DFA Master Question Essay

Assignment Questions Total Worth this assgt=40%. Due 20 August in class.

Question 1-60%
(a) For the main bearing housing shown below, complete the attached Manual DFA worksheet.

Notes:
The main bearing assembly, assembly is made by first placing the screws into a fixture to hold both screws in an inverted (upturned) position:
The fixture has a fixed, dummy screw driver bit at its base:
The cost of Manual Assembly is 0.5c/second:
Neither Screwheads nor tips have easy-to-align features.

Required Diagram is the image from the hub entitled ‘Diaphragm Valve”

Complete the Table

Standard Design for Manual Assembly Worksheet with st. column nos.

1
2
3
4
5
6
7
8
9 Items to be handled: Actions for Assembly



P= Prismatic: C= Cylindrical Envelope t s
1
2

Upturn screws and place into a fixture.

2
1

Place inverted bearing housing onto screw

3
1

Assemble plate onto screw

4
2

Assemble washers onto screws

5
2

Tighten regular nuts onto screws

TM
CM
NM
=
(=100*(3*NM/TM))

(b) A redesign of the assembly is shown below:

This diagram will be handed out in class

Complete the attached Manual DFA worksheet for the re-design, noting additionally that the joining process requires a special 3 second heat weld.

Re-Design for Manual Assembly Worksheet

1
2
3
4
5
6
7
8
9 Item

4
1

Place inverted, redesigned bearing housing onto fixture
180
360
540
P
10
48
3
1

Place plate into bearing housing
180
180
360
P
1.5
60 1

9x
3

3 second heat weld bearing housing to plate

TM
CM
NM
=

(=100*(3*NM/TM))

In all cases (a) and (b) , TM, CM NM and efficiency η% are required.

Question 2…20%

(a) You are required to design a product that fits into the boot of a new automobile to effect owner-assisted wheel changing. The device will comprise a minimum number of components.

You are to consider the following: a typical car jack will lift a vehicle sufficient to provide only a maximum of 100mm ground clearance for the damaged wheel: a modern wheel is bulky and heavy.

(b) Wheel changing needs to be performed from a low body posture – typically from a kneeling position on the ground. From here, it is awkward and difficult to: lift the wheel onto the wheel studs: both hold and rotate the wheel to align holes in the wheel’s hub with the studs protruding from the rear axle: do so in the absence of even a small, projecting stub axle on which to temporarily suspend the wheel. consider that once a vehicle is jacked up sufficiently to allow removal of the damaged wheel, this height setting is not to be altered for any other purpose- particularly to incorporate your solution.

(c) You may assume hat the driver has lifted the wheel from the vehicle’s wheel well and placed the wheel on the ground:

You are to design a device that will address the points in (b), using the principles of product design for assembly (DFA).
Your 1-A4 page only submission must:

provide an annotated, self-explanatory, exploded diagram of your solution: specify the total number of individual parts in your design solution: not include sub assemblies: you must not use the car jack to micro-adjust the height of the car to suit the stud holes in the wheel. It is your device that must lift the wheel into position,

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