Task 4  Axis motion commissioning and maintenance

Targets of the task                                        

By setting the axis parameters independently, trainees gain the fundamental knowledge and skills for machine axis motion control and will be able to commission and troubleshoot the axis motion.

Task description                                                            

Trainees are requested to perform axis motion commissioning and maintenance of CNC lathe with FANUC 0i Mate-TD. Working results should be:

?  The machine is able to move in correct direction.

?  The machine is able to be positioned to correct position.

?  The machine is able to move at specified feed rate.

Training equipment                                              

YALONG YL-569 0i Mate-TD CNC Lathe Practical Training Equipment (manufactured by Zhejiang YALONG Educational Equipment Joint Stock Co., Ltd)

Configuration

• CNC control: FANUC 0i Series Mate-D

• Servo motor: βi Series, βis4/4000 (X-axis), βis4/4000 (Z-axis)

• Built-in pulse coder: β128iA serial pulse coder

• Fully closed loop control for X-axis with linear scale, semi-closed loop control for Z-axis without direct measuring device.

• Motion amount for each motor revolution: 5mm/r

• Ball screw travel: 280mm

• Servo amplifier: βi Series, βi SV 20 (X-axis), βi SV 20 (Z-axis)

• Spindle drive: universal inverter OMRON SYSDRIVE 3G3JZ-A4004

Tools and measuring tools                                                    

Crank, Vernier caliper, steel ruler or linear scale with DRO, marker

Safety                                                            

• Avoid electric shock and mechanical impacts.

• Before you do work on the amplifier or inverter, check that the DC link charge confirmation LED is off. Neglecting this check creates electric shock hazard.

• Always keep your eyes on the moving parts of the machine when you operate the machine.

• Keep putting tools and measuring tools in order.

• Pay attention to human safety and environment protection.

Achievements submitted                                                

1. Well-functioned machine axes  

2. Basic data for machine control system

3. List of SERVO SETTING

4. List of axis parameters setting

5. Minute of the training

Operation instruction                                    

4.1 Basic operations

4.1.1 Enable and disable parameter writing

Enable and disable parameter writing procedures are as follows:

1. Select MDI mode or emergency stop state.

2. Press function key OFFSET/SETTING.

3. Press soft key [SETTING] and SETTING page will appear, as shown fig. 4-1.

4. Move the cursor to PARAMETER WRITE.

5. Press [OPRT] and [1:ON] to switch PARAMETER WRITE to 1. This makes parameter writing possible and meanwhile, CNC will display message P/S No.100 “PARAMETER WRITE ENABLE”.

Fig.4-1 SETTING page

When you finish all parameter setting, please return to SETTING page. Move the cursor to PARAMETER WRITE and press [OPRT] and [0:OFF].

Message P/S No.100 can be removed with RESET and CANCEL key pressed at the same time.

4.1.2 Displaying SERVO SETTING page

With FANUC 0i Mate-D CNC, displaying SERVO SETTING procedures are as follows:

1. Press function key SYSTEM several times.

2. Move the cursor to SERVO SETTING.

3. Press soft key in turn [OPRT], [SELECT], [?] and [CHANGE]. SERVO SETTING page for the first and second axis will appear, as shown in fig. 4-2.

4. Press PAGE DOWN key to display SERVO SETTING for the third axis.

4.1.3 AXIS PARAMETER setting

There are two types of axis parameters: bit parameter and data parameter. AXIS PARAMETER setting procedures are as follows:

1. Press function key SYSTEM.

2. To search the parameter to be set, just input the parameter No. (for instance, 1420), and press soft key [NO. SRH]. The screen will display as fig. 4-3.

3. Select MDI mode and key in correct parameter value, then press INPUT key. If parameter writing is disabled (PWE=0), the screen will blink the message “WRITE PROTECT”. If CNC is not in MDI mode, the screen will blink the message “WRONG MODE”.

4.2 Steps for axis motion commissioning

Before starting servo initialization, confirm the following basic data:

·   Type of CNC control:                                                                

·   Type of servo motor:                                                                  

·   Motor built-in pulse encoder:                                                      

·   Whether separate detectors are used. If used, confirm the type:                                                                                                    

·   Motion amount for each motor revolution:                                    

·   Detection unit:                                                                              

·   CNC command unit:                                                                    

4.2.1 Measure the ball screw pitch for each machine axis and calculate F·FG

1. Screw pitch measuring

When you try to measure the ball screw pitch by using Vernier caliper, it is not easy to measure one single pitch. So you may measure 10 pitches. Another method is that you can set the caliper for 10mm and count how many pitches there are within 10mm. See fig. 4-4. Pitch value is usually an integer.

2. Calculation of F·FG

For the calculation of F·FG, follow the formula below:

3. Ref.C setting

Reference counter is set to the number of position pulses corresponding to the amount of travel caused by one revolution of servomotor.

4.2.2 Determine the motor direction

When you determine the value of DIRECTION SET, you have to first recognize the machine coordinate system and the positive direction of each axis. Generally, you can turn the ball screw by a crank (in the case of power off) and observe the rotating direction of servo motor when the axis is moving in positive direction. Set 111 if the servo motor rotates clockwise as viewed from the pulse coder and set -111 if the servo motor rotates counterclockwise as viewed from the pulse coder. See fig. 4-5.

However, the practice described above is only possible for horizontal axes. For vertical axis, due to brake, it is not possible to turn the ball screw in the case of power off. Therefore, you may have to adjust your direction set when you verify the axis direction.

Warning: Incorrect direction set may cause machine overtravel or damage. Operators have to jog the machine at low feed rate override to prevent it from overtravel.

4.2.3 Display SERVO SETTING page

To display the servo setting screen, follow the procedure described in “Displaying SERVO SETTING page”. Each item of servo setting is also called initialization parameter.

4.2.4 Set the initial set bits to 0

Enable parameter writing (PWE=1). Select MDI mode, and reset initialization bit 1 to 0. This starts initialization and CNC will issue Alarm No. 000 “PLEASE TURN OFF POWER”. Please do not power off the CNC until all the initialization parameters are set. After initialization is completed, initialization bit 1 is automatically set to 1.

Caution: Before you make any change to any of the items of servo setting, you must first set the initial set bits to 0. Otherwise, any modification will not become active.

4.2.5 Key in servo settings one by one

Set the items shown in table 4-1. In MDI mode, input correct setting value for each item of servo setting. For motor ID No., refer to table 4-2.

Table 4-1 SERVO SETTING

Table 4-2 List of βis series servo motor ID No.

Note: HRV2 is used in current motors. Second line of some motor ID No. means motor with brake.

4.2.6 Restart CNC

Switch CNC off and on again by pressing the red button, then the green button in fig.4-6. This completes servo parameter initialization. When a setting value is incorrect, say, beyond an allowable range, or when an overflow occurs during internal calculation in the servo software, an invalid setting alarm will be issued. For example, Alarm No. 466 (n AXIS: MOTOR/AMP COMBINATION) means the maximum current rating for the amplifier does not match that for the motor.

Caution: Please wait for 5 seconds or so before you switch CNC on again after you switch it off.

4.2.7 Set axis parameters one by one

Set the parameters shown in table 4-3, following the procedure described in “AXIS PARAMETER setting”.

Table 4-3 Main axis parameters

4.2.8 Feed in JOG mode

In JOG mode, hold down jog direction keys as shown in fig. 4-7 and the axis will continually jog until you take your finger off the button. If there is neither motion nor alarm, probably the axes are interlocked (diagnosed by CNC diagnostic data shown in fig. 4-9). You may modify PRM No.3003 for unlocking the axes.

4.2.9 Feed in HANDLE mode

In HANDLE mode, turn the handle as shown in fig. 4-8 to move the axes you select. If there is no position display change, probably the handle is deactivated. You may modify PRM No.8131 bit 0 (HPG) to 1 to activate the handle.

4.2.10 Verify direction, position and feed rate

1. Axis direction verification

It should conform to right hand rule. Keep in mind this is tool movement. When we’re talking about X-, that’s the tool moving in the negative direction. So while you’re holding the X- key down, the tool is moving in the negative direction, which means the table is moving to the right.

2. Axis position verification

Axis position change displayed on the screen should consistent with actual movement distance. F·FG setting affects the accuracy of positioning. You may verify the position following the procedure below:

Firstly, mark the initial position of the slide and origin the axis in relative position display. Next, move X-axis in HANDLE mode, say, 100mm. Then, mark the current position and measure the actual movement distance of the slide using steel ruler or Vernier caliper. If the reading of the ruler is consistent with the position displayed in the screen, F·FG setting is correct. Otherwise, F·FG is wrong.

3. Axis feed rate verification

Feed rate set in PRM.No.1423 can be monitored by “ACTUAL FEEDRATE” displayed on the lower left corner of the POS screen. If there is no “ACTUAL FEEDRATE” display, please modify PRM No.3105 bit 0 (DPF) to 1.

Minutes of the task                                      

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