Week 5: Assembly and Automation Flashcards
What is assembly?
Assembly is the process where the manufactured components that form products are joined together to form the final product.
What is a workbench (cell) assembly system?
In workbench system a single fitter at a single bench does all the work required for a product. To increase production rate the number of benches is increased and they work in parallel.
What are the advantages of a workbench assembly system(2)?
- Flexible: it is possible to add or remove cells without affecting the rest of the factory
- Good accountability: easy to determine who was responsible for any quality issues
What are the disadvantages of a workbench assembly system(4)?
- Require more space (low output per m^2): the work is duplicated across workbenches, the same tools and auxiliary resources should exist at each bench. Redundant use of space
- Require more assembly stores: duplication results in the need of more additional space
- Require more equipment: the same set of equipment is required at each workstation
- Difficult to track products
What is an assembly line?
In assembly lines the work for each product is split into a number of packages, each workstation carries out the work in one package.
What is cycle time?
Cycle time is the time between two consecutive finished products coming off the assembly line
What is takt time?
Takt time is the maximum cycle time that can meet the customer demand
What are the advantages of a fixed fitter line(6)?
- Fast throughput times
- Minimise tooling
- Minimise stores
- Allow fitter specification
- High output and quality
- Very efficient when on
What are the disadvantages of a fixed fitter line(4)?
- Low flexibility
- Need consistent demand
- Difficult to balance
- Typically on or off
What are the advantages of a moving fitter line(6)?
- High flexibility
- High product variation
- Multi-skilled fitters
- Fast throughput times
- Minimise tooling
- Minimise stores
What are the disadvantages of a moving fitter line(2)?
- Multi-skilled fitters
- Difficult to manage
What is the advantage of hybrid lines?
It combines moving fitter lines with fixed fitter lines
What are the disadvantages of hybrid lines(2)?
- Very difficult to balance
- Large complicated lines
What is line balancing?
Ensuring an even workload and maximum throughput across workstations in an assembly line with the given resources
Draw a precedence diagram
Diagram
What is the equation for a cycle time of N workstations?
C=60/P
- P is number of products produced per hour
What is the equation for the minimum number of required workstations?
Nmin - 1 < sum(tn)/C < Nmin
- tn is the sum of times of the activities assigned to workstation n
Describe the RPW algorithm
Rank Positional Weighting Table:
Element Weight: task time plus all subsequent task times Time Precedence Work station Time remaining
Assign larger task times first
What are the goals of Industry 4.0/Automation (6)?
- Integrate various aspects of the manufacturing system to improve product quality and uniformity while minimising cycle times
- Improve productivity to reduce costs by better control of the production
- Improve quality by using repeatable processes and thus reducing variance
- Reduce human involvement, boredom and thus potential for human error
- Raise the level of safety, especially in hazardous environments, for personnel
- Economise space by arranging machines, materials handling etc. more efficiently
What is hard automation?
Machines are designed to produce standard parts, these machines are not flexible only some parameters can be changed (product size, machining speed, feed, depth of cut etc.)
What is soft automation?
In soft automation, or flexible or programmable automation, greater flexibility is achieved through the use of computer controlled machines. The machines can be easily reprogrammed to produce new parts that are completely different to the previous parts. This is mainly enabled by numerical control
What is numerical control?
Numerical control is a method for controlling the movements of machine components by directly inserting coded instructions. This uses open loop and closed loop circuits(uses feedback sensors).
Define two types of numerical control
Point-to-point systems: axes of movement are controlled independently and move with various velocities i.e. positioning operation is completed before the machining operation commences. (drilling)
Contouring systems: continuous path systems where the axes of movement are controlled simultaneously and therefore it is possible to perform machining operations at the same time. (milling)
What are the types of interpolation used in contouring systems(3)?
- Linear interpolation
- Circular interpolation
- Parabolic and cubic interpolation
