Planar and spatial markings. Planar and spatial markings A mechanic's tool for marking points on parts
In the production of metal products, the source material - castings, sheet and profile products - does not correspond in size and shape to the designer's drawing. To cut off excess metal, drill, stamp, weld, or otherwise process a workpiece, key points of the drawing are applied to it. Applying to these points and lines, the processing is carried out.
Basic concept and types of markup
As a rule, unique parts and products produced in small and ultra-small series are marked. For large-scale and mass production, the workpieces are not marked; instead, they are used special equipment and control programs.
What is markup
The operation of applying the dimensions and shape of a product to workpieces is called marking. The purpose of the operation is to designate the places where the part should be processed and the boundaries of these actions: drilling points, bend lines, weld lines, markings, etc.
Marking is done with points, which are called cores, and lines, which are called risks.
Marks are scratched into the metal surface with a sharp tool or applied with a marker. Cores are packed special tool- center punch.
According to the method of execution, there are such types of markup as:
- Manual. It is made by mechanics.
- Mechanized. Performed using mechanization and automation tools.
Based on the application surface, they are distinguished
- Superficial. It is applied to the surface of the workpiece in one plane and is not associated with the lines and marking points applied to other planes.
- Spatial. It is carried out in a unified three-dimensional coordinate system.
The choice between surface and is determined, first of all, by the complexity of the spatial configuration of the part.
Markup requirements
Plumbing markings must meet the following requirements:
- accurately convey the key dimensions of the drawing;
- be clearly visible;
- not to be abraded or lubricated during mechanical and heat treatment operations;
- don't make things worse appearance finished product.
Marking of parts must be carried out with high-quality inventory tools and devices that are subject to periodic verification.
Applying marks
The standard regulates the procedure for drawing marking lines:
- horizontal;
- vertical;
- inclined;
- curvilinear.
Applying curved elements after straight ones provides another opportunity to check their accuracy. The arcs must close the straight lines, the interface must be smooth.
Direct marks are carried out with a well-sharpened scriber, without tearing off, in one step. At the same time, the scriber is tilted away from the ruler or square so as not to introduce distortions.
Parallel lines are drawn using a square and moving it along the reference ruler to the required distance.
If the workpiece already has holes, then a special tool, a center finder, is used to attach marking lines to them.
In order to mark inclined lines, use a marking protractor with a hinged ruler fixed at its zero point.
For particularly precise markings in plumbing use calipers. They allow you to measure distances and scratch marks with an accuracy of hundredths of a millimeter.
In order to more accurately carry out the risk, cores are placed at its beginning and end. This allows you to visually control the position of the ruler while drawing.
On long risks, auxiliary cores are also placed every 5-15 cm.
Circle lines are marked at four points - the ends of perpendicular diameters.
If already treated surfaces are marked, then punching is used only at the beginning and end of the marks.
After finishing, the marks are extended to the side surfaces and the cores are placed on them.
Marking techniques
The following techniques are used in plumbing:
- According to the template. Used in case of small-scale production. The template is made from rolled metal, the entire batch is marked (or even processed) through once marked slots and holes in this sheet. For details complex shape Several templates can be made for different planes.
- Following the example. The dimensions are transferred from the part - the sample. Used in manufacturing new part to replace the broken one.
- By location. Used in the production of complex multi-component products and structures. Blanks are placed on a plane or in space in the order in which they enter the final product and are marked together.
- Pencil (or marker). Used for workpieces made of aluminum alloys so that the scriber does not destroy the passivated protective layer.
- Accurate. It is done using the same methods, but measurements and special precision are used.
The selection of techniques is carried out in accordance with design and technological instructions.
First of all, when marking, defects that occurred at previous stages of production emerge. Products from procurement sites or workshops, as well as materials purchased from other enterprises, reveal:
- violation of dimensions
- shape distortion
- warping.
Such castings or rentals are not subject to further marking operations, but are returned to the department or organization that caused the defect to correct it.
At the marking stage itself, defects can be caused by the following factors:
- Inaccurate drawing. The mechanic, without hesitation, displays wrong sizes onto the parts, and during further processing, defective products are produced.
- Inaccuracy or malfunction of instruments. All marking tools are subject to mandatory periodic verification by the metrological service of the enterprise or an authorized metrological center.
- Incorrect use of tools or marking accessories. There are known cases when instead of calibrated measuring pads, ordinary pads were used to set the level. In this case, erroneous application of angles and slopes is also possible.
- Inaccurate placement of the workpiece on the marking table or plaza. They lead to distortions when setting aside dimensions, violation of parallelism and coaxiality.
- Wrong choice of reference planes. It is also possible that some of the dimensions were applied from the base planes, and some from the rough surfaces of the workpiece.
Separately among the reasons for defects are the marker's errors. These include:
- Incorrectly read drawing. It is possible to apply the radius instead of the diameter and vice versa, inaccurate application of the centers of the holes relative to the center marks, etc. If difficulties arise, the mechanic must seek clarification from the foreman or foreman.
- Carelessness and inattention when punching and drawing lines.
The human factor, unfortunately, is the most common cause of marking defects.
Negligence can be committed by both the mechanic himself and his supervisors, who did not check the tool on time or issued inappropriate marking devices.
Typically, marking operations are entrusted to the most experienced and responsible workers, counting on the fact that they will not mechanically transfer dimensions from the drawing to the workpiece, but will treat the matter thoughtfully and promptly notice and eliminate the causes of possible defects on their own or by contacting their managers.
Marking- the operation of applying marking lines (marks) to the workpiece being processed, which determine the contours of the future part or place to be processed. The marking accuracy can reach 0.05 mm. Before marking, it is necessary to study the drawing of the part to be marked, find out the features and dimensions of the part, and its purpose. The marking must meet the following basic requirements: exactly match the dimensions indicated in the drawing; Marking lines (marks) must be clearly visible and not erased during processing of the workpiece. To install the parts to be marked, marking plates, pads, jacks and rotating devices are used. For marking, scribers, center punches, marking calipers and surface planers are used. Depending on the shape of the blanks and parts to be marked, planar or spatial (volumetric) markings are used.
Planar marking performed on the surfaces of flat parts, as well as on strip and sheet materials. When marking, apply to the workpiece contour lines(risks) according to given sizes or patterns.
Spatial marking most common in mechanical engineering and differs significantly from planar. The difficulty of spatial marking is that it is necessary not only to mark the surfaces of the part located in different planes and at different angles to each other, but also to link the markings of these surfaces with each other.
Base- a base surface or baseline from which all dimensions are measured when marking. It is selected according to the following rules: if the workpiece has at least one machined surface, it is selected as the base; If there are no machined surfaces on the workpiece, the outer surface is taken as the base surface.
Preparing blanks for marking begins with cleaning it with a brush from dirt, scale, and traces of corrosion. Then the workpiece is cleaned with sanding paper and degreased with white spirit. Before painting the surface to be marked, you must make sure that the part is free of holes, cracks, burrs and other defects. To paint the surfaces of the workpiece before marking, use the following compositions: chalk diluted in water; ordinary dry chalk. Dry chalk is used to rub the marked untreated surfaces of small non-critical workpieces, since this coloring is fragile; solution copper sulfate; alcohol varnish is used only for precise marking of the surfaces of small products. The choice of coloring composition for application to the base surface depends on the type of workpiece material and the method of its preparation: the untreated surfaces of workpieces made of ferrous and non-ferrous metals obtained by forging, stamping or rolling are painted aqueous solution chalk; the treated surfaces of ferrous metal workpieces are painted with a solution of copper sulfate, which, when interacting with the workpiece material, forms a thin film of pure copper on its surface and ensures clear identification of marking marks; the treated surfaces of non-ferrous metal workpieces are painted with quick-drying varnishes.
Marking methods
Template marking is used in the production of large batches of parts of the same shape and size, and sometimes for marking small batches of complex workpieces. Marking according to a sample is used during repair work, when dimensions are taken directly from a failed part and transferred to the material being marked. This takes wear and tear into account. A sample differs from a template in that it has a one-time use. Marking in place is carried out when the parts are mating and one of them is connected to the other in a certain position. In this case, one of the parts serves as a template. Markings with a pencil are made using a ruler on blanks made of aluminum and duralumin. When marking workpieces made from these materials, scribers are not used, since when marks are applied, the protective layer is destroyed and conditions are created for the appearance of corrosion. Defects in marking, i.e. Non-compliance of the dimensions of the marked workpiece with the data in the drawing occurs due to the inattention of the marker or the inaccuracy of the marking tool, or a dirty surface of the slab or workpiece.
Metal cutting.
Metal cutting is an operation in which excess layers of metal are removed from the surface of the workpiece or the workpiece is cut into pieces. Chopping is carried out using cutting and impact tools. The cutting tools used for chopping are a chisel, a crosspiece and a groover. Percussion instrument- plumber's hammer. Purpose of cutting: - removal of large irregularities from the workpiece, removal of hard crust, scale; - cutting out keyways and lubrication grooves; - cutting edges of cracks in parts for welding; - cutting off the heads of rivets when removing them; - cutting holes in sheet material. - cutting of rod, strip or sheet material. The cutting can be fine or rough. In the first case, a layer of metal 0.5 mm thick is removed with a chisel in one pass, in the second - up to 2 mm. The processing accuracy achieved when cutting is 0.4 mm.
Editing and straightening.
Editing and straightening- operations for straightening metal, blanks and parts with dents, waviness, curvature and other defects. You can edit manually on steel correct plate or a cast iron anvil and a machine on the right rollers, presses and special devices. Manual editing used when processing small batches of parts. Enterprises use machine editing.
Flexible.
Bending- an operation as a result of which the workpiece takes the required shape and dimensions due to stretching of the outer layers of metal and compression of the inner ones. Bending is performed manually using hammers with soft strikers on bending plate or using special devices. Thin sheet metal is bent with mallets, wire products with a diameter of up to 3 mm are bent with pliers or round nose pliers. Only plastic material is subject to bending.
Cutting.
Cutting (cutting)- separation of varietal or sheet metal to pieces using hacksaw blade, scissors or other cutting tool. Cutting can be carried out with or without chip removal. When cutting metal with a hand saw, on hacksaw and cutting-off lathes, chips are removed. Cutting materials with manual lever and mechanical scissors, press shears, wire cutters and pipe cutters is carried out without removing chips.
Dimensional processing.
Metal filing.
Filing- an operation to remove a layer of material from the surface of a workpiece using a cutting tool manually or on filing machines. The main working tools for filing are files, needle files and rasps. Using files, flat and curved surfaces, grooves, grooves, and holes of any shape are processed. The accuracy of filing processing is up to 0.05 mm.
Hole machining
When processing holes, three types of operations are used: drilling, countersinking, reaming and their varieties: drilling, countersinking, counterbore. Drilling- operation to form through and blind holes in solid material. It is performed using a cutting tool - a drill, which makes rotational and translational movements relative to its axis. Purpose of drilling: - obtaining non-critical holes with a low degree of accuracy and roughness class of the machined surface (for example, for fastening bolts, rivets, studs, etc.); - obtaining holes for threading, reaming and countersinking.
Reaming- increasing the size of a hole in a solid material produced by casting, forging or stamping. If required high quality treated surface, then the hole after drilling is additionally countersinked and reamed.
Countersinking- pre-processing of cylindrical and conical drilled holes in details with a special cutting tool - a countersink. The purpose of countersinking is to increase the diameter, improve the quality of the machined surface, and increase accuracy (reducing taper, ovality). Countersinking can be the final operation of machining a hole or an intermediate one before reaming the hole.
Countersinking- this is the processing with a special tool - a countersink - of cylindrical or conical recesses and chamfers of drilled holes for the heads of bolts, screws and rivets. Countering is carried out using counterbores to clean the end surfaces. Counters are used to process bosses for washers, thrust rings, and nuts.
Deployment- This is the finishing of holes, providing the greatest accuracy and surface cleanliness. Reaming of holes is carried out with a special tool - reamers - on drilling and lathes or manually.
45. What is markup?
Marking is the operation of applying lines and dots to a workpiece intended for processing. The outline of lines and points serves as the processing boundary for the worker.
46. Name the types of markings. „.
There are two types of markings: flat and spatial.
47. What is the difference between flat and spatial markings?
The marking is called flat when lines and points are applied to a plane, spatial - when marking lines and points are applied to a geometric body of any configuration.
48. Name the methods of spatial marking.
Spatial markings can be made on a marking plate using a marking box, prisms and squares. When marking in space, prisms are used to rotate the workpiece being marked (Fig. 9).
49. What is absolutely necessary for marking?
For flat and spatial marking, a drawing of the part and the workpiece for it, a marking plate, a marking tool and universal marking devices are required, measuring tool and auxiliary materials.
50. Name the marking tool and the main devices necessary for marking.
TO marking tool include: scriber (with one point, with a ring, double-sided with a curved end), marker (there are several types), marking compass, center punches (regular, automatic, for stencil,
for a circle), calipers with a conical mandrel, hammer, center compass, rectangle, marker with a prism. Marking devices include: a marking plate, a marking box, marking squares and bars, a stand, a thicknesser with a scriber, a thicknesser with a moving scale, a centering device, a dividing head and a universal marking grip, a rotating magnetic plate, double strubs, adjustable wedges, prisms , screw supports.
51. Name measuring instruments for marking
Measuring tools for marking are:
Graduation ruler, height gauge, sliding scale thicknesser, caliper, square, protractor, caliper, level, surface control ruler, feeler gauge and reference tiles.
52. Name auxiliary materials for marking. TO auxiliary materials for marking include:
Chalk, white paint(a mixture of chalk diluted in water with linseed oil and the addition of a composition that prevents the oil from drying out), red paint (a mixture of shellac with alcohol and the addition of dye), lubricant, washing and etching materials, wooden blocks and slats, a small tin container for paints and a brush.
53. Name simple marking and measuring tools used in plumbing work.
Simple marking and measuring tools used in plumbing work are: a hammer, a scriber, a marker, an ordinary center punch, a square, a compass, a marking plate, a graduated ruler, a caliper and a caliper.
54. On what basis are parts marked?
Planar or spatial marking of the part is carried out on the basis of the drawing.
55. Name the operations performed before marking the part.
Before marking, the workpiece must undergo mandatory preparation, which includes the following operations: cleaning the part from dirt and corrosion (do not do it on a marking plate); degreasing the part (do not do it on a marking plate); inspection of the part in order to detect defects (cracks, cavities, bends); examination overall dimensions, as well as processing allowances; determination of the marking base; white paint coating
surfaces to be marked and lines and dots applied to them; determination of the axis of symmetry.
If a hole is taken as a marking base, then a wooden plug should be inserted into it.
56. What is a marking base?
A marking base is a specific point, axis of symmetry or plane from which, as a rule, all dimensions on a part are measured.
57. What is capping?
Penciling is the operation of applying small dots-indentations on the surface of a part. They define
Centerlines and hole centers required for machining, defined straight or curved lines on a product. Marking is done with the purpose of marking on the part persistent and noticeable marks that define the base, processing boundaries or drilling location. The punching operation is performed using a scriber, a center punch and a hammer.
58. What is the pattern marking technique?
Marking using a template is used in the manufacture of a significant number of identical parts. A template made of tin 0.5-2 mm thick (sometimes stiffened with a corner or wooden strip) is placed on flat surface details and traced along the contour with a scriber. The accuracy of the applied contour on the part depends on the degree of accuracy of the template, the symmetry of the scriber's tip, as well as on the method of advancing the scriber's tip (the tip must move perpendicular to the surface of the part). The template is a mirror image of the configuration of parts, lines and points that must be applied to the surface of the part (Fig. 10).
59. What is marking accuracy?
Marking accuracy is the accuracy of transferring the dimensions q of the drawing onto the part that is being marked.
60. What determines the accuracy of marking?
The accuracy of marking depends on the degree of accuracy of the marking plate, auxiliary devices (squares and marking boxes), measuring tools, the tool used for transferring dimensions, the degree of accuracy of the marking method, as well as the qualifications of the marker.
Marking accuracy can be obtained in the range from 0.5 to 0.08 mm. When using standard tiles - in the range from 0.05 to 0.02 mm.
61. How should marking be done to avoid accidents?
To avoid accidents when marking, you should first of all be careful when using pointed scribers. To protect the worker’s hands from the tip of the scriber, it is necessary to put on a cork, wooden or plastic cover on the tip before marking begins.
Oil or other liquid spilled on the floor or marking plate can also cause an accident. When marking heavy parts, you should use hoists, hoists or cranes to install them on the marking plate.
Marking is the process of transferring the shape and dimensions of a part or part of it from a drawing to a workpiece in order to indicate the places and boundaries of processing on the workpiece. Processing boundaries separate the material that must be removed from the material that remains and forms the part.
Marking is done using various instruments, which are divided into the following types: (Fig.1.2)
1) for marking and making indentations (scribers, compasses, center punches);
2) for measuring and monitoring linear and angular quantities (metal rulers, calipers, squares, micrometers, protractors, etc.);
3) combined, allowing for measurements and marking (marking calipers, height gauges, etc.).
Scribblers are used to apply marks on the surface of workpieces.
Marking compasses in design and purpose they correspond to the drawings and are used for drawing circles and transferring linear dimensions.
The steel legs of scribers and compasses are made from U7 and U8 steels; the working ends of scribers and compasses are sharply sharpened.
Kerner serves to apply recesses on marking marks 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 steel (У7А, У8А) steel. Its working part is hardened and sharpened at an angle of 60 degrees.
Squares used for drawing lines, angles and checking them .
Marking caliper serves 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.
Chopping
Chopping - a method of machining workpieces using a chisel or cross-cutting machine. Chopping removes excess metal, cuts off burrs on parts, cuts out cavities, non-metallic inclusions, lubricating and key grooves, and cleans welds.
Chopping is carried out in cases where special processing precision is not required and a small layer of metal needs to be removed from the part. This work is labor-intensive and low-productivity, requiring large expenses physical strength, performed using a chisel, cross-cutting tool and hammer, used only in cases where it is impossible to use machine processing.
During the cutting process cutting tool hold the middle part with the left hand, and the hammer in the right, and strike with the hammer with such force that the chisel blade cuts into the metal.
To increase the productivity (6-8 times) of the cutting process, pneumatic and electric chipping hammers are used. Due to air pressure R = 5-6 atm. and electric magnetic field ensures the reciprocating movement of the striker.
Bench chisels(GOST 7211-94) are used for cutting metals and are available in lengths and widths of 100 (5), 125 (10), 150 (15), 175 (20) and 200 (25) respectively. mm. The angle of the tip is selected: for hard metal 70 o, for medium - 60 o and for soft metal - 45 o. (Fig. 1.4)
Kreutzmeisel - used for cutting out narrow grooves and keyways and differs from a chisel in having a narrower cutting part. The sharpening angles and hardening are similar to those of a chisel.
Chisels and cross mixers are made of alloy steel (7ХФ and 8ХФ) or carbon steel (У7А and У8А).
Marking is the operation of applying marking marks to the surface of a part or workpiece to be processed, defining the contours of the part profile and the places to be processed. The main purpose of marking is to indicate the boundaries to which the workpiece must be processed. To save time, simple workpieces are often processed without preliminary marking. Blanks are received for processing in the form of castings (obtained from metal poured into pre-prepared molds - earthen, metal, etc.), forgings (obtained by forging or stamping), or in the form of rolled material - sheets, rods, etc. (obtained by passing metal between rollers rotating in different directions, having a profile corresponding to the resulting rolled product).
During processing, a certain layer of metal (allowance) is removed from the surface of the workpiece, as a result of which its size and weight are reduced. When manufacturing a part, its dimensions are laid down on the workpiece exactly according to the drawing and marked with lines (marks) indicating the processing boundaries to which the metal layer should be removed.
Marking is used mainly in single and small-scale production. Three main groups of markings are used: mechanical engineering, boiler room and ship. Mechanical marking is the most common metalworking operation. Planar marking is the application of flat workpieces on sheet and strip metal, as well as on the surfaces of cast and forged parts of various lines.
When marking in space, marking lines are applied in several planes or on several surfaces.
Apply various ways markings: according to drawing, template, sample and location. The choice of marking method is determined by the shape of the workpiece, the required accuracy and the number of products. The accuracy of marking significantly affects the quality of processing. The degree of marking accuracy ranges from 0.25 to 0.5 mm.
Errors made during marking lead to defects.
TO technical requirements Marking concerns, first of all, the quality of its execution, on which the accuracy of the manufacture of parts largely depends.
The marking must meet the following basic requirements: 1) exactly match the dimensions indicated on the drawing; 2) marking lines (marks) must be clearly visible and not erased during processing of the part; 3) do not spoil the appearance and quality of the part, i.e. the depth of the marks and core recesses must comply with the technical requirements for the part.
When marking workpieces you must:
1. Carefully inspect the workpiece, when
If shells, bubbles, cracks, etc. are detected, they should be accurately measured and removed during further processing.
2. Study the drawing of the part to be marked, find out the features and dimensions of the part, its purpose; mentally outline the marking plan (installation of the part on the slab, method and order of marking, etc.). Particular attention should be paid to allowances. Allowance for processing, depending on the material and size of the part, its shape, and method of installation during processing, is taken from the relevant reference books. All dimensions of the workpiece must be carefully calculated so that after processing there are no defects left on the surface.
3. Determine the surfaces (bases) of the workpiece from which dimensions should be taken during the marking process. At planar marking The bases can be the processed edges of the workpiece or the center lines, which are applied first. It is convenient to take tides, bosses, and platikil as bases.
4. Prepare surfaces for painting.
For painting, i.e. covering surfaces before marking, use various compositions, in this case, a solution of susnendil chalk with the addition of glue is most often used. To prepare sus-netsdil, take 1 kg of chalk per 8 liters of water and bring to a boil. Then liquid wood glue is added to it again at the rate of 50 g per 1 kg of chalk. After adding glue, the composition is boiled again. To avoid damage to the composition (especially in the summer), it is recommended to add a small amount of linseed oil and drier to the solution. This paint is used to cover untreated workpieces. Coloring is done paint brushes, however, this method is ineffective. Therefore, whenever possible, painting should be done using sprayers, which, in addition to speeding up the work, provide uniform and durable painting.
Dry chalk. When rubbing the surface to be marked with dry chalk, the color becomes less durable. This method is used to paint the untreated surfaces of small non-critical workpieces.
Copper sulfate solution. Three teaspoons of vitriol are dissolved in a glass of water. The surface, cleared of dust, dirt and oil, is covered with a vitriol solution with a brush. A thin layer of copper is deposited on the surface of the workpiece, on which marking marks are well applied. This method is used to paint only steel and cast iron workpieces with surfaces pre-treated for marking.
Alcohol varnish. Fuchsin is added to a solution of shellac in alcohol. This painting method is used only for precise marking of treated surfaces on large parts and products.
Quick-drying varnishes and paints are used to coat the surfaces of large machined steel and cast iron castings. Non-ferrous metals, hot-rolled sheet and profile steel are not painted with varnishes or paints.
