1. DMFA (CORDLESS
SCREWDRIVER)
GROUP 10

2. INTRODUCTION
• Weighing at only 0.28 kg, this affordable screwdriver costs only £ 6.99
• Ergonomic and flexible handle design: The handle can be twisted and adjusted forming a
straight classic screwdriver like shape and a modern gun shape screwdriver to aid drilling
at difficult angles.
• This powerful 3.6 V screwdriver, also features a 50mm screwdriver bit and one torque
setting, producing a maximum of 2Nm torque.
• It is supplied with rechargeable battery which needs 3-5 hours charging time.
• It has a Customer’s overall rating of 3.5 out of 5.
• Most of the customers feel that it is a great screwdriver for the price involved. It is not the
most powerful, but for around the house stuff does the job perfectly with no aching
wrist/s involved.

3. PARTS LIST
Motor sub-
assembly
Electronic sub-
assembly
Outer sub-
assembly
Motor Battery Pack 4 shorter
screws
Input gear PCB 2 longer
screws
6 small gears Charging Point
Plug
Screw head
Sun gear PCB Lock switch
and spring
Annulus gear Switch Outer casing
Washer Output shafts
Circlip Wire Protectors
Motor
Epicyclic Gear
System

4. IDENTIFICATION OF SUB-ASSEMBLIES
• MOTOR
i. Circlip
ii. Input gear
iii. 6 small gears
iv. Washer
v. Motor head
vi. Sun gear
vii. Annulus
viii. Motor
ix. Output Shaft
• Power
i. Printed circuit board (PCB)
ii. Charging point plug
iii. Battery pack
Motor
Printed Circuit
Board

5. IDENTIFICATION OF SUB-ASSEMBLIES
• Outer Body
i. 4 shorter screws
ii. 2 longer screws
iii. Wire protector
iv. Lock switch & spring
v. Outer casing
Black outer casing with the screws

6. ASSEMBLY SEQUENCE
• Standard component electrically
soldered (switches, battery, motor,
power)
• Drill head Sub-assembly
1. Shafts and gears loaded into
corresponding slots
2. Washer placed on drill head
3. Circlip used to secure gears
4. Lubricate
5. Washer inserted
• Motor head screwed to motor.
• Outer casing rotation lever and
spring inserted into body, both
sub-assemblies placed in casing
and securing.
• Screws fastened to hold product
together.

7. COMPONENT MANUFACTURING AND
ASSEMBLY PROCESSED USED
Component Manufacturin
g and
Assembly
Processed
Material
Outer Casing Injection
Molded
Acrylonitrile
butadiene
styrene (ABS)
Outer Switch Injection
Molded
LED PCB Handmade • Circuit
Board
• LED
• Resistors
• Diode
Motor
attachment
to gearbox
Injection
Molded
Nylon
Component
Manufacturin
g and
Assembly
Processed
Material
Input Injection
Molded
Nylon
Sun Injection
Molded
Nylon
Output Injection
Mold
Acrylonitrile
butadiene
styrene (ABS)
Annulus Injection
Molded
Nylon

8. REDESIGN MOTIVATIONS AND
IMPROVEMENTS
• Remove spring and replace with molded
spring section
• Longer screws to improve visibility and
access when fixing together body
(however potentially more weight and
cost)
• Self securing drill head (may not be strong
enough instead of circlip to hold the head
on)
• Equal length screws to remove chance of
assembly with incorrect length screws)
• Put a magnetic drill head for holding drill
bit in place.
• Button for reversing drill direction only
good for right handed – shift button.

9. PART COUNT REDUCTION
• Lock adjust switch and spring
to be made into a single
component.
• The screws and the motor
head to be made into one
single component.
How do we reduce the number of
parts?

10. 0
5
10
15
20
25
30
CI HI AI
Assembly Analysis Results After Re-Design
Motor Sub-Assembly Electrical Sub-assembly
0
5
10
15
20
25
30
CI HI AI
Original Assembly Analysis Results
Motor Sub-Assembly Electrical Sub-assembly Case Sub-Assembly
Study of indices

11. 0
5
10
15
20
25
30
35
CI CI(after) HI HI(after) AI AI(after)
Assembly Analysis Results Before and After Re-Design
Motor Sub-Assembly Electrical Sub-assembly Case Sub-Assembly
Comparison of results before and after
Re-Design

12. COMPARISON
POSITIVES
• Turning handle-good design
allows for multi facet use
• Ergonomically well designed
• Protrusion to hang on wall
• Better grip surface, Light weight
• Rechargeable
NEGATIVES
• Turning handle wires may
twist and break
• Low stability while screwing
• Screws of different sizes
• Biased to right handed people