W5 Assembly and Automation Flashcards
Assembly
Assembly is the process where the manufactured components that form products are joined together
to form the final product. There are two principal types of assembly systems: Workbench (or cell)
and Lines.
Workbench (Cell) assembly systems
In workbench systems 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.
Advantages of workbench systems
Flexible
Since the complete set of activities take place
in each single cell, it is possible to add or
remove cells without affecting the rest of the
factory
Good accountability
A single fitter assembles each product. It is
therefore, very easy to determine who would
be responsible for any quality issues.
Disadvantages of workbench systems
- Require more space (Low output per m2)
The work is duplicated across all workbenches.
Consequently, the same tools and auxiliary
resources should exist at each workstation.
This results in redundant use of space. - Require more assembly stores
The duplication would result in a
need for additional storage space. - Require more equipment
The same set of equipment
is required at each workstation.
Difficult to track products
Manual VS Automated Cells
- Cells categorized into Manual or Automated
- Automated cells constructed using robots or a single machine
- Usually implemented when long-term demand and investment justify it
- High output rate but limited variety of parts manufactured
- Highly flexible within designed product range
- Manual cells allow workers to choose work patterns
- Performance level negotiated for each worker
- Suitable for products with high variety and low volume
- Can accommodate products of various sizes
Kitted assemblies and bench stores
- Cells require storage space for necessary parts
- Two prevalent approaches: kitted assemblies and bench stores
- Kitted assemblies for high variety, low volume production
- Components for a single part loaded into a kit
- Kits kept together with products in the factory
- Bench stores for smaller products with cheap components
Cycle time
The time between two
consecutive finished products coming off the line is called cycle time
Takt time
The maximum cycle time that
can meet the customer demand is called takt time.
Assembly lines
- Assembly systems split work for each product into packages
- Each workstation completes work in one package
- Product moves through various workstations
- Work packages sequentially executed to assemble the product
Fixed fitter lines
- Fixed fitter lines have stationary fitters, products move from station to station
- Variations:
- Single fitter stations: each manned by one operator, suitable for small products
- Multi fitter stations: manned by multiple operators, suitable for large products
- Categorization based on product variety:
- Single product lines: assemble one product
- Multi-product lines: assemble several types of products using same workstations
- Mixed product lines: parts of assembly lines used for multiple products, others unique to single product
Moving fitter and Hybrid lines
- Moving fitter lines involve fitters walking or riding, products are often stationary
- Hybrid lines combine moving fitter and fixed fitter line features
Adv Disad of fixed fitter lines
Adv:
Fast throughput times
Minimise tooling
Minimise stores
Allow fitter specialisation
High output and quality
Very efficient when on
Disadv:
Low flexibility
Need consistent demand
Difficult to balance
Typically on or off
Adv Disad of moving fitter lines
Adv:
High flexibility
High product variation
Multi-skilled fitters
Fast throughput times
Minimise tooling
Minimise stores
Disad:
Multi-skilled fitters
Difficult to manage
Adv and Disad of Hybrid lines
Adv: Combines the adv of fixed and moving
Disadv: Very difficult to balance
Large complicated lines
Line Balancing
- Line balancing: assignment of assembly tasks to workstations
- Goal: eliminate uneven workload, bottlenecks, stock holdups
- Achieve smooth flow of components throughout system
- Critical in assembly lines for even workload, maximum throughput with given resources
