Resistance Welding Schedule Development Book Bob Szabo

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Table of Contents
Chapter 1
INTRODUCTION
1-1.
Resistance welded products
25
1-2.
Poorly welded products
Weld schedule problems
Excessive weld times
Two weld hits necessary
Inadequate trial and error
Big mistakes
26
27
27
27
27
28
1-3.
Weld parameter combination
Robust weld schedule
Many weld schedules work OK in short term
28
29
29
1-4.
Weld schedule developed from process windows and lobes
Is best for long run
Successful example
Case for Organized development
Only one setting to adjust on all machines
30
30
31
31
1-5.
Justification
32
1-6.
Process windows introduction
32
1-7
Weld lobes introduction
Weld lobes for different parameters
Weld lobes for three parameters
Middle of volume reveals optimum combination
33
35
36
37
1-8
History
Early introduction to the development of weld schedules from process windows and lobes
Industry examples
Further discussion of the savings
Savings estimate stands up
Cheaper the first time
38
38
39
40
40
Chapter 2
BACKGROUND
2-1.
Why weld lobes and process windows
Misleading visual indications on weld surface
41
42
2-2.
Weld metallographs
42
2-3.
Adjustment for visual appearance
Problem with visual appearance
Spreading a habit
No color with Aluminum or Titanium
44
44
44
45
2-4.
Automatic or semi-automatic control
45
2-5.
Visual inspection in arc welding
45
2-6.
Resistance weld testing for hidden weld characteristics
Repeatability is necessary
46
46
2-7.
The weld schedule
47
2-8.
Other resistance welding processes
% heat setting weld controls
Constant current weld controls
Settings that effect the outcome
48
48
49
49
2-9.
Standard weld schedule for resistance welding
49
2-10.
Experiment: Weld Schedule Selection
50
2-10.1
Purpose
50
2-10.2
Resources
50
2-10.3
Procedure
50
2-10.4
Results
51
2-10.5
Conclusion
51
2-11.
Need for a custom weld schedule
Resistance welding behavior
Some minimum amount of a parameter necessary
The solution
52
53
53
53
2-12.
Complicating factors
Shunting
Metal thickness ratios
Polarity
Other complications
54
54
54
55
55
2-13.
The weld schedule developer
Technician #1
Machine standards allowed for his behavior
His behavior limited
Technician #2
56
56
56
57
57
2-14.
Robust weld settings
Example of what is not robust
57
58
2-15.
Weld schedule development environment
59
2-16.
Need for a procedure
60
2-17.
Need for written records
Without written records
Hidden benefit from written records
Three days wasted
60
61
61
61
2-18.
Repair weld facilities
Repair weld process control oversight
62
62
Chapter 3
WELD STRENGTH VS. WELD SIZE
65
3-1.
Why measure weld size
65
3-2.
Weld size strength relationship
65
3-3.
Maximum strength
68
3-4.
Process capability study
When size does not assure strength
Introduction to experiments
69
69
69
3-5.
Experiment: Weld strength and size relationship in mild steel
70
3-5.1.
Purpose
70
3-5.2.
Resource
70
3-5.3.
Procedure
70
3-5.4.
Results
72
3-5.5.
Discussion
Column 1: % heat
Column 2 & 3: test & failure mode
Column 4 & 5: shear strength pounds & kilograms
Column 6 & 7: nugget diameter inches & millimeters
72
72
73
73
73
3-5.6.
Results: Strength VS. size
74
3-5.7.
Discussion
74
3-5.8.
Results: Weld nugget size vs. % heat
75
3-5.9.
Discussion
Not a trivial problem
75
76
3-5.10.
Recommendations for further experimentation
Note 1: problem with high % heat
Note 2: problem with raising tap
Note 3: value of this method is shown
Note 4: problem from inadequate written records
76
77
77
77
78
3-6.
Experiment: Weld strength and size relationship in one aluminum application
78
3-6.1.
Purpose
78
3-6.2.
Resources
78
3-6.3.
Procedure
79
3-6.4.
Results
80
3-6.5.
Discussion
80
3-6.6.
Results: Weld nugget size vs. strength
81
3-6.7.
Discussion
81
3-6.8.
Results: Weld % heat vs. shear strength
82
3-6.9.
Discussion
Aluminum surface preparation problem
Recommended aluminum surface preparation
Inadequate amount of data
However data was adequate for the conclusion!
82
82
83
83
83
3-6.10.
Recommended additional exp.
Note 1: number of data points
Note 2: conclusions about aluminum, resistance welding
from this experiment should be limited
Note 3: limitations from absence of rec.
Note 4: even experiments with problems should be reported
Conclusions from both experiments
Typical experiment size
84
84
84
85
85
86
86
3-7.
Weld size and strength data from US Government Military Specification Mil-W-6858D
Effect of metal strength on the weld strength requirement
Sources for weld strength and size data
88
89
89
3-8.
Adequate written records
When weld strength is difficult to measure in production
Inadequate data even from good setups
Later on without written records
89
90
90
90
3-9.
Example of unshared findings
91
3-10.
Note about the remainder of the book
91
Chapter 4
PROCESS WINDOWS
4-1.
Process window introduction
Common example
93
93
4-2.
Weld % heat and weld current
Tip-off: weld % heat not absolute
Limitation of weld % heat process window
93
94
94
4-3.
Other weld characteristics goals
Process window goals
Electrode sticking
95
95
96
4-4.
Fragile weld schedules
96
4-5.
Preliminary view
96
4-6.
Squeeze time process window
Squeeze time periods
97
97
4-7.
Shift to shift variations
During second shift
During first shift
Remedy
Common problems
Solution discussion
98
98
99
99
99
100
4-8.
Undersized air supply components
100
4-9.
Pressure switch initiation
Another way for pressure switch utilization
101
102
4-10.
Weld current process window
102
4-11.
Weld time process window
Benefits of longer weld time
103
104
4-12.
Hold time process windows
Weld valve mechanical delay note
Perils of long hold time
105
106
106
4-13.
Electrode force process window
108
4-14.
Process window summary
109
4-15.
Experiment: Weld current and time windows
110
4-15.1.
Performance objective
Develop weld current and time windows for optimum welding
110
110
4-15.2.
Resources
110
4-15.3.
Weld current window procedure
111
4-15.4.
Weld current window data
111
4-15.5.
Weld time window procedure
112
4-15.6.
Weld time window data
112
4-15.7.
Conclusion
112
4-15.8.
Recommendations
Added weld sample tests
Added experimental goals
112
113
113
Chapter 5
WELD LOBES
5-1.
Weld lobe introduction
Lobe determines the center
115
115
5-2.
Weld current range
116
5-3.
Weld time range
117
5-4.
Weld lobe for current and time
117
5-5.
When to start with a current and time lobe
118
5-6.
About the shape of a lobe
119
5-7.
Experiment: Weld lobe for current and time
119
5-7.1.
Performance objective
119
5-7.2.
Resources
120
5-7.3.
Weld current and time lobe procedure
120
5-7.4.
Weld current and time lobe data
121
5-7.5.
Weld current and time result
122
Chapter 6
WELD FORCE LOBES
6-1.
Introduction
123
6-2.
Weld current and force lobe
123
6-3.
Why current and force lobe development
A case for current and force lobe first
123
124
6-4.
Note: look at slope, pulsation……….
124
6-5.
Note: Assumption of best electrodes
124
6-6.
Note: Assumption of the best resistance welding process
125
6-7.
The lobe gets to the answer quickly
Weld lobe development cuts to chase real fast
125
125
6-8.
Some cases that do not work
Process window and lobe experiments analytically sort out conclusions: good or bad
125
126
6-9.
Back to the current and force lobe
126
6-10.
The chart
127
6-11.
Discussion for weld current and force lobe result
Good welds
Bad welds
Cold welds
Hot welds
127
128
128
128
128
6-12.
Weld force and time lobe
A case for weld force and time lobe first
128
128
6.13.
Back to the force and time lobe
129
6-14.
The chart
129
6-15.
Discussion for weld force and time lobe
Good welds
Bad welds
Cold welds
Hot welds
130
130
130
130
130
6-16.
Summary
131
6-17.
Weld lobe procedure (for optimum weld size with no expulsion)
Resources:
Machine setup:
Complicating factors:
Current window:
Weld time window:
Plot data
Force lobe
132
132
132
133
133
134
134
134
6-18.
Experiment: Weld lobe for current and force
135
6-18.1.
Performance objective
135
6-18.2.
Resources (same as Experiment 5-7)
135
6-18.3.
Weld current and force lobe procedure
136
6-18.4.
Weld current and force lobe data
136
6-18.5.
Weld current and force lobe results
137
6-18.6.
Conclusion
137
Chapter 7
WELD SCHEDULE EXAMPLE DEVELOPED FROM WELD LOBES
7-1.
The setup
139
7-2.
Seasoned electrodes
141
7-3.
Worn electrode condition setup
Electrode life observation
Worn electrodes from factory production did not work for simulation
Worn condition confirmation
Electrode parallelism chart
141
141
142
142
143
7-4.
The weld schedule chart
143
7-4.1.
Weld
schedules for bare and electroplate galvanized steel
144
7-5.
Complicating factors
For example
146
147
7-6.
Use of the values
The alternative
148
148
Chapter 8
PROCESS WINDOWS FOR OTHER SETTINGS
8-1.
Introduction
149
8-2.
Upslope
Benefits of low starting heat
Summary recommendation
About the shape of a lobe
Theoretical effect of upslope on the weld lobe process window
Caution with some weld equipment
Caution for certain aluminum materials and other materials that may be slope sensitive Note: sometimes slope without choice
149
150
151
151
151
152
153
153
8-3.
Pulsation
Typical pulsation weld schedule
Theoretical effect of pulsation on the weld lobe process window
Why go to the trouble
Automobile wheel weld impulse schedule
Impulse schedule for steel wheel welding
Narrow flange width welding
Pulsation equipment warning
154
154
154
155
155
155
156
156
156
8-4.
Decay or temper current
Theoretical current decay lobe in aluminum
Summary decay current tip
Other decay or temper studies
157
157
158
159
8-5.
Stepper lobe for spot welding
Problem
One solution
Advanced stepping of weld time and/or force
159
159
160
162
8-6.
Current vs. force lobe results for bad fitting parts
Test simulation for poorly fitting aluminum parts
Use of electrically insulated shim
163
163
163
8-7.
Experiment: Stepper lobe for current & weld count
164
8-7.1.
Performance objective
164
8-7.2.
Resources
164
8-7.3.
Stepper lobe procedure
165
8-7.4.
Stepper lobe data
166
8-7.5.
Weld current vs. count lobe results
167
8-7.6.
Conclusion
167
8-8.
Experiment: Adjacent welds supplement
167
8-8.1.
Performance objective
167
8-8.2.
Procedure
168
8-8.3.
Data for second weld
168
8-8.4.
Results
168
8-8.5.
Discussion
Repeated for many applications in one facility
Adjacent weld tip
Remaining work
169
171
171
171
Chapter 9
EXPANDING PROCESS WINDOWS AND LOBES
9-1.
List of process windows that can be developed
Section summary
173
174
9-2.
List of weld lobes that can be developed
175
9-3.
List of weld characteristics to be indicated on a weld lobe chart
Section summary
176
177
9-4.
Three dimensional weld lobes
Expanding the value of the experiment
178
178
9-5.
Advanced experimental tools
179
9-6.
Long weld time example
179
9-7.
Avoid blindness from experimental plan
180
9-8.
Design of experiments
Not a substitute for the basics
180
181
9-9.
Other applications
Other manufacturing processes
182
182
9-10.
Conclusion
Resistance welding benefits, successful in certain large industries, are available to other industries
183
183
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