The Bullwhip – Effect

21 05 2010

Characteristics of the bullwhip effect:

When each member of a group in a supply chain tries to maximize his or her own benefit without regard to the impact of other members of the group, the overall effectiveness may suffer. Such inefficiencies often creep in when rational members of supply optimize individually instead of coordinating their efforts. A well known example of such inefficiency in staged supply chains is the bullwhip effect. This effect refers to the tendency of replenishment orders to increase in variability as one moves up the supply chain from retailer to manufacturer. A lack of coordination may even outweigh the benefits from specialization and economics of scale. Therefore it can be said that the bullwhip effect is the key example for supply chain inefficiency. So the bullwhip effect is near-hand term for a dynamical phenomenon in supply chains.

An example may clarify what the bullwhip effect is all about:

The Barilla company, a major pasta producer located in Italy provides a demonstrative of issues resulting from the bullwhip effect. Barilla offered special discounts to their customer who ordered full truckload of their goods. Such marketing deals created customer demand-patterns were highly peaked and volatile. The supply chain costs were so high that they outstripped the benefits from full truckload transportation. The Barilla case was one of the first published cases that empirically supported the bullwhip phenomenon.

The 5 major reasons leading to the bullwhip effect according to Lee:

  • Demand signal processing is the is the practice of decision makers adjusting the parameters of the inventory replenishment rule. Target stock levels, safety stocks and demand forecasts are updated in view of information or deviations from targets.
  • Another major cause of the bullwhip problem is the lead-time, which is caused by two components. The physical delays and also delays in cause of information. The lead-time is a key parameter to calculate safety stocks.
  • The third bullwhip creator is the practice of order batching. Economies of scale in ordering, production set-ups or transportation will quite clearly increase order variability.
  • The fourth major cause of bullwhip is highlighted by Lee has to do with price fluctuations. Price discounts and quantity discounts are often offered by retailers. So the retailers buy goods in advance and quantities and store them. This do not reflect their immediate needs.
  • The fifth cause of bullwhip is connected with rationing and shortage gaming. Inflated orders placed by supply chain occupants during shortage periods tend to boost the bullwhip effect.

Possibilities to minimize the bullwhip effect (in order to avoid costs):

  • improve communication in the supply chain
  • simultaneousness of actions (therefore time delays and reaction times can be avoided)
  • centralization of disposition
  • establish strategic alliances
  • reduce the variability

A video explaining the Bullwhip Effect:

Werner, Hartmut (2008), “Supply Chain Management”, Gabler.

Disney, Steven M.; Lambrecht Marc R. (2007), “On Replenishment Rules, Forecasting, and the Bullwhip Effect in Supply Chains”, Publishers Inc.

Advertisements




SMED – What is it & what is it good for

4 04 2010

SMED is the shortcut for Single Minute Exchange of Die and it’s a method for reducing waste along the value chain (lean production). It provides a fast and efficient way of converting a a manufacturing process from runnig the current product to running the following product.

The setting up process can be divided into internal and external setting up:

Internal setting up: has to took place directly at the machine -> downtime -> loss of capacitiy (which means also a waste of money)

External setting up: hasn’t to took place directly at the machine -> no downtime -> no loss of capacity

So you see: the main aspect of SMED is to set up preliminarily tools where ever it is possible or in other words try to convert as much internal setting up time as possible into external setting up time (caused due the fact that there is no downtime at external setting up).

Approach at SMED:

  1. Observation and measurement
  2. Seperate internal and external setting up
  3. Convert external -> internal setting up
  4. Rationalize the internal parts
  5. Alignment of a new standard

Requirements for SMED:

  • employees with an adequate qualification
  • time (training of the employees, accomplish the 5 steps mentioned above)
  • capital

Results of SMED:

  • enhancement of the machinecapacity through minimizing setup time
  • customer orientated prodcution ( fast reaction to volatile demands, short throughput times)
  • cost reduction


Similiar methods:

  • Zero-Changeover (setting up within 3 minutes)
  • OTED (=One Touch Exchange of Die)
Literature:
Changeover

Umrüsten innerhalb von drei Minuten

nOTED (=One Touch Exchange of Die)

Umrüsten durch eine Armbewegung





Just in time

4 04 2010

Hey logistic fans out there!

Due to semana santa i wasn’t able to blog in the last days but now i am back in business and i’am trying to provide you with the most exciting information concerning the topic logistc.

Firstly i want to tell you something about the principles of Just in Time (JIT), a principle which is based on the pull production system:

Definition: Just in time is the provision of the market with the needed goods, at the time when they are needed, in the appropriate quantity. Read the rest of this entry »