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MECH2200 - Sensors Actuators and Mechanism > CNC Machines, G-Code and Sensors > Flashcards

CNC Machines, G-Code and Sensors Flashcards

1
Q

Define “Absolute position”

A

This is the position of any point on an object relative to the absolute origin

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2
Q

Define “Relative position”

A

This is the position of any point on an object relative to a temporary origin away from the absolute origin.

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3
Q

What are some examples of CNC machines?

A

> 2 axis laser cutter

> 5 axis CNC machine

> 3 axis NC milling machine

> Arcade grabbing machine

> Industry 7 DoF Robot

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4
Q

What is G-Code?

A

This is code that defines where the end effector of the machine moves to and when to turn on and off its end effector

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5
Q

What are the number of poles of a switch?

A

How many switches are activated by a single mechanism

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6
Q

What are the number of throws of a switch?

A

The number of possible contacts that the switch can switch to

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7
Q

What is a maintained switch?

A

The throw position is maintained when switched

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8
Q

What is a momentary switch?

A

The throw position reverts to a static position when released

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9
Q

What is this switch? [Picture 17]

A

SPST (Maintained)

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10
Q

What is this switch? [Picture 18]

A

SPST (Momentary)

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11
Q

What is this switch? [Picture 19]

A

SPDT (Maintained)

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12
Q

What is this switch? [Picture 20]

A

SPDT (Momentary)

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13
Q

What is this switch? [Picture 21]

A

DPST (Maintained)

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14
Q

What is this switch? [Picture 22]

A

DPDT (Maintained)

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15
Q

What is this switch? [Picture 23]

A

3P4T

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16
Q

What is a snap action switch?

A

A moving contact quickly moves from one fixed contact to another fixed contact with minimal relation to the speed at which the switch is operated

17
Q

What are the properties of a snap action switch?

A

> Very little force required to activate them

> Repeatable and precise switching action

> Natural hysteresis (movement differential) due to snap action

> Reliable

18
Q

What sort of switches are used for origin and limit detection?

A

> SPDT (Momentary)

> 3 Contacts

  • Common
  • Normally open
  • Normally closed
19
Q

How are magnetic reed switches made?

A

> They are made using a reed of ferrous metal which is attracted by a magnetic field

> The distance between the reeds is extremely small (μm)

20
Q

What are the disadvantages of reed switches?

A

> Reed switch activation is not precisely predictable

> The activation and release is dependent on magnetic field strength

> Limited current capacity

21
Q

What are the advantages of reed switches?

A

> Hermetically sealed and therefore can be incorporated into specialist environment

> High speed response time

> No physical contact switch

> They can be made very small

> They have a massive mechanical life

> They are cheap

22
Q

What is the function of a rotary incremental encoder?

A

> They inform that a step has taken place

> They inform about the direction of travel

> They inform when you have reached a full rotation

23
Q

What is the setup of a multiple light source encoder?

A

> 3 optical transmitters

> 3 optical receivers

> 3 output signals (A,B,Z)

  • A and b are shifted by 90° relative to each other.
  • Z is used to indicate a full rotation
24
Q

What is the setup of a single light source encoder?

A

> 1 Optical transmitter

> 3 optical receivers

> A mask is used to single out each light

25
Q

What equation is used to calculate the angle between A and B?

A

SD = (360 / #windows) × (N + 0.25)

26
Q

How are more finite angle calculated?

A

This is done by measuring the amount of light that passes through the holes and are detected at A and B

27
Q

How is the direction determined?

A

Depending on whether A leads B or B leads A

28
Q

What is a linear incremental encoder?

A

> The same as a rotational one but in linear form.

> No disk is used

29
Q

What is an absolute encoder?

A

> This is an encoder that works by using gray code to inform the exact position.

> Lots more sensors are required

30
Q

What is Gray code?

A

This is a binary sequence where only 1 bit changes at a time

MECH2200 - Sensors Actuators and Mechanism (8 decks)

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