Cams Part 2 👍

Question 1

What is a cam?

Answer 1

Cams are mechanisms which are used to change one type of motion to another. The
edge, or profile, of the cam guides the motion of the follower. A cam may be given an
input motion which is rotary or reciprocating. A cam converts this input motion into the
reciprocating motion of the follower.

Question 2

What are cams usually made from?

Answer 2

Cams are usually made from hardened steel but small plastic or wooden cams can be
used if wear and tear is not going to be a problem.

Question 3

What are the 4 main types of rotary cams?

Answer 3

Circular/eccentric cams.
Heart shaped cams.
Pear shaped cams.
Snail cams.

Question 4

Circular/eccentric cams

Answer 4

This cam profile is a circle. The centre of rotation is offset from the centre of the
circle and the cam causes the follower to rise and fall at a uniform rate. The circular
cam produces a smooth form of movement called simple harmonic motion. These cams
are often used in pumps and steam engine valves.

Question 5

Heart shaped cams

Answer 5

These cams cause the follower to rise at a height which remains constant until the
follower reaches the groove, where it falls sharply at a uniform rate before rising
again. This type of cam can be used to wind threads evenly onto the bobbin of a sewing machine

Question 6

Pear cams

Answer 6

Pear-shaped cams cause the follower to rise rapidly as it comes into contact with the
bump part of the cam. The rise and fall of the follower will happen with equal speed.
For half the revolution the cam follower will not move. This is known as dwell. These
cams are often used fr controlling valves for example on motorcar cam shafts to
operate the engines valves.

Question 7

Snail cams

Answer 7

This type of cam causes the follower to rise slowly, them fall sharply into the step. To
ensure that the rotation of a snail cam is smooth, the vertical/centre line of the cam
must be positioned slightly off centre. Snail cams can be used in cutting products,
when the blade is required to fall sharply.

Question 8

What is a follower

Answer 8

The part that rests on the cam and moves up and down is called the follower

Question 9

What can followers be made from

Answer 9

Followers can be made from a range of materials including materials, wood, plastic and sometimes, when wear and tear is not a design consideration, mild steel.

Question 10

What are the 3 main types of follower

Answer 10

Flat follower. Knife follower. Roller follower.

Question 11

Flat followers

Answer 11

This type of follower has a large flat surface at its base. It is used when it is not
necessary that it follows a very precise cam profile (for example it would not be used
with a heart shaped cam). The cam will move in rotary motion (round and round!) while
the follower will move in reciprocating motion (up and down!).

Question 12

Knife followers

Answer 12

These are mainly used with heart shaped cams as they can follow a very detailed
profile. They normally have a hardened steel tip and are designed to go down into the
tight curves of the cams.

Question 13

Roller followers

Answer 13

This type of follower has a small roller bearing at the end. They are useful for reducing friction and wear between the cam and the follower.

Question 14

What is once cycle

Answer 14

One rotation/revolution of the cam

Question 15

What does dwell mean

Answer 15

when the cam rotates but the follower does not rise or fall

Question 16

Rise

Answer 16

the part of the cam that causes the follower to rise

Question 17

Fall

Answer 17

The part of the cam that causes the follower to fall.