The location of the coordinate axes in CNC machines. Designation of coordinate axes and directions of movement of the executive bodies on the schemes of machine tools with numerical control (CNC). Development of a control program and technological

13.07.2018

1. By the nature of the work performed: turning, milling, drilling, jig boring, grinding, electroerosive, sheet bending, hole punching, etc.

2. According to the degree of universality: universal (for processing parts of a wide range), specialized (for processing parts of the same type in a certain range of sizes), special (for processing one specific part, less often - several parts of the same type).

It's much more interesting to know what's going on, and mastering the coordinates is one of the first steps. Plus, it's just not that hard - we'll show you how now. Raise your right hand with your index finger extended and your thumb up as if you were imitating a gun. Now extend the second finger at a right angle to the index finger.

Even if the table is moving instead of the spindle, the manual is based on the assumption that it is moving by the spindle! This means that for table movements, we reverse the direction. This whole routine thing is just a way of reminding yourself which direction the coordinates are going. Otherwise, it doesn't matter much and you'll get used to what your machine uses pretty quickly.

3. According to the degree of accuracy: normal accuracy (N), increased accuracy (P), high accuracy (B), extra high accuracy (A), extra precise (C) machines. Foreign gradation: conventional (no designation), high precision (H), precision (P), super precision (SP), ultra precision (UP).

4. By weight: light (up to 1 t), medium (up to 10 t), heavy (up to 100 t) machines, unique (more than 100 t).

Development of a control program and technological

Each machine will have its own specific axle orientation, which you should be familiar with. Mill axes for a typical vertical machining center. Handmade- spindle movement and reverse! The cylinders in each drawing represent the machine spindle. Be sure to look at exactly how the axes are laid out on your computer.

Much more complex configurations are possible when you have more axles. For example, there is a 5-axis setup here. It's pretty simple: just take the letter of the axis and add the value. Spaces between a letter and its value are optional. You get used to them all working together quickly, but you can format them with spaces to make them more readable.

5. According to the location of the spindle: horizontal, vertical, inclined and combined.

6. According to the degree of automation: semi-automatic machines (a machine operating with an automatic cycle, the repetition of which requires the intervention of a worker), automatic machines (performs all working and auxiliary movements of the technological operation cycle and repeats them without the participation of a worker who only observes the operation of the machine, controls the quality of processing and, if necessary, adjusts the machine).

It's actually the easiest to read once you get used to it. You should be aware, by default, the system comes in and changes units as needed. Try not to change units in the middle of a program, do it at the very beginning, and then stay with the same units. They don't change your program. We'll talk more about changing units in a future article, but for now, just stay tuned. For rotation axes, we don't use dimensions for units, we use angles, usually in degrees.

Incremental and absolute coordinates

Sometimes it is very convenient to refer to incremental or relative rather than absolute coordinates. But let's say your cutter is positioned at some point and you need to cut 1 square with the corner aligned to that point. You may have used your edging lens to find a cutting tool exactly on a feature of the part. This is easy to do with relative moves.

7. By standard sizes(on largest size workpiece, table dimensions, etc.)

8. By appointment: single-purpose and multi-purpose

Machine Coordinate System (Right Hand Rule)

The standard coordinate system is a right-handed Cartesian coordinate system. The positive directions of the coordinate axes are determined by the rule right hand: the thumb indicates the positive direction of the X-axis, the index finger indicates the Y-axis, the middle finger indicates the Z-axis. The x-axis is basically always horizontal.

We now have 1 square whose bottom left corner is the starting point. There are many cases where relative movements are convenient, so the ability to switch back and forth is a lot. Sometimes we refer to relative coordinates with special axis symbols.

Origin of standard coordinate system

For now, it is enough to know that there are incremental coordinates. Displacements are another fancy way to think about relative motions. Suppose you want to process 2 identical parts. At the same time, each of them is held in a vise on your table.

Rotational movements around the axes are denoted by Latin letters A (around the X-axis), B (around the Y-axis) and C (around the Z-axis). The positive directions of rotation around these axes are defined as follows: if you place the thumb of the right hand along the axis in the positive direction, then the other bent fingers will show the positive direction of the axis of rotation.

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How to make one program that can do both parts without having to change the program for the position of each part? We can put one on the first vise and another one on the second vise. Now, by simply changing the work offset, the same program can work to make the part on the vise. We will look at them in more detail later. It is convenient to apply to aircraft for various purposes. A plane is a flat two-dimensional space defined by two axes.

You know how to visualize coordinate systems relative to your car using the left hand rule. You know what units are used to measure coordinators. You know that there is the possibility of both relative and absolute coordinates.

Additional movements parallel to the X, Y, Z axes are respectively U, V, W (secondary) and P, Q, R (tertiary). For secondary angular movements around the axes, the letters D and E are used.

Structural elements of CNC machines

Beds, columns, bases are the basic elements. They are made with increased rigidity and vibration resistance, due to the introduction of additional stiffeners. The beds are: cast iron, welded steel, concrete, granite and ceramic.

Polar coordinate system

You know that offsets allow you to move the coordinate system around for various convenient purposes. But first, we need to get you set up for use during these tutorials. Hey, one more thing, just in case you were wondering.

Create your own left and right coordinate systems and visualize how the axes will work on your machine. Which direction is positive for each axis? Pull out the manual for your machine and look for a diagram showing how its coordinate system works. Be sure to keep the manual handy, whether on paper or online. We will refer to it several times as we go through the various exercises.

Guides CNC machines have high wear resistance and provide low friction, which makes it possible to reduce the power of the servo drive and increase the accuracy of movement. They come in several types: sliding, rolling and combined guides. Sliding guides to reduce the coefficient of friction are created in the form of a sliding pair "steel (or cast iron) - plastic coating". Rolling guides have high durability and are characterized by low friction. In such guides, hardened steel strips are used, along which roller bearings move.

Views are available for perspective, top, front, and right. Download a sample engraving file from our. Look at it in every view. Their control commands were received using punched tape or magnetic cassettes. Twenty years later, in mass production, a single machine has become a machining center: its external feature is complete encapsulation. With tool storage and automatic tool change, complex workpieces can now be completely machined.

For machines, great importance is attached to good performance. This data is stored by the machine during operation or. A distinction is made depending on the processing concept. Flexible production elements Flexible production systems. The coordinate system mainly refers to the clamped workpiece.

Main drive must be capable of stepless speed control, accept large overloads and operate in a polluted environment. Usually, asynchronous electric motors serve as drives, less often - adjustable DC electric motors and electric motors together with hydraulic boosters.

In milling machines, the work spindle is the carrier of the rotating tool. If the tool is removed from the workpiece, the movement is in the positive direction. It is located parallel to the clamping surface of the workpiece. DC motors move the router table and milling head. What is the difference between DC motors and three-phase motors?

DC motors are widely used in industry, automobiles and households. Almost everyone in the house kitchen appliance and every electric tool is equipped with it. Even in industrial applications, a DC motor has its advantages; It is considered reliable and auspicious movement.

Feed drive is one of essential elements machine, which determines the total processing error. The feed movement drive is characterized by the minimum possible gaps, short acceleration and deceleration times, smooth running, low friction forces, increased kinematic chain rigidity, and an extended feed control range. As a drive, synchronous (valve) motors with permanent magnets are used, they are equipped with sensors feedback and brakes. Less commonly used asynchronous motors.

Each car has a series of DC motors, for. They are flexible and versatile. They are also preferably used in production machines. Their typical applications are where it does not depend on too much power and a compact design. DC motors are powered by direct current.

They have fixed excitation windings and moving armature; the rotor carries the armature winding while the commutator provides a regular reversal of the current direction to maintain continuous rotation. Three-phase motor A three-phase motor requires sufficient space for its control electronics, which are generally not available in household appliances. A three-phase motor operates with a so-called three-phase alternating current. These are three separate voltages alternating current, which are delivered in time offset on three separate lines.

Spindle machine tools must have increased rigidity, high rotational accuracy, increased wear resistance of seating and locating surfaces. The design of the spindle is much more complicated due to the automatic unclamping and tool clamping devices built into it, the heat removal system, and sensors.

Auxiliary elements of CNC machines include tool changers (magazines, autooperators, turrets), lubrication system, loading devices, clamping devices, chip removal devices, etc.

Three AC voltages are applied to three different coils that are set 120 degrees around in the motor. This results in a temporary displacement of sinusoidal AC voltages. Thus, three magnetic fields accumulate in three motor coils, which are also offset in time. Thus, a magnetic rotating field is generated inside the motor. In the center of the three coils is the so-called rotor, which consists of a magnetic material. The magnetic rotating field sets the rotor in a rotational motion, which exactly corresponds to the time of change of the three magnetic fields.

CNC lathes

CNC lathes are designed for outdoor and internal processing cutting workpieces of parts such as bodies of revolution, where the rotational movement of the workpiece is the main movement, and the movement of the cutting tool is the translational movement of the feed.

Lathes perform a traditional set of technological operations: turning and boring of cylindrical, conical and shaped surfaces, threading, trimming and end processing, drilling, countersinking and reaming of holes, etc. CNC lathes make up the largest share in the fleet of machine tools with CNC.

Absolute Dimension A mapping type that specifies measurement points from the origin. Rejection of web pages. When machining workpieces, the deviation of the actual web from the target path. Path deviation occurs due to programming errors, as well as games and machine tolerances.

Structural elements of CNC machines

Path control In path control mode, two or more motion axes are simultaneously controlled so that the tool tip can travel along any path. There is a possibility that the axes are only driven by simple interpolation or more complex web sync.

CNC lathes have two controlled coordinates: Z - carriage movement along the spindle axis; X - movement of the sled perpendicular to this axis. On the cross slide, either a tool holder or a revolving rotary tool head is installed, the axis of rotation of which can be parallel to the spindle axis, perpendicular or oblique. Turrets are available in four, six and twelve positions, and each position can be equipped with two tools for external and internal processing of the workpiece. Sometimes machines are equipped with two turrets, in one they fix tools for outdoor processing, in the other - for the internal.

Machining centers are mainly used in mass production, which allows you to get most of the products for a short time. The workpiece is formed using a processing material. Turning method for processing rotationally symmetrical components. The workpiece is rotated and processed by the tool.

Single block mode A special programming mode in which the machine code always traverses the block. Blueprint Drawing A drawing of a part that describes the unique outline, dimensions, and features. All requirements for the manufacture of a part must be recorded in the product drawing.

CNC lathes are equipped with a tool magazine (with a capacity of up to 20 tools), but they are rarely used, since practically no more than 10 tools are required for turning a workpiece. The use of a larger number of tools is advisable when processing hard-to-cut materials, when tools have a short tool life and when processing complex parts with a large number of operations.

Anodizing to coat aluminum for better corrosion resistance, more pleasant appearance and better wear resistance. The workpiece is firmly fixed on the workpiece holder. Rotary tool removes material. Cutting radius compensation function in machine code to automatically adjust the programmed path according to the cutter radius.

The teeth and cutters of the locknut work in opposite directions. Gear cutter teeth and workpiece work in the same direction. The result is high wear resistance and gliding properties. Semi-finished products A semi-finished product is a finished product that is subsequently processed. Example: pipes, metal plates, rods. A workpiece is made from a semi-finished product.

Multi-purpose machines (machining centers)

A multi-purpose machine is a metal cutting machine designed to perform several various kinds machining, having a numerical control system and equipped with an automatic tool change system.

Multi-purpose machines are universal equipment and are divided into two groups:
- turning-drilling-milling-boring, designed for processing workpieces of parts such as bodies of revolution (the layout of such machines is similar to the layout of traditional CNC lathes);
- milling-drilling-boring, designed for processing blanks of body and flat parts (the layout of these machines is similar to the layout of CNC milling machines);

There are linear curved connections or even smooth splines, parabolic and circular connections. Chain measurement For a chain or incremental dimension, the dimensions are set at the previous control point. Due to the dimensions of the chains, the dimensional tolerance of the chain adds up.

There are rotational bodies and tensile bodies. Digital control Device for electronic control machine. Previously, without a computer, today there is only. Bias English word for "shift". Offset often performs zero offsets and tolerance compensation.

Rotational machining centers differ from conventional CNC lathes in that they can perform machining with a rotating tool, have the ability to accurately angular position the spindle, and rotate the spindle in circular feed mode. Therefore, these machines can perform all types of turning, as well as milling, drilling, boring and other operations (processing off-center holes, milling flats, keyways, shaped grooves, longitudinal and transverse planes, profile grooves, etc.)

CNC milling-drilling-boring machines are designed for processing flat and shaped surfaces, bodies of revolution, gears, etc. The main movement is rotational and is reported to the tool fixed in the machine spindle, and the workpiece fixed on the table makes a translational feed motion. These machines perform the following technological operations: milling, drilling, boring, threading, countersinking, reaming, processing quality control, etc.

CNC milling-drilling-boring machines are equipped with an automatic tool change system of manipulator or non-manipulator types. The necessary stock of tools is created in turrets or tool magazines of drum or chain designs. Some machines have 1, 2 or 3 axis swivel head and table designs, allowing the most complex surfaces to be machined with a minimum number of setups. Many machines are equipped with automated workpiece change systems. At the same time, during the operation of the machine, the workpiece is installed (or the part is removed) on the interchangeable table-satellite, and together with it it enters the main table of the machine.

The layout of the machining center of any model, in addition to the usual parameters, is determined by its technological capabilities. These include: the size of the working space, the characteristics of the tool block, the capacity of the tool magazine, the tool change time, the number of satellite tables, their dimensions, the time for changing satellite tables, the type of control system, the number of simultaneously controlled coordinates, the discreteness and accuracy of movements along coordinates and others

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What is a post processor?
The post processor is software module, designed to convert the control trajectory generated by the CAM system into a control program for a specific CNC machine, taking into account the features of its kinematics

The operation of a CNC machine is closely related to the concept of a coordinate system. Each CNC machine has its own coordinate system. The coordinate axes are parallel to the guides of the machine, which allows you to program the direction and magnitude of movement of the working bodies. In accordance with GOST 23597, a right-handed coordinate system is adopted in which the positive direction of movement is taken to be such a movement in which the tool and the workpiece move away from each other. The standard designations X, Y, Z are accepted for the main axes. Circular movements of the tool, for example, angular displacement of the spindle milling machine, denoted by the letters A - around the X axis, B - around the Y axis, C - around the Z axis. It should be noted that the concept of circular rotation does not include the rotation of the spindle carrying the tool or the spindle lathe. To indicate the direction of movement of two working bodies along one straight line, the so-called secondary axes are used: U (parallel to X), V (parallel to Y), W (parallel to Z). For three movements in one direction, the tertiary axes P, Q, R are used.

In the machine coordinate system selected in accordance with GOST 23597, the positive directions of the coordinate axes can be determined by the right hand rule. The thumb indicates the positive direction of the X axis, the index finger indicates the Y axis, and the middle finger indicates the Z axis. Positive rotation around these axes is determined by another right hand rule. If you point the thumb in the positive direction of the axis, then the other bent fingers will indicate the positive direction of rotation.

The orientation of the axes of the coordinate system is determined in accordance with the following considerations: on boring, drilling, milling, turning machines, the Z axis is always associated with a rotating element of the machine - the spindle. In this case, the direction of withdrawal of the drill from the workpiece is taken as positive. The X-axis is perpendicular to the Z-axis and parallel to the workpiece installation plane. If two axes fit this definition, then the X-axis is taken to be the one along which the greatest movement of the machine unit is possible. The Y-axis is then defined according to a right-handed rectangular coordinate system.

The origin of the machine coordinate system is aligned with the base point of the node carrying the workpiece. The point taken as the origin of the coordinate system is called the zero point of the machine or machine zero. For example, for lathes, most often the machine zero along the X axis is taken as the axis of the machine centers, and the machine zero along the Z axis is the plane of the spindle or chuck.

In practice, a fixed position of the working body of the machine is used (for example, a tool turret). In this case, the fixed position is described by a point with coordinates relative to the zero of the machine. Machine zero and fixed position are linked through machine parameters stored in the CNC memory. Most often, when starting the machine, for example, at the beginning of the working day, the operator or adjuster needs to move the working body of the machine to a fixed position, for which the CNC has a special mode, and a special key on the control panel. To implement the "exit to a fixed point" mode on CNC machines, microswitches are used that are installed on the moving parts of the machine and cams that are set to the desired position on the stationary parts of the machine, for example, on the bed. When moving the working body in the “exit to a fixed point” mode, the microswitch button is pressed (released) when hitting the cam, the CNC registers this circumstance, gives a command to stop the movement and remembers this position of the working body in its own memory. Thus, information about the position of the working body relative to the zero of the machine is recorded in the memory of the machine. Further, during the operation of the machine, the CNC constantly monitors the movement of the working body of the machine and provides information about the location of the working body relative to the zero of the machine to the display device (for example, a display).