CNC Technology – Page 75 – CNC Machining & Turning, Milling, Metal parts

CNC machining – precision hardware parts

In the production of CNC lathe, precision control has an important influence on the product quality. The machining accuracy depends on the mechanical accuracy, programming accuracy, servo accuracy and error compensation value accuracy. In order to improve the machining accuracy of CNC lathe, the machining accuracy of CNC lathe can be effectively improved in the design stage through CAD design and computer simulation technology. Strengthening the maintenance of the machine in use can effectively guarantee the high precision state of the CNC lathe.

1. Analysis of machining accuracy of CNC lathe

At present, the classification of CNC lathe is mainly set precision, position precision and machining precision. Different brands of CNC lathes have different material rigidity (the quality of CNC lathe equipment), and the working temperature will have a variety of effects on the machining accuracy of CNC lathes. The geometric accuracy of CNC lathe can be further subdivided into spindle geometric accuracy and linear motion accuracy.

In the machining operation of CNC lathe, the relative position between the main shaft and the rotating shaft remains relatively fixed. In actual production and theoretical knowledge, the relative spatial position between the two shafts does not have to be relatively fixed. This is because the bearing elements that make up the spindle may have different degrees of errors in the production plant where the lathe equipment is manufactured, and will be affected by the temperature, working strength, lubrication and other conditions during the use process. Due to the bearing accuracy of the main shaft, the manual assembly quality of the main shaft box is different, the mechanical vibration of the main shaft and rotating parts in the process of processing causes the runout, the roundness of the bearing journal of the central shaft is unstable in the manufacturing process, the concentricity before and after has certain error, and the thermal deformation may occur in the working process of the main shaft. All these factors affect the spindle geometric accuracy of CNC lathe.

In addition to the geometric accuracy error caused by the spindle in CNC lathe machining, the orbit may also affect the position accuracy of the machine due to the friction and the inertia matching of the servo motor used in CNC lathe machining. Some parts of CNC lathe that need to work continuously, such as cylinder pump, motor, hydraulic machine, etc., need to work continuously for a long time (even 24 hours). In the process of working, friction causes the specific internal parts. Because of the thermal expansion and deformation of the processing heat, the actual production size of the parts deviates from the designed predetermined size. Because of the role of internal heat, the asymmetry of the components of CNC lathe equipment results in the deformation of the production and processing parts. Therefore, the thermal deformation of the components of CNC lathe equipment will have a great impact on the position accuracy of the machine The effect of the key.

The machining accuracy of CNC lathe is closely related to the geometric accuracy of the whole CNC lathe, not only to the position accuracy, but also to the transmission system failure of CNC lathe machining, the inspection of fault compensation system, the friction of machine structural parts, the position error of cutting tools, etc., as well as to whether the program editing of CNC lathe machining is correct and the production process is reasonable. Therefore, in the actual production, in order to improve the machining accuracy of CNC lathe, we must improve the geometric accuracy and position accuracy of CNC lathe machining.

Analysis of CNC machining structure technology

The structural processability of large CNC machining parts refers to the adaptability of parts to machining methods, that is to say, the designed parts structure should be easy to machining and forming, with low cost and high efficiency. When machining parts on CNC lathe, we should carefully examine the rationality of part structure according to the characteristics of CNC turning. In the structural analysis, if any problem is found, the designer or relevant department shall generally ask for instructions and put forward modification opinions.

When CNC machining CNC lathe turning parts, the tool only makes plane movement, its forming movement form is relatively simple, and the tool path is not too complex. In the process of structural technology analysis, for the parts with narrow space and poor structural rigidity, such as small deep hole, thin-walled part, narrow deep groove and so on, the factors such as tool path, tool type, tool angle, cutting amount, clamping method and so on should be specially considered when arranging the working procedure, so as to reduce the tool loss, improve the machining accuracy, surface quality and labor productivity.

How to change tools in CNC operation

When programming a large-scale computer gong, the selection of tool setting point should be considered first. The determination of tool setting point and tool change point is the starting point of tool movement relative to workpiece in the process of numerical control machining. Since the program is also executed from this point, the tool setting point is also called the program starting point or starting point. When the machining accuracy requirements are not high, some surfaces on the workpiece or fixture can be directly used as the tool alignment surface; when the machining accuracy requirements are high, the tool alignment point should be selected on the design basis or process basis of the part as much as possible, for example, for the parts with hole positioning, the axis of the hole taken as the tool alignment point is more appropriate. The tool setting point must have a certain coordinate relationship with the positioning datum of the workpiece. In this way, the relationship between the coordinate system of the machine tool and the workpiece can be determined. The selection of tool setting point in computer gong processing should be convenient for the calculation of coordinate value and the tool setting. During the tool setting, the tool setting point shall coincide with the tool position. The so-called tool point refers to the intersection of the tool axis and the tool bottom surface for the flat end milling cutter; the ball end milling cutter refers to the ball center of the ball head part; the turning tool refers to the tool tip; the drill bit refers to the drill tip; for the machining of Dongguan Mechanical parts, for the WEDM machine, it refers to the focus of the WEDM axis and the part surface. (1) Stress and warpage analysis based on double side flow technology

According to the analysis results of gate solidification effect and pressure and temperature distribution, the stress and warpage analysis module calculates the change of stress with time in the wall thickness and plane direction of the product and the shrinkage of the product in the wall thickness direction at the time of demoulding. A special double-layer shell element is used to predict the warpage of the product at the time of demoulding.

(2) The combination of numerical calculation and artificial intelligence technology

Traditional CAE software is basically a passive computing tool. Before analysis, users need to design the forming scheme and process parameters first, and often do not know how to use the analysis results to guide production after analysis. To a certain extent, this has affected the promotion and popularization of CAE software. In order to play a greater role in CAE software, HsCAE 6.10 successfully introduced artificial intelligence technology. In the simulation system, the parameters with continuous value space, such as injection time and injection temperature, are optimized by the method of artificial neural network, and the interpretation and evaluation of the analysis results are processed by the method of rule-based reasoning.

There are two lights on the power supply of NC machining center unit, one is the power indicator light, which is green; the other is the power alarm light, which is red. The power supply unit here includes the power input unit and the power control part.

When the power of CNC machining center cannot be connected, if the power indicator light (green) is not on.

Fuse F1 and F2 of power supply unit have been blown. This is caused by high input voltage, or the components of the power supply unit itself are damaged.

The input voltage of CNC machining center is low. Please check the voltage entering the power supply unit. The allowable voltage is AC 200V + 10%, 50Hz ± 1Hz.

The power supply unit is poor, and there is damage in the unit

The power indicator light is on and the alarm light disappears, but the power cannot be connected.

This is because the power on condition is not met. By the following switch circuit, the conditions for power on are as follows:

There are three conditions for turning on the power supply of CNC machining center: (1) the source on button is closed. Dongguan Mechanical parts processing (2) power off button is closed. (3) The external alarm contact is open.

In the process of using CNC machining center, there may be tool imbalance. If not adjusted in time, the processing effect will be affected. Therefore, we should always pay attention to the tool balance of CNC machining center. The main reasons for the imbalance of the tool handle are the asymmetry of the tool design, the defects in the tool body, and all the adjustments on the tool. The tool with correct balance can significantly reduce the noise and vibration, which can increase the tool life and improve the accuracy consistency of parts.

The centrifugal force of CNC machining center magnifies the vibration caused by unbalance in proportion to the square of speed. The vibration of CNC machining center caused by this increase minimizes the life of bearing bush, bearing, shaft, spindle and gear.

Before balancing the tool in CNC machining center, it is necessary to measure the unbalance and the angle position of each selected correction plane. These variables are measured on two general types of balancing machines: non rotating or gravity machines for measuring single plane imbalance, and rotating or centrifuge for measuring single plane or two plane imbalance.

After determining the magnitude and angle of the unbalance in the correct plane, you can correct it by adding or removing material from the workpiece. Machining center for components that are not tools, the most widely used material adding method of drilling and tapping center is to weld the counterweight on the components. Other methods for components with slight unbalance include adding solder to the component body or adding weight in pre drilling.

, stable high precision:

The main parts of gantry milling equipment, such as crankshaft, gear, transmission shaft and so on, have high wear resistance after hardening and heat treatment. The long-term performance is stable, ensuring the requirements of high accuracy and stability.

2、 Slider adjustment mechanism:

The sliding speed adjustment is divided into manual adjustment and electric adjustment, which is convenient, reliable, safe and fast with an accuracy of 0.1mm.

3、 Reliable and safe operation performance:

CNC machining selection and positioning reference

① Try to choose the design basis as the positioning basis;

② When the positioning datum and the design datum cannot be unified, the positioning error shall be strictly controlled to ensure the machining accuracy;

③ When the workpiece needs to be clamped for more than two times, the selected benchmark can complete the processing of all key precision parts in one clamping and positioning

④ The selected benchmark shall guarantee to complete as many processing contents as possible;

⑤ In batch machining, the positioning datum of parts should coincide with the tool setting datum of workpiece coordinate system as much as possible;

⑥ When it is necessary to clamp several times, the benchmark shall be uniform.

Contents and scope of CNC machining self inspection

1. Before processing, the processor must clearly see the contents of the process card, clearly know the parts to be processed, shapes, dimensions of drawings and know the processing contents of the next process.

2、 Before clamping the workpiece, measure whether the blank size meets the drawing requirements. When clamping the workpiece, carefully check whether the placement is consistent with the programming operation instruction.

3. After rough machining, self inspection shall be carried out in time so as to adjust the data with errors in time and effectively. The content of self inspection is mainly the position and size of processing parts. For example: (1). Whether the workpiece is loose; (2). Whether the workpiece is correctly divided; (3). Whether the dimension from the processed part to the reference edge (reference point) meets the drawing requirements; (4). Position and dimension of machining parts. After checking the position and dimension, measure the rough machined shape ruler (excluding arc).

4. Finish machining can only be carried out after rough machining and self inspection. After finishing, the workers shall conduct self inspection on the shape and size of the processed parts: inspect the basic length and width of the processed parts of the vertical surface; measure the base point size marked on the drawing for the processed parts of the inclined surface. 5。 The workers can remove the workpiece and send it to the inspector for special inspection after completing the self inspection of the workpiece and confirming that it is in conformity with the drawings and process requirements.

What are the processing methods of CNC milling machine

With the continuous development and innovation of high technology, there are more and more CNC milling machine processing methods. What are the specific processing methods? People may not know how to process it. If there is anything else you don’t know, you can pay attention to the following information!

1. Flat hole system parts

It is commonly used to process point and line controlled computer gongs (such as CNC milling machine and drilling machine). When selecting the process route, two principles of processing accuracy and efficiency are mainly considered.

2. Rotating parts

Commonly used CNC lathe or grinder processing.

a. Consider machining efficiency: when machining on lathe, the machining allowance is usually large, so the rough machining route must be reasonably arranged to improve the machining efficiency. In practical programming, it is generally not suitable to use cycle command (otherwise, there are too many empty knives with working speed). Shenzhen computer gongs processing a better way is to use a rough car as soon as possible to cut materials, and then fine car.

b. Consider the tip strength: the CNC lathe often uses low strength tools to process small grooves.

3. Flat profile part

a. Direction control of cut in and cut out: radial cut in, with pits left on the workpiece surface; horizontal cut in and cut out, with smooth workpiece surface.

b. Selection of the first approximation method: when the computer gong machine tool which only has the function of line and arc interpolation processes the irregular curve contour, it needs to use the small straight line segment or arc segment to approximate the processed contour (its error is called the first approximation error). When approaching, the Shenzhen computer gong processing should make the workpiece error within the qualified range and the number of program segments less.

What are the classifications of machining centers for large CNC milling machines

There are many kinds of machining centers for large-scale gantry CNC milling machines. Here is a brief introduction:

A horizontal machining center: refers to the machining center with the spindle axis parallel to the workbench, which is mainly suitable for machining box type parts.

B vertical machining center: it refers to the machining center set vertically between the spindle axis and the workbench, which is mainly used for machining complex parts such as plates, plates, molds and small shells.

C multi axis linkage machining center, also known as universal machining center: it refers to the machining center that can control linkage change through the angle between the machining spindle axis and the rotary axis of the worktable to complete complex space surface machining. It is applicable to the machining of impeller rotor, mould, cutting tool and other workpieces with complex space curved surface

How to add the fourth and fifth axis in CNC machining

CNC is a typical set of high-tech in one machining equipment, its development represents the level of a country’s manufacturing industry, has been highly valued at home and abroad.

Compared with general CNC machine tools, CNC has the following outstanding features:

1. Fully enclosed protection all CNC have protective doors. When processing, closing the protective doors can effectively prevent personal injury accidents.

2. In the process of centralized processing, CNC processing is connected with multiple feeding shafts (more than three shafts), even multiple spindles, and the number of linked shafts is also very large, such as three-axis linkage, five axis linkage, seven axis linkage, etc., so it can actively complete the processing of multiple planes and multiple view points, and complete the high-precision processing of disordered parts. The last clamping in CNC can finish milling, boring, drilling, expanding, reaming, tapping and other processing, with highly centralized process.

3. With the use of multiple tools, the active AC CNC with tool magazine and active tool change equipment, the required tools are loaded into the tool magazine before machining, and the active tool change can be controlled by the program during machining.

4. If there are active communication worktables on the worktable active communication CNC machining, one worktable can be finished together and the other worktable can be finished to clamp the workpiece, and then greatly shorten the auxiliary time and improve the processing power.

5. It has powerful functions and tends to compound machining. CNC machining can compound turning and grinding functions. For example, the circular worktable can drive the workpiece to rotate at high speed, the cutter only makes the main movement without feeding, and the turning process is similar. This makes CNC have a wider processing scale

6. High active, high-precision and high-power CNC has high spindle speed, feed speed and rapid positioning accuracy, which can be reasonably selected by cutting parameters, fully show the cutting performance of the tool, reduce the cutting time, and all the processing processes are connected, all kinds of auxiliary actions are fast, high degree of initiative, and reduce the auxiliary action time and shutdown time. Therefore, the production power of CNC is very high High.

7. Due to the high level of intelligence, messy structure and powerful function of CNC, the cost of one-time investment and routine maintenance of CNC computer gongs is much higher than that of general machine tools.

8. It is very important for the rational application of CNC to show the best efficiency of CNC machine tools under proper conditions, that is, to show the advantages of CNC machine tools in the process of application, and to fully reflect the efficiency of CNC machine tools.

Six basic actions of fixed cycle in CNC machining center

he fixed cycle of computer gong processing center is generally composed of six movements:

Action 1 – x-axis and y-axis positioning: make the cutter quickly position to the hole machining position.

Action 2 – break to R point: the tool feeds rapidly from the initial point to R point.

Action 3 – hole machining: the action of hole machining is performed in the way of cutting feed.

Action 4 – hole bottom action: including pause, spindle quasi stop, tool shift and other actions.

Action 5 return to R point: select r point when the hole processing can be continued and the tool can be moved safely.

Action 6 return to the initial point: generally, the initial point shall be selected after the hole processing is completed.

CNC machining center common instruction programming

Many instructions often used by machining centers are the same as those of CNC machine tools, which will not be described here. Only some instructions reflecting machining center features are described below:

1. Accurate stop verification instruction G09

Instruction format: G09;

It can be used for machining parts with sharp edges and corners.

2. Tool offset setting command G10

Instruction format: g10p_ R_ ;

P: Command offset number; R: offset

Tool offset can be set by program setting.

3. Single direction positioning command G60

Instruction format: G60 x_ Y_ Z_ ;

10. Y and Z are the coordinates of the end point to be accurately located.

For hole machining that requires precise positioning, using this command can make the machine tool realize single direction positioning, so as to eliminate the machining error caused by reverse clearance. The positioning direction and overshoot are set by parameters.

4. Precise stop verification mode command G61

Instruction format: G61;

This instruction is modal instruction. In G61 mode, it means that every program contains G09 instruction.

5. Continuous cutting mode command G64

Instruction format: G64;

This command is a modal command and also the default state of the machine tool. After the tool moves to the end of the command, it will not slow down and continue to execute the next program segment, which will not affect the positioning or verification in G00, G60 and G09. G64 is used to cancel G61 mode.

6. Automatically return reference point instructions G27, G28, g29

(1) Return reference point verification instruction G27

Instruction format: G27;

10. Y and Z are the coordinate values of the reference point in the workpiece coordinate system, which can check whether the tool can be positioned on the reference point.

Under this command, the commanded axis moves back to the reference point quickly, decelerates automatically and makes positioning inspection at the specified coordinate value. If it is positioned to the reference point, the signal light of the axis reference point will be on; if it is inconsistent, the program will check again.

(2) Automatic return to reference point instruction G28

Instruction format: G28 x_ Y_ Z_ ;

10. Y and Z are coordinate values of intermediate point, which can be set arbitrarily. The machine moves to this point first and then returns to the reference point.

The intermediate point is set to prevent movement interference with workpiece or fixture when the tool returns to the reference point.

Example: N1 G90 x100.0 y200.0 z300.0

N2 G28 x400.0 y500.0; (middle point is 400.0500.0)

N3 G28 z600.0; (the middle point is 400.0500.0600.0)

(3) Automatically return g29 from reference point

Instruction format: g29 x_ Y_ Z_ ;

10. Y, Z are the returned end coordinates

In the return process, the tool moves from any position to the middle position determined by G28, and then moves to the end point. G28 and g29 are generally used in pairs, and G28 and G00 can also be used in pairs.

For example, as shown in Figure 5-7, after machining, the tool has been positioned to point a (100170), point B (200270) is taken as the middle point, and point C (500100) is the point to be reached when g29 is executed. The procedure is as follows:

G91 G28 X100. 0 Y100.0;

M06;

G29 X300.0 Y-170.0;

Test standard before CNC machining

Inspection standard before processing:

1. After the completion of each middle division, first copy the work coordinates, and then check whether the distance from the center to both sides is the same again after clearing, so as to ensure that the middle division and the reading are correct.

2. Select, install, set and read the coordinates of Z axis. Select the appropriate tool according to the programming list, clean the tool head and the nozzle thoroughly before installing the tool, and check whether the tool is skewed with the calibration table after installing the tool. Check again after reading

Check once to avoid wrong knife and wrong number, which will cause great loss to the company.

3. Transfer program, start machining: use single section to execute before cutting, adjust the transfer speed and feed speed to the slowest speed, lower the cutter slowly, watch the machine tool display Z axis allowance, check if there is any abnormality, press the pause key immediately if there is any abnormality, and find out the original

To solve the problem, confirm that everything is normal and adjust to the right speed to start processing.

4. In the process of machining, pay attention to observe whether the machining is abnormal, whether the cutter is worn or not. If the cutter is seriously worn, pause the grinding to ensure the normal machining.