NOTE: This portion of the documentation covers the advanced topics 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


« 8: Linear Current Steppers | 10: Fault Diagnostics »

Chapter 9: Advanced Topics

In this section:

 


Percent of Available Volt-Seconds Welding Mode


Percent of Available Volt-Second Welding

 


Constant Current Welding Mode


Constant Current Welding

 


C-Factor


introduction to c-factor

C-Factor (or Capacity Factor) is a parameter, which is used to track changes in the weld tooling. C-Factor is calculated by determining the amount of total capacity utilized to create the target current and dividing this value by the actual current created.

The C-Factor feature can be used as a maintenance tool to monitor the following:

  • Weld tooling degradation
  • Current shunting paths (primary or secondary)

C-Factor is calculated by the weld processor after each weld and is displayed in the Weld Data Display of the DEP-300s.

Perform the following steps on the DEP-300s to navigate to the Weld Data Menu.

STEP
DESCRIPTION
01:
Press Status Mode (F3).
02:
Press More (F5).
03:
Press Weld Data (F3).
04:
Press ENTER.

Below is an example of the Weld Data Menu. The C-Factor parameter is circled in red.


Decreasing C-factor

As the weld tooling degrades over time, its resistance (either primary or secondary) increases. As the resistance increases, the weld control must compensate for this change, otherwise the welds would gradually grow colder. Weld tooling degredation can be caused by the following conditions:

  • Frayed or undersized (MCM) welding cables.
  • Welding cables too long for application.
  • Broken or undersized leaf shunts.
  • Loose hardware connections.
  • Incorrect hardware (mild steel vs. stainless steel).
  • Incorrect weld caps for application.

As the resistance of the weld tooling gradually increases, the weld control gradually increase its "on-time" (or use more of its available capacity) to deliver the requested target current. This gradual decrease in available capacity of the weld control is reflected by a gradually decreasing the C-Factor parameter.


increasing c-factor

Current shunting (either primary or secondary) is essentially an unintended, alternate path of current flow occuring in the weld tooling. Current shunting causes the overall resistance of the weld tooling to decrease. As current is shunted across the alternate path, less current passes through the work piece, resulting in colder welds. Secondary current shunting paths can be caused by the following conditions:

  • Cable shorts to weld tooling or part.
  • Weld expulsion (slag) build-up around the hinge of the weld gun.
  • Cooling water conductivity issues.

As the resistance of the weld tooling gradually decreases, the weld control gradually decrease its "on-time" (or use less of its available capacity) to deliver the requested target current. This gradual increase in available capacity of the weld control is reflected by a gradual increase in the C-Factor parameter.


C-Factor Setup

  1. Prior to using the C-Factor feature, it is important to establish what the reference C-Factor parameter is for a known good weld tool. After completing several tip-to-tip test welds, record the C-Factor parameter displayed in the Weld Data Menu of the DEP-300s for future reference.

  2. Insert function #92 (C-FACTOR LIMIT: HI= nnnn LOW= nnnn) near the beginning of the weld schedule. See example schedule below:

NOTE: Function #92 must be inserted in the weld schedule before function #85 (PROCESS WELD FAULTS).

FUNCTION NO.
FUNCTION NAME
00:
START OF SCHEDULE # 1
82:
LINEAR STEPPER #1 ASSIGNED (0=0FF)
92:
C-FACTOR LIMIT: HI= 220 LOW= 150
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
85:
PROCESS WELD FAULTS
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. Calculate the C-Factor HI / LOW Limit values:

NOTE: The following instruction provides a starting point for the C-Factor HI / Low limits. These values will require adjustment as the user becomes more familiar with the weld tooling and what the C-Factor parameters are when weld quality issues occur (caused by either weld tooling degredation or current shunting).

LOW C-FACTOR LIMIT

The Low C-Factor Limit is used to detect an increase in resistance in the weld tooling, which is caused by cable and connection degredation. See Decreasing C-Factor above.

To calculate the Low C-Factor Limit value, subtract a 20% margin from the reference (tip-to-tip) C-Factor parameter for a known good weld tool.

For example, if the reference C-Factor parameter is 200: 200 *.80 = 160. Therefore, the Low C-Factor Limit would be 160.


HIGH C-FACTOR LIMIT

The High C-Factor Limit is used to detect a decrease in resistance in the weld tooling, which is caused by shunting paths. See Increasing C-Factor above.

To calculate the High C-Factor limit value, add a 20% margin to the reference (tip-to-tip) C-Factor parameter for a known good weld tool.

For example, if the reference C-Factor parameter is 200: 200 * 1.2 = 240. Therefore, the High C-Factor Limit would be 240.


  1. Set the HI and Low C-Factor Limit Faults in the Setup Parameters as follows:
FAULT NAME
VALUE
LOW C-FACTOR LIMIT
(ALERT)
HIGH C-FACTOR LIMIT
(FAULT)
  • Gradual weld tool degradation is an expected process. Therefore, Low C-Factor is set as an ALERT.
  • Secondary current shunting is not an expected process and requires immediate attention. Therefore, High C-Factor is set a FAULT.


SPC Indexing Capabilities


Spc (STATISTICAL PROCESS CONTROL) functions


Function #87: SET SPC OFFSET TO nn

For the purpose of statistical data collection, each weld is assigned a data storage bin number (00-99). This function establishes the starting bin number for SPC Indexing. Consider the following example:

CAR TYPE #1
Weld Schedule #20 SET SPC OFFSET TO 01
Weld Schedule #01 15 Welds Made (Bins 1-15)
Weld Schedule #02 15 Welds Made (Bins 16-30)
Weld Schedule #03 15 Welds Made (Bins 31-48)
CAR TYPE #2
Weld Schedule #21 SET SPC OFFSET TO 51
Weld Schedule #04 12 Welds Made (Bins 51-62)
Weld Schedule #05 12 Welds Made (Bins 63-74)
Weld Schedule #06 15 Welds Made (Bins 75-88)

After establishing a bin number, the processor stores the data for each weld made in its own individual bin. The bin numbers increase by one each time a weld is made. This will continue until another schedule containing function #87 (SET SPC OFFSET) is executed.

Bin #99 is the last usable bin. If the weld processor reaches bin #99 and is still collecting data, the data for each weld will be stored in bin #99 until a new offset is assigned, therefore making the data unsuitable for analysis.

NOTE: This function does not tell the weld processor to collect weld data. It only assigns a data storage bin number. To setup SPC data collection parameters, see SPC Setup Parameters below.


Function #88: SEND ALL SAMPLES UNTIL NEXT SPC OFFSET

This function is useful to verify tool conditions after a tip-dress operation.

This function tells the weld processor to collect and sample 100% of the weld data within the schedule. It overrides the "global" Data Collection Sample Size and Data Collection Sample Frequency setup parameters, described in SPC Setup Parameters below.

Function #87 (SET SPC OFFSET) should be inserted before #88 in the weld schedule, to ensure the data is sent to the appropriate bin. Otherwise, it will be sent to default bin #0.

The processor will continue collecting and sampling 100% of the weld data within the schedule until the weld processor executes another weld schedule containing function #87 (SET SPC OFFSET). At which point, the "global" Data Collection Sample Size and Data Collection Sample Frequency setup parameters regain their hierarchical priority.

For more information, see SPC Data Collection and Binning.


spc setup parameters

PARAMETER
RANGE
DATA COLLECTION SAMPLE SIZE: 5 (1-99)
DATA COLLECTION SAMPLE FREQUENCY: 100 (1-9999)

These two parameters set a global command, which allows the weld processor (WCU) to sample data for analysis at controlled intervals.

  • The sample size is the number of consecutive welds collected for analysis (per bin).
  • The sample frequency is the total number of welds, from which the samples are taken from (per bin).

For example:

Let's assume function #87 (SET SPC OFFSET) is inserted in the weld schedule and set to bin #1:

87
SET SPC OFFSET TO 01

Let's also assume in the Setup Parameters, the Data Collection Sample Size is set to (2) and the Data Collection Sample Frequency is set to (8):

DATA COLLECTION SAMPLE SIZE: 2
DATA COLLECTION SAMPLE FREQUENCY: 8

By setting the Data Collection Sample Size to (2) and the Data Collection Sample Frequency to (8), the WCU will collect data for the first two consecutive welds (in bin #1) and flag the WebView to retrieve the data. It will then collect data for the six remaining welds (without flagging the WebView) before repeating the process.

The following table illustrates the example above:

BIN #1
SAMPLE / FREQUENCY
WCU PROCESS
WEBVIEW PROCESS
1/8 Data Flagged for Retrieval Data Uploaded
2/8 Data Flagged for Retrieval Data Uploaded
3/8 Data Collected Data Ignored
4/8 Data Collected Data Ignored
5/8 Data Collected Data Ignored
6/8 Data Collected Data Ignored
7/8 Data Collected Data Ignored
8/8 Data Collected Data Ignored
1/8 Data Flagged for Retrieval Data Uploaded
2/8 Data Flagged for Retrieval Data Uploaded
3/8 Data Collected Data Ignored
4/8 Data Collected Data Ignored
5/8 Data Collected Data Ignored
6/8 Data Collected Data Ignored
7/8 Data Collected Data Ignored
8/8 Data Collected Data Ignored

NOTE: Weld data collection is bin dependent. Each bin has its own independent counter and is uploaded to the WebView separately.

For more information, see SPC Data Collection and Binning.



Tip Dress Schedule Setup


standard TIP dress schedule

The following is an example tip dress schedule when the weld control is not controlling the tip dress motor.

 

FUNCTION NO.
FUNCTION NAME
00
START OF SCHEDULE # n
58
TURN ON WELD IN PROGRESS
01
SQUEEZE 30 CYCLES
93
TIP DRESS ADVANCE: GROUP 01 - STEP 2
59
TURN OFF WELD IN PROGRESS
63
TURN ON WELD COMPLETE
03
HOLD 5 CYCLES
51
TURN OFF WELD COMPLETE
100
END OF SCHEDULE

 

TIP DRESS CHECK SCHEDULE

The following is an example tip dress schedule where the weld control is controlling the tip dress motor. This feature requires an optional tip dress motor control circuit installed in the weld control cabinet (see note below). This schedule also monitors or "checks" the current draw of the tip dress motor. The purpose of this check is to (1) protect the motor from damage and (2) determine if the weld caps were properly cut.

NOTE: If your weld control cabinet does not have the optional motor control circuit installed and you are interested in using this feature, contact your WTC sales representative for assistance.

 

FUNCTION NO.
FUNCTION NAME
00
START OF SCHEDULE # n
16
MOTOR CURRENT LIMITS HI=6000 ma LO=1000 ma
58
TURN ON WELD IN PROGRESS
18
START TIP DRESS MOTOR CHECK
17
TIP DRESS TIME 5 SEC BLANK 500 ms
19
STOP TIP DRESS MOTOR CHECK
59
TURN OFF WELD IN PROGRESS
63
TURN ON WELD COMPLETE
03
HOLD 5 CYCLES
51
TURN OFF WELD COMPLETE
100
END OF SCHEDULE

 

Description of the special functions (in red above) used in the tip dress check schedule:

  1. Function #16 (MOTOR CURRENT LIMITS HI=nnnn ma LO=nnnn ma) sets the HIGH and LOW current limits for the tip dress motor current being measured.
  1. Function #18 (START TIP DRESS MOTOR CHECK) tells the weld processor to turn the tip dress motor ON.

NOTE: This function must be inserted in the schedule after function #16 (MOTOR CURRENT LIMITS HI=nnnn ma LO=nnnn ma).

  1. Function #17 (TIP DRESS TIME nn SEC BLANK nnnn ms) sets the total amount of time (in seconds) the tip dress motor is ON. The blanking time (in milliseconds) is the period of time the weld processor does not measure the motor starting (in-rush) current.

NOTE: This function must be inserted in the schedule after function #18 (START TIP DRESS MOTOR CHECK) and before function #19 (STOP TIP DRESS MOTOR CHECK).

  1. Function #19 (STOP TIP DRESS MOTOR CHECK) tells the weld processor to turn the tip dress motor OFF.

 

Mode of Operation:

  1. After the blanking time, the motor current is checked every 8ms until either a function #19 (STOP TIP DRESS MOTOR CHECK) is reached or a fault occurs.
  2. If the measured motor current is above the LOW limit for 1 or more seconds of accumulated time, the tip dress is considered good.
  3. If the measured current is above the LOW limit for less than 1 second of accumulated time, a TIP DRESS FAULT is generated. Probable causes include:
    • Insufficient gun pressure on the cutting blades.
    • Weld caps did not come in contact with cutting blades (no load on motor).
    • Improper weld cap fit-up on the cutting blades.
  4. If the measured motor current is above the HIGH limit any time during the 8ms checking period, the motor is immediately turned off and a HI / NO MOTOR CURRENT FAULT is generated. Probable causes include:
    • Motor stall caused by a mechanical failure in the cutting head.
    • Motor stall caused by a Jam in the cutting blades.
    • Too much gun pressure on the cutting blades (excessive load on motor).
  5. If the measured current is <=20ma any time during the 8ms checking period, the motor is immediately turned off and a HI / NO MOTOR CURRENT FAULT is generated. Probable causes include:
    • Motor did not turn on (motor starter relay did not energize).
    • Current feedback coil did not measure any current (loose/open wire).

 

Notes:

  1. The Tip Dress Time includes the Blanking Time. Therefore, If the Tip Dress Time minus the Blanking Time is less than 1 second, a TIP DRESS FAULT will occur.
  2. As a good starting point: Tip Dress Time = Blanking Time + 1010ms (1.01 sec). The idea is to ensure the time the motor current is actually being measured is greater than 1 second (1 second = 1000ms).
  3. Set properly, the Blanking Time prevents erroneous HIGH / NO MOTOR CURRENT FAULTS from occuring, caused by the motor starting (in-rush) current. The Blanking Time will vary depending on the design specifications of the motor being used. The idea is to blank-out (or not measure) the motor starting (in-rush) current.

 

motor current measurement results

The results of the tip dress motor current check are displayed in the Weld Data Menu. Perform the following steps on the DEP-300s to navigate to the Weld Data Menu.

STEP
DESCRIPTION
01:
Press Status Mode (F3).
02:
Press More (F5).
03:
Press Weld Data (F3).
04:
Press ENTER.

In the example below, the results are displayed in the Sec I column (circled in red) in milliamps. There are three current measurements displayed: MAX current, AVG current and MIN current.

 



Application Error Codes


I/O STATUS

To navigate to the I/O Status Menu, perform the following steps on the DEP-300s:

STEP
DESCRIPTION
01:
Press Status Mode (F3).
02:
Press More (F5).
03:

Press IO Status (F2)

04:
Press Page 2 (F5) to view more bits (if applicable)

In the example above, the I/O Status Menu shows the mapped bits relating to the application error codes (circled in red). It should be noted this is a simplified example and the customers application requirements may require these bits to be mapped to different I/O locations.

Each bit is represented by a tag. Each tag will have either a "1" or "0" underneath it:

  • "1" indicates the bit is HIGH or ON.
  • "0" indicates the bit is LOW or OFF.
TAG NAME
BIT NAME
BIT TYPE
FACK
APP ERR ACKNOWLEDGE
Input
EVAL
APP ERROR AVAILABLE
Output
ER1
APP ERROR BIT 1
Output
ER2
APP ERROR BIT 2
Output
ER4
APP ERROR BIT 4
Output
ER8
APP ERROR BIT 8
Output
ER16
APP ERROR BIT 16
Output

NOTE: For more information on mapping I/O bits, see Reference Chapter E: Inputs and Outputs.

 

how error codes are reported

The following example is a robot welding application where the weld processor is reporting three application error codes:

Error Code
Fault Family
Weld Control Fault
5
End of Stepper
End of Stepper
7
High / Low Current Limit
Low Current Limit Fault
19
C-Factor Limit
Low C-Factor Limit

Note: Multiple application error codes are reported in ascending order.

  1. When a faults occurs, the EVAL output bit goes HIGH and application error code (5) is binarily displayed on the ER1-ER16 output bits.
  2. The HIGH EVAL output bit tells the robot to read the ER1-ER16 output bits.
  3. When the robot has read the ER1-ER16 output bits, it toggles the FACK input bit.
  4. The toggling FACK input bit causes the EVAL output bit to toggle. When this toggle occurs, the next application error code (7) is binarily displayed on the ER1-ER16 output bits.
  5. The toggling EVAL output bit tells the robot to read the ER1-ER16 output bits a second time.
  6. When the robot has read the ER1-ER16 output bits, it toggles the FACK input bit.
  7. The toggling FACK input bit causes the EVAL output bit to toggle. When this toggle occurs, the next application error code (19) is binarily displayed on the ER1-ER16 output bits.
  8. The toggling EVAL output bit tells the robot to read the ER1-ER16 output bits a third time.
  9. When the robot has read the ER1-ER16 output bits, it toggles the FACK input bit.
  10. The toggling FACK input bit causes the EVAL output bit to toggle. When this toggle occurs, the weld processor scrolls and re-displays application error code (5) on the ER1-ER16 output bits.
  11. The toggling EVAL output bit tells the robot to read the ER1-ER16 output bits a fourth time.
  12. When the robot reads the ER1-ER16 output bits, it recognizes that it has previously read application error code (5) and the reporting process ends.

 

Click HERE to see the Application Error Codes for timer software G08300.

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