Friday 14 December 2018

What is load leveling

A load leveling is the technique used to plan and level the demand of customers in volume and variety during a period of time, usually a day or work shift?

A new entry for the block of quality of our corner, little by little, is becoming one of the most important.

Within what are techniques Lean, have already spoken of a variety of instruments: the 5s, SMED, Jidoka, Poka Yoke

today we'll talk of other techniques, the heijunka technique designed to plan and level the demand of customers in volume and variety over a period of time.


Techniques that represent the paradigm of production Heijunka technique and the Kanban, which we have already spoken on this corner, are Lean. Arising specifically in the automobile industry represent the highest degree of commitment with the JIT philosophy and are techniques which require specific environments for your application, both with regard to the products, as in the processes and availability of means.

Obviously, this tool is not applicable if there is no or little variation of product types. The practical management of the Heijunka requires a good knowledge of the customer’s demand and the effects of this demand in the processes and, in turn, requires strict attention to the principles of standardization and stabilization. Customers’ orders are relatively constant are considered on average within a sufficiently large time period, but they are unpredictable if analyzed with a range of small time and out of an agreed program.

The process & Techniques

In the first case, the production variations are due to the process (planning, size of the lots, incidents, opportunities of business, etc.). In the second case, is the extreme application of the unit size of the lot which leads companies to try instant adjustment of demand, supporting all the variations of the orders. Through a continuous production level, smoothed and in small batches, is achieved result with the minimum level of possible waste.

For the application of the Heijunka there are a number of techniques, integrated whole, enable an advanced production system with constant flow, determined pace and standardized work, which provides some very significant advantages from the point of view of optimization of labor, minimization of inventories and customer response times.

These techniques are:

  • Use work cells.

  • Continuous flow piece by piece.

  • Produce to the Takt time (rhythm).

  • Level the mix and production volume.

Use work cells.

One of the first steps in the implementation of a system Lean is the creation of flow on the floor, which leads to a product-oriented layout. In this type of distribution, the workstations are located side by side according to the phases of the production process and the product moves to the corresponding operations are done. This form creates an efficient sequence that allows a continuous and soft commodity movement to develop products from beginning to end.

Design that best meets the basic requirements of management Lean is the so-called "flexible cell" (or work), which responds to the concept of workflow activities very close and that takes the physical form of "U". Basics of distribution in U is that the input and output of a line are in the same position. Continuous flow transforms several processes working independently in a joint work cell where all processes are linked one after the other.

Each cell is designed to produce a family of parts or a limited number of families of parts. A family of parts is a group of parts or sub assemblies of the main product that have similarities in the geometrical form and size, or in the phases of manufacturing. The cell includes special production equipment and techniques and custom brackets to optimize the production of families of parts. In this situation, each cell becomes a factory within the factory.

When designing cells become necessary certain requirements:

  • Identify families of products, often using technology groups.

  • Have trained and flexible staff.

  • Have staff support or imaginative and flexible employees to establish the initial work cells.

  • Design systems anti-error catch in each cell station.

The adoption of cells allows for some very significant advantages in efficiency

  • Better compliance with the requirements established by the customer, quality and deadlines.

  • Reduction of inventory in process since the work cell is established to provide a balanced flow of machine to machine.

  • Reduction in the floor space needed less space between the machines for the inventory in the process.

  • Lower inventory of raw materials and finished products, because with less work in process is speeds up the movement of materials.

  • Greater use of equipment and machinery due to the faster flow and better programming.

Continuous flow piece by piece.

The concept of continuous flow is summed up by a simple phrase: "move one, produce one" (or "move a small batch, make a small batch"). It is fundamental to the role of flow within philosophy read which should make sure that an operation "upstream" never made more than what requires an operation "downstream", so is never produced more than what a client requested.

Can also be defined as work so that product flow continuously, from the supplier to the client, with the shortest possible production and a minimum waste production.

The continuous flow is set throughout the process so that the flow is interrupted as little as possible, so that you can work to a fluid rhythm and, to make it possible, are needed to see three distinct levels:

Flow of information standard for decisions applying the techniques following:

  • Leveling to distribute production of the more fluid form.

  • Kanban cards to indicate the need for material.

  • The daily monitoring of processes to locate deviations and solve problems as soon as possible.

Material flow. Reduce step by step waste, creates a flow of materials with the shortest possible production through the use of the following techniques:

  • A flow pulls between all processes to reduce work-in-process.

  • A necessary equipment for the process flow.

  • A multithreaded organization.

  • Frequent deliveries.

Flow of operators (standardized work). To train personnel and providing them with proper techniques, workstations that offer great flexibility and efficiency are created. For this it is necessary:

  • Synchronize the process according to the takt time.

  • Create cells or flexible lines.

  • Train operators to work on lines multi threaded (poly valence of staff).

  • Normalize the work for different number of operators according to the demand of the market.

Produce on the Takt time (rate)

The takt, "compass" in German, is used to synchronize production with the sales time, becoming a reference number that gives a sense of the rhythm he must produce. It is calculated by dividing the available production time by the demand of the client, all in a given period. Thus, the takt time can be described by the following formula:

Takt time = (operating time per period in seconds.) /

(Demand customer for period units).

If the shift is eight hours (480 minutes), 22 working days a month and customers buy 79.200 units per month, 3,600 units should be made a day or a unit every 8 seconds. In a workflow process piece by piece, each process should be designed and prepared to produce a unit every 8 seconds. If you are faster, it will produce too much and if you slow down, will create a Department bottleneck. The takt is used to synchronize the rhythm of production with the sales and also allows alert operators when they are developed (overproduction) or delayed.

Given that the volume of requests fluctuates, the takt time is adjusted so that there is a synchronization between production and demand. However, clients do not ask a single article each time but a more or less standardized amount to be delivered in a container or pallet. When this happens, must convert the takt time in a unit called passing time.

Step time is, therefore, the product of the takt time (defined by the demand of customers) for the joint amount (defined by the company). Produce to the rhythm of the takt sounds simple, but it requires effort to give quick response to problems, eliminate causes of inefficiencies and eliminate times of change in processes types of Assembly downstream.

Level the mix and volume of production.

Programming of large series or batches at the end of Assembly processes or regulatory processes prevents many changes but this creates serious problems in the rest of the value stream.

Large lots make it difficult to serve customers who want something different from the series that is occurring at the time. This translates into more stock of finished products and longer period of maturation requirements. The inventory in the course of processes upstream is also increased and amplified by the need for sets in large lots. Similarly, small fluctuations of the orders in the regulatory process affect and distort upstream capacity requirements.

Many companies charge lots great work to plant processes, which causes the following problems:

  • There is not sense of takt time or pull with that answer.

  • Workload is responsible for randomly with peaks and valleys to cause chaos in machines, workers, and supermarkets. The situation becomes difficult to monitor.

  • With such amount of work each process tends to sequence the orders on their own, which increases the ripening period or lead time and the need to issue warrants.

  • Respond to changes in customer requirements becomes very complicated.

One of the most effective ways of preventing this effect consists of making a mix or mixes as steady as possible in the regulatory process. Leveling the mix of production means to produce in small lots, increasing the number of changes and maintaining variants of components available in the section

level production volume on the other hand, means trigger the production ordering and removing small and consistent job unit in the regulatory process. He is that the frequency of time management, the amount of work that each time and time devoted to the production control are minimal. Establish a rhythm of production creates a predictable production flow, which gives the alarm about problems and enables you to take quick corrective actions.

A good way to start is to provide in the regulatory process small work units valued between 5 and 60 minutes or 15 minutes and 2 hours, depending on which copyright whether, and, simultaneously, to remove the same amount of finished product. This process is also called paced withdrawal or rhythmic retreat.

The work unit valued at time is called pitch (pass), and it is usually calculated based on the number of packing units or a multiple of that amount. An environment in which we work on request should be that the pitch is calculated based on the capacity of the bottleneck. For example, for a takt time 30 seconds with size of packing of 20 units, the pitch will be up to 10 minutes of work (30 sec * 20 pieces). Therefore, every 10 minutes:

  • An order to the regulatory process is given for producing a packaging unit.

  • Withdraws a pitch of finished product.

Thus, the pitch becomes the basic unit of the program of production for the product family. If you sequence and each pitch is controlled, you can respond to problems quickly and keep the takt time.

Plank Heijunka.

Pattern is often displayed in a Board Heijunka (Heijunka Box, leveling Board). This is a table with a lot of slots to add Kanban cards or manufacturing orders. Usually, nearby the place of manufacture. Different rows and columns in a case of such account time (often days or shifts) and types of products (row separated for runners high, often shared rows of alien species). Cards are added to represent the production sequence, and are removed once the product is completed.

A Heijunka box can display the situation within the pattern very well, but it is also an important effort to maintain, especially if there are frequent changes in the pattern. Short leave this presentation which contains pretty well all the exposed here.

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