DMFA (CORDLESS SCREWDRIVER)

GROUP 10

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.

PARTS LISTMotor 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 casingWasher Output shaftsCirclip Wire

Protectors

Motor

Epicyclic Gear System

IDENTIFICATION OF SUB-ASSEMBLIES

• MOTOR i. Circlipii. Input geariii. 6 small gearsiv. Washerv. Motor headvi. Sun gearvii. Annulusviii. Motorix. Output Shaft

• Poweri. Printed circuit board

(PCB)ii. Charging point plugiii. Battery pack

Motor

Printed Circuit Board

IDENTIFICATION OF SUB-ASSEMBLIES

• Outer Bodyi. 4 shorter screwsii. 2 longer screwsiii. Wire protectoriv. Lock switch & springv. Outer casing Black outer casing with the screws

ASSEMBLY SEQUENCE• Standard component electrically

soldered (switches, battery, motor, power)• Drill head Sub-assembly 1. Shafts and gears loaded into corresponding

slots2. Washer placed on drill head3. Circlip used to secure gears4. Lubricate5. 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.

COMPONENT MANUFACTURING AND ASSEMBLY PROCESSED USEDComponent Manufactur

ing 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

Gears Injection Molded

Component Manufacturing and Assembly Processed

Material

Input Injection Molded

Nylon

Sun Injection Molded

Nylon

Output Injection Mold

Acrylonitrile butadiene styrene (ABS)

Annulus Injection Molded

Nylon

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.

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?

CI HI AI0

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Assembly Analysis Results After Re-Design

Motor Sub-Assembly Electrical Sub-assembly

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Original Assembly Analysis Results

Motor Sub-Assembly Electrical Sub-assembly Case Sub-Assembly

Study of indices

CI CI(after) HI HI(after) AI AI(after)0

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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

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