maandag 9 september 2013

Ter inspiratie voor integrale zorglogistiek: hoe werkt de planning bij Toyota?

Onderdeel van mijn portefeuille 'Lean en zorglogistiek' in het het Sint Antonius Ziekenhuis is het ontwikkelen van een integrale aanpak voor zorglogistiek. Onderdeel daarvan is de samenhang tussen de planning van spreekuren, opnames, OK schema en beddenhuis. Ter inspiratie heb ik het boek 'Toyota Supply Chain Management' van Iyer, Seshadri en Vasher gelezen wat interessante nieuwe inzichten geeft, vooral ook hoe push en pull methoden samengaan in het systeem om flow en gelijkmatig werkritme te optimaliseren met zo min mogelijk verspilling en zoveel mogelijk flexibiliteit om in te spelen op de actuele vraag. Zie hieronder voor een weergave hoe de planning bij Toyota werkt.

‘The sales division of Toyota provides a rolling three-month plan with the first month categorized as a firm order and the next two months as a forecast. The aggregate production plan is agreed upon between the sales division and the manufacturing division. The sales division wants to remain flexible and respond quickly to market changes and to limit the use of incentives to sell vehicles. The manufacturing division wants to operate at full capacity and produce high-profit vehicles. The agreed month implies that the sales division commits to buying these units and the manufacturing division has agreed to produce them. The total volume of cars for the coming month cannot change anymore; the specifications of the cars (engine, colour, options, etc.) can change up to a week in advance. Manufacturing than assigns a production date and sequence to each vehicle for the operational planning. The objective is to create a levelled schedule that avoids congestion, workload imbalance and inventory.

Manufacturing schedules staff with standard work hours and preschedules usually a limited amount of overtime, for example one hour per shift. Day-to-day adjustments to the overtime are made just prior to the start of each shift based on operational conditions of that day. Suppliers receive detailed schedules that specify exactly how much of what needs to be delivered at an exact time. Under normal circumstances there is a maximum of +5 and -5% variation of the volumes to be delivered. Dealers can specify changes until a week before production. Toyota ensures that this deadline is longer than the lead-time of at least 80% of the suppliers. Of the remaining 20% a small inventory is accepted.

Toyota is able to manage it’s supply chain externally and internally as described in an extremely balanced and smooth manner because of a vary carefully decided product mix planning. The objective of mix planning is to strongly reduce the number of variants of vehicles. It is undertaken during major model change preparation and can be adjusted annually and to a lesser degree during the year.

Fluctuations in demand per type of vehicle can be absorbed by changing the product mix that is produced in the month plan, by extra overtime or extra temporary workers on a daily basis and by changing the ‘takt time’, the rhythm how many cars are produced per hour. The latter can be changed approximately once every two months.

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