Product (Assembly Line) Manufacturing


The Economist (“A Long March”, July 12, 2001) had this to say about the intensely competitive environment facing automotive companies:

“The goal is to deliver precisely the car that a customer wants, as and when he wants it: goodbye inventory, hello ‘mass customization’.”

The automotive industry is highly competitive. Increasing market share is a primary objective:

  • Growing global capacity has led to intense price competition, making cost control very important for profitability.
  • Consumers are being offered more choice in terms of models, options and colors.
  • All of this is combined with the need to reduce delivery times.
  • Plants need to maintain high throughput and control costs.

This makes assembly line sequencing / scheduling a process of strategic importance. Effective scheduling can help meet all the objectives: manage expanded product range, reduce delivery time, reduce cost and increase profitability.

Assembly line scheduling has a significant impact on all of the above trends:

  • The complexity of the scheduling problem is greatly increased as more features and options are added.
  • Order to delivery lead time reduction will require quicker, more accurate and more frequent scheduling since the scheduling process itself is a major component of the lead time.
  • High throughput and cost reduction can be achieved by a schedule that considers all rules and constraints. Ignoring a rule/constraint usually results in increased cost due to reduced productivity, higher inventory, increased offline work, overtime etc.


Sequencing is the process of assigning a manufacturing slot to each unit or vehicle. Then the schedule for each order is established by applying the line speed and build rate to the manufacturing sequence while considering capacities and breaks. The schedule specifies when each operation of each unit is expected to enter (the line on) and leave (the line off or final off) the line.


An OEM’s (a car manufacturer, say) top level assembly line schedule is the input for scheduling and execution through the supply chain, which can be several levels deep. For example:

  • Engine Groom line: feeder line.
  • Engine Assembly plant: tier 1 supplier.
  • Engine Block Machining & Die-casting: tier 2 level.

Assembly line scheduling is a key element in the order-to-delivery cycle. Many important processes are dependant on the assembly line schedule:

  • Customer Relationship Management
  • Dealer Order Management
  • Material planning
  • Scheduling of feeder lines
  • Vendor supply chain management

Hence, the scheduling process can directly influence the cost and time required to deliver an order. A complete and effective sequencing / scheduling system provides a competitive advantage to a product manufacturer.