ASSEMBLY + AUTOMATION Flashcards
Define Assembly?
Manufactured components are joined together to form the final product
What are the 2 principal types of assembly?
- Workbench (Cells)
- Assembly lines
Define / Describe workbench assembly?
- A single fitter at a single bench does all the work required for the product
- To increase productivity, the number of benches is increased and they work in parallel
Advantages of workbenches?
- Flexible: it is possible to remove workbenches without affecting the rest of the factory, as each bench independently completes the entire set of activities
- Good accountability: since a single fitter assembles the entire product, it would be easy to determine who is responsible for quality issues
Disadvantages of workbenches?
- Requires more space (low output per m^2): Since work is duplicated at each bench, the same tools/resources will exist at each bench. This results in an efficient use of space.
- Requires more assembly stores: As in point 1, duplication will results in the need for more storage space.
- Requires more equipment: like above.
- Difficult to track products
Differences between manual / automated cells (workbenches)?
Automated:
- Used when long term demand is assured and investment is justified.
- High output rate but typically limited variety of products
- Flexible but only within the range of products for which they have been designed
Manual:
- Workers choose their own working patterns
- Highly flexible and are suitable for high variety and volume
- Negotiated so that the worker agrees to produce a certain number of products a day (or week/month etc)
- Usually used for new products; if successful and demand increases then assembly system will change to automated cells or assembly lines
Describe the 2 types of storage spaces for workbenches?
Kitted assemblies: high variety, low volume. Components necessary for a single part are loaded into a kit and kept with the products
Bench stores: Used for smaller products with cheaper components. Therefore high volume.
Define / describe assembly lines?
- The work for each product is split into a number of packages
- The product goes through various workstations and work packages are consecutively carried out to assemble the product
Define cycle and takt time?
Cycle time: time between 2 finished products coming off the assembly line (usually measured in minutes)
Takt time: the maximum cycle time required to just meet consumer demand
Define fixed fitter / moving fitter / hybrid assembly lines
Fixed fitter: fitters remain stationary and product moves between stations. The stations can be single / multi-fitter (manned by 1 or several workers respectively). Single for small products and multi for large.
Moving fitter: fitters are either walking / riding and products often remain stationary.
Hybrid: Combines moving and fixed.
Advantages / disadvantages of fixed fitter lines
Advantages:
- Fast throughput times
- Allows fitter specialisation
- High quality
- Efficient when on
Disadvantages:
- Low flexibility
- Needs consistent demand
- Difficult to balance
Advantages / disadvantages of moving fitter lines?
Advantages:
- High flexibility
- High product variation
- Multi skilled fitters
- Fast throughput times
Disadvantages:
- Multi skilled fitters (?)
- Difficult to manage
Disadvantages / advantages of hybrid lines?
Advantages:
- Combines moving / fixed
Disadvantages:
- Very difficult to balance
- Large and complicated lines
What are assembly precedence diagrams used for?
Determines the various ways a product can be assembled. Some tasks will depend on the completion of previous tasks.
Minimum theoretical workstations equation?
Sum of all activity times for all stations / Cycle time
