CNC milling machine spindle quasi stop and positioning

In addition to the basic speed control, the CNC milling machine spindle also has position control, such as spindle quasi stop, spindle positioning, thread turning, rigid tapping and other control methods.

1. Spindle quasi stop

Spindle quasi stop is also called spindle orientation. The instruction code is M190 and the general spindle stop (M05) is different. When the spindle is stopped, the spindle must be stopped at the specified position, while the milling machine spindle motor has a torque to keep the spindle in a quasi-stop position and against the external load of the spindle. Spindle quasi-stop for the following occasions: the center of the machining center when the spindle orientation, so that the handle keyway into the spindle end key, as shown; fine boring retract the spindle when the first directional quasi-stop, the radial offset a short distance, and then axially retract the knife to avoid scratching the machined surface, as shown.

To achieve the milling machine spindle directional control, there must be a turn signal support. A turn signal is obtained according to the different spindle configuration has three ways: one is the spindle motor is installed with a rotary encoder signal; two is a rotating spindle encoder signal; three is the main external a turn signal (proximity switch).

2. Spindle positioning

In the full-function CNC milling machine, the spindle can be fixed angle positioning, such as 45°, 90°and 135°. Spindle positioning function with the power tool holder can be parts of the drilling and milling and other processing. When the workpiece cylindrical cylindrical cutting is completed, the tool holder from the drive head to the processing position. At the same time spindle positioning, drilling from the drive head.

Milling machine spindle rigid tapping

Rigid tapping is also one of the important control modes of the milling machine spindle. In the tapping process, the spindle speed and the Z-axis feedrate f_Z must be satisfied:

                    f_Z = tap pitch x spindle speed

In the normal way to tapping processing, due to the spindle and Z axis feed acceleration and deceleration characteristics are inconsistent, tapping screw on the tap must be equipped with spring chuck, in order to compensate for the Z axis feed and spindle does not synchronize the pitch error. 

The handle with a spring chuck is shown in the figure. When the thread is tapped in this way, when the tap is rotated and the Z axis is stopped, the spindle does not stop immediately, the tapping spring chuck is compressed for a distance; when the tap is rotated in the reverse direction of the Z axis, the milling machine spindle accelerates, the spring chuck is stretched again. Common way to attack the thread cycle can only meet the general accuracy of the processing of screw holes. In addition, if the spindle speed is high when the thread is tapped, the telescopic range of the spring chuck must be large enough so that the spindle speed can only be limited to 600r/min or less when tapping the thread in this way.

Rigid tapping, also known as synchronous feed tapping. Rigid tapping does not require a spring chuck and a rigid taper shank as shown. Rigid tapping, the milling machine spindle speed and Z-axis feed speed to establish a synchronous relationship, so that the spindle speed and Z-axis feed speed to ensure a linear proportional relationship, as shown.

When the tapped thread is machined with a rigid tapping thread, the spindle rotates synchronously with the Z axis feed and decelerates simultaneously when the Z axis is tapped to the command position. The spindle reverse start acceleration is also synchronized with the Z axis reverse feed start acceleration. In addition, the rigid tapping in the tap strength allows the case, the milling machine spindle speed can be high, up to 4000r/min, processing efficiency significantly improved, and the thread accuracy is guaranteed.

Siemens milling machine spindle motor and driver

Siemens milling machine spindle motor and driver are commonly used on machines. Let's get to know it today.

1. Siemens AC spindle motor

As shown in the figure for the Siemens 1PH7 AC spindle motor appearance and composition.

1PH7 AC milling machine spindle motor is a forced air-cooled asynchronous motor that is dissipated through a separately installed fan. The stator winding is embedded with a thermistor for detecting the temperature of the motor. The rotor shaft ends are connected to an encoder for detecting rotor speed and angular displacement. The encoder is connected to an external device via a cable plug or DRIVE- CLiQ interface, and the encoder can select an incremental encoder or an absolute encoder.

2. Siemens 611Ue driver

Siemens 611Ue driver is a DC common bus inverter, composed of power modules and power modules. 611Ue driver and Siemens SI-NUMERIK 802D CNC system supporting the use of milling machine spindle and servo drive. The appearance and composition of the 611Ue drive are shown in the figure.

The power module consists of rectifier module, filter capacitor and control circuit, etc., through the input of the three-phase AC rectifier, filtering, power module to provide DC bus voltage, while the power supply module also provides +5 V, +15 V and +24 V control power, through the equipment bus for the power supply module and power module internal control circuit. The control circuit, in addition to monitoring the DC bus, also performs temperature and operation monitoring, as well as enable control. There are two forms of power supply module, one is the uncontrolled power supply module (also known as feeding power module); Second, regenerative feedback power supply module (also known as feed / regenerative feedback power supply module).

The above is the basic introduction about Siemens milling machine spindle motor and driver.

FANUC milling machine spindle motor

FANUC AC spindle motors have αi series and βi series. The former is a high-performance milling machine spindle motor, and αi series of drives supporting; the latter for the ordinary spindle motor, and βiSVSP series drive matching. FANUC AC milling machine spindle motor is a variable frequency dedicated motor. As shown in the figure is FANUC αi / βi AC spindle motor appearance and composition.

FANUC αi AC spindle motor stator no chassis, stator core shape was polygonal. The core of the edge of the axial ventilation holes, the motor has a separate power supply at the end of the cooling fan, the milling machine spindle motor forced cooling, the stator core in the air directly heat; rotor and ordinary three-phase AC motor, in addition, the stator winding is also equipped with thermistor. When the motor due to overload or winding short circuit caused by winding temperature rise to a certain value, the thermistor resistance changes. The temperature detection circuit in the spindle amplifier monitors the change of the resistance value and is fed back to the CNC system via the serial bus. The CNC system can stop the control signal of the spindle immediately after the judgment and processing, and issue the alarm that the milling machine spindle motor is overheating or overload.

FANUC αi spindle motor in the magnetic sensor for rotor speed and angular displacement measurement, a 128 pulse/turn, 256 pulse/turn, 512 pulse/turn three specifications, without zero position signal (also known as a turn signal) for the Mi series, with zero position signal for the MZi series.

The above is about FANUC milling machine spindle motor basic introduction, you are welcome to continue to focus on updates.

CNC milling machine spindle motor (Part 2)

In the previous article we mainly introduced the composition of the CNC milling machine spindle motor, today we come to explore the operating principle of the spindle motor and frequency control mode.

1.Operating principle

CNC milling machine three-phase AC induction motor operating principle is shown in the figure.

Three-phase AC asynchronous motor stator winding into the three-phase AC generated after the rotating magnetic field, the speed no known as the synchronous speed. n_o = 60f/p, p for the stator winding pole pairs, f for the stator winding power supply frequency, change f to change n_o. The rotating magnetic field cuts the guide bar in the rotor core and generates an induced current in the guide bar. In this way, the rotor bar with induced current interacts with the rotating magnetic field to generate electromagnetic torque, and the rotor rotates with the rotating magnetic field at the rotational speed n_M under the action of the electromagnetic torque. Because the motor running state when the rotor speed can only be less than the synchronous speed, so called asynchronous motor; and because the rotor bar in the current from the rotating magnetic induction, it is also known as induction motor. When the power frequency f decreases, the rotating magnetic field speed no decreases, but because of the rotor mechanical inertia, the rotor speed n_M instantly remain unchanged, at this time, the rotor speed is greater than the rotating magnetic field speed, the motor is in the power brake state, the motor winding flows out.

2. Frequency control

Changing the power frequency of the milling machine spindle motor can realize the speed regulation of the motor. Three-phase AC induction motor frequency conversion speed is usually U/f and vector control. In order to meet the requirements of the three-phase AC asynchronous motor stator winding electromagnetic frequency requirements, in the rated frequency (50Hz) below the frequency control, change the frequency f at the same time also change the stator voltage U, and keep the voltage / frequency is not change. In this speed range, the maximum electromagnetic torque remains constant and constant torque is achieved. Rated frequency above the frequency control, the stator winding voltage U to maintain the rated voltage (380V) unchanged. In this speed range, the electromagnetic torque decreases with the frequency rise, and the electromagnetic power unchanged, to achieve constant power speed, as shown.

The above is a brief introduction about the CNC milling machine spindle motor operation principle and frequency control mode. 

CNC milling machine spindle motor (Part 1)

CNC milling machine spindle is driven by the spindle motor. CNC system through the control of the spindle motor to achieve the control of the spindle. At present, CNC milling machine spindle motor commonly used three-phase AC asynchronous motor and variable frequency drive.

Spindle motor drive has two configurations: First, the ordinary three-phase AC asynchronous motor and inverter; Second, the CNC system supporting the spindle motor and spindle drive. The former is often used in ordinary CNC milling machine, to achieve frequency control, positive, reverse start and stop and other basic control; the latter for multi-function CNC milling machine, in addition to the basic control of the spindle, but also to achieve orientation, positioning and spindle servo control.

Ordinary three-phase AC induction motor is consist of stator and rotor, as shown.

The stator includes a base, stator core and stator three-phase windings. The stator core is made of silicon steel sheet, and the inner circumference is covered with a coil groove. The coil groove is fitted with three symmetrical windings. The winding terminal is introduced into the junction box on the base frame and can be connected into a triangular winding or star winding. Made of silicon steel sheet stacked, the outer circumference are covered with a coil groove, coil groove cast with aluminum guide bar.

Ordinary asynchronous motor rotor is also installed on the cooling fan, when the ordinary three-phase AC asynchronous motor with the inverter speed, and the rotor speed is low, the cooling fan air volume is not enough to cool the motor, the motor easy to heat, serious will damage the stator winding insulation, resulting in short circuit. In order to meet the needs of frequency control, the development of a special frequency asynchronous motor, as shown. Frequency conversion special asynchronous motor has a special cooling fan motor, the motor body for forced cooling, fan motor power supply alone, the fan air flow and the motor speed has nothing to do. In addition, the frequency conversion asynchronous motor also improves the insulation performance of the stator winding, some frequency conversion special asynchronous motor stator winding is also embedded in the thermistor, for the motor temperature detection.

The above is the introduction about CNC milling machine spindle motor structure, welcome you continue to pay attention to the updated content.

CNC milling machine tool changer manipulator

For the use of disc magazine CNC milling machine, tool changer manipulator is essential. Cam-type tool changer manipulator and spindle with the ability to continuously achieve grasping knife, knife exchange and insert the action, the structure shown in figure.

1) Grasping the knife. The manipulator starts the motor for the first time. The motor drives the end cam and the cylindrical cam through the bevel gear. The cylindrical cam drives the cam roller to rotate the spline shaft. The spline sleeve drives the mechanical shaft by rotating it in the counterclockwise direction 65° or 75°, the manipulator grasping knife action. When the manipulator handle the knife in place switch is turned on, the robot electric brake immediately stops, completes the manipulator grasping knife control. During this time, the manipulator does not move axially.

2) Milling machine spindle loose knife mechanism action. The claws release the milling machine spindle handle, and issued the spindle release in place signal.

3) The second start of the manipulator motor, through the bevel gears simultaneously drive the end of the cam and cylindrical cam rotation, the mechanical hand shaft order to complete the knife, exchange and insertion of three movements: ①the end of the cam control rocker swing, so that the movement of the shaft , To achieve a knife action. During this time, the cam roller does not rotate, so the manipulator does not rotate. ②the end of the knife, the cylindrical cam through the cam roller to drive the spline shaft rotation, and then by the spline shaft drive the manipulator shaft rotation 180°, to achieve tool exchange action. During this period, the rocker arm does not swing, the manipulator does not move axially. ③the end of the cam again control the rocker swing, so that the movement of the robot shaft to achieve the knife action. During this time, the cam roller does not rotate, so the manipulator does not rotate. When the knife in place switch is turned on again, the manipulator brake immediately stops.

4) Milling machine spindle loose knife mechanism action, the claw clamping spindle in the handle, and issued a spindle clamping in place signal.

5) The third time the manipulator is started, the cylindrical cam drives the cam roll to rotate the spline shaft. The spline sleeve drives the mechanical hand shaft to rotate 65°or 75°clockwise to achieve the reset action. When the manipulator returns to its original position, the home switch is turned on and the manipulator's motor stops immediately.

The above is the work of CNC milling machine tool change manipulator. Tool changer through the cam and other mechanical transmission mechanism, with the manipulator motor 3 times start and stop, to achieve the original position → grasping knife → knife (spindle loose knife) → exchange → plug (spindle cutter) → reset the action process.

CNC milling machine disc tool magazine

The disc tool magazine is also a magazine that is often used in CNC milling machine. 

Disc tool magazine tool change process by the knife chopper, knife sets flip, tool changer and spindle and other action linkage to achieve. The entire tool change process by the CNC system control PLC. The disc magazine tool change is a random tool change, that is, after each tool change, the tool number and tool holder number is not necessarily the same. During the tool change, the robot can simultaneously grasp the knife from the magazine and the spindle, the knife and the knife, the tooling efficiency is high.

The disc magazine consists of cutter head motor, rotary cutter, indexing mechanism, knife cover and inverting mechanism. The cutter head motor drives the rotary cutter through the indexing mechanism. The cutter cover is fixed on the rotary cutter by the bracket, Rotate with the cutter head.

1. Select knife

When the T command is executed, the system first determines whether the tool is in the magazine. If not, the system will issue a T code error alarm. In addition, but also to determine whether the selected tool on the spindle, if already on the spindle, then complete the tool change control. And then determine the specific position of the selected tool in the magazine, if the selected tool is in the current tool change position, the turntable motor does not act, waiting for the robot to exchange the tool.

If the selected tool is not in the tool change position, the system determines the shortest path and the number of steps of the current position of the selected tool to the tool change position. The output control signal causes the turntable motor to turn forward or reverse, The count switch on the turntable moves once. When the selected tool to the tool change position, the turntable motor brake stopped to complete the T code of the knife control.

2. Knife sets flip

Since the tool axis in the magazine is perpendicular to the tool axis in the milling machine spindle, the tool holder is turned 90°downward before the tool change so that the tool axis in the tool holder is parallel to the axis of the spindle. After the tool change, turn the tool cover upside down 90°.

When the tool set of the selected tool is turned to the tool change position, the roller in the rear of the tool holder enters the fork, the front chamber of the cylinder is fed, the piston is moved up and the fork is driven to turn the tool cover 90°, knife cover down flip detection switch signal. When the cylinder is in the back chamber, the piston moves down and drives the fork to turn the tool cover up 90°, and the tool set reset detection signal is signaled.

The above is the composition of the CNC milling machine disc tool magazine and the process of change tool introduction.

CNC milling machine bamboo hat type tool magazine (Part2)

Today, let us talk about the tool change process of the CNC milling machine bamboo hat type tool magazine.

The bamboo hat type tool change is an absolute tool change, that is, after each tool change, the tool number and tool holder number is one-to-one correspondence.

Bamboo hat type tool magazine without the need to manipulate the tool, through the spindle box and spindle mechanism to achieve the linkage, the tool change process:

1) CNC system to get the tool change instructions, the spindle automatically return to the tool change point, while the spindle to achieve quasi-stop control.

2) The milling machine cutter rotates to the tool change point corresponding to the tool number (set to the old tool) on the current spindle.

3) The cutter head from the original position by the cylinder piston, when the clip to grasp the old tool on the spindle, the knife in place switch switch, said the grasping knife to complete.

4) Spindle knife action, the old knife loose, and the spindle cone hole blowing, when the spindle loose knife in place switch, said the loose knife to complete.

5) The milling machine spindle is moved up and the old tool on the spindle remains on the tool holder and the knife is finished.

6) The magazine rotates again, and the tool holder (set to the new tool) corresponds to the tool holder number to the tool change point.

7) The spindle is moved down again to the tool change point, the new tool is inserted into the spindle taper hole, and the tool change is completed.

8) Spindle knife action, the new tool in the spindle in the knife, when the spindle cutter in place switch, said the tight knife to complete.

9) Cutter cylinder cylinder retraction, when the knife reset switch is turned on, the tool change process is over.

The above is the tool change process introduction of the CNC milling machine bamboo hat type tool magazine, the next article we will introduce other types of tool magazines.

CNC milling machine bamboo hat type tool magazine (Part1)

There are a variety of CNC milling machine tool magazines. We first take a look at the bamboo hat type tool magazine.

The bamboo hat type tool magazine is mainly used for vertical machining center automatic tool change, installed in the milling machine column, the structure shown in figure.

The cutter head is equipped with a clip, each clip corresponds to a tool holder number, used to hold the handle, the tool number corresponds to the tool holder number. The entire cutter head is suspended from the two cylindrical rails on the magazine holder through the sleeve. The cylinder holder is fitted with a cylinder, the cylinder piston is connected to the cutter head, and the piston is extended or retracted. The limit of the extension or retraction of the cutter head is extended by the magnetic switch installed on the cylinder (some tool magazines are fitted with a stroke switch or a proximity switch on the bracket).

The upper part of the cutter head is equipped with an indexing sheave, and the cutter head motor drives the cam to rotate, and the roller is rotated around the motor axis. The roller cooperates with the indexing sheave. When the cam is rotated for one week, The disk turns through a knife seat, and the counting switch is turned off once. The milling machine CNC system PLC counts the input count switch signal and is controlled by the PLC to judge whether the tool holder corresponding to the tool has been transferred to the tool change position.

The above is the structure introduction of the CNC milling machine bamboo hat type tool magazine.

CNC milling machine spindle drive mode

The spindle drive modes of CNC milling machine are belt drive and gear shift drive in two ways. Now let's look at these two ways separately.

1.Belt drive

In the case of the spindle motor with a special three-phase AC asynchronous motor and a variable frequency speed control, since the spindle motor has a wide range of constant torque and constant power speed range, the spindle motor can be connected to the milling machine spindle through the drive belt. Spindle motor control to achieve the spindle speed and steering control, simplifying the spindle drive mechanism. The belt drive is used for spindle milling of CNC milling machines and medium and small machining centers.

2.Gear shift drive

In the case of spindle motor with ordinary three-phase AC asynchronous motor and frequency control, in order to obtain the spindle low speed and increase the constant power speed range, some CNC milling machine spindle gear shift.

Gear shift mechanism with hydraulic fork and electromagnetic clutch in two forms, as shown in the figure, the gear shift using hydraulic cylinder and fork for high and low two switch. When the high-speed gear, the solenoid valve action, the hydraulic cylinder piston out, through the fork to slip gear shift, Z₁ and Z₂ meshing, Z₃ and Z₄ off, high-speed detection device in place SQ1 signal, drive path: spindle motor → drive belt d₁ / d₂ → I axis → Z₁ / Z₂ → spindle. In the low gear, the solenoid valve moves, the hydraulic cylinder piston retracts, moves the slip gear by the fork, Z₃ and Z₄ are engaged, Z₁ and Z₂ are disengaged, the low gear detection switch SQ2 sends the signal, the transmission path: the spindle motor → drive belt d₁ / d₂ → I axis → Z₃ / Z₄ → spindle.

Gear shift has manual and automatic (M command) two kinds of operation.  Electromagnetic reversing valve movement and the shift position detection are controlled by the PLC of the CNC system.

The above is about CNC milling machine two kinds of spindle drive mode introduction, welcome you continue to pay attention.

Milling machine ball screw pair

The ball screw pair is an important part of the mechanical transmission of CNC milling machine. It is a transmission part that converts the rotational motion into linear motion. As shown in the diagram, the application of ball screw pair in feed transmission of CNC milling machine.

The ball screw is supported by bearings at both ends, one end is connected with the servo motor, servo motor rotates with the moving parts; nut and table connection, screw rotation, milling machine table with linear movement along the guide nut. The speed servo motor determines the feed speed of the table speed, reversing the servo motor determines the direction of feed table, servo motor rotation angle determines the moving distance table.

Circulation mode of ball screw

The ball screw is composed of a lead screw, a nut and a ball. The outer surface of the screw rod and the inner surface of the nut are provided with a spiral raceway whose cross section is arc. When the guide screw is rotated, the ball ball is rolled in the nut. There are two forms of ball bearing circulation in the nut, as shown in the diagram.

In the internal circulation mode, the ball roller changes the raceway through the reverse device arranged in the nut to achieve the purpose of circulation. In the outer circulation, the ball passes through the guide tube on the nut to change the raceway, so as to achieve the purpose of circulation.

There are a lot of knowledge about the ball screw pair of milling machine, and some basic contents are introduced here. Want to know more, welcome everybody to continue to pay attention.

CNC milling machine basic control

Although CNC milling machine has many different types and the control is simple and complex, the basic control of CNC milling machine includes spindle control, feed control and auxiliary function control.

1. Spindle control

The basic functions of spindle control include spindle reversing and spindle speed control. Control of the spindle, in fact, the spindle motor control, that is, the spindle motor forward and reverse determines the steering of the spindle; spindle motor speed determines the spindle speed. The drive of the spindle motor is realized by the spindle drive. The basic requirement for spindle control is to keep the spindle speed stable. For this reason, an encoder is provided on the spindle motor or spindle for speed detection and feedback.

In order to ensure the accuracy of position control, usually in the spindle to install the encoder for spindle position detection and feedback. With the development of technology, some milling machines use electric spindle technology.

2. Feed control

Feed control includes point control and trajectory control, as shown.

(1) point control

Machining center drilling, reaming, reaming, tapping and boring are all point control. In the point control, the tool is not cut during the rapid movement from the current position to the next position. The movement path can be set artificially, but the position accuracy between the point and the point is guaranteed.

(2) trajectory control

CNC milling machine for contour processing are trajectory control. Trajectory control, the tool according to the provisions of the path cutting the workpiece, it is necessary to ensure the accuracy of the location, but also to ensure the stability of the tool movement speed.

The control target of the feed movement is the position control and the speed control, and the accuracy of the position control, the stability of the feed speed and the fastness of the command response are ensured. To achieve this goal, the CNC milling machine has a feed motion control for position detection and speed detection, such as gratings and encoders. With the development of technology, some CNC milling machine adopts linear motor drive, eliminating the ball screw, shortening the feed mechanical transmission chain, improve the mechanical transmission stiffness and accuracy, and the rapid response speed of the servo system.

3. Auxiliary function control

The auxiliary function is controlled by the M command and the T command through PLC control of the CNC system. It involves milling machine side input and output switch, such as button, key switch, proximity switch, proximity switch, relay, contactor and solenoid valve, and PLC ladder diagram. Among them, the spindle is reversing and stopping, lubrication and cooling are all CNC milling machine with auxiliary functions, the other also includes the knife knife selection, machining center tool change, machining center spindle tensioner, and rotary table and tray exchange, etc.

Milling machine guide rail

The guide rail is one of the important parts of the feed and drive mechanism of the milling machine, supporting and guiding the moving parts such as the worktable. CNC milling machine commonly used rails have sliding guide rails and rolling guide rails and so on.

1.Sliding guide rails

CNC milling machine sliding rails are usually rectangular - rectangular, triangular - rectangular combination form, as shown.

Rectangular - Rectangular guide is guided by side, with two types of guide for narrow and wide, with wide guide oriented with inner side of two rails; narrow guide oriented with both sides of a guide rail, as shown The Rectangular - Rectangular guide rails need to use the strip to adjust the gap and preload, commonly used in general precision CNC milling machine and machining center. The triangular guide is guided by two bevels, as shown. Triangular guide rails do not need to adjust the gap, commonly used in flat bed CNC lathe.

Metal-to-metal sliding guide due to friction characteristics of the reasons, there is a low-speed crawling phenomenon. In order to improve the friction characteristics, improve wear resistance and positioning accuracy, CNC milling machine sliding rails often use plastic rails. Plastic guide is a polymer made of thin film, with adhesive paste in the polished metal rail surface, as shown.

2. Rolling guide rails

Rolling guide rails by the professional factory production, have formed a standardized series of products. The rolling guide is made up of slides and sliders, which have circular rolling elements (such as balls or rollers), as shown.

When the slider and the guide rail relative movement, the rolling body along the guide rail rolling, at the end of the slider rolling body through the inverter and then into the raceway, which cycle movement. Both ends of the inverter are equipped with a dust-tight cover to effectively prevent dust from entering the slider. The rolling elements in the slider are lubricated with grease or lubricated through the grease nipples. Slider and slide between the rolling friction, friction resistance is small, no crawling phenomenon, after a long time after the use of small precision loss. The slide rails are fixed on the milling machine bed, the slide is fixed on the moving parts such as the table, and the slide rails and sliders are positioned by means of wedges.

CNC milling machine basic composition

Today we are going to talk about the basic composition of CNC milling machine and machining center. Come on and pay attention.

1. CNC milling machine

CNC milling machine according to function is divided into ordinary type and full function type.

(1) Main movement

The main movement of the mechanical transmission device, including the spindle, belt, spindle box ; spindle electrical drive devices, including spindle motors and spindle drives. CNC system on the input instruction data processing, the output control signal to the spindle drive, the spindle driver that the spindle motor to start, stop and frequency control and other control. In the multi-function CNC milling machine, the spindle in addition to speed control, there are spindle orientation, positioning and other control.

(2) Feed movement

The feed motor drives include X-axis and Z-axis ball screw pairs, rails, skids, etc. The feed electrical drive includes the X and Z axis servomotors and servo drives. The numerical control system carries on the data processing to the input instruction, outputs the control signal to the servo drive, the servo drive drives the servo motor to drive the ball screw, causes the slide to realize the feeding motion along the X axis and the Z axis, and finally makes the tool relative to the workpiece according to the processing program the specified movement trajectory and velocity movement.

(3) Auxiliary function

CNC milling machine basic auxiliary functions include cutting fluid switch control, lubrication control, tool change tool control, and the spindle box gear shift control. For multi-function CNC milling machine, auxiliary functions include hydraulic tailstock control and hydraulic chuck control. Auxiliary functions from the CNC system PLC and electrical control cabinet in the I / O modules, relays, contactors, and milling machine on the side of the various types of detection switches and gas hydraulic solenoid valve, according to the control logic to complete.

2. Machining Center

The spindle unit is installed in the main shaft box and is driven by the spindle motor through the transmission belt. The spindle drive receives the control signal from the numerical control system, drives the spindle motor to realize the frequency conversion speed control, and starts, stops and quasi-stop.

Before and after the exercise and the spindle box of X axis, Y axis and Z axis ball screw servo motor to achieve the milling machine table about sports, saddle up and down movement of the control signal; receiving a servo drive CNC system, drive X axis, Y axis and Z axis servo motor.

Besides the lubrication, cooling and other basic auxiliary functions, the machining center also has two important auxiliary functions: one is the loose and tight knife control in the spindle; the other is the cutter selection of the tool stock and the mechanical tool change control for the knife.

CNC milling machine features

CNC milling machine is a typical product of mechanical and electrical integration. It is a computer as the control core, set milling machine, motor and drag, power electronics, sensors, automation, machine tools and PLC, and gas and hydraulic technology as one of the automated metal cutting equipment. The CNC system (Computer Numerical Control, referred to as CNC) is the core of control, is generally a dedicated computer. Compared to the ordinary milling machine, CNC milling machine processing parts are automatically carried out according to the processing program. The machining process is shown in the figure.

The programmer prepares the machining process (machine selection, tool selection, fixture selection, cutting quantity determination, etc.) according to the part drawing.

The operator will enter the processing program into the CNC system, after the workpiece clamping, tool adjustment and knife operation, the implementation of processing procedures.

CNC system on the processing program for data processing, the output control signal control machine parts of the action, automatic cutting, such as spindle start, stop and spindle speed conversion, tool relative to the workpiece feed track adjustment, automatic tool change, cutting fluid open, off and so on.

The basic features of CNC milling machine are:

1) There is no need to intervene too much in the process of machining, and the effect of machining accuracy is reduced to the minimum.

2) CNC milling machine itself mechanical precision and control accuracy are higher, every step in the processing process strictly in accordance with the processing procedures to ensure the accuracy of parts processing and consistency of accuracy.

3) CNC milling machine has high degree of automation, such as automatic tool change, automatic tool setting, etc., effectively shorten the non cutting time, high processing efficiency.

4) After adopting standardized and modularized cutters and clamps, different parts can be machined only by changing the corresponding processing program, and the adaptability is strong.

Milling machine processing dovetail groove

As a common special groove, the dovetail groove is widely used. Today we will introduce how to use the milling machine to process the dovetail groove.

1.Application and main technical requirements of dovetail groove

The dovetail groove is used in conjunction with the dovetail as shown. Often use the dovetail structure as a linear movement of the guide or fasteners, such as milling machine dovetail groove between the dovetail groove and the dovetail between the relatively linear motion, therefore, the angle, width, depth of the higher accuracy requirements, slope flatness requirements higher, and the surface roughness value Ra is smaller. Dovetail angle α has a variety of general use 55°dovetail.

Dovetail groove and dovetail in the match, in the middle of a strip, used to adjust the gap. In order to facilitate the adjustment of the gap, but also the side of the dovetail side of the dovetail side made with the same slope with the same slope of the strip match, as long as the location of the moving strip, you can easily and accurately adjust the gap and compensation wear.

2. Dovetail groove and dovetail milling methods

When milling the dovetail groove and the dovetail, first use a milling cutter or a face milling cutter to cut a right angle groove or step on a vertical milling machine, and then slot the milling cutter into the dovetail or dovetail as shown. Dovetail groove milling cutter should be selected according to the angle of the dovetail, the width of the milling should be greater than the width of the workpiece dovetail groove slope.

Single-piece production, the use of single-angle milling cutter to milling the dovetail groove, dovetail. Milling the dovetail groove with slope, after milling the straight groove, first use the dovetail groove milling cutter without the slope of the side, milling and then release the pressure plate, the workpiece according to the provisions of the slope to adjust to the requirements and clamping, and then milling.

3. Dovetail groove detection method

1) Dovetail groove, dovetail groove angle α can be measured with a universal angle ruler.

2) The depth of the dovetail groove, the height of the dovetail can be measured with depth, height vernier caliper.

3) Dovetail groove, the width of the dovetail as the workpiece free knife slot and chamfer, use two standard rods indirect measurement.

The above is how to use the milling machine processing dovetail groove, you are welcome to continue to pay attention.

Milling machine processing T-shaped groove

T-shaped groove is also a common special groove. Today we talk about how to use the milling machine to process the T-groove.

1.Application and main technical requirements of T-shaped groove

T-groove is used for milling machine table, machine tool accessory, matching jig positioning and fixing.

The T-groove is composed of a straight groove and a bottom slot. According to the requirements, sub reference slot and fixed groove. The dimension accuracy and shape and position accuracy of the reference groove are higher than that of the fixed groove. Its shape, size and so on have been standardized, and the main technical requirements of T groove are:

1) straight groove width accuracy, reference trough IT8, fixed groove IT12 level.

2) the straight groove of the reference groove is two sides parallel or perpendicular to the reference plane of the workpiece.

3) the two sides of the bottom trough are symmetrical with the central plane of the straight groove.3) Both sides of the bottom groove are symmetrical with the center plane of the straight groove.

2. T-groove milling method and procedure

The T-groove is machined as shown. T-groove milling, generally first with a three-edge cutter or end mill milling straight groove, slot at the end of about 1mm margin, and then in the vertical milling machine with T-groove milling cutter to the bottom of the slot to the depth, and finally Use the angle milling cutter to chamfer the notch; the T-groove cutter should be selected according to the width of the straight groove.

The diameter of the milling cutter is the basic size of the T-groove (straight groove width); T-shaped groove at both ends, the hole should be drilled at one end of the groove before milling. The diameter of the hole should be larger than that of the T-groove The diameter and depth of the cutting part of the milling cutter shall be greater than the depth of the T-groove bottom groove. After milling the straight groove, punch the bottom slot with the T-slot milling cutter.

3. T-groove detection method

T-groove can be used vernier caliper, lever dial indicator detection.

The above is about how to use the milling machine processing T-shaped groove of the relevant content. Welcome to continue to pay attention.

Milling machine processing V-shaped groove

Common tern grooves are V-shaped, T-shaped and dovetail. Today we are going to discuss how to use a milling machine to process V-grooves.

1. V-groove applications

V-shaped groove is widely used in milling machine fixtures, such as milling machine guide, workpiece crossed, clamping measurement. V-shaped groove between the sides of the angle between the general is 90°or 60°, commonly used 90°V-shaped groove.

2. The main technical requirements of V-groove

The symmetry of the V-shaped groove center plane to the center of the workpiece, the parallelism of the upper plane plane of the V-shaped block, the verticality of the center plane of the V-shaped groove to the bottom plane.

3. V-groove milling method

(1) Milling the V-groove with an end mill

A V-shaped groove with an angle greater than or equal to 90°can be used to clamp the milling cutter at the milling machine. Milling should be completed before the narrow slot, and then transferred to the milling head, with an end mill milling V-shaped groove. After milling the V side of the side, turn the vertical milling head at the angle of the other side of the V-face; or loosen the workpiece 180°after clamping, and then milling the other side V-shaped surface. When milling, the base of the fixture or workpiece should be parallel to the horizontal feed direction of the milling table.

(2) Adjust workpiece milling V-groove

V groove angle greater than 90 degrees, accuracy is not high, one side can be corrected by crossed V slot, and make the milling machine table and parallel clamping, side milling, re correction clamping on the other side, and then milling, when the angle is equal to 90 degrees, V groove size the one time clamping milling.

(3) With angle milling cutter milling V-groove

A V-shaped groove with an angle of less than 90°is used to mill the narrow slot with a symmetrical double-angled cutter with the same angle. The reference plane of the fixture or workpiece should be parallel to the longitudinal feed direction of the milling table. If there is no suitable symmetrical double-angle milling cutter, can be combined with two different edge, the same specifications of the single-angle milling cutter combined milling.

4. V - shaped groove detection method

V-groove detection items are V-groove width B, V-shaped groove angle α and V-groove symmetry.

(1) V-groove width B detection

1) Measure the groove width B directly with the vernier caliper, but the detection accuracy is poor.

2) With the standard weight bar indirect measurement of width B, high precision, as shown. Measurement, the first measured size h, and then calculated.

(2) Detection of V-groove angle α

1) Measure with angle pattern. Observe whether the V-groove angle α is acceptable by observing the gap between the workpiece and the model.

2) Measure with the universal angle of the cursor.

3) Indirect measurement of groove angle α with standard rod. This method has high accuracy.

(3) V-groove symmetry error detection

When measuring, the V-groove put a standard bar, respectively, V-shaped frame on both sides of the reference, placed on the flat datum plane, with a lever dial indicator measuring the highest point of the bar, twice the difference between the measured reading For the symmetry error. If the readings of the two measurements are the same, it indicates that the center plane of the V-shape coincides with the V-plane center plane.

The above is about how to use the milling machine processing V-shaped groove of the relevant content. Welcome to continue to focus.

Milling machine processing keyway (part 2)

In the previous article, we introduced the technical requirements for processing keyway in milling machine and the preparation before machining. Today, let's introduce the specific method of milling keyway.

1. Milling method for keyway on shaft

1) Milling the keyway on shaft. Shaft groove for the groove or one end of the arc-shaped half-slot, generally use disc-shaped slot cutter to milling. If the part is longer and the outer circle has been ground accurately, you can use the flat clamp clamp for milling. In order to avoid the workpiece out of the jaw is too long and produce vibration and bending, can be extended in the jack with the jack support, as shown. If the workpiece diameter only after rough processing, the use of three-jaw self-centering chuck and tailstock to the top of the folder, and the middle need to use jack support. Workpiece clamping is completed and adjusted to the center, adjust the side cutting depth ae.

When adjustment, first turn the milling cutter cutting edge and the workpiece cylindrical contact, and then exit the workpiece, then the table up ae to the depth of the shaft, you can start milling. When the cutter starts cutting into the workpiece, move the work table slowly and carefully. In the width of the milling layer ap close to the width of the cutter, if the side of the axis of the phenomenon, indicating that the cutter is not aligned with the workpiece center, the workpiece should be a side of the side of the cutter side Move to the center. When the workpiece is clamped with a V-shaped block or a central T-shaped platen of the table, the press plate can be pressed against the end of the workpiece. The length of the workpiece is drilled from the end of the workpiece and then stopped to move the platen to the end of the workpiece. Mat on the copper to re-press the workpiece, as shown in the figure, observe the milling cutter will not touch the plate, and then start the spindle, milling full length.

2) Milling the close keyway on the shaft. With keyway cutter cut slot, commonly used methods are as follows:

①Layered milling method. Milling with a milling cutter with a keyway width size. Layered milling method in the cutter with blunt, just sharpen the end face, cutter diameter is not affected, it will not produce a clear "knife" phenomenon. But in the ordinary milling machine processing, the production efficiency is low. The stratified milling method is mainly suitable for milling with short length, single or small batch slot.

②Expansion milling method. First with a diameter less than 1mm slot width of the keyway cutter for stratified rough milling to the groove depth, groove at both ends of the remaining margin of 0.2 ~ 0.5mm, and then use the exact size of the key milling cutter fine milling.

2. Shaft groove detection method

1) The width of the shaft groove detection. Common plug or plug block detection, as shown

2) The length and depth of the shaft groove detection, as shown.

3) The measurement of the symmetry error of the axis of the center plane of the shaft groove. As shown in the figure, the workpiece is placed in the V frame, choose a gauge block and the shaft groove width of the same size in the axial groove, and the block plane in a horizontal position, with dialgage detection gauge A surface and plane and reading, and then the workpiece is rotated 180 degrees, with a dial indicator measuring gauge B the flat surface and the reference surface and reading, reading two times the difference is half shaft keyway symmetry error.