¿Qué es Lean Manufacturing? El pensamiento Lean desde cero.
«El pensamiento lean es ‘lean’ porque proporciona un método de hacer más y más con menos y menos –menos esfuerzo humano, menos equipamiento, menos tiempo y menos espacio–, al tiempo que se acerca más y más a ofrecer a los clientes aquello que quieren exactamente.» James P. Womach & Daniel T. Jones – «Link Thinking» (2003)
- La sobreproducción, o el exceso de producción: Es uno de los desperdicios más nocivos para lean. Aparece cuando fabricamos más productos que los que el cliente precisa, o los fabricamos antes de que los precisen.
- El tiempo de espera: son todos los ‘tiempos muertos’ entre procesos. Un proceso que precisa materiales o información del proceso anterior que aún no finaliza, o un cliente esperando.
- El transporte: todo movimiento de materiales, ya sea materia prima, piezas o producto de un lado a otro, de un proceso a otro, o al almacen.
- El exceso de procesamiento: cualquier procedimiento que no sea necesario para la producción. Se incluye toda maquinaria o método que entregue un producto de mayor calidad cuando el cliente no lo precisa.
- El exceso de inventario: un exceso de material, ya sea materia prima, producto en proceso o producto terminado en el almacen. Material que no se precisa porque no existe aún demanda que lo justifique.
- Los movimientos: cualquier movimiento innecesario o redundante que no genere valor agregado al producto. Por ejemplo, el traslado del operario a otro sector para la búsqueda y selección de piezas necesarias.
- Los defectos: todo descarte de material o producto no conforme, así como el re-trabajo sobre productos que retornan de procesos posteriores o del mismo cliente.
- Kaizen: la mejora continua como filosofìa de trabajo.
- Producción pull: la producción se basa en la demanda del cliente. El cliente ‘tira’ del proceso de acuerdo a sus necesidades, no es el fabricante quien ‘empuja’ productos no deseados al consumidor (producción push).
- Poka-Yoke: es una técnica a prueba de fallos. Consiste en diseñar los procesos y las piezas de una manera tal que no puedan cometerse errores. Por ejemplo, una pieza que sólo encaja con otra en un sólo sentido. Muchos lo definen como sistemas ‘a prueba de tontos’, pero son una herramienta muy sencilla y útil para optimizar procesos y reducir tiempos y errores.
- Flexibilidad en la producción: una mayor variedad de productos en valores menores de producción, en contraposición a la teoría fordista de producción seriada y en grandes cantidades de productos idénticos. En ese caso la sobreproducción producía la demanda. Una demanda forzada por el fabricante. Aquí la demanda real hace que se produzca sólo lo que precisa el cliente, en el momento que lo precisa el cliente.
¿Por dónde comenzamos?
Lean is simply a method, a management model, a way of thinking, that seeks to conserve those resources and processes that create value and eliminate all types of waste. What creates value is only what is intended to satisfy the customer.
Lean Manufacturing (which could be translated as ‘lean production’ or ‘lean production’) is the production method based on lean thinking.
«Lean thinking is ‘lean’ because it provides a method of doing more and more with less and less – less human effort, less equipment, less time and less space – while getting closer and closer to offering customers that exactly what they want. » James P. Womach & Daniel T. Jones – «Link Thinking» (2003)
In short, it seeks to optimize the processes to the maximum by creating value streams, with the use of the minimum possible resources, in pursuit of customer satisfaction. The secret of the success of lean lies in the elimination of waste, or waste. In Japanese there is a specific term for waste: muda. The change is all that takes resources but does not create value. The molt is everywhere. Taiichi Ono defined 7 specific types of molts:
Overproduction, or overproduction: It is one of the most harmful waste for lean. It appears when we manufacture more products than the customer needs, or we manufacture them before they need them.
The waiting time: they are all the ‘dead times’ between processes. A process that requires materials or information from the previous process that has not yet finished, or a client waiting.
Transportation: all movement of materials, whether raw material, parts or product from one side to another, from one process to another, or to the warehouse.
Overprocessing: any procedure that is not necessary for production. It includes any machinery or method that delivers a higher quality product when the client does not need it.
Excess inventory: an excess of material, whether raw material, product in process or finished product in the warehouse. Material that is not needed because there is no demand that justifies it.
The movements: any unnecessary or redundant movement that does not generate added value to the product. For example, the transfer of the operator to another sector for the search and selection of necessary parts.
The defects: all discarding of material or non-conforming product, as well as re-working on products that return from subsequent processes or from the same client.
James P. Womach and Daniel T. Jones added, many years later, an eighth type of molt: underutilized human potential. The staff must be able to identify the 7 types of changes, through training in the development of creativity and criteria. Not only can we completely eliminate the molt, but in many cases we can convert the molt into value.
There are fundamental tools for a correct implementation of lean:
Kaizen: continuous improvement as a work philosophy.
Pull production: production is based on customer demand. The customer ‘pulls’ the process according to their needs, it is not the manufacturer who ‘pushes’ unwanted products to the consumer (push production).
Poka-Yoke: it is a fail-safe technique. It consists of designing the processes and the pieces in such a way that mistakes can not be made. For example, a piece that only fits with another in only one direction. Many define it as ‘foolproof’ systems, but they are a very simple and useful tool to optimize processes and reduce time and errors.
Flexibility in production: a greater variety of products in lower values of production, in contrast to the Fordist theory of serial production and in large quantities of identical products. In that case, overproduction produced the demand. A demand forced by the manufacturer. Here the actual demand causes that only what the client needs to produce occurs, at the moment that the client needs it.
To be able to read correctly, it is extremely important that there is clear and fluid communication with suppliers and customers.
Where do we start?
An excellent step prior to the implementation of lean completely is to design and implement a ‘5S’ system within the organization. This is a very good strategy to understand the philosophy of continuous improvement (kaizen) and detect unnecessary processes and materials for the manufacture of our products. For more information, we suggest visiting the related publications, which are mentioned at the end.
In future publications we will deal in greater depth aspects of lean. In particular, we will know what the value flows are, we will see how the Just in Time management method (JIT) works for the pull production, we will explain the use of the kanban cards, the application of poka-yoke and the power integration of lean thinking with Six Sigma (Lean Six Sigma – LSS), among other topics.[:]