Plumbing markings

TO category:

Marking

Plumbing markings

Marking is the process of transferring the shape and dimensions of a part or part of it from a drawing to a workpiece. The main purpose of marking is to indicate on the workpiece the places and boundaries of processing. The processing locations are indicated by the centers of the holes obtained by subsequent drilling or by bending lines. Processing boundaries separate the material that must be removed from the material that remains and forms the part. In addition, markings are used to check the dimensions of the workpiece and its suitability for the manufacture of a given part, as well as to control the correct installation of the workpiece on the machine.

Workpieces can be processed without marking, using jigs, stops and other devices. However, the costs of manufacturing such devices are recouped only in the production of serial and mass-produced parts.

Marking (which is essentially close to technical drawing) is performed using special tools and devices on the surfaces of workpieces. Marking marks, i.e. lines applied to the surface of the workpiece, indicate the boundaries of processing, and their intersections indicate the positions of the centers of the holes or the position of the centers of the arcs of circles of mating surfaces. All subsequent processing of the workpiece is carried out according to the marking marks.

Marking can be mechanized or manual. Mechanized marking performed on jig boring machines or other devices that ensure precise movements of the workpiece relative to marking tool, used for large, complex and expensive workpieces. Manual markings are performed by toolmakers.

There are surface and spatial markings. Surface marking is carried out on one surface of the workpiece, without linking its individual points and lines with points and lines lying on the other surface of this workpiece. The following methods are used: geometric constructions; according to a template or sample of a part; using devices; on the machine. The most common type of surface marking is planar, used in the manufacture of flat gauges, jig plates, die parts, etc.

Spatial marking is carried out by linking dimensions between points and lines lying on various surfaces blanks. The following methods are used: for one installation; with rotation and installation of the workpiece in several positions; combined. Spatial markings are used in the manufacture of parts of complex shapes.

Tools and devices for marking. According to their purpose, marking tools are divided into the following types:
1) for making marks and making indentations (scribers, surface planers, compasses, center punches);
2) for measuring and monitoring linear and angular quantities (metal rulers, calipers, squares, micrometers, precision squares, protractors, etc.);
3) combined, allowing you to take measurements and carry out risks (marking calipers, gage gauges, etc.).

Scribblers are used to apply marks on the surface of workpieces. Steel scribers are used to mark untreated or pre-processed surfaces of workpieces, brass scribers are used to mark ground and polished surfaces, and soft sharpened pencils are used to mark precise and final processed surfaces of workpieces made of non-ferrous alloys.

Marking compasses correspond in design and purpose to drawing ones and are used for drawing circles and dividing them into parts, transferring linear dimensions and so on.

Rice. 1. Marking tool: a - scriber, b - compass, c - center punch, d - square

The steel legs of scribers and compasses are made from U7 and U8 steels (the working ends are hardened to 52-56 HRC3) and from hard alloys VK.6 and VK8. The working ends of scribers and compasses are sharpened sharply. The thinner and harder the tips of these tools, the thinner the marks are and the more accurately the part will be made.

The center punch (Fig. 1, c) is used for making recesses (cores) on marking marks. This is necessary so that during processing the marking marks, even when erased, are noticeable. A center punch is a steel round rod made of alloy (7ХФ, 8ХФ) or carbon (У7А, У8А) steel. Its working part is hardened and sharpened at an angle of 609. The head of the punch, which is struck with a hammer, is made rounded or chamfered and also hardened.

Reismas used for spatial markings for making horizontal marks on the surface to be marked and for checking the position of the workpiece on the marking plate, it is made in the form of a stand on which the scriber can be moved in height and secured in the required position. In the simplest planner in design, the scriber is set to the required height using a vertical scale ruler or using gauge blocks. In tool production, gauges are mainly used, and sometimes (if necessary) thickness gauges special design(for example, a multi-seam gauge having several scribers on a stand, independently set in height to a given size). Combined surface gauges are also used, i.e. regular surface gauges equipped with additional various devices and tools (for example, a surface gauge with a center finder).

The square is used to draw lines, construct angles and check them.

Marking calipers are used to measure the dimensions of external and internal surfaces and for marking marks. It differs from a conventional caliper by the presence of sharply sharpened carbide tips on its jaws.

Devices used for marking and used for installation, alignment and securing of workpieces include adjustable wedges, prisms, linings, jacks, chucks, collets, rectangular magnetic plates, rotary tables, sine tables, dividing heads and many others.

To prepare workpiece surfaces for marking, use auxiliary materials. The workpieces are cleaned from dust, dirt, rust, scale and oil using steel brushes, files, sandpaper, wiping ends, napkins, brushes, etc. In order for the marking marks to be clearly visible during subsequent processing, the cleaned surface is usually painted smooth and thin layer. The paint should adhere well to the surface, dry quickly and be easily removed. Untreated or roughly processed surfaces of steel and cast iron workpieces are painted with chalk dissolved in water with the addition of wood glue and turpentine (or linseed oil and drier). Pre-treated surfaces are coated with a solution copper sulfate. Treated surfaces large sizes And aluminum alloys coated with a special marking varnish. For this purpose, you can use a solution of shellac in alcohol, colored with fuchsin. Coloring small surfaces produced by cross movements of the brush. Large surfaces are spray painted. The painted surface is dried.

Sequence of work during marking. Marking includes three stages: preparation of blanks for marking; actual marking and marking quality control.

The preparation of the workpiece for marking is carried out as follows:
1. Carefully study and check the drawing of the part.
2. Preliminarily inspect the workpiece, identify defects (cracks, scratches, cavities), control its dimensions (they must be sufficient to produce a part of the required quality, but not excessive).
3. Clean the workpiece from dirt, oil, and traces of corrosion; paint and dry those surfaces of the workpiece on which the marking will be made.
4. Choose base surfaces, from which the dimensions will be set aside, and their preparation will be carried out. If the edge of the workpiece is chosen as the base, it is pre-aligned; if there are two mutually perpendicular surfaces, they are processed at a right angle. The base lines are applied already during the marking process. The location of the bases should ensure that the part fits into the contour of the workpiece with the smallest and uniform allowance.

The actual marking is performed in the sequence determined by the marking method. When marking according to a template, the latter is installed on the workpiece, correctly oriented relative to the bases, and secured. The template should fit tightly to the workpiece along the entire contour. Then they trace the outline of the template on the workpiece with a scriber and unfasten the template.

Marking using the geometric construction method is carried out as follows. First, all horizontal and then all vertical marking marks are drawn (relative to the base); then make all the fillets, circles and connect them with straight or inclined lines.

When marking, the surface gauge stand is taken by the base and moved along the marking plate relative to the surface of the workpiece, without allowing skewing. The surface scriber touches vertical surface workpiece and leaves a horizontal mark on it. The scriber should be positioned at an acute angle to the direction of movement, and the pressure on it should be light and uniform. The marks are drawn parallel to the working surface of the marking plate. In order for the marks to be strictly linear and horizontal, the supporting surfaces of the surface planer and the marking plate must be processed with great precision. The quality of marking improves if a flat scriber is used in the surface planer.

Quality control of markings and cores is The final stage markings. The centers of the cores must be located exactly along the marking marks; the cores should not be too deep and differ in size from each other. On straight lines, cores are punched at distances of 10-20 mm, on curved ones - 5-10 mm. The distances between the cores are the same. As the size of the workpiece increases, the distance between the cores also increases. The points of intersection and intersection of marking marks must be cored. On the processed surfaces of precision products, marking marks are not punched.

Marking defects can lead to significant material losses. The most common causes are: incorrect choice of databases and their poor preparation; errors when reading the drawing, when setting aside dimensions and in calculations; incorrect choice of marking tools, devices, their malfunction; wrong ways and marking techniques.

The widespread use of mechanized marking tools and devices improves the quality and productivity of marking. Therefore, mechanical, electrical and pneumatic punches, calipers and gage gauges with electronic indication, and mechanized devices for installing, aligning and securing workpieces should be widely used. The use of microcalculators for calculations significantly speeds up work and reduces the number of errors. It is necessary to create more universal and easy-to-use marking tools and devices. Where economically feasible, it should be used for marking coordinate machines, coordinate measuring machines, or eliminate marking altogether by processing workpieces on CNC machines.

The invention relates to gas-arc cutting technology, namely to air-plasma cutting of parts with a curved contour, mainly hoods of stamped parts, using a work table and equipment and can be used in small-scale and pilot production at machine-building plants. The part to be trimmed (2) is placed between the elements of the equipment containing a cradle fixed to the base of the work table and a template equipped with a handle and a guide along its contour. The plasma torch nozzle is rested on the side against the guide and the part is trimmed along the outer contour of the guide by sliding the nozzle relative to the latter while simultaneously orienting the plasma torch axis perpendicular to the plane of the part being cut. The cradle, template and cut part have a volume-spatial shape similar to each other, providing conditions for their self-fixation with each other. The contour of the cradle is smaller than the contour of the template, and the contour of the latter is smaller than the contour of the part of the reference dimensions (1). As a cradle and a template, ready-made parts of the same name are used, obtained by trimming them to a standard level with subsequent processing of the edges. This will reduce the labor intensity of the process and the cycle time of cutting one part while ensuring the required geometric dimensions and quality of the cut edge. 8 ill.

The invention relates to gas-arc cutting technology, in particular to air-plasma cutting, and can be used at mechanical engineering enterprises in small-scale and pilot industrial production.

Parts obtained, for example, by stamping, require circular cutting. In mass production conditions, trimming dies are usually used, which is not always economically justified in small-scale and pilot production, since this requires significant capital investments. Automation of the process of cutting parts obtained by cold die stamping, for example, those that are body elements passenger cars, presents certain difficulties, since they usually have a complex volume-spatial shape, which leads to the need to use expensive and difficult to operate and maintain robotic systems and manufacture equipment that ensures the spatial orientation of the cut part. In the case of a wide range of cut parts, frequent changes of equipment and readjustment of process parameters are necessary.

For small-scale and pilot production manual cutting each part by mechanical means requires its preliminary marking, is labor-intensive and low-productivity. Cutting with scissors leads to deformation of the cut edges and the need for subsequent straightening.

Compared to manual cutting with scissors, air plasma cutting allows you to avoid mechanical deformations of the edge and, as a consequence, subsequent straightening operations.

Plasma cutting can be carried out using a template or equipment, excluding preliminary marking, while the labor intensity of cutting volumetric body parts is significantly reduced, and productivity increases.

For the convenience of cutting products with complex spatial orientation, the product has to be installed in various positions using devices, one of which is, for example, a positioner - a device designed to install the product in a spatial position convenient for cutting. Typically, the positioner does not move the workpiece at welding speed, but only holds it in a given position.

There is a known method of fixing a part during welding, which consists in holding the part in the welding position with several clamps and after welding it is transferred to the control position, in which the actual position of the specified control points on it is determined. The position of these points is compared with their reference location, and if deviations from the reference location are detected, the deviations are compensated by readjusting the clamps in order to eliminate the error when welding the next part [US Patent No. 6173882, cl. B 23 K 31/12, B 23 K 26/00, 2001].

This method does not provide conditions for error-free carrying out of the welding process itself, and also requires additional time for monitoring and readjustment.

There is a known method for cutting parts, taken as a prototype, which involves air-plasma cutting of these parts along the contour using a work table and equipment [Automated installation for air-plasma cutting for the manufacture of car body parts. Nesterov V.N., Truck and bus, trolleybus, tram. 2001, No. 1, pp. 34-35].

This method can be used in serial and mass production, but it is complex and expensive.

The problem to be solved by the claimed invention is to develop a cutting method in which it would be possible to reduce the labor intensity of the process and the cycle time of cutting one part while ensuring the required geometric dimensions and quality of the cut edge.

This problem is solved by the fact that in the method of cutting parts, mainly extracts of stamped parts, including air-plasma cutting of these parts along the contour using a plasma torch with a nozzle, a work table and equipment, the cut part is placed between the elements of the equipment containing a support fixed on the base of the work table, and a template, equipped with a handle and a guide along its contour, rest the plasma torch nozzle on the side against the guide and actually trim the part along the outer contour of the guide by sliding the nozzle relative to the latter with the simultaneous orientation of the plasma torch axis perpendicular to the plane of the part being cut, while the cradle, template and trimmed the part has a volumetric-spatial shape similar to each other, providing conditions for their self-fixation among themselves, the contour of the cradle is smaller than the contour of the template, and the contour of the latter is less than the contour of the part of the reference dimensions, and as the cradle and template, ready-made parts of the same name are used, obtained by their reference trimming followed by edge processing.

Placing the part to be cut between the elements of the equipment containing a cradle fixed to the base of the work table and a template equipped with a handle and a guide along its contour, in general, allows you to rigidly fix the part and ensure the necessary conditions to carry out the cutting process.

The use of a cradle as a tooling element provides support for fixation (fastening) and stable spatial orientation of the part being trimmed.

Attaching the cradle to the base of the work table allows you to obtain a convenient position for cutting the part.

The use of a template as a tooling element ensures that, after trimming, a part with outlines corresponding to the outline of the drawing is obtained, while the template itself is used as a device used directly in the trimming process, and not for preliminary marking.

Equipping the template with a handle allows you to quickly install it on the part before cutting, and quickly remove it after the end of the cycle without the risk of exposure to temperature.

Providing the template with a guide along its contour provides conditions for the lateral support of the plasma torch nozzle into the guide and sliding relative to it during the cutting process.

The abutment of the plasma torch nozzle on the side against the template guide allows cutting to be carried out practically without vibration of the nozzle, that is, ensuring the spatial orientation of the plasma torch at each point of the cutting trajectory (contour).

Cutting the part along the outer contour of the guide by sliding the plasma torch nozzle relative to the latter ensures reproducibility of the cutting path (contour).

The simultaneous orientation of the plasma torch axis perpendicular to the plane of the cut part ensures cutting quality with minimal slopes, burns, burrs, etc.

The use of a lodgement, a template and a trimmed part with a volume-spatial shape similar to each other, providing conditions for their self-fixation with each other, eliminates the need for additional devices.

The similarity of the lodgement, the template and the cut part to each other means that each of them can be obtained from the other by increasing or decreasing the linear dimensions in the same ratio.

Making the contour of the cradle smaller than the contour of the template, and the contour of the latter smaller compared to the contour of the part of the reference dimensions, allows you to take into account the dimensions of the plasma torch used in the process of cutting the part, thereby providing conditions for accurately reproducing the contour of the part when cutting it (using a template), and also not obstructing the passage cutting products and ensure stable spatial orientation of the cut part in a position convenient for cutting (using a support).

Using ready-made parts of the same name as a template and cradle by trimming them according to the standard followed by processing the edges makes it possible to special costs obtain samples from these parts that can serve as a standard for small-scale and serial reproduction of the same parts, and in the cutting process ensure high accuracy this process.

The proposed method is illustrated by drawings that show:

figure 1 - outline of the finished part 1, for example the base of the rear seat of a car, plan view;

figure 2 - the contour of the hood 2 of the stamped part in comparison with the contour of the finished part, indicated by a dotted line, plan view;

figure 3 - the contour of the cradle 3, made from a serial part, in comparison with the contour of the finished part, indicated by a dotted line, plan view;

figure 4 - the outline of the template 4, made from a serial part, in comparison with the outline of the finished part, indicated by a dotted line, and the contour of the cradle, indicated by a dashed line, plan view;

Fig. 5 shows the assembly elements of the tooling with the part to be cut before their mutual fixation, where position 5 indicates the base of the work table, and position 6 indicates the handle of the template;

in Fig.6 - the same, in a fixed position, the plasma torch is not shown;

Fig.7 - view A in Fig.6, before the operation of the plasma torch, where position 7 indicates the guide of the template, 8 - plasma torch, 9 - axis of the plasma torch;

in Fig.8 - the same, when the plasmatron is operating, where position 10 indicates the electrode, and 11 indicates the plasma-forming nozzle.

The method of cutting parts with a curved contour is carried out as follows.

The cradle 3 (Figs. 5 and 6), made in accordance with the method, is attached to the base 5, which is a platform, inside the contour of which there are means for securing the cradle holder (not shown), and in a position that provides the most favorable (optimal) conditions for the operator's work. Next, the trimmed part 2 is placed on the cradle 3 and fixed on it, and then the template 4 is placed on top, after which the plasma torch 8 (Fig. 7) is brought to the part 2, its nozzle is placed on the side against the guide 7 of the template 4 and the part is trimmed along the outer contour guide by sliding the nozzle relative to it with the simultaneous orientation of the axis 9 of the plasma torch perpendicular to the plane of the cut part.

With the correct speed of movement of the cutter, the width of the cut is uniform and amounts to 1.0-2.0 times the diameter of the plasma nozzle 11 (Fig. 8), and the edges are clean, with minimal bevels and virtually no burr.

After the equipment is manufactured, it is used to trim the installation (test) batch of parts, which is then submitted for metrological measurements to verify compliance of the geometric and other parameters with the requirements of the design documentation. If this compliance is established and confirmed, then this part is considered a standard, and the process is considered standard. In the future, if necessary, standardization can be repeated at intervals determined by the technology.

The use of the proposed invention allows, in a short time and with minimal costs organize the process of cutting parts of complex shapes.

Example. Extracts of stamped parts were trimmed along the contour using a manual air plasma cutting installation type DS-90P (NPP Technotron, Russia), equipped with a plasma torch PSB-31 (Alexander Binzel, Germany), in which outside diameter the nozzle part is 11.0 mm, the diameter of the plasma nozzle is 1.0 mm. The amount of guide displacement was calculated using the formula:

Δ=1/2(d n.c. -(1.0-2.0)d p.c.),

where Δ is the displacement value;

d n.c. - outer diameter of the nozzle part;

d p.c. - diameter of the plasma-forming nozzle.

The coefficient (1.0-2.0) takes into account the change in the width of the cut depending on the wear (erosion) of the plasma nozzle 11 (Fig. 8), the electrode 10 and the cutting parameters (speed, current).

In our example, Δ min =1/2(11-1.0)=5.0 mm, Δ max =1/2(11-2.0)=4.5 mm, i.e. in the nominal value you can select the displacement value Δ=(4.75±0.25) mm.

The calculation is illustrated in Fig. 8.

On the base of the work table, a cradle 3 was placed, obtained by trimming 30 mm from the edge of the part (>5 mm), the trimmed part 2 was fixed on it, and template 4 was placed on top, obtained by trimming 4.75 mm from the edge of the part (taking into account the size of the used plasmatron). After completion of the assembly, the hood 2 was trimmed, maintaining lateral contact of the outer generatrix of the nozzle part with the guide 7 on the template 4 along its contour, resting the plasma torch nozzle on the part to be trimmed while simultaneously orienting the axis 9 of the plasma torch perpendicular to the plane of this part.

Marking is the initial operation of the process of processing body parts. Sheets and profiles are received for marking, parts of which will be cut on mechanical equipment, portable thermal cutting machines or manual gas cutters. Marking can be done manually, using photo-projection, sketch or template methods, on program-controlled marking and marking machines and using other methods.

The photoprojection method is used to mark sheet steel parts. With this method, negatives from scale template drawings are issued to the workshop marking area from the plaza.* Marking in life size The contours of parts on the material are carried out according to the image from the negatives using special projection equipment.

The actual marking process is as follows. A sheet of metal is fed onto the marking table. If the sheet does not lie tightly on the table (there are gaps between the sheet and the table top), then it is pressed to the table with clamps. They turn on the projection equipment, into which the corresponding negative is inserted in advance, and set it up. Since the lines and marks of a scale drawing are drawn in black ink, these lines and marks appear light on the negative and its projection. Using the light lines and marks on the surface of the marked sheet, the contours of the parts and their markings are recorded (core).

The sketch marking method is used mainly for marking parts made of rolled profiles. The use of this method for parts made of sheet metal is allowed only in cases of marking measuring waste, the absence of photoprojection equipment and marking and marking machines.

Marking parts using sketches comes down to the fact that the marker draws on a sheet or life-size profile the contours of the parts shown in the sketches. The contours of parts are obtained by performing simple geometric constructions using conventional measuring and marking tools. To mark the most complex parts, slats or templates are attached to the sketches, which are specifically specified in the sketches. Both sketches and slats, as well as templates, arrive at the workshop marking area from the plaza.

Parts that have curved edges, the construction of which geometrically presents significant difficulties, as well as parts made of bent profiles, are subject to marking using templates.

Mark the parts according to the templates as follows. A template is placed on the sheet to be marked. After this, a scriber is used to trace the outline of the part along the edges of the template. Then all the cutouts on the template are outlined. Next, the template is removed and the parts are marked. After this, break lines, welding lines and all other lines necessary for processing and assembling parts are punched or drawn (along the notches).

Rice. 11.5. Measuring instrument: a - steel tape; b - folding meter; c - calipers; g - micrometer.

As measuring tool by doing marking works used (Fig. 11.5):
- tape measures with metal tape up to 20 m long, metal rulers up to 3 m long, folding meters for measuring lengths;
- calipers and calipers for measuring internal and external diameters, as well as material thickness with an accuracy of 0.1 mm;
- protractors, protractors for measuring and constructing angles;
- micrometers for measuring material thickness with an accuracy of 0.01 mm.

Rice. 11.6. Marking tool: a - compass; b - caliper; c - squares; g - marking punch; d - control punch; e - thread; g - thicknesser.

The following is used as a marking tool (Fig. 11.6):
- compass and caliper for drawing circles and constructing perpendiculars;
- squares for constructing perpendiculars;
- cores for marking points on metal;
- threads for drawing straight chalk lines;
- thickness gauges for drawing parallel lines on profile steel shelves, etc.;
- scribers for drawing lines.

All dimensions applied to parts that do not have allowances must correspond to the dimensions or drawings.

Below are the values ​​of permissible deviations of the actual dimensions of the marked parts from the nominal ones (in millimeters):
From overall dimensions For sheet parts:
with a length (width) of up to 3 m.............. ±0.5
with a length (width) of more than 3 m................±1.0
From overall dimensions to profile parts:
for lengths up to 3 m...................±1.0
with a length of more than 3 m................±2.0
From the dimensions of the cutouts for the set, etc............ 1.0
Diagonal difference................... 2.0
From straightness or other edge shape:
with a length of edges or chord (with curved edges) up to 3 m. .................±0.5
with an edge or chord length of more than 3 m........±1.0
When marking, the width of the chalk line should not be more than 0.7 mm. The width and depth of the line drawn by the scriber should not exceed 0.3 mm.

When marking some parts, allowances are left along their edges. An allowance is a part of the metal removed from the workpiece to obtain parts in drawing or dimensional dimensions. Allowances are intended to compensate for possible dimensional deviations that occur during processing of parts, assembly and welding of components and sections. The allowance values ​​assigned based on the manufacturing conditions of the parts are usually taken within the range of 5-50 mm.

To preserve traces of markings until the end of processing and assembly of parts and restoring markings (if necessary), all marking lines are cored.

Body parts made of light alloys are marked with a simple soft pencil. It is allowed to punch only the centers of the holes, the installation sites of the set (subject to the obligatory further covering of them with welded parts), as well as contour lines that are removed during subsequent processing.

A mark must be applied to each marked part.

The advent of automatic thermal cutting machines made it possible to eliminate the operation of marking these sheets, but the marking of parts remained. In order to automate the process of marking parts on production lines for thermal cutting of parts, program-controlled marking machines have been created. Currently, a sample of a laser marking and marking machine has been created.

* Template drawings were discussed in detail in Chapter. 10.

The top is the main decorative part of any jewelry. The size and shape of the top are determined by the type of product, size, quantity, shape and arrangement of stones. Its design depends on the sample and the decision of the master. The elite may be made up of castes; smooth, made of rolled stock, with or without castes, carmized (karmaziring - a dense accumulation of stones at the top); openwork, carved and assembled with various fastening of stones. The tops are made according to finished sample, drawing or drawing made on a 1:1 scale, or specific dimensions.

The top of the castes is flat (without a common convexity) and can be assembled on a letkale by successively soldering one caste to another. If the castes should not fit tightly to each other, they are soldered on the veins. The lower base of the caste is cut diagonally with a jigsaw to the depth of the vein (rolled onto the plane of the wire) and placed on it. The vein is first bent according to the location of the castes, then castes are placed on it at the required intervals and soldered to the vein. In a multi-row arrangement, several castes collected on the veins are soldered together.

The tops, which have a general curvature (convexity), are conveniently assembled on a mounting compound, which can be a mixture of kaolin with asbestos or fire-resistant gypsum. The kaolin-asbestos mass, softened by water, is molded to the shape of the top and seated in castes as indicated on the sample. The soldering areas are fluxed with a liquid solution and dried with a burner. At large quantities It is advisable to solder places with sawn solder, which, when heating the product evenly, allows you to solder all connections at the same time. The assembled top with the mounting mass is placed in water, the mass softens and can be used during the next assembly.

To assemble the top, a cast is made from plasticine on plaster mass the desired shape and seat him in the same way as in the previous case. Then a cutout is made in a piece of cardboard in the shape of the top and placed on the cast so that the top rises slightly above the platform. After this, the top is filled with gypsum mortar (the solution is compacted by lightly tapping the cast), a cardboard platform protects the mortar from dripping. The cast, filled with plaster, is placed with the top up until the solution completely hardens. Then the plasticine cast is separated from the hardened plaster and the cardboard is removed. The exposed bases of the casts are degreased, fluxed and soldered. After soldering, the gypsum is dissolved in hot bleach (in a separate bleach pot) and washed off in water with a stiff brush.

The top is considered smooth (Fig. 81) if it is made of rolled metal without castes (for finishing with engraving, enamel or niello) or in the form of a rim around the caste (several castes). The thickness of the rolled material for a smooth top is taken depending on the specified weight of the product, but not thicker than 0.7 mm. The production of flat tops is elementary - the outline is drawn at a rental, cut out and filed along the contour. But, as a rule, the top has a curved surface (convex and sometimes concave). The manufacturing process is as follows.

On flat rolled products, annealed and darkened (when annealed in air, the metal is covered with a dark film of oxide), the contour of the top is drawn, and if castes are planned to be placed in it, then this is also marked immediately. The workpiece is cut along the contour and filed. Depending on the shape of the contour, the top and curvature of the surface, it is buffed (given curvature) in an anchor (Fig. 82), a lead matrix or wood using punchels - rods with a spherical working part. In case of complex or deep drawing, the workpiece is subjected to intermediate annealing, and after completion of this operation - final annealing. The resulting curvature of the surface is corrected so that the contour of the apex is parallel. For most products, the contour of the top should be in a plane, while for bracelets and sometimes rings it should be curved in an arc inward. In the first case, the top is straightened on a leveling plate, in the second - on a crossbar of the appropriate diameter. The base of the top is finished off with files and needle files until a belt of even width appears. If the top is marked to accommodate castes, then holes are cut into it, into which pre-made and processed castes are inserted. In the case when the caste should be in the top with a gap, it is planted on veins, which are either pre-soldered onto the caste, or left during the cutting of the hole, and the hole itself in the top is made larger to the width of the gap. The casts are pressed tightly into the holes and soldered.

The top of the karmaziring (Fig. 83), as a rule, is a stone surrounded by smaller stones. For the production of this top, rolled stock of 1.2-1.3 mm is used. The task should determine the setting of the central and shrinkage stones. In the option when the central stone needs to be fixed in a blind caste, and the shrink stones - directly at the top - in a fadan-grisant, the initial stage of production is similar to the production of a smooth top until the cutting out of holes for the stones. Drilling occurs according to the markings for all stones at once. The hole for the central caste, made in advance, is cut out first, and the caste is inserted to such a depth that its lower base does not extend beyond the inner (reverse) surface. Then, using a jigsaw, holes are cut out for small stones, and each hole must correspond to the shape of “its” stone. The holes are made conical with a narrowing of 20°. For stones with ideal round shape the holes are drilled to a certain depth (depth of the socket) with a sharpened drill or a special conical cutter (bur). The distance between the stones must be coordinated with the cutting option for the future setting.

For individual execution of products, except front side tops, the reverse side is also processed. The treatment consists of sharply enlarging all the holes for small stones with a jigsaw, as a result the holes take the shape of a hollow funnel. Jewelers call this operation “cutting the openwork to look like a stone.” The openwork can be of any shape, but must be combined with the shape of the top and the arrangement of stones. A series of holes cut in this way form a beautiful pattern (Fig. 84), visible only from the inside of the product. However, the openwork is made not so much for beauty, but in order to open access to light to the stones and facilitate their washing.

The openwork cut-out top (Fig. 85) is also made from rolled steel with a thickness of 1.2-1.3 mm. The stones at the top can be fixed into castes, tsargi and directly into the metal of the top (into its carved elements). First, as usual, the frames and castes are made, and then they begin to mark the top, which is carried out on flat rolled products. The markings must be clear and deep enough so that the lines are preserved after bundling. Next, as in previous cases, the top is cut out along the outer contour, filed, bundled and straightened. Then they cut out holes for the castes and fit them in. If the tsars (according to the design) are planted on the veins, they are inserted after processing the cut out pattern of the top. Holes for the casts, and then for the stones, are cut out in sequence from large to small, and only after all the holes are adjusted to the stones, the pattern itself is cut out. The openwork pattern is processed with needle-shaped and specially sharpened needle files, and in places where these files cannot be reached, finishing is carried out with a jigsaw. After processing the slotted pattern, the openwork for stones is cut from the front and back sides. The assembly of the top with the castes is carried out in such a manner that the already soldered castes or tsars do not interfere with the soldering of the next ones.

Stacked tops are made up of separately manufactured elements: castes, all kinds of overlays, curls, corners, etc.

A set of elements is produced, as a rule, around the caste. The elements soldered on one side to the caste with the other side rest on the welt, forming patterns that are clearly visible from above.

Figure 86 shows a ring with a stacked top and its details.

The welt is the lower contour rim soldered to the caste or top. In most cases, its shape copies the contour of the apex, but in size it does not go beyond its limits. The welt does not significantly increase the height of the top and leaves its reverse side open. It is used for all types of products.

The blank for the welt is a flat rolled product (0.8-1.0 mm thick), slightly larger than the size of the top. The workpiece must be tightly fitted to the base of the top and soldered with tin in two or three places. The soldered workpiece is cut along the contour of the top and filed flush. The plate, which already has an external edge contour, is separated from the top by heating and the tin is completely removed from both parts. The inner contour of the welt is marked with a compass at a distance of 1.5-2.0 mm from the outer contour. Thus, the preliminary width of the welt will be 1.5-2.0 mm. The welt hole is cut along the intended internal contour, which is then tucked in.

For the tops intended for rings, the variety of welts is somewhat wider than for other products (Fig. 87). In particular, under the top, which has a flat base, the welt can be made curved (along the finger), it serves as a transition from the top to the shank of the ring. When making such a welt, its width (distance along the bend) is taken to be 1.5-2.0 mm less than the width of the top. High welts for rings are made from rolled material like a conical cast and are split along the contour of the top without going beyond its limits. The height of such a welt is specified by the sample.

The top with the welt is assembled by soldering, in most cases on the veins. Veinscan serve as pieces of round and rolled wire or a tubular blank. The cross-section of the veins is determined by the distance at which the top should be separated from the welt. The sections for the veins are soldered onto the welt. The number of veins and the distance between them are chosen depending on the size of the product and its contour. For tops set with small stones, the veins are soldered so that each vein is under the top stone. The veins soldered onto the welt are tucked flush with the inner contour of the welt, and the outer side is cut off after assembly with the top. Then the welt is tied to the top and all the veins are soldered to it, after which the assembled unit is processed along the outer contour. The veins extending beyond the contour are cut off, and the contour of the node is filed down.

Dikel (Fig. 88) is a type of welt. It does not extend beyond the horizontal dimensions of the top, but, being convex, it increases the dimensions in height and covers a significant part of the back side of the top. If the dikel is made smooth, then in the center it should have a significant cutout in the shape of the top, but if it is openwork, then the central cutout may be smaller. The openwork pattern of the dikel is chosen, if possible, so that back side stones fixed at the top was open for washing.

Dikel is used mainly for rings and earrings.

The dimensions of the dikel are determined by the contour of the top. It is made from rolled steel with a thickness of 0.7-0.9 mm. The marking is carried out on a flat workpiece. If the dikel is blind, mark the central hole, and if it is openwork, mark the entire pattern. The base of the workpiece is sawed onto a plane and adjusted to the base of the top. The pattern is cut out with a jigsaw and processed with a needle file.

When assembling tops with dikel, veins are used mainly for blind dikels, which are sometimes connected to the tops through veins. In all other cases, the dikel is soldered directly to the top with the entire base or individual sections of an openwork cut base.

Not all machine parts have contours outlined by straight lines, like those discussed in previous chapters; many details represent flat surfaces limited on the sides by curved contours. In Fig. 222 shows parts with curved contours: wrench(Fig. 222, a), clamp (Fig. 222.6), cam for the automatic lathe (Fig. 222, c), engine connecting rod (Fig. 222, d).

The curvilinear contour shown in Fig. 222 parts consists of straight segments conjugated with curves or circular arcs various diameters, and can be obtained by milling on a conventional vertical milling or special copy milling machine.

Milling curved contours on a vertical milling machine it can be carried out: by marking by combining manual feeds, by marking using a round turntable and by copier.

Milling a curved contour using a combination of manual feeds. Milling by combining manual feeds means that a pre-marked workpiece (fixed either on the table) milling machine, either in a vice or in special device) is processed with an end mill, moving the table by hand in the longitudinal and transverse directions simultaneously so that the cutter removes the metal layer in accordance with the marked curved contour.

Let's consider an example of milling along markings by combining manual feeds of the contour of the bar shown in Fig. 223.

Choosing a cutter. For milling we select end mill, the diameter of which would allow us to obtain the rounding R = 18 mm required by the drawing. We take an end mill with a diameter of 36 mm with six teeth. The cutter material is high-speed steel.

Preparing for work. The bar is installed directly on the table of the vertical milling machine, securing it with clamps and bolts as shown in Fig. 224. A parallel backing is used to ensure that the cutter does not touch the work surface machine table.

During installation, care must be taken to ensure that chips or dirt do not get between the contacting surfaces of the machine table, backing and workpiece.

Setting up the machine for cutting mode. Since in our case the feed is carried out manually, we will take it equal to 0.08 mm/tooth, considering the cutting depth to be 5 mm. According to the table 211 of the “Handbook for Young Milling Operators” for these conditions the recommended cutting speed is 27 m/min and the corresponding number of cutter revolutions n = 240 rpm.

Let's select the closest speed available on the machine and set the gearbox dial to n = 235 rpm, which corresponds to a cutting speed of 26.6 m/min.

Contour milling. We will carry out milling with manual feed, following the markings, for which we will start processing from the area where there is the smallest allowance, or we will carry out the plunge gradually, over several passes, in order to avoid breakage of the cutter.

Milling is carried out by simultaneous feeding in the longitudinal and transverse directions, respectively, along the marking line. It is impossible to mill the contour completely in one pass, so first the curved contour is rough-milled, and then completely along the marking line, including the curves at the wide part of the plank.

Milling of a central groove 18 mm wide and 50 mm long is carried out using the method of milling a closed groove (see Fig. 202).

Curvilinear contours in the shape of a circular arc in combination with or without straight segments are processed on a round turntable (see Fig. 146 and 147).

When processing on a round rotary table, the arc contour is formed without combining two feeds as a result of the circular feed of the rotary table, and the accuracy of the contour here depends not on the ability to combine two feeds, but on correct installation preparations on the table.

Let's consider an example of milling a part, where the processing of the outer contour is combined with the processing of internal circular grooves.

Let it be necessary to process the contour template shown in Fig. 225.

The workpiece has the form of a rectangle measuring 210×260 mm, 12 mm thick. The workpiece is pre-drilled with a central hole with a diameter of 30 mm (for mounting it on a round table) and four auxiliary holes with a diameter of 30 mm (for milling). The outline of the part is marked on the workpiece.

Milling will be carried out on a vertical milling machine. Since external and internal contours, then milling must be done in two settings:

1. Having secured the workpiece on the round table with bolts passed through any two holes on the workpiece, we mill the outer contour according to the markings, using the rotational movement of the round table (Fig. 226, a).

2. Having secured the workpiece on the round table with clamping strips, we mill the internal circular grooves according to the markings, using the rotational movement of the round table (Fig. 226,

Since it is desirable to process the outer contour and internal grooves without changing the cutter, we select an end mill made of high-speed steel with a diameter of 30 mm corresponding to the width of the circular groove.

Before installation round table it is necessary to place it on the edge and wipe its base. Then insert clamping bolts with nuts and washers into the grooves of the machine table on both sides and secure the round table with the bolts. To base the workpiece, you need to insert a centering pin with a diameter of 30 mm into the central hole of the round table.

We secure the workpiece with a centering pin and bolts during the first installation (Fig. 226, a) and with a centering pin and clamps during the second installation (Fig. 226, b).

Setting up the machine for milling mode. Select the cutting speed according to the table. 211 of the “Young Miller’s Handbook” for a cutter with a diameter of 30 mm and a feed for £tooth = 0.08 mm/tooth, with the greatest cutting depth t = 5 mm. Cutting speed v = 23.7 m/min and, accordingly, n = 250 rpm.

We set the machine to the nearest speed n = 235 rpm, which corresponds to the cutting speed v = 22.2 m/min, and begin processing the outer contour.

Having secured the end mill to the machine spindle, turn on the machine and bring the part to the cutter in the place where there is the smallest allowance (Fig. 226, a).

A rotating cutter is cut into the workpiece by hand feed to the marking line and, turning on the mechanical longitudinal feed, straight section 1-2 is milled (Fig. 225). When manually rotating a round table, milling curved section 2-3 external circuits. After this, a straight section 3-4 of the outer contour is milled using mechanical longitudinal feed, and finally, a curved section 4-1 of the outer contour is milled again with manual rotation of the round table.

The workpiece for milling circular grooves is installed as shown in Fig. 226, b.

By rotating the handle vertical, longitudinal and cross feed bring the cutter (see Fig. 226, b) and insert it into hole 5 (see Fig. 225). Then the table is raised, the table console is locked and the internal groove 5-6 is smoothly milled using a manual circular feed of the round table, slowly rotating the handwheel. At the end of the pass, lower the table to its original position and remove the cutter from the groove. By rotating the circular and vertical feed handles, insert the cutter into hole 7 and mill the internal groove 7-8 in the same way using a circular feed.

Copier milling. Milling of parts having a curved contour, curved grooves and other complex shapes can be done, as we have seen, either by combining two feeds, or by using a rotary round table; in these cases, preliminary marking is required.

When producing large batches of identical parts with a curved contour, use special copying devices, or use special copy-milling machines machines.

The operating principle of copying devices is based on the use of longitudinal, transverse and arc feed of the machine table to impart a curvilinear movement to the workpiece, exactly corresponding to the contour of the finished part.

To automatically obtain this contour, copiers are used, i.e., templates that replace markings. In Fig. 227, b shows the milling of the contour of the large head of the engine connecting rod. Copier 1 is placed on part 2 and securely fastened to it. Acting with the circular feed handwheel of the round rotary table and the longitudinal and transverse feed handles, the milling operator ensures that the neck 3 of the end mill is constantly pressed against the surface of the copier 1.

copier processing,

The end mill used for is shown in Fig. 227, a.

In Fig. 228 shows a diagram of a copying device for milling the contour of a large engine connecting rod head similar to that shown in Fig. 227, but using, in addition to the copier, a roller and a weight. Under the influence of load 1, roller 2 is always pressed to the copier 5, rigidly connected to the table of the copying device 5, on which the connecting rod 4 being processed is fixed. The cutter 3 will describe a curved path corresponding to the contour of the large head of the connecting rod if, using a circular feed, we rotate the round rotary table .