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    • M3: Coupled axes
      • Electronic gear (EG)
        • Electronic gear (EG)
        • Definition of an EG axis group
        • Activating an EG axis group
        • Deactivating an EG axis group
        • Deleting an EG axis group
        • Interaction between rotation feedrate (G95) and electronic gearbox
        • Response to POWER ON, RESET, operating mode change, block search
        • System variables for electronic gearbox
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    Entry type: Manual, Entry ID: 109476441, Entry date: 01/04/2015

    SINUMERIK 840D sl / 828D Special Functions

    Document: Special functions (01/2015, English)
    Type of topic: Fact

    Electronic gear (EG)

    Function

    With the aid of the "Electronic gearbox" the movement of a following axis FA can be interpolated dependent of up to five leading axes LA. The relationship between each leading axis and the following axis is defined by a coupling factor. The following axis motion components derived in this manner from the individual leading axis motion components have an additive effect.

    FAset = SynPosFA + (LA1-SynPosLA1)*CF1 +... +(LA5-SynPosLA5)*CF5

    with:

    SynPosFA, SynPosLAi: from call EGONSYN (see below)

    FAsetpoint: Partial setpoint of the following axis.

    LAi: Setpoint or actual value of the ith leading axis (depending on the type of coupling - see below)

    KFi: Coupling factor of the ith leading axis (see below)

    All paths are referred to the basic co-ordinate system BCS.

    When an EG axis group is activated, it is possible to synchronize the leading axes and following axis in relation to a defined starting position.

    From the part program a gearbox group can be:

    • defined,
    • activated,
    • deactivated,
    • deleted.

    Extensions

    The influence of each of the 5 leading axes can be specified using a curve table as an alternative to a transmission ratio (KF=numerator/denominator).

    It is thus possible for each curve (except for the special case of a straight line) for the leading axis to influence the following axis in a non-linear manner. The function can only be used with EGONSYN.

    The function EG can be activated with curve tables with EGON.

    The function EGONSYNE is available for approaching the synchronized position of the following axis with a specified approach mode.

    For special applications, it may be advisable configure the position controller as a PI controller.



    Caution

    Application faults

    Knowledge of the control technology and measurements with servo trace are an absolute prerequisite for using this function.



    References:

    • CNC Commissioning Manual: NCK, PLC, drive
    • Function Manual, Basic Functions; Velocities, Setpoint-Actual Value Systems, Closed-Loop Control (G2)

    Coupling type

    The following axis motion can be derived from either of the following:

    • Setpoints of leading axes
    • Actual values of leading axes

    The reference is set in the definition call for the EG axis group:

    EGDEF

    (see Chapter "Definition of an EG axis group")

    Coupling factor

    The coupling factor must be programmed for each leading axis in the group. It is defined by numerator/denominator.

    Coupling factor values numerator and denominator are entered per leading axis with the following activation calls:

    EGON

    EGONSYN

    EGONSYNE

    (see Chapter "Activating an EG axis group")

    Number of EG axis groups

    Several EG axis groups can be defined at the same time. The maximum possible number of EG axis groupings is set in the following machine data:

    MD11660 $MN_NUM_EG

    The maximum permissible number of EG axis groups is 31.


    Note

    The option must be enabled.



    EG cascading

    The following axis of an EG can be the leading axis of another EG. For a sample configuration file, see Chapter "Examples".


    Figure: Block diagram of an electronic gearbox

    Synchronous positions

    To start up the EG axis group, an approach to defined positions for the following axis can first be requested.

    Synchronous positions are specified with:

    EGONSYN (see below for details)

    EGONSYNE (extended EGONSYN call).

    Synchronization

    If a gear is started with EGON(), EGONSYN() or EGONSYNE() see below, the actual position of the following axis is only identical to the setpoint position defined by the rule of motion of the gear specified by the positions of the leading axes at this time if the part program developer makes sure that it is. The control then uses the motion of the following axis to ensure that the setpoint and actual positions of the following axes correspond as quickly as possible if the leading axes are moved further. This procedure is called synchronization. After synchronization of the following axis, the term synchronous gearing is used.

    Activation response

    An electronic gearbox can be activated in two different ways:

    1. On the basis of the axis positions that have been reached up to now in the course of processing the command to activate the EG axis group is issued without specifying the synchronizing positions for each individual axis.

      EGON (see Chapter "Activating an EG axis group")

    2. The command to activate the EG axis group specifies the synchronized positions for each axis. From the point in time when these positions are reached, the EG should be synchronized.

      EGONSYN (see Chapter "Activating an EG axis group")

    3. The command to activate the EG axis group specifies the synchronized positions and approach mode for each axis. From the point in time when these positions are reached, the EG should be synchronized.

      EGONSYNE (see Chapter "Activating an EG axis group")

    Synchronization with EGON

    With EGON(), no specifications are made for the positions at which the following axis is to be synchronized. The control system activates the EG and issues the signal "Synchronized position reached".

    Synchronization for EGONSYN

    1. With EGONSYN(), the positions of the leading axes and the synchronization position for the following axis are specified by the command.
    • The control then traverses the following axis with just the right acceleration and velocity to the specified synchronization position so that the following axis is in position with the leading axes at its synchronization position.
    • If the following axis is stationary: If the "Feed stop/spindle stop" DB 31, ... DBX 4.3 is set for the following axis, the following axis is not set in motion by EGON or EGONSYN. A traverse command is issued and block changing is blocked until the axis-specific feed is enabled. EGOSYN is topped by RESET transformed into EGON. The programmed synchronized positions are deleted.
    • If the following axis is not stationary: The NST "Feed Stop/Spindle Stop" DB31, ... DBX4.3 has no direct influence on the electronic gearbox. As before, it does have an indirect effect on the leading axes, if these are located in the same channel.
    • For channel specific feed enabling and for override nothing is implemented. Override still has no direct influence on the electronic gearbox. The axis-specific feed enable is set, depending on the current override setting.

    Synchronization for EGONSYNE

    With EGONSYN(), the positions of the leading axes and the synchronization position for the following axis are specified by the command.

    The control system moves the following axis to the synchronized position according to the program approach mode.

    Synchronization abort with EGONSYN and EGONSYNE

    1. The EGONSYN/EGONSYNE command is aborted under the following conditions and changed to an EGON command:
    • RESET
    • Axis switches to tracking

    The defined synchronization positions are ignored. Synchronous traverse monitoring still takes synchronized positions into account.

    Aborting position synchronization generates alarm 16774.

    The alarm may be suppressed with the following machine data:

    MD11410 $MN_SUPPRESS_ALARM_MASK Bit31 = 1

    Synchronous monitoring

    The synchronism of the gearbox is monitored in each interpolator clock cycle on the basis of the actual values of the following and leading axes. For this purpose, the actual values of the axes are computed according to the rule of motion of the coupling. The synchronism difference is the difference between the actual value of the following axis and the value calculated from the leading axis actual values according to the rule of motion. The synchronism difference can be queried from the part program (see below).

    Changes in the synchronism difference

    The mass inertia of the axis systems during acceleration can cause dynamic fluctuations in the synchronism difference. The synchronism difference is checked continuously and the tolerance values in the machine data used to produce interface signals.

    The synchronism difference is compared with the following machine data:

    MD37200 $MA_COUPLE_POS_TOL_COARSE

    MD37210 $MA_COUPLE_POS_TOL_FINE

    Depending on the result of this comparison, the following signals are set:

    NST "Synchronous travel fine" DB31, ... DBX98.0

    NST "synchronous traverse coarse" DB31, ... DBX98.1

    Difference > .. TOL_COARSE

    As long as the synchronism difference is greater than the following machine data, the gearbox is not synchronized and neither IS "Coarse synchronism" DB 31, ... DBX 98.1 nor IS "Fine synchronism" DB 31, ... DBX 98.0 is active:

    MD37200 $MN_COUPLE_POS_TOL_COARSE

    Instead, the following interface signal is displayed:

    NST "synchronization running" DB31, ... DBX99.4

    Difference < .. TOL_COARSE

    As long as the synchronism difference is smaller than the following machine data, IS "Coarse synchronism" DB 31, ... DBX 98.1 is at the interface and IS "Fine synchronism" DB31, ... DBX99.4 is deleted:

    MD37200 $MN_COUPLE_POS_TOL_COARSE

    Difference > .. TOL_FINE

    If the synchronism difference is smaller than the following machine data, then NST "synchronous traverse fine" DB31, ... DBX98.0 is at the interface:

    MD37210 $MA COUPLE_POS_TOL_FINE

    Synchronism difference for EG cascades

    Synchronism difference for EG cascades is the deviation of the actual position of the following axis from setpoint position that results fro the rule of motion for the real axes involved.

    Example:


    Figure: Three-level EG cascade

    According to the definition given, the synchronism difference of following axis FA3 in the example below is determined by the value of following axis FA3Act and the value of leading axis FA2Act and LA2Act, but not by LA1Act and FA1Act.

    If FA2 is not a real axis, the actual value FA2Act is not available. In this case, the setpoint of the axis derived solely from the leading axis value FA1Act must be used instead of the actual value of the setpoint of the axis.

    Other signals

    If an EGON(), EGONSYN() or EGONSYNE() block is encountered in the main run, the signal "Coupling active" is set for the following axis. If the following axis is only overlaid, the signals "Coupling active" and "Axis override" are set. If EGON(), EGONSYN() or EGONSYNE() is active and the following axis is also overlaid, the signals "Coupling active" and "Axis override" are also set.

    IS "following spindle active" DB31, ... DBX 99.1: Coupling active,

    IS "overlaid movement" DB31, ... DBX98.4: axis is overlaid,

    IS "Enable following axis override" DB31, ... DBX26.4

    In the case of the commands EGON() and EGONSYNE(), the "Enable following axis override" signal must be present for the gear to synchronize to the specified synchronization position for the following axis. If it is not present, alarm 16771 "Override movement not enabled" is issued. If the signal is present, the following axis travels to the synchronized position with the calculated acceleration and at the velocity set for the approach mode.

    Further monitoring signals

    Machine data MD37550 $MA_EG_VEL_WARNING allows a percentage of the speeds and accelerations to be specified in the following machine data MD32000 $MA_MAX_AX_VELO and MD32300 $MA_MAX_AX_ACCEL, with reference to the following axis, which results in the generation of the following interface signals:

    IS "Speed warning threshold" DB31, ... DBX98.5

    IS "Acceleration warning threshold" DB31, ... DBX98.6

    The monitoring signals can be used as trigger criteria for emergency retraction (see Chapter "Trigger sources").

    Machine data MD37560 $MA_EG_ACC_TOL allows a percentage with reference to machine data MD32300 $MA_MAX_AX_ACCEL of the following axis to be defined, and the IS signal "axis accelerates" DB31, ... DBX99.3 to be generated.

    Request synchronism difference

    1. The result of the synchronism difference calculation can be read as an amount in the part program with system variable $VA_EG_SYNCDIFF. The relevant value with sign is available in the system variables $VA_EG_SYNCDIFF_S. The following meanings apply:
    • Negative value (in positive traverse direction for lead and following axis): The following axis lags behind its calculated setpoint position.
    • Positive value (in positive traverse direction for lead and following axis): The following axis leads before its calculated setpoint position (overswing).

    The amount of the synchronism difference with sign corresponds to the system variables without sign from $VA_EG_SYNCDIFF.

    $VA_EG_SYNCDIFF[ax] = ABS($VA_EG_SYNCDIFF_S[ax])

    Block change mode

    1. When an EG axis group is activated, it is possible to specify the conditions under which a part program block change is to be executed:
    2. The specification is made with a string parameter with the following meaning:
    3. "NOC": Immediate block change
    4. "FINE": Block change if "Fine synchronism" is present
    5. "COARSE": Block change if "Coarse synchronism" is present
    6. "IPOSTOP": Block change if "Setpoint synchronism" is present

    Note

    When programmed in activation calls EGON, EGONSYN, EGONSYNE, each of the above strings can be abbreviated to the first two characters.



    If no block change has been defined for the EG axis group and none is currently specified, "FINE" applies.



     

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