it adheres evenly and firmly to the frame.

For degreasing, various aqueous washing agents and organic solvents are used: acetone, refined gasoline or alcohol. The operation is carried out immediately before gluing. Caustic soda is used for degreasing with caution, as it chemically reacts with aluminum.

In addition to degreasing, the surfaces are roughened for better adhesion to the adhesive. Frames are treated with abrasive materials or sandblasting.

Different types of glue

The adhesive, which hardens in about 30 seconds, holds the fabric firmly so that the frame does not need to be further tensioned and after a few minutes of drying can be released from the tensioner.

Glue is applied to the frame and to the stretched fabric. When the adhesive dries, the bonding surfaces are pressed together and the mesh is then further smoothed with a plastic spatula for better contact.

Although a hardener is added, this adhesive is not effective enough when in contact with some solvents. Therefore, the bonding surface must be additionally protected with a varnish coating.

Spare

These adhesives can be applied to frames beforehand and then simply reconstituted during bonding with acetone or any other suitable medium. This adhesive must also be protected by a varnish coating.

Two component solvent resistant

Two-component epoxy adhesive is prepared immediately before use by mixing the resin and hardener in the proportions specified by the manufacturer (usually 1 part hardener to 10 parts resin). Such an adhesive gives a strong, hard film that is insoluble in water, petroleum solvents and alkalis, which are most often used in technological processes. If the glue turned out to be viscous for applying it with a brush, then it is diluted with acetone to the required consistency.

For optimal contact of the grid and the planes of the frames during the curing of the adhesive, additional metal bars with a cross section of 30 x 30 mm or strips are used as weights, which are placed in the middle of each

frames and between frames. The mesh is slightly bent and tightly pressed against the glued plane of each frame.

Marking

A screen printer working on a range of different fabrics must mark the frames to avoid confusion.

Thin Line Problems

The specificity of screen printing does not allow printing lines thinner than 0.15 - 0.2 mm. Part of the printed area is occupied by intertwined threads, which prevent a decrease in resolution. In principle, the line thickness can correspond to the distance between

threads, provided that when copying the stencil, this line will fall into the free spaces between the threads. If the projection of the image falls on the thread, then the line will be absent. Based on this, we conclude that the width of the printed element cannot be less than twice the width of the cells of a given mesh number and plus the diameter of the thread used to make the fabric.

While printing various tables, you may encounter another problem. Some vertical or horizontal lines do not come out the same thickness all the way. Often a narrowing in one direction is noticeable. The thinner the lines, the more often this factor is noticeable. Explanation

simple enough.

Usually the fabric is stretched over a shaped frame so that the warp threads are parallel to the sides of the frame. When photocopying, future vertical and horizontal image lines are formed by intersecting warp threads. Thread running

parallel to the line, partially covers the printed gaps. In practice, it is impossible to stretch the sieve with absolute geometric accuracy and match the copied pattern. Therefore, it is better to make sure that the threads of the fabric do not coincide with the main lines of the image. To do this, the mesh fabric is deliberately fixed on the frame at a certain angle.

When the grid is rotated up to 15°, proceed as follows. Cut out a pattern of the required size from paper and lay it on the fabric. Turn to the specified angle and cut the workpiece. The resulting piece of mesh is inserted into the clamps of the tensioner and then proceed as usual.

Everything is simplified when using a special auxiliary frame, into which the working frame is inserted and rotated at any angle. The fabric itself is stretched in the normal mode, without distortion.

It is more difficult to control the web tension in such a device, since the clamps do not abut directly against the frame ribs. If the bars are not stiff enough, then after the stress is removed from the clamps, a highly stretched fabric can deform the frame, which will reduce the tension of the mesh.

PROCESSING THE MESH BEFORE APPLYING THE PHOTO SOLUTION

When the mesh is stretched, we can assume that the first stage of stencil manufacturing is completed - the carrier base is prepared. The next step is to create areas on the mesh that do not let ink through during printing. Whatever the way to create such areas, first of all, we must remember that various physical loads will be applied to the stencil. The insulating sections must be firmly held on the deformable mesh and retain their qualities.

until the end of printing.

First of all, you need to pay attention to how firmly the reserve composition adheres to the threads.

If the sieve is woven from natural or artificial silk, then the threads twisted from the finest fibers are quite rough and allow you to firmly hold the substance from which the printed elements will be formed.

Looking at the monofilament mesh fabric, at high magnification we can see that the threads are like glass rods with a very smooth surface. The photolayer is poorly retained on such threads, and small printed elements (dots, strokes) easily crumble under the pressure of the squeegee and from deformation of the stencil. To overcome this problem, it is necessary to make the threads rough. There are several ways:

mechanical method

Pumice stone is crushed into powder and sifted through a No. 20 or No. 30 sieve. Pumice powder is used to wipe the entire surface of the mesh from the inside and outside in circular motions. De-

bark it with the help of a soft felt or cloth swab. The monofilaments of the fabric become rough, with the smallest burrs, which increase the adhesion area of ​​the solutions. The remains of the powder are washed out of the fabric with a strong jet of water, while wiping with a stiff brush to remove pumice particles accidentally stuck in the cells.

Instead of pumice, water-resistant sanding papers or cloths with grit size from No. M40 to No. M5 can be used. Handle mesh both dry and wet

Abrasive micropowders (corundum, silicon carbide and others) not fixed on the base are convenient in work, which are applied to the sieve in a wet state with a sponge and wipe the inside and outside for 3-5 minutes. Abrasive grain size from No. M40 to No. M10. Rinse off the powder with a strong water jet.

Abrasives, according to their physical data, are very hard and sharp crystals, can be repeatedly used for subsequent application.

opinion. Heavy powder quickly settles in water. If the washer pan is tilted in the opposite direction from the drain hole, then all the abrasive will accumulate at the bottom. Low transverse partitions at the bottom will not only retain all the powder used, but also save the money spent.

We do not recommend the use of household cleaners containing abrasive additives of any size. There is always a danger of scratching the threads with a large abrasive particle, which can further contribute to tissue rupture. In addition, large particles clog mesh cells and are difficult to wash out with water, and do not let ink through when printing.

Chemical method

Some chemical solutions destroy the material used to make mesh fabrics. In small concentrations and with short-term exposure, the monofilament corrodes only in the surface layer, retaining its strength and elasticity. Liquid chemicals impregnate the fabric and completely wet all the threads, creating a beautiful rough surface throughout the fabric structure, which is so necessary in the manufacture of a durable stencil.

For polyamide yarns:

The solution is applied with a brush on the grid and treated for 3 minutes.

Instead of orthocresol, zinc chloride is used:

Within 15 minutes, the tissue is treated with a solution.

To stop further exposure of the solution to the material, it is thoroughly washed off with clean water.

"Branded" way

Foreign firms specializing in the field of screen printing offer processing and degreasing solutions under various names, which can be purchased in Russia from sales agents or ordered directly from the manufacturer. Apply them according to the attached instructions and recommendations.

Chemical processing is safer than mechanical processing, and several times more effective due to the maximum impact on the entire surface of the threads. Uniform roughness allows you to firmly hold the smallest printed elements of the picture.

Aluminum frame bikes are among the most common on the market today. This is due to the lightness of the material, combined with low cost. If steel has a specific gravity of 7.8 grams per cubic centimeter, then aluminum has a specific gravity of about 2.7 grams. In terms of wall thickening, this material also outperforms iron, since the minimum parameter is 0.8 mm, while the product will weigh less than a 0.4 mm thick steel frame. Reliability is further enhanced by the absence of welded seams. In addition, they can be performed in various configurations. Consider their features, advantages and disadvantages.

Description

Aluminum-framed bikes are lighter in weight and gain speed faster and are easier to climb. For the same reason, the bike stops faster after the rider stops pedaling. Aluminum in its pure form is not used, this material means its alloy with zinc, manganese, nickel, copper or magnesium.

These bikes are more difficult to get into tight turns, because they are stiffer than their steel counterparts, they can not bend as well. Due to the rigidity of the frame, the energy from the efforts of the cyclist is transferred to the wheels with less loss. Such subtleties play a role for professionals, for amateurs this is not a critical indicator. A stiffer and less comfortable ride becomes noticeable. Bicycles with an aluminum frame practically do not dampen the vibrations transmitted to the saddle and handlebars on uneven surfaces and bumps. A bike like this requires a good suspension unit and a comfortable saddle. This will allow part of the blows to be leveled, which will favorably affect the movement.

pros

Let's start with the advantages of the product in question. These include:

• Light weight for improved speed and acceleration.
• Maximum resistance to corrosive processes.
• High driving performance even when driving uphill.

Minuses

Bicycles with an aluminum frame have a number of disadvantages, namely:

• High rigidity, which is especially felt on models without a suspension fork.
• Rapid roll loss. Due to its light weight, the bike stops faster than its steel frame counterpart after the rider stops pedaling.
• A small working resource during active operation. After a few years, cracks may appear. Manufacturers give a guarantee of 5 to 10 years, but after this period it is recommended to lubricate the part to check for possible deformations.
• When dropped on an aluminum frame, there is a higher chance of dents.
• Poor maintainability. It is very problematic to weld such a part, it is better to purchase a new one.
• Pretty high price.

Folding bikes with aluminum frame

Below we list several popular brands of this type and name their brief characteristics:

1. The expensive city bike Strida SX has an original exterior. It folds down to the size of a compact cart that can be transported on its own. The steering wheel can also be transformed. The advantages of the bike include the fact that the cables and wires are hidden in the cavity of the frame, it is easy to assemble, there is a trunk, disc brakes. With good maneuverability, the device weighs only 11.6 kg. Among the minuses are a small carrying capacity, narrow wheels, poor depreciation.
2. Smart 20. Stylish city bike, considered one of the best in its price category. Can be used by women without any problems. Among the advantages are a solid frame, a convenient transformation mechanism, the presence of reflectors and other accessories. The disadvantages include the lack of a handbrake and the quality of centering of the wings.
3. Stealth bike. The aluminum frame of the Pilot-710 model does not interfere with the softness of the ride. The transport picks up speed well on coast, has a discreet design, fits into the luggage compartment of any car in the folded position, is equipped as standard with a luggage rack and chain protection. The disadvantages are the presence of a wide steering wheel and an uncomfortable fit for tall people. The intended purpose of the modification is city trips.

Children's bicycles with an aluminum frame

Below is a brief description of some children's and teenage models:

• Mars. This one is for kids ages 3 and up. Comes with extra polyurethane wheels. The frame and fork are made of aluminum alloy, there is a handlebar height adjuster. Wheel diameter - 12 inches, model weight - 4.5 kg.
• Forward Timba‏. One of the best for kids 6-9 years old. It has a beautiful design, affordable price, chain protection and removable safety wheels. The disadvantages include a decent weight (almost 14 kg), as well as the need to adjust some moving parts.
• Shulz Max. These children's aluminum frame bikes are in the middle price range. The weight of the bike is 14.3 kg. It is aimed at adolescents 12-16 years old, has a load capacity of up to 110 kg. The advantages of the model are the ease of assembly / disassembly, a good set of speeds, equipment with 20-inch wheels and quality. Among the minuses are incorrect factory adjustment, brake pads of dubious quality.

Peculiarities

When choosing a bike, the question often arises of whether to choose an aluminum or steel bike frame. The final decision depends on the financial capabilities of the buyer, the purpose of the machine and the subjective requirements of the user. It should be noted that thick-walled pipes of large diameter are used in the manufacture of aluminum structures.

This is due to the fact that, according to the laws of physics, if the pipe size is doubled, its rigidity will increase by eight times, and if the wall thickness is doubled, the stiffness index increases by the same amount. Therefore, of the available options, increasing the diameter is preferable.

As a rule, the minimum wall thickness of a pipe on an aluminum frame is 0.8 mm. Often manufacturers make pipes by butting or using different sections, which also makes it possible to strengthen the product.

Used alloys

There are many aluminum alloys that are used to make bicycle frames. The most common are the brands 7005T6 and 6061T6. The T index indicates that the material has undergone heat treatment. For example, a 6061 alloy product is heated to 530 degrees Celsius, then actively cooled by a liquid. Further, for 8 hours, the material is artificially aged at a temperature of 180 degrees. The output is 6061-T6. Analog number 7007 is air-cooled, not water-cooled.

Below are the comparative characteristics of the materials before and after heat treatment (in parentheses):

• Alloy 2014 (2014T6) - tensile strength is 27 (70) thousand PSL, yield strength - 14 (60), elongation percentage - 18 (13), Brinell hardness - 45 (135).
• Similar indicators of material 6061 (6061T6) - 18 (45), 8 (40), 25 (17), 30 (95).

The first alloy uses 4.5% copper, 0.8% carbon and manganese, 0.5% magnesium. The second material includes 1% magnesium, 0.6% silicon, 0.3% copper, 0.2% chromium, about 0.7% iron.

Finally

The strongest bike is 16 ”, the aluminum frame of which is made of 70005 or 7005 alloy. Nevertheless, the 6061 analog is more technologically advanced, which makes it possible to make pipes with a complex section from it, and this increases the strength of the product. In addition, such aluminum lends itself better to welding. When choosing a frame, consider the financial possibilities and the intended use of the bike. With proper maintenance, a bike with a frame made of any material, including steel, aluminum or carbon, will last quite a long time.

frame metal structures are distinguished by a wide variety of static schemes, the number of spans, configuration, etc., which makes it possible to build buildings of various purposes and sizes.

Figure 3.2.1 shows some types of flat and spatial steel frame structures. Static schemes of frame structures are shown in Figure 3.2.2.

Most often, the sections of frame structures are made of solid I-beam or box section. Some possible options for solid sections of steel frames are shown in Figure 3.2.3.

The use of one or another type of frames, their static scheme and type of section is determined by the size and configuration of the building being designed, the availability of appropriate technological equipment for the manufacture of structures, and other factors.

Depending on the calculation scheme of the frame, the crossbars are of constant or variable section. In double-hinged frames (Fig. 3.2.2 c), the height of the crossbar of constant height is taken equal to 1/30-1/40 of the span. Racks usually have a variable section, decreasing towards the supports.

With spans of more than 50-60 m, through (lattice) frames are economical (Fig. 3.2.4). In double-hinged through frames with hinged coupling of racks and foundations, the height of the crossbar of the frame is taken within 1/8-1/15 of the span.

Hingeless through frames, usually used in hangar covers, have very large spans (120-150 m). The height of the crossbar in such frames is taken equal to 1/12-1/20 of the span. In hangar building, double-console and single-console frames are also used. Single-console frames are suitable for canopies of sports facilities. In buildings with a span of 40–50 m and a height of 16–20 m, it is possible to use through double-hinged frames with a broken crossbar (Fig. 3.2.1 h) of a constant height equal to 1/15-1/25 of the span.

The lattice of crossbars of through frames is usually taken triangular. Racks of frames can be designed solid (Fig. 3.2.4 a) or lattice (Fig. 3.2.4 b). Lattice racks can have a triangular or diagonal lattice. The sections of the rods and the nodes of the through frames are designed similarly to the trusses of large spans. However, it is most expedient to use bent profiles of rectangular section.

Below are examples of typical frame structures used in industrial buildings.

Fig.3.2.1. Types of frame structures

a - a frame made of flat frames; b - from spatial frames; c - a spatial frame of flat frames and power spatial connections; g - single-span frame; e - multi-span frame; e - U-shaped frame; g - a frame with a slope of racks and crossbars; h - polygonal outline frame

Fig.3.2.2. Static schemes of frame structures.

a - double-hinged frame; b - three-hinged frame; c - a frame with rigid support of the posts on the foundations and rigid junctions of the crossbar with the posts; g - a frame with rigid support of the racks on the foundations and hinged joints of the crossbar-rack; e - a frame with hinged end and intermediate posts, rigid junctions of the crossbars with the end posts and a hinged connection with the middle ones; f, g - frames with split or continuous crossbars hinged on pinched posts; h - a frame with a developed middle stance, which acts as a core of stiffness; and -, k - mixed schemes.

Fig.3.2.3. Types of sections of frame structures.

a - from welded I-beams of constant or variable section with flat walls; b - from rolled I-beams of variable height, formed from ordinary ones by diagonal dissolution and welding; c - from rolled I-beams without reinforcement and with reinforcement with haunches; g - from welded I-beams with a corrugated wall; e - box-section (type "PLAUEN" or "ORSK").

Rice. 3.2.4. Lattice frame types

a - with solid racks; b - with lattice racks

Frame structures according to series 1.420.3-15 "Steel frame structures of frames of the Kansk type" of one-story industrial buildings using load-bearing frames made of rolled wide-shelf and welded thin-walled I-beams "are designed for one-story buildings with spans of 18 and 24 m, the number of spans from one to five and a height of 4.8 - 10.8 m to the lower girder of the crossbar. Frame spacing for single-span buildings, 6 m is adopted, and for multi-span buildings - 6 and 12 m.

The building can be equipped with overhead cranes with a lifting capacity of 1 to 3.2 tons or overhead cranes of light and medium duty with a lifting capacity of 5 to 32 tons.

For structures of the Kansk type, two options for solving the ends have been developed:

With the presence of frames at the end, offset by 500 mm inward, and a non-bearing fachwerk;

Instead of frames, an end-bearing fachwerk is installed at the end, including racks, horizontal beams and vertical ties.

The option with non-bearing fachwerk is used in cases where it is planned to expand the building in the future, while the end frames will serve as twin frames of the expansion joint. The second option is appropriate if further construction is not provided.

The crossbars of the frames are designed from thin-walled welded beams, and the posts are made from rolled wide-shelf I-beams. The coupling of crossbars and racks of single-span frames is rigid. The crossbars of the multi-span frames are hingedly connected to the columns of the outer rows, and rigidly to the columns of the middle rows.

The racks of the supporting fachwerk are designed from cold-formed thin-walled box-section profiles or from composite C-shaped profiles.

In buildings with overhead cranes, the crane tracks at the end of the building are attached to half-timbered posts or to supporting steel beams.

In buildings with overhead cranes, a built-in crane trestle is installed, consisting of racks rigidly fixed to the foundations and typical crane beams laid on them.

In the longitudinal direction, the rigidity of the building is ensured by vertical ties installed along each row of columns and racks of the crane trestle in the middle of the temperature block with a length of no more than 72 m.

According to the series, all mounting units of frames of the Kansk type are bolted, which excludes the use of welding at the construction site.

The layouts of the frame elements and nodes of steel structures of the "Kansk" type are shown in Figure 3.2.5 - 3.2.7.

Rice. 3.2.5. Frame structures of the "Kansk" type

Rice. 3.2.6. Structural units of frame structures of the "Kansk" type

The nodes are marked in Figure 3.2.5.

Rice. 3.2.7. Structural nodes and fastening of crane tracks for frame structures of the Kansk type

Frames from I-beams of variable section(codes 828 KM, 828 KM-1, 941 KM, 961 KM) are used in one-story single-span industrial buildings with spans of 18 and 24 m and with a crossbar top mark of frames 6.940 and 8.140 m without light-aeration lamps. The frame spacing is 6 m. Buildings can be equipped with overhead cranes with a lifting capacity of up to 3.2 tons.

The frame of a building with frame structures consists of transverse frames, purlins, vertical braces and braces along the frame posts, posts and beams of the end fachwerks.

Elements of variable I-section in the crossbar and posts are made from rolled I-beams with parallel flange edges by their longitudinal dissolution along an inclined line into tees of variable height.

The connection of the racks with the foundation is assumed to be articulated. The conjugations of the elements in the cornice and ridge assemblies are assumed to be rigid and are made on 25 mm thick flanges using high-strength bolts.

The rigidity of the frame in the transverse direction is ensured by the operation of the frames, in the longitudinal direction - by vertical cross braces and struts along each row of frame racks, which ensure the stability of the racks from the plane of the frames.

The slope of the upper chord of the crossbar is assumed to be 0.025 when using a typical roll roofing and 0.100 when using roofing panels with metal sheathing.

The bearing end fachwerk is designed from wide-shelf I-beams.

Frame diagrams and junctions of frame structure elements are shown in Figure 3.2.8.

Frames made of I-beams of variable section are widely used in the construction of industrial and public buildings. Frame structures can also be cited as an example. "ASTRON".

They use welded I-beams of both variable and constant section. Single-span buildings with overlapping spans of up to 72 m have been developed. With additional internal supports, overlapped spans can reach 150 m. The frame spacing is taken from 5 to 12 m. The height along the gutter can reach 20 m. If necessary, frames of other geometric dimensions can be developed .

Buildings can be equipped with overhead cranes with a lifting capacity of up to 20 tons.

Frames are usually hinged to the foundation. However, if necessary, the connection can be rigid. The end fachwerk is carried out as a carrier of welded or hot-rolled racks and crossbars. Coating purlins are adopted from cold formed galvanized Z-profile.

An example of a building made of frame structures "ASTRON" is shown in Figure 3.2.9.

Rice. 3.2.8. Steel frame structures from I-beams

variable section

Flat frame system box-section frame type "Orsk"(code 135, series 2.420-4 issue 3) consists of single-span transverse frames located in 6 m increments, purlins, vertical braces, racks and beams of end fachwerks. It is not recommended to use Orsk-type structures in multi-span buildings.

Frame structures are designed for heated buildings with spans of 18 and 24 m, having a height of 6980 mm and 8180 mm to the top of the frame crossbar on the support. They are used in buildings without lanterns and in buildings with skylights, craneless and with overhead cranes with a lifting capacity of 5 tons. The slope of the frame crossbar is assumed to be 1.5%.

The pairing of the frame racks with the foundations is assumed to be articulated. The conjugations of the elements in the ridge and cornice units are assumed to be rigid and are made on 16 mm thick flanges using high-strength bolts.

Schemes and nodes of frame structures of the "Orsk" type are shown in Figures 3.2.10 and 3.2.11.

UNITEC steel frames of one-story industrial buildings using structures made of bent-welded pipes are designed for use in heated and unheated buildings without cranes, with overhead cranes with a lifting capacity of 1 to 5 tons and with overhead support cranes with a lifting capacity of 5, 10 and 16 tons with operating modes 1K-5K with non-aggressive or a slightly aggressive environment with a relative humidity of no more than 70% indoors.

Cranes are suspended symmetrically about the central axis of the frame span. At the ends of the building with overhead cranes, the crane tracks rest on beams or directly on the racks of the supporting half-timbered frame.

As enclosing structures, as a rule, panels with profiled sheet sheathing or layered assembly structures for heated buildings and profiled sheet for unheated buildings are used.

The main load-bearing structures of UNITEC frameworks are through single- and multi-span frames made of bent-welded pipes. The step of the main supporting structures is 6 m. If necessary, with large vertical loads (snow bag, etc.), the step of the frames can be reduced.

The coupling of the structures of the outer racks of frames with the foundation is articulated, the middle racks of frames and racks of half-timbered houses are rigid.

The connection of the crossbar of the frame with the outer posts is rigid, with the middle posts - articulated.

The mark of the bottom of the supporting structure of the crossbar at the point of junction with the extreme rack of the frame ( H) is provided from 4.8 to 14.4 m.

The binding of the extreme racks to the longitudinal axes is accepted as "0" or "250" for spans of 12 - 18 m, depending on the possibility of placing an overhead crane. In craneless buildings with a span of 21-30 m, zero binding is accepted.

The length of the temperature block is not more than 96 m.

At the end of the building, a supporting end fachwerk is installed, consisting of racks and beams. The rigidity of the half-timbered system is ensured by the installation of a system of flexible connections and struts. In the case of the proposed expansion

the main bearing frame with self-supporting half-timbered racks is installed at the end of the building.

The stability and geometric immutability of the building is ensured by:

in the transverse direction - by the structures of the supporting frames;

in the longitudinal direction - a system of vertical ties and struts.

The rigidity of the coating is provided by a system of horizontal braces and spacers along the crossbar of the frame.

Coating runs are made according to the cut scheme. The spacing of the roof runs is assumed to be 1.5 or 3.0 m, depending on the load on the roof and the bearing capacity of the roofing enclosing structures. With a run spacing of 1.5 m, the crossbar lattice is made with additional posts. The sections of the coating runs are taken from rolled and bent channels.

The wall purlins are made according to the split scheme. The spacing of wall purlins is assigned from 1.2 to 3.0 m in multiples of 0.6 m in accordance with the location of windows, gates and other openings, as well as depending on vertical and horizontal loads and the bearing capacity of wall enclosing structures. Sections of wall girders are taken from rolled and bent channels, as well as from bent-welded pipes.

Horizontal and vertical ties on the frame and fachwerk - cross flexible from round steel Ø 20 and Ø 24 mm.

Spacers between frames are made of bent-welded pipes.

All factory connections are welded. Mounting connections on bushings and on ordinary and high-strength bolts.

Dimensional diagrams of buildings with overhead cranes are shown in Figure 3.2.12, structural junctions for frames - in Figures 3.2.13 and 3.2.14.

Buildings equipped with overhead cranes with a lifting capacity of 5, 10 and 16 tons can be single or double-span with a span of 12 and 18 m with a mark to the bottom of the crossbar H from 6.0 to 14.4 m.

steel arches can also have a solid or through section.

Solid arches usually have a constant cross section and are used for spans up to 60 m (Fig. 3.2.15). The sectional height of such arches ( h) is usually taken equal to 1/50 - 1/80 of the span ( L). With spans of more than 60 m, through (lattice) arches are usually used. The height of the section in this case is 1/30-1/60 of the span. Geometric schemes and types of sections of through frames are shown in fig. 3.2.16.

The most widespread are metal arches operating on a two-hinged scheme. The design of the support hinge is determined by the span of the arch and the magnitude of the acting load. Figure 3.2.17 a shows the simplest design (with the help of a tiled hinge), typical for a light arch of a solid section.

Rice. 3.2.10. Steel frame structures of box-section type "Orsk

Rice. 3.2.11. Schemes of end faces, arrangement of girders and vertical connections in buildings with steel frame structures of box section of the "Orsk" type

Rice. 3.2.12. Dimensional schemes of buildings using

frames UNITEC

The most complex solution, with the help of a balancing hinge, is the support units of heavy large-span arches (Fig. 3.2.17 b). Because near the support, the sections of the through arches turn into solid ones; the supporting nodes of such arches are performed similarly.

Rice. 3.2.13. Eaves and support units of the UNITEC frame

(nodes are marked in Fig. 3.2.12)

Rice. 3.2.14. Overhead track beam attachment points

and half-timbered racks to the frame crossbar

Rice. 3.2.15. Structural scheme and types of sections of solid arches

Fragment of a metal frame welded from two corners

Very often, during the construction of residential buildings, situations arise when it is necessary to close up an opening in the wall of a building or use a metal frame for the opening. The frame, in turn, serves as the basis for fastening doors, hatches, louvered grilles to it, filling various profiles such as round timber, square, or simply the opening is “sewn up” with solid sheet metal. One way or another, the metal frame for the opening plays an important role in the construction of buildings. Therefore, it makes sense to talk about it separately from the point of view:

• Rolled metal for the frame.
• Frame details.
• How to weld a metal frame.

Rolled metal for the opening frame

Which profile to use to frame the opening with a frame depends on the size of the opening itself. If we have a small opening, for example, 500 x 500 mm, where the louvered grille will be inserted, a small door will be enough ∟ 45 x 45 x 5 or ∟ 50 x 50 x 5. In the case of mounting a simple metal gate in the opening, the size of the corner can be will apply 63 x 63 x6 or 70 x 70 x 7. In some cases, if these corners are not available, you can use channel N 8 - 10.

Main parts of the metal frame

As noted above, the details of the frame include a metal profile corner or channel, which are prepared taking into account the width and length of the frame. Moreover, it is very important to prepare cutouts in one of the parts for docking with other parts. In the corners, these can be 45º cutouts or special cutouts in a shelf of one of the sizes. In the channel, a shelf is also cut off on one of the parts for connection with another part so that the connected unit looks like one piece. It should be noted that steel for welding frames should be grade St 3 PS or St 3 SP, but not carbon steel.

You can learn about carving in the corners by reading my previous article about. As for how the joining of the spirit of the channels will look like, just look at the attached drawing.

Docking channels at 90 degrees

An important role is played by anchors that are welded to the frame to fix it in the opening. If the opening is any type of brickwork, then round steel anchors are welded to the frame. Usually it is round steel Ǿ 10 - 16 A II - III. If the opening is wooden, self-tapping screws of the appropriate length are used, but for this, a hole of the required diameter is pre-drilled in the frame. The diameter of the metal anchors depends on the size of the frame. If the perimeter of the structure is small and it is welded from a small angle, it will be enough to make an anchor from wire rod Ǿ 5-6 mm.

How to weld a metal frame

First of all, you need to have a flat surface for assembling the frame. The ideal option in this case would be a steel sheet with a thickness of 10 - 12 mm. You need to have a steel square with you to control the right angles of the structure and a tape measure of at least 3 meters to measure the diagonals at the inner corners of the assembled frame.

Frame welding. You can see the abutting corners with a notch at the right

If the channel is usually even, then the corner often has a certain helical shape. This is especially true for small corners, so they need to be straightened before assembling the frame. And again, it will be more convenient to do this on a metal plate, where you can not only straighten, but also check the result on a flat surface of the plate. Everyone knows how to straighten, but the only thing I want to notice is that if the straightened shelf lies on the slab, then hammer blows must be applied to the edge of the shelf, which is perpendicular to it.

To control right angles, as already noted, measure the length of the diagonals at the inner corners of the frame. It is quite clear that they should be equal. Electrodes for frame welding should be taken grade ANO - 4, and for welding anchors made of reinforced steel, electrodes DSK - 5 are used. The diameter of the electrodes depends on the thickness of the profile shelves. For a corner of 50 x 5, 4 mm will be enough, and for welding channels - 5 mm. After welding, all welding seams, after removing the scale, are cleaned with a circular grinder.

Note

All welding work must be carried out only in a dry room and in dry welding gloves!

In industrial and public buildings built using modern technologies, the load-bearing elements are metal frames different sections (solid, lattice and I-beam). Depending on the purpose, parameters and planned loads, the necessary calculations are carried out, on the basis of which metal structures are manufactured. Our company is engaged in the design and production of different types of frames, performs their processing and installation. We also produce in any quantity.

Steel frames: scope and installation

Mixed construction of buildings consists of steel and reinforced concrete elements. This technology is used when the transportation or installation of reinforced concrete products is unprofitable.

In our company you can order the following metal products:

• Latticed frames of through type. Such elements are a structure with large spans, are relatively light in weight and are used to create the frame of buildings with sloping or flat roofs.
• I-section welded frames, in which the wall thickness, height and width of the shelves do not have constant dimensions and vary along the structure. Welding of elements is carried out semi-automatically in accordance with GOST. Products are used to create light frame buildings for various purposes - these are hangars, warehouses, shopping centers, offices, shops, industrial buildings, etc.
• Distribution frames for equipment, machines and technological installations. Such products are manufactured according to industry and national standards, as well as according to customer drawings.

Metal frame structures that serve as visors or are the basis for a banner are attached directly to the facade of the building using special fasteners.

Where to order metal frames?

Our company accepts any complexity. The production process consists of design, manufacture, delivery and installation. Strict quality control is carried out at all stages. Turning to us, customers receive a 100% guarantee of timely completion of the order.