Appunti di Industrial Technologies

Factory layout planning

Definition of the physical organization of the factory, search for the most efficient location of the shops. Objective: minimization of the costs respecting the plant constraints (multi-objective: min distances, max proximity). Final result: CAD drawing of the factory layout.

Systematic layout planning methodology

• Analysis
  • Products (volume and amount of goods to produce)
  • Material flow (requirements for movement between shops)
  • Relations between activities
• Design
  • Graph method
  • Space diagram method

Computerized layout techniques

HP: given space is rectangular, every shop is rectangular or composed of rectangular pieces.

• CRAFT -> layout improvement procedure (based on the minimization of moving cost among the shops, needs a starting layout).
  • Find the tables trips/day, €/m and compute the meters/trip calculating Euclidean distances
  • Calculate the total costs table
  • Try all the possible horizontal or vertical switches for the first iteration and find the less expensive
  • Calculate the real cost of the less expensive iteration and switch if it is actually less expensive.
  • Restart if you want to do a second iteration.
• ALDEP -> layout construction procedure (not working on the minimization of costs as CRAFT, it is considering in the best way the relationship between different areas).
  • Division of the area in blocks
  • Construction of the relationship chart
  • Start to allocate the shops from the upper left corner with a zig-zag U-shaped path and with the decided sweep width (2 blocks usually)

Job shop

Organizing production systems in shop areas based on the job that the machine has to do; machines are grouped on the basis of technological processes; each grouping is called a shop.

Strengths

• High flexibility (mix, volume, product customization, product innovation)
• Low impact of breakdowns
• Low obsolescence of the system

Weaknesses

• Limitations in machine efficiency (high waiting time, many WIP, can’t use resources at max availability)
• Qualitative characteristics of the product can vary from different pieces
• Production management is difficult
• Difficult to calculate production capacity

Manufacturing cells

Parts are grouped into part families and machines into cells, the machines are grouped because they have to process the same type of product. Each product has its own routing within the cell when no inter-cell move is required.

Strengths

• Rationalization of material flows
• Setup time reduction
• Production management is easier
• WIP reduction
• Lead time reduction
• Better estimates of delivery lead times
• Job enlargement and enrichment for employees
• Teamwork within the cell
• Unification of product and process responsibilities
• More control on quality of products

Weaknesses

• Difficulties with workload balancing between cells
• Problems related to production mix variability
• Difficulties with the application to the whole stages of the production chain
• In some cases, more machines than job shop
• Difficulties to manage technological operations outside the cells
• Problems related to breakdowns

Group technology

Technological activities that we should run in designing a manufacturing system as a cell.

Methods

• Informal methods: those with the same shape in the same product family (based on geometrical or technological features)
• Part coding analysis method