Robotics

Question 1

Robot

Answer 1

A re-programmable device designed to both manipulate and transport parts, tools or specialised manufacturing implements through variable programmed motions for the performance of specific manufacturing tasks

Question 2

Configurations

Answer 2

Robot arm:
anthropomorphic: 6-axis robot that resembles a human arm
SCARA Robot: typically 4-axis configuration and stiff in the Z-axis
Delta Robot: major axis motors and gearboxes in the base to allow for a lightweight robot arm
Cartesian: 4,5,6 axis configuration with multiple axes at right angles to each other

Question 3

Comparison

Answer 3

Cartesian
low speed, very good reach, goodish repeatability and payload

Anthropomorphic
Mid reach but cant reach closer
okay speed
high payload and low repeatability

SCARA
Very fast, low working reach, low payload, high repeatability

Delta
Very low reach, very high speed, mid range repeatability, very low payload

Question 4

Safety

Answer 4

Safety guarding: The pick and place system should have appropriate guarding to ensure
people can’t be hit by fast moving machinery / components or get
crushed between equipment in a trapping zone. Typically guarding is
used as physical barrier to stop inappropriate access and is supplied
either as wire mesh or Perspex panels.

E-stop: E-Stop systems are robust dedicated control systems (safety relay /
PLC) that are used to control the mode of equipment operation within
a production environment. Typical modes of operation include
(Maintenance, Teach and Auto). The E-Stop system monitors the status
of E-Stop buttons, safety pull cords and guard access points and limits
the operational performance of the equipment appropriately.
(Stopping equipment, Reducing maximum motion speeds or requiring
addition safety interlocks such as dead manhandles to be used.)

Fortress Lock
Access Control: A fortress lock is a key interlock system that is used to gain access to
the production equipment through access points in the safety guards.
The locks can be found in pairs, one external to the access point and
one internal to the access point. A pair of locks has only one key and
location of the key changes the operational mode of the system. If the
key is external to the access point, the system will run at full speed
automatically. If the key is internal to the access point, the system will
run at a reduced speed requiring addition safety interlocks. If the key is
not present in either lock, the system will not run

Air compressor: The air compressor is a piece of equipment that is used to compress air
to storage pressure. There are three types of compressor that are in
common use; Wale, Rotary Vane and Screw. Compressors typically
need a three phase mains supply.

Air tank: Once the air has been compressed it needs to be stored. The air tank
provides this storage reservoir. The tank should be fitted with a safety
relieve valve to ensure that the stored air pressure never exceeds the
limits of the tank.

Main Line Filter: Removes contaminates from the compressed air supply passing
through the element to a nominal size dependent upon that element (
0.01 to 5 micron depending upon the element)

Air dryer: The air dryer is used to reduce the amount of water vapour in the
compressed air. Air after compressing can be hot and hold more
moisture than when it is cold. Often air dryers include a chiller
function

Filter regulator: This is a single unit that provides a filtering and pressure regulation
function. The filter reduces contaminates and condensate from the air
stream and the pressure regulator reduces the pressure to a working
level

Air lubricator: Not commonly used today but this allows lubricants to be added to the
air flow. (Still need when operating air motors

Isolation Valve: Isolation valves can be used to isolate the air supply and dump air in
the system to atmosphere. They also provide a Lock Out Tag Out
(LOTO) mechanism, effectively allowing the isolator to be locked while
maintenance work is in progress.

Question 5

Pros and Cons

Answer 5

SCARA:
Good for inserting screws, stiff in Z so can apply significant loads in this direction
Best repeatability
Very fast

Only operates in X and Y planes
Limited working volume, which is cylindrical in nature
Payloads can be limited if faster speeds required

Cartesian:
Large working volumes
Significant payloads
Good repeatability

Limited compliance in the x.Y plane
Slowest

Anthropomorphic
Very flexible
Re-taskes easily

Limited stiffness in Z
Spherical working volume
One of the slowest
mid-range repeatability

Delta
Good repeatability

Working volume limited in Z axis
Payloads limited
Not very stif fin the Z axis

Question 6

Comparison

Answer 6

Let’s break down the comparison in terms of repeatability, speed, reach, and payload for SCARA, Cartesian, Anthropomorphic, and Delta robots:

1. Repeatability:
   
   • SCARA: Offers high repeatability due to its rigid structure and controlled compliance, typically in the range of 0.01-0.05 mm.
   • Cartesian: Provides excellent repeatability, often in the range of 0.01-0.1 mm, depending on the quality of components and calibration.
   • Anthropomorphic: Repeatability can vary but generally falls within the range of 0.1-0.2 mm, influenced by the number and quality of joints.
   • Delta: Offers good repeatability, typically in the range of 0.1-0.2 mm, thanks to its parallel kinematic structure.
2. Speed:
   
   • SCARA: Known for its high-speed operation, capable of rapid movements in the horizontal plane, often reaching velocities of several meters per second.
   • Cartesian: Speed varies depending on the design and load, but it can achieve high speeds, especially in linear motions, commonly ranging from 1 to 10 meters per second.
   • Anthropomorphic: Speed is influenced by the number of joints and payload, with typical speeds ranging from 0.5 to 2 meters per second.
   • Delta: Offers impressive speed, especially in vertical movements, with velocities reaching up to 2-3 meters per second.
3. Reach:
   
   • SCARA: Limited reach compared to other configurations, typically optimized for a specific workspace, with reach varying based on arm length and configuration.
   • Cartesian: Offers a rectangular workspace with linear motion along three axes, providing flexibility in reach and workspace size, often customizable to application needs.
   • Anthropomorphic: Offers a wide range of reach and dexterity due to its articulated joints, allowing it to access complex workspaces and perform various tasks.
   • Delta: Generally provides a circular or spherical workspace, offering a compact design with a large effective reach relative to its footprint.
4. Payload:
   
   • SCARA: Capable of handling moderate payloads, typically ranging from 1 to 20 kilograms, depending on the specific model and configuration.
   • Cartesian: Payload capacity varies widely depending on the design and construction, with systems capable of handling payloads from a few kilograms to several hundred kilograms.
   • Anthropomorphic: Payload capacity depends on the size and strength of the robot’s joints and structure, typically ranging from a few kilograms to over 100 kilograms for industrial models.
   • Delta: Offers relatively lower payload capacity compared to some other configurations, typically ranging from a few kilograms to around 20 kilograms, depending on the specific model and design considerations.

Each robot type has its strengths and limitations in terms of repeatability, speed, reach, and payload, making them suitable for different applications depending on the specific requirements of the task at hand.