On the blank or workpiece, the outline of the part to be processed or the point or line as the benchmark is drawn with the marking tool, which is called marking. Only by drawing a line on a plane can the processing boundary of the workpiece be clearly expressed, which is called plane delineation. Machine tools need to draw lines on several different directions of the workpiece at the same time, in order to clearly indicate the processing boundary of the workpiece, which is called stereo delineation.

1. The function of machine tool marking

1) It can check whether the shape and size of the blank conform to the pattern, whether it can meet the processing requirements, and scribe the semi-finished products. It can be difficult to check the previous process.

2) Determine the processing position and allowance of each processing surface on the workpiece.

3) When some defects occur on the billet, the possible remedy can be achieved by the so-called "borrowing" method when marking.

4) Layout the material according to the scribed line on the sheet metal, so that the correct layout can be achieved and the material can be used reasonably.

2. Commonly used marking tools for machine tools and their usage

(1) Machine tool metal ruler

Metal ruler is a simple size measuring tool. The ruler body is engraved with dimension lines. The minimum distance between the lines is. Smm, its length specifications are 150 mm, 300 mm, 500 mm, lOOOmm and so on. It is mainly used to measure size and workpiece. It can also be used as a guide tool when drawing a straight line.

(2) Machine tool marking plate marking plate

Made of cast iron, the working surface is finely planned or scraped as the reference plane for marking. The scribed flat plate is generally shelved on a wooden frame. When placed, the working surface of the flat plate should be kept in a horizontal state. The working surface of the flat plate should always be kept clean. Workpieces and tools should be handled and laid down lightly on the flat plate. They should not damage the working surface. After use, they should be wiped clean and coated with oil for rust prevention of the whole loss system.

(3) Machine tool needle scribing

It is used to draw lines on the workpiece. It is made of spring steel wire or high speed steel. Its diameter is generally 3 ~ 5mm, and its tip is ground to 15. One 20. The sharp corner is hardened by heat treatment and quenching. Some scribers are welded with cemented carbide at the tip and have better wear resistance.

When in use, the needle tip should be close to the edge of the guide tool, and the upper part should be inclined outward by 15. ~ 20. It inclines about 450 to 75 in the direction of marking. As shown in Figure 24. The needle tip should be sharp, and the line should be drawn as far as possible once, so that the line drawn is accurate and clear. When the scriber is not in use, the plastic pipe should be put on to keep the tip of the needle out of the cupboard, and remember not to insert it in the pocket.

(4) Machine tool scriber

The scribed disk is used to scribe the workpiece on the scribed plate or to locate the processing position of the workpiece. The straight end of the scribed disk is used to scribe, and the elbow end is often used to correct the processing position of the workpiece, as shown in Figure 2-5.

When marking, the marking needle should be in the horizontal position as far as possible. It should not tilt too much. The extension part of the marking needle should be as short as possible. It should be firmly clamped to avoid the size change when marking. When marking, the base should always be close to the planar surface of the marking plate without shaking or jumping, and the angle between the marking needle and the surface of the workpiece marking should be kept at 40. ~ 60. (along the direction of marking) in order to reduce the resistance of marking and prevent needle tips from penetrating into the workpiece surface, the marking disc should be in an upright state after use, to ensure safety and reduce the occupied position of curved space.

(5) Sample punching of machine tools

Sample punching is used to punch holes in the processing lines drawn by the workpiece, to mark the processing boundary and to mark arcs or drill holes to locate the center. It is usually made of tool steel and hardened at the tip. Its tip angle is about 40 when used to strengthen marking. The drilling time is about 600.

When punching, the sample is flushed outward to align the tip to the center of the line, and then the sample is flushed upright to suit.

Punching clothing requires accurate location, and the midpoint should not deviate from the line, as shown in Figure 2-7. The punching distance on the curve should be smaller, the circle line with diameter less than 20 mm should punch four punches, the circle line with diameter greater than 20 mm should have more than 8 punches, and the punching distance on the straight line can be larger, but there are at least three punches in the shorter straight line, the punching distance at the intersection of the lines must be controlled appropriately, the punching depth on the thin wall or smooth surface should be shallow, and the rough surface should be shallow. It's deeper up.

3. Machine tool marking paint

In order to make the drawn lines clear, a thin and uniform coating is usually applied to the drawn parts of the workpiece.

(1) Lime water can be added with appropriate amount of kraft rubber in lime water to increase the adhesion force. It is generally used to scribe the rough surface of casting and forging blanks.

(2) Alcohol solution (lacquer and blue pigments are added to alcohol) and copper sulfate solution are used to mark the processed surface.

4. Selection of Marking Benchmark for Machine Tools

According to the difference of workpiece shape, there are three types of benchmarks perpendicular to each other on the plane.

The so-called benchmark is used to determine the points, lines and surfaces on which the geometric relations between the geometric elements on the production object are based.

1) Based on two perpendicular centerlines.

2) Based on two vertical plane projection lines in two perpendicular planes.

3) Based on a central line and its vertical plane.

5. Definition of marking benchmark for machine tools

The datum for weighing design used in drawings is called the datum for marking. The datum for marking should be consistent with the design datum. In order to reduce the unnecessary dimension conversion and make the marking convenient and accurate, it is necessary to start with the datum first, that is, to determine the position of the datum line, and then to draw the position line and shape line of other surfaces in turn.