NOTE: This portion of the documentation covers the linear current steppers of the WT6000 Weld Control. This section of the manual is geared towards line builders, maintenance personnel and welding engineers to assist with procedures related to programming the weld control.

Table of Contents


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Chapter 8: Linear Current Steppers

In this section:



The Purpose of Linear Current Steppers


During the welding process, the face of the welding cap gradually deforms or "mushrooms." As it does, the contact diameter with the work piece increases, which causes the current density at the weld interface to decrease. As a result, the weld nugget gradually grows colder.

The purpose of a Linear Current Stepper is to gradually increase the welding current, in incremental steps, to compensate for the gradual decrease in current density at the weld interface, caused by the "mushrooming" of the welding caps. This gradual increase in welding current ensures the appropriate amount of heat is continuously present at the weld interface to repeatedly form good weld nuggets.



Introduction to Linear Current Steppers


The WT6000 weld control with timer software G08300 has 10 available linear current stepper programs. Each stepper program has 5 programmable steps.

Within each of the 5 steps, the user can program the current boost (rise) over a number of welds (run). The current boost for each step can be expressed as either a percentage value or an absolute amps value. The current boost (rise) is delivered in equal, incremental steps, over the total number of welds (run) in each step.

To use a linear current stepper, function #82 (LINEAR STEPPER #nn ASSIGNED) must be inserted into the first line of the weld schedule.

Stepper programs are only active during the execution of a weld function and will increment when the following functions are used in the weld schedule:

PERCENTAGE OF AVAILABLE VOLT-SECONDS WELD FUNCTION
20
WELD nn CY. nn %VS

CONSTANT CURRENT WELD FUNCTION
30
WELD nn CY. nnnn0 AMPS

 

STEPPER PROFILES

Each stepper program has a stepper profile. In the example below, each step has two current values. The first value (blue) is a percentage value and the second value (red) is an absolute amps value. If a Percentage of Available Volt-Seconds weld function is used, the current boost (rise) must be expressed in a percentage value. If a Constant Current weld function is used, the current boost (rise) must be expressed in absolute amps.

NOTE: If a Percentage of Available Volt-Second weld function is used in the weld schedule and both a percentage and absolute amps value is entered in the step, the absolute amps value is ignored by the weld processor. Conversely, if a Constant Current weld function is used, the percentage value is ignored.

EXAMPLE STEPPER PROFILE
STEP #01 00 % 1000 AMPS 100 WELDS
STEP #02 00 % 500 AMPS 100 WELDS
STEP #03 00 % 200 AMPS 100 WELDS
STEP #04 00 % 100 AMPS 100 WELDS
STEP #05 00 % 050 AMPS 100 WELDS
STEPPER GROUP 1
MAXIMUM TIP DRESSES = 0
AUX. COUNTER MAX COUNTS = 0

 

stepper groups

In a typical welding application, multiple weld schedules can be assigned to a single stepper program. Also, if desired, the user may assign a single weld schedule to an individual stepper program.

In the case of a specific weld gun, it is advantageous that all the stepper programs used on that gun increment their weld counters, each time the gun makes a weld. Assigning these stepper programs to a common "Group" causes all the stepper programs within that group to increment together each time a weld is made by that gun, regardless of what weld schedule stepper combination was initiated. In addition, stepper grouping allows the user to advance or reset several stepper programs at one time. The stepper group range is 0-99.



Example Stepper Program #1 (No Tip Dress)


The following is an example of a linear stepper program without tip dressing. This example would typically be used in either a hard-tool welding application or any other application where dressing of the weld caps is not required.

  1. Function #82 (LINEAR STEPPER #nn ASSIGNED) is inserted into the first line of Weld Schedule #1 and is assigned to Linear Stepper Program #1.
  2. Current weld function #30 (WELD nn CY. nnnn0 AMPS) is used and is programmed to deliver 10000A of base current for 10 cycles.
EXAMPLE SCHEDULE #1
00:
START OF SCHEDULE # 1
82:
LINEAR STEPPER #1 ASSIGNED (0=0FF)
76:
SEC. CURR LIMITS: HI=00 LOW=99990
81:
TRANSFORMER TURNS RATIO 73:1
88:
TURN ON ISOLATION CONTACTOR
58:
TURN ON WELD IN PROGRESS
01:
SQUEEZE 30 CYCLES
30:
WELD 10 CY. 10000 AMPS
03:
HOLD 5 CYCLES
63:
TURN ON WELD COMPLETE
59:
TURN OFF WELD IN PROGRESS
75:
EXTEND UNTIL NO INITIATE
64:
TURN OFF WELD COMPLETE
89:
TURN OFF ISOLATION CONTACTOR
100:
END OF SCHEDULE # 1

 

  1. Below is the stepper profile as viewed from the DEP-300s Data Entry Panel. The following explains each parameter within the profile:

 

  • Step #01:

    Step 1 is programmed to deliver a 1000A boost over 100 welds. If the base current is 10000 Amps, the boost current will increment by 10A after each weld, thus by the 100th weld, the target current will be at 11000A.

 

  • Step #02:

    Step 2 is programmed to deliver a 500A boost over 100 welds. If the base current is 11000 Amps, the boost current will increment by 5A after each weld, thus by the 100th weld, the target current will be 11500A.

 

  • Step #03:

    Step 3 is programmed to deliver a 200A boost over 100 welds. If the base current is 11500 Amps, the boost current will increment by 2A after each weld, thus by the 100th weld, the target current will be 11700A.

 

  • Step #04:

    Step 4 is programmed to deliver a 100A boost over 100 welds. If the base current is 11700 Amps, the boost current will increment by 1A after each weld, thus by the 100th weld, the target current will be 11800A.

 

  • Step #05:

    Step 5 is programmed to deliver a 50A boost over 100 welds. If the base current is 11800 Amps, the boost current will increment by .5A after each weld, thus by the 100th weld, the target current will be 11850A.

    STEPPER APPROACHING MAX: At the first weld of Step 5, a STEPPER APPROACHING MAX ALERT is generated. This alert indicates the stepper program has started its final step.

    END OF STEPPER : At the last weld of Step 5, an END OF STEPPER FAULT is generated, which indicates the stepper program has ended. See Stepper Reset Options below.

    When the stepper program reaches the last weld of Step 5, the Tip Change Required output bit will go HIGH.

 

  • STEPPER GROUP:

    In example #1, Stepper #1 is assigned to Stepper Group 1. For more information, see Stepper Groups above.

 

  • MAXIMUM TIP DRESSES:

    This parameter is only used when tip dress functionality is required. Setting this parameter to zero disables the tip dress functionality within the stepper program. In example #1, this parameter is set to zero. Thus, tip dress functionality is disabled.

     

  • AUX. COUNTER MAX COUNTS:

    Attached to each stepper program is an Auxiliary Weld Counter, which is located in the Stepper Status Menu. When a stepper increments, its auxiliary weld counter also increments. When the counter reaches the value programmed in this parameter, the Aux Counter at Max output bit goes HIGH. This output bit can be used for any purpose by the user. Turning the Stepper Aux Weld Cntr Reset input bit HIGH resets the Auxiliary Weld Counter to zero and turns the Aux. Counter at Max output bit LOW. In example #1, the Aux. Counter Max Counts is set to zero. Therefore, the Aux Counter at Max output bit is disabled.



Example Stepper Program #2 (Tip Dress)


The following is an example of a linear stepper program with tip dressing. This example would typically be used in a robot welding application.

  1. Function #82 (LINEAR STEPPER #nn ASSIGNED) is inserted into the first line of Weld Schedule #1 and is assigned to Linear Stepper Program #1.
  2. Current weld function #30 (WELD nn CY. nnnn0 AMPS) is used and is programmed to deliver 10000A of base current for 10 cycles.
EXAMPLE SCHEDULE #1
00:
START OF SCHEDULE # 1
82:
LINEAR STEPPER #1 ASSIGNED (0=0FF)
76:
SEC. CURR LIMITS: HI=00 LOW=99990
81:
TRANSFORMER TURNS RATIO 73:1
88:
TURN ON ISOLATION CONTACTOR
58:
TURN ON WELD IN PROGRESS
01:
SQUEEZE 30 CYCLES
30:
WELD 10 CY. 10000 AMPS
03:
HOLD 5 CYCLES
63:
TURN ON WELD COMPLETE
59:
TURN OFF WELD IN PROGRESS
75:
EXTEND UNTIL NO INITIATE
64:
TURN OFF WELD COMPLETE
89:
TURN OFF ISOLATION CONTACTOR
100:
END OF SCHEDULE # 1

 

  1. Below is the stepper profile as viewed from the DEP-300s Data Entry Panel. The following explains each parameter within the profile:

 

  • Step #01:

    Step 1 is programmed to deliver a 1000A boost over 100 welds. If the base current is 10000 Amps, the boost current will increment by 10A after each weld, thus by the 100th weld, the target current will be at 11000A.

 

  • Step #02:

    Step 2 is programmed to deliver a 500A boost over 100 welds. If the base current is 11000 Amps, the boost current will increment by 5A after each weld, thus by the 100th weld, the target current will be 11500A.

 

  • Step #03: (First Tip Dress)

    At the first weld of Step 3 the weld processor will turn the Tip Dress Request output bit HIGH. Upon receiving the request, the robot initiates a tip dress schedule. Upon completion of the tip dress schedule, the weld processor will return the stepper program back to the first weld of Step 2.

 

  • Step #02:

    If the Remaining Tip Dresses Count is > 0, the stepper program will continue towards Step 3 again.

    Step 2 is programmed to deliver a 500A boost over 100 welds. If the base current is 11000 Amps, the boost current will increment by 5A after each weld, thus by the 100th weld, the target current will be 11500A.

 

  • Step #03: (Second Tip Dress)

    At the first weld of Step 3 the weld processor will turn the Tip Dress Request output bit HIGH. Upon receiving the request, the robot initiates a tip dress schedule. Upon completion of the tip dress schedule, the weld processor will return the stepper program back to the first weld of Step 2.

 

  • Step #02:

    If the Remaining Tip Dresses Count has decremented to 0, the stepper program will proceed to Step 3 again.

    Step 2 is programmed to deliver a 500A boost over 100 welds. If the base current is 11000 Amps, the boost current will increment by 5A after each weld, thus by the 100th weld, the target current will be 11500A.

 

  • Step #03: (Zero Tip Dresses Remaining)

    When the stepper program reaches the first weld of Step 3 and the Remaining Tip Dresses Count has decremented to 0, the Tip Dress Request output bit will not go HIGH and the stepper program will proceed to Step 5.

 

  • Step #04:

    Step 4 is programmed to deliver a 100A boost over 100 welds. If the base current is 11700 Amps, the boost current will increment by 1A after each weld, thus by the 100th weld, the target current will be 11800A.

 

  • Step #05:

    Step 5 is programmed to deliver a 50A boost over 100 welds. If the base current is 11800 Amps, the boost current will increment by .5A after each weld, thus by the 100th weld, the target current will be 11850A.

    STEPPER APPROACHING MAX: At the first weld of Step 5, a STEPPER APPROACHING MAX ALERT is generated. This alert indicates the stepper program has started its final step.

    END OF STEPPER : At the last weld of Step 5, an END OF STEPPER FAULT is generated, which indicates the stepper program has ended. See Stepper Reset Options below.

    When the stepper program reaches the last weld of Step 5, the Tip Change Required output bit will go HIGH.

 

  • STEPPER GROUP:

    In example #2, Stepper #1 is assigned to Stepper Group 1. For more information, see Stepper Groups above.

 

  • MAXIMUM TIP DRESSES:

    In example #2, the Maximum Tip Dresses parameter is set to 2. This parameter defines the maximum number of times the weld caps may be dressed before they must be changed. The value programmed in this parameter sets the starting value of the Remaining Tip Dresses Count. Each time the weld processor receives a tips dressed index, the Remaining Tip Dresses Count decrements by one. When this count decrements to zero and the stepper program has reached the last weld of Step 5, an END OF STEPPER FAULT is generated. This indicates the weld caps must be changed.

    NOTE: Setting this parameter to zero disables the tip dress functionality within the stepper program.

 

  • AUX. COUNTER MAX COUNTS:

    Included in each stepper program is an Auxiliary Weld Counter, which is located in the Stepper Status Menu. When a stepper increments, its auxiliary weld counter also increments. When the counter reaches the value programmed in this parameter, the Aux Counter at Max output bit goes HIGH. This output bit can be used for any purpose by the user. Turning the Stepper Aux Weld Cntr Reset input bit HIGH resets the Auxiliary Weld Counter to zero and turns the Aux. Counter at Max output bit LOW. In example #2, the Aux. Counter Max Counts is set to zero. Therefore, the Aux Counter at Max output bit is disabled.



Stepper Status


stepper status menu overview

Perform the following steps on the DEP-300s to navigate to the Stepper Status Menu:

STEP
DESCRIPTION
01:
Press Status Mode (F3).
02:
Press Stepper Status (F3).
03:
Press Stepper# (F3).
04:
Enter Stepper Number.
05:
Press ENTER.

 

The following chart describes the parameters, which appear on the Stepper Status Menu:

PARAMETER
DESCRIPTION
Stepper

Turns the stepper either ON or OFF. The default postion is ON.

NOTE: This parameter is disabled in timer software version G08300.

Step #
The step number the stepper program is currently in (1 through 5)
Step Count
The weld count within the step the stepper program is currently in.
Boost %I

The current boost being applied to each weld.

NOTE: If a Percentage of Available Volt-Seconds weld function is used, this value will be displayed as a percentage. Conversely, if a Constant Current weld function is used, this value will be displayed in absolute amps.

Total Weld Count
The total weld count since the beginning of the stepper program.
Tip Dresses

The Remaining Tip Dresses Count is a decrementing counter, which starts at the number entered in the Maximum Tip Dresses parameter in the stepper profile. This counter defines the maximum number of times the weld caps may be dressed before they must be changed. Each time the weld processor receives a tip dress advance request (see note below), the Remaining Tip Dresses Count decrements by one. When this count decrements to zero, an END OF STEPPER FAULT is generated. This indicates the weld caps must be changed.

NOTE: A tip dress advance request occurs when (1) either the Tip Dress, Tip Dress Group 1 or Tip Dress Group 2 Input bits go HIGH or (2) function #93 (TIP DRESS ADVANCE: GROUP nn - STEP n) is used in the schedule.

Aux. Counter
The Auxiliary Counter is an incrementing counter, which mirrors the Total Weld Count counter above. Its max count is set by the value entered in the Aux Counter Max Counts parameter in the stepper profile.
Stepper #
The stepper program number currently displayed.
Advance

Pressing the Advance (F2) key, advances the stepper program to the first weld of the next step. When the stepper advances, the following changes will occur in the Stepper Status Menu:

  • The Step Count will reset to zero.
  • The Total Weld Count will advance to where its count would be at the first weld of the next step..
  • The Aux. Counter will not change when the stepper is advanced. If the user wants the Aux. Counter count to match the Total Weld Count, the value will have to be manually entered here.
Stepper #
Pressing the Stepper # (F3) key, allows the user to change the stepper program that is displayed.
ResetALL
Pressing the ResetALL (F4) key, globally resets all stepper programs.



Stepper Reset Options


An END OF STEPPER FAULT indicates the stepper program has ended. At this point, the weld caps must be replaced on the gun and the stepper program(s) must be reset. Stepper Reset changes all counts within the stepper program back to their beginning value. See example below:

stepper_status

In weld timer software G08300, there are three ways in which the user can reset stepper programs:


global stepper reset Option #1

Stepper programs can be globally reset by pressing the ResetALL (F4) button in the Stepper Status Menu. When this is done, all 10 stepper programs are "globally" reset, regardless of what group they are assigned to. The user needs to be cautious to only use this method if they are absolutely certain they want to globally reset every stepper program within the weld timer simutaneously.

Perform the following steps from the DEP-300s Stepper Status Menu to globally reset the stepper programs:

STEP
DESCRIPTION
01:
Press ResetALL (F4).
02:
The message "Do you want to RESET ALL STEPPERS" will appear.
03:
Press Confirm (F4).

global stepper reset option #2

Stepper programs can be globally reset by turning the Stepper Reset input bit HIGH. When this is done, all 10 stepper programs are "globally" reset, regardless of what group they are assigned to. The user needs to be cautious to only use this method if they are absolutely certain they want to globally reset every stepper program within the weld timer simutaneously.


group stepper reset

Stepper programs assigned to either Group 1 or Group 2 can be reset as a group. When the Stepper Reset Group 1 input bit is turned HIGH, all the stepper programs assigned to Group 1 will be reset. Likewise, when the Stepper Reset Group 2 input bit is turned HIGH, all the stepper programs assigned to Group 2 will be reset.


NOTE: Timer software version G08300 does not support the cabability to binarily reset individual stepper programs.


the following occurs at stepper reset

  1. STEPPER APPROACHING MAX ALERT is reset.
  2. END OF STEPPER FAULT is reset.
  3. All counts within the stepper program are changed back to their beginning value.

NOTE: Pressing the Fault Reset button on the DEP-300s will only reset the STEPPER APPROACHING MAX ALERT and the END OF STEPPER FAULT. It does not reset the stepper program(s).



Editing the Stepper Profile


  1. Perform the following steps on the DEP-300s to navigate to the Review Stepper Menu:
STEP
DESCRIPTION
01:
Press Program Mode (F2).
02:
Press Review Stepper (F3).
03:
Press Stepper# (F2)
04:
Enter Stepper Number.
05:
Press ENTER.

 

  1. Perform the following steps on the DEP-300s to edit a parameter on the Review Stepper Menu:
STEP
DESCRIPTION
01:
Press the UP or DOWN arrow keys to move the cursor onto the parameter line to be edited.
02:
Press ENTER.
03:
Enter parameter.
04:
Press ENTER.
05:
For parameters with two or more data fields, press the RIGHT arrow key to move the cursor to the next data field box, then repeat steps 3 & 4. When complete, proceed to step 6.
06:
Press APPLY (F2). [Saves changes to the DEP-300s only.]
07:
To edit more parameter lines, repeat steps 1 through 6. When complete, proceed to step 8.
08:
Press DOWNLOAD (F3). [Downloads the changes to the weld timer. When complete, a "Download Complete" message wil appear.]

 

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