Spot Welder
BY MOHAMED ABUZAID
Design Brief
I will be building a spot welder. My spot welder will
be able to weld two metal pieces together using
electric power which creates heat. To complete this
project I must first build and test the electronics. My
second step will be to build the wooden case for
the electronics meeting all specifications. Then
combining the two and completing the project. I will
attempt to complete the project before the end of
the year.
Specifications

Stay on budget $75

Use 4 to 0 AWG wire

Use 120v 60Hz transformer

Use momentary pushbutton switch to prevent
shock and unintended use

Use heavy gauge wire for input
Specifications
 Students must be capable of transporting their
project home.
 Individual projects may have additional
specification, determined by the individual
student or instructor.
 A professionally developed plan must be used to
create a product.
 Chosen designs must be approved by the
instructor.
 Products must be designed and built with
attention to detail. Emphasis must be place on
both form and function.
 Designs must be capable of being completed by
the end of the year.
Investigation
1. How can I dissipate the heat produced by the
modified transformer?
I can drill holes on the top of the case and add a fan.
2. What is the voltage to amperage ratio of the
modified transformer?
The voltage to amperage 2-3 volts and 600 amps < x
3. How big will the copper contacts need to be so that
they do not melt?
About a ¼” or thicker for long usage
4. What functions or components can be added to
reduce chance of injury?
I can add a circuit breaker, a momentary on/off
button, and master power switch.
Investigation
5. Are there any materials which I will need to obtain
myself? If yes, what is it, how much do I need, and
where can I get it?
6 ft. of 4 to 0 gauge copper wire, 1 circuit breaker, two
copper welding cable lugs, a foot of solid copper wire,
2 120v on/off switch and 2 copper offset these items
can be found at Lowes other items needed include
60hz 120v transformer and input cabling can be found
in any microwave. I also need a 120 mm fan, 5v
transformer, and a multimeter for testing I have all of
these items.
6. Will I be able to transport my project home after it is
completed?
The spot welder is small enough so that it can fit in my
car
Research
• Many safety features
• Heat is dissipated well
• Switch placement is far enough
To avoid injury but close enough
To adjust objects in between the
Copper contacts
• Small and easy to build but
Momentary switch placement
Is dangerous because it is near the
Hot surface
Research
Small portable but seem
uncomfortable and get hot
Because transformer is under
the handle
Large power requirements would
be too high but the durability of the
Contacts is good because the are large
And will not melt easily
Possible Solutions
Strength/
Durability
Solution 1
Solution 2
Solution 3
Solution 4
Safety
8
7
5
0.5
2.5 2.5
10
5
Functionality
7
10
5
10
Simplicity
Total
8.5 30.5
8 23.5
2
12
1 26
The table above is based on a 1-10 scale. 1 is poor, 10 is the best
Chosen Solution
Chosen Solution
Chosen Solution
Chosen Solution
Chosen Solution
Chosen Solution
Bill of Materials
Student(s)
Project
Mohamed Abuzaid
Spot Welder
Number of
Name of Part
Pieces
1
4 Gauge copper wire
6
Period
Lumber Species
L
72
Size (INCHES)
W
x
x
T
Board
Feet
6.00
Cost of
Material
$0.99
Cost of
Piece
$5.94
1
60Hz 120v Transformer
x
x
0.00
$0.00
$0.00
1
120v to 5v Transformer
x
x
0.00
$0.00
$0.00
1
input power cable
x
x
0.00
$0.00
$0.00
1
120 mm computer fan
x
x
0.00
$0.00
$0.00
1
Momentary Switch
x
x
0.00
$0.00
$0.00
2
120v on/off switch
x
x
0.00
$5.00
$10.00
1
copper screw type lugs
x
x
0.00
$4.50
$4.50
1
two copper welder calbe lugs
x
x
0.00
$4.50
$4.50
x
x
0.00
$4.00
$4.00
2
120v 15 to 20 amp circuit
breaker
Arm
Poplar
25
x
2
x
1
0.69
$1.24
$0.86
1
Base
Poplar
42
x
6
x
1
1.75
$1.24
$2.17
2
Side
Poplar
24
x
6
x
1
2.00
$1.24
$2.48
1
Top
Poplar
24.5
x
7
x
1
1.19
$1.24
$1.48
2
1
Arm Holder
Back
Poplar
Poplar
7
7
x
x
5
6
x
x
1
1
0.49
0.29
$1.24
$1.24
$0.60
$0.36
1
Name:
Mohamed Abuzaid
Total Bd.Ft.
6.41
20% Extra Bd.Ft.
1.28
Subtotal of Pieces
$36.89
Cost of 20% Extra
$1.59
Shipping
$2.25
Total Cost of Project
$40.73
Sources

http://hackaday.com/2009/06/23/how-to-buildyour-own-spot-welder/