Design 101 http://goo.gl/wIql8w Week 2 Machine Element Design New Approach Course Objective =============== This is a fundamental course to discuss the criteria of Mechanical Design for both machine elements design and product design . The course will discuss the design as a process in making a lot of products by terms of manufacturing , sustainability and environmental aspects The Course is online and free to all Instructor Mohamed Mostafa Adam This course was presented by PED 2016 Production Engineering Department - Faculty of Engineering - Alexandria University - Egypt

1. Machine Element
Design New Approach
Week 2

2. Week Content
• Terminologies
• Building the Foundation of Machine Element Design
• Manufacturing Consideration (Process & Planning)
• Examples on Machine Element Design
Belts
Chains
Gears
Springs

3. Terminologies
• What is a Machine ?
A device consisting of fixed and moving parts that modifies
mechanical energy and transmits it in a more useful form

4. Terminologies
What is an Element
• All the machines are made up of elements or parts and units.
• Each element is a separate part of the machine and it may have to be designed
separately and in assembly.
• Each element in turn can be a complete part or made up of several small pieces
which are joined together by riveting, welding etc.
• Several machine elements are assembled together to form what we call as complete
machine.

5. Terminologies
• What is (DFA) Design for Assembly
is a process by which products are designed with ease of assembly in mind
If a product contains fewer parts it will take less time to assemble

6. Building the Foundation of Machine Element Design
• Types of Machines
 Mechanical
 Hydraulic
 Pneumatic
 Electrical
 Complex Systems
 Robotics

7. Building the Foundation of Machine Element Design
• If we want to build up a machine what the main parameters to
be consider ?
Material
Geometry
Dimension
But how to control this 3 factors
Fourth Factor

8. The 4th Factor (Manufacturing)
Historical Brief
The word “manufacture” appeared in the 16th century and it is
derived from the Latin
“manu factus” which means “made by hand” .
Manufacturing appeared at 5000-4000 BC, the earliest forms of
manufacturing were invented by Sumerians around 3500 BC

9. Manufacturing Consideration
• What is manufacturing?
• A combination of processes applied on materials to convert it
into products

10. Manufacturing Consideration
• What is DFM?
• DFM is abbreviation for Design For Manufacturing and it
expresses a comprehensive approach to integrate the design
with production methods.
DFM includes the Manufacturing considerations

11. Manufacturing Considerations
• was discussed from many points of view and classifications, no
doubt that all these ones must be covered under the
Manufacturing Plan.
Here we will discuss the most common Considerations
Cost
Time
Quality
Safety
Environment

12. The Role And Requirements Of Manufacturing Engineer
• The main role is to carry out the design through planned manufacturing
processes into the desired product so, the manufacturing engineer must
have these abilities :
 designing new systems and processes for the introduction of new products or for
the improvement of existing ones
 working with other engineers, such as chemical engineers, mechanical
engineers, electrical engineers, to ensure all product and system requirements
 examining and tendering for new equipment to ensure the highest quality at the
best price
 organizing plant start-up and shut-down schedules

13. Examples on Machine Element Design
• This Elements were chosen based on this 3 criteria
Famous and can be found in most of machines
Have many types and shapes
Don’t need high based knowledge to design and manipulate

14. Belts
• The belts or ropes are used to transmit power from
• one shaft to another by means of pulleys which rotate at the
• same speed or at different speeds

15. Belts
• The amount of power transmitted depends upon the following
factors
The velocity of the belt.
 The tension under which the belt is placed on the pulleys.
The conditions under which the belt is used.

16. Belts Classification
Belt DrivesType of Belt
 Light Drives
 Medium Drives
 Heavy Drives
 Flat Belt
 V-Belt
 Circular or Robe Belt

17. Materials of Pulleys
Cast Iron
Cast Steel
Paper Pulleys

18. Timing Belt
• It has other names notch belt, tooth belt and cog Belts
Advantages
No slipping happens
Constant speed during transmission than that of all belt types
Transfers direct motion for indexing and timing purposes

19. Material used for Belts
Leather Belt
Cotton BeltRubber Belt
Balata belts

20. Belt Failure
Normal
Failure
Wear
Shock
Load

21. Chains
• In order to avoid slipping, steel chains are used.
The chains are made up of number of rigid links which are hinged
together by pin joints in order to provide the necessary flexibility
for wrapping round the driving and driven wheels.

22. Chain

23. Classification of Chains
Hoisting and
hauling
Conveyor
Chain
Power
Transmitting
 Block or bush chain
 Bush roller chain
 Silent chain

24. Power Transmitting Chains
• These chains are used for transmission of power, when the
distance between the centers of shafts is short.
• These chains have provision for efficient lubrication.

25. Power Transmitting Chains
• The power transmitting chains are of the following three types.
1. Block or bush chain
2. Bush roller chain
3. Silent chain

26. Transmission Chain Selection
Selection in transmission chains depend
on three factors
 fatigue strength of link plate
 bush and roller fatigue
 pin galling (damage due to lubricate
breakdown at high loads)
therefore according to pervious factors
we will choose the suitable power and
speed so not to damage Chain parts

27. Chain Failures

28. Chain Failures

29. Chain Failures

30. Gears
The effect of slipping is to reduce the velocity ratio of the system
In precision machines, in which a definite velocity ratio is of importance (as in watch
mechanism), the only positive drive is by gears or toothed wheels.
A gear drive is also provided, when the distance between the driver and the follower is
very small.

31. Advantages and Disadvantages of Gear Drives
Advantages
• 1. It transmits exact velocity ratio.
• 2. It may be used to transmit large power.
• 3. It may be used for small center distances of shafts.
• 4. It has high efficiency.
• 5. It has reliable service.

32. Advantages and Disadvantages of Gear Drives
Disadvantages
1. Since the manufacture of gears require special tools and
equipment, therefore it is costlier than other drives.
2. The error in cutting teeth may cause vibrations and noise
during operation.
3. It requires suitable lubricant and reliable method of
applying it, for the proper operation of gear drives.

33. Gear Material
The main characteristics considered in the design of gears are:
• surface fatigue limit (Ssf).
• root bending fatigue limit (Sbf).
• wear resistance of tooth’s flank.
• Machinability.

34. Design Considerations for a Gear Drive
1. The power to be transmitted.
2. The speed of the driving gear,
3. The speed of the driven gear or the velocity ratio, and
4. The center distance

35. Helical Gears
A helical gear has teeth in form of helix around the gear.
The helixes may be right handed on one gear and left
handed on the other.
The pitch surfaces are cylindrical as in spur gearing, but the
teeth instead of being parallel to the axis, wind around the
cylinders helically like screw threads

36. Helical Gears Specifications
 Helical gear teeth "curved", teeth are cut at an angle
 Durable and ideal for high load applications
 Plastic, brass, steel, and aluminum are the materials generally used for
manufacturing
 Helical gears operate with less noise and vibration than spur gears, and at any given
time their load is distributed over several teeth, resulting in less wear.

37. Helical Gears Standards
The Catalog Number for KHK
stock gears is based on the
simple formula listed below
Caution in Selecting the Mating Gears.
Right hand and left hand helical gears
mate as a set.

38. Gear Failure
Pitting
WearPlastic
Flow
Breakage

39. Springs
 A spring is a resilient member capable of providing large elastic deformation.
 A spring is basically defined as an elastic body whose function is to distort when
loaded and to recover its original shape when the load is removed.
 Mechanical springs are used in machines and other applications mainly
 To exert force
 To provide flexibility (Control of motion)
 To store or absorb energy.
 To measure forces

40. How does a spring work
Imagine you have a piece of straight steel wire about 10cm (4 in) long—
something like a long paperclip you've unwrapped.
If you pull it with your fingers, it's extremely difficult to stretch it.
Coil it around a pencil and with a bit of effort you can make yourself a small but
perfectly functioning spring.
Now pull or push it with your fingers and you'll find you can stretch and squeeze it
quite easily.

41. Springs are great for storing or absorbing energy
. When you use a pushing or pulling force to stretch a spring, you're
using a force over a distance so, in physics terms, you're
doing work and using energy. The tighter the spring, the harder it is
to deform, the more work you have to do, and the more energy
you need

42. Types of springs
wire springs
flat springs
Special shaped
springs

43. Spring manufacturing processes
If springs are of very small diameter and the wire diameter is also small then the
springs are normally manufactured by a cold drawn process through a mangle
However, for very large springs having also large coil diameter and wire diameter one
has to go for manufacture by hot processes. First one has to heat the wire and then use
a proper mangle to wind the coils

44. Failure in springs
Relaxation
Corrosion
Buckling
Occurs when a
spring is held at
load or cycled
under load. (Cyclic
fatigue load).
The absence
of Coating
Compression springs
with a free length more
than 4 times the mean
coil diameter may
buckle when
compressed.

45. Failure in springs

46. Machine Element Selection
• Now we know many transmitting elements how we choose between
them

47. Thank You