Lean Production

Because of more demanding customer requirements, industrial plants are being forced to offer products tailored to customer needs and/or a large number of different product versions. In addition, it is necessary for companies to have high productivity in order to remain competitive.

Lean Production is the term used to describe the systematic organization of production originally introduced at Japanese automobile manufacturers. The goal is to use production factors such as operating equipment, personnel and materials without waste and efficiently and to optimize product quality.

Higher productivity and improved quality

Productivity can be increased by, among other things, optimizing the production processes and shortening the processing time as well as by reducing underutilized personnel capacity. As part of Lean Production, inventory levels are reduced as far as possible - raw materials and intermediate products are stocked only in an amount that can be used quickly and efficiently. This frequently requires just-in-time deliveries.

Improved quality of the products manufactured is achieved, on the one hand, through optimized manufacturing processes and, on the other, through improved quality control as well as more efficient handling of rejects and product defects.

High flexibility and customer orientation

Finally, Lean Production is characterized by relatively high flexibility in terms of production factors, production quantities and product versions. This flexibility allows a faster response to unexpected fluctuations among suppliers, in one's own production and on the market.

Design principles of lean production

At the same time, a lean production system can be successful only if the entire system is oriented toward a customer benefit. Alignment of the production system on the principle of Lean Production distinguishes eight design principles:

1.     Avoidance of waste
2.     Continuous improvement (Kaizen)
3.     Standardization
4.     Zero-defect principle (Poka-Yoke)
5.     Flow principle
6.     Pull principle
7.     Employee orientation and goal-oriented management
8.     Visual management

A central component of Lean Production is Identifying and eliminating waste. Waste includes all efforts and activities that do not contribute to value creation and customer benefit. In addition, defects mean that already created customer benefit is lost.

Thus, the objective of the zero-defect principle is not to pass defects on to subsequent process steps, thereby increasing product and process quality. To prevent unintentional defects, the poka-yoke principle, for instance, usually employs technical aids.

Based on the desire for perfection, the objective is to improve existing processes and systems continuously. After all, with every improvement, defects, problems and waste are identified and eliminated. A prerequisite in this regard is inclusion all employees, for instance, in the form of internal idea management. Goal-oriented management can also help to include employees more strongly in company processes and drive continuous improvement.

Standardization is intended to eliminate activities that do not contribute to value creation. With this in mind, handling steps are specified for repetitive processes, procedures and manufacturing steps.

To achieve the shortest possible processing times, the products should move from one process step to the next without intermediate storage. The objective of the flow principle is to configure the material and information flows to be continuous and have little turbulence. To minimize control activities and inventories here, the pull principle is based on customer orders and "pulls" them through the production process.

A visual presentation of information relating to processes and procedures provides greater transparency regarding goals and performance. Key data, problems and deviations from goals are identified more quickly in this way and employees identify more strongly with their tasks.

Lean production with Lehmann rotary tables

For more than 40 years, the Swiss company pL LEHMANN has been building compact, high precision CNC rotary tables. The products offer not only a wide variety of workpiece clamping options, but also maximum utilization of the machine compartment and traversing strokes, very short cycle times through special clamping management and a favorable energy balance through use of smaller motor sizes.

With innovative CNC rotary tables, organized in a standard modular system, the company strives to meet the international needs for economical production of very small to medium-sized workpieces in the machining industry by satisfying individual requirements with appropriate combinations.

With four basic types/sizes of rotary tables, it is possible to cover a performance range for which other products need twice the number of basic types. Moreover, thanks to the modular system it is possible to build a large number of standard combinations. Machine manufacturers and machine dealers (OEMs) thus need to manage and stock fewer types, benefit from very short lead times and can provide a great deal of adaptability. The user can also profit, above all, from the spare parts business and service in addition to short lead times.

CNC rotary tables for economical manufacturing

Complicated workpiece geometries require multiple and flexible workpiece clamping and motions in the machine compartment. Based on a high level of standardization, pL LEHMANN is able to offer an appropriate and economical solution for the most varied of applications. Short setup times increase productivity and the degree of utilization. At the same time, the user has the ability to automate one step at a time: e.g. starting with manual loading, progressing to simple linear feed systems and ultimately to fully automated production with robots. With interfaces for different clamping systems, supplemented with the appropriate clamping cylinders and rotary unions and possibly even stroke and pressure monitoring, a wide range of modules is available.

Fields of application include:

  • Automotive
  • Medical / Dental
  • Watches/ Micro Technology
  • Aerospace/Turbines
  • Mechanics

Flexible with fast setup/conversion

Lean Production Is characterized by high flexibility as well as short processing times and setup times. With over 20 standardized systems, pL LEHMANN offer a wide range of workpiece clamping options. At the same time, by using the modular combiFlex® system it is possible to achieve a number of customer-specific rotary tables solutions with the aid of standard elements. The standardized interfaces that designed for the combinations permit special adaptations at any time. The rotary tables can also be converted and retrofitted long after original purchase. Two EA-type rotary tables can be converted to a two-axis T-type rotary table at a later date – or the other way round – an existing T-type rotary table can be converted to a different version. Thanks to simple handling, the systems allow very short setup times.

Furthermore, precision classes can be adapted to requirements through use of various angular position measuring systems and two geometry tolerance classes. Radial and axial run-out values as low as 2 μm are possible.

Greater productivity, accuracy and reduced space requirement

The CNC rotary tables from pL LEHMANN ensure a high power density and the best possible accessibility – this is provided from above. Tool and workpiece are clamped quickly, making it possible to increase productivity and accuracy while achieving optimal machine compartment utilization. The compact outside dimensions allow more working spindles per square meter. A compact rotary table is lighter and the reduced moving mass saves energy.

Higher speeds - up to 210 per minute - and short cycle times - 90° from 0.2 sec - reduce the manufacturing time needed for workpieces, thereby increasing productivity.

A 3+2-axis solution, for instance, also has advantages. Compared to a 5-axis machine, the floor space required is reduced significantly, which allows more machines to be installed on the same floor space and reduction of aisleways for employees and material. This solution also has benefits in terms of flexibility. Furthermore, the procurement costs are usually considerably lower than those for a 5-axis machine – provided the same capabilities are compared.

Can be automated

To achieve automation, it must also be possible to automate the clamping means. A wide variety of clamping devices can be built on the basis of the ripas zero-point clamping system. The system is based on standard HSK clamping. The driver/carrier cams, however, are machined precisely and give axially. The counterpart (ripas adapter) has a precise groove as well as a positioning bore for the guide bolt.

The clamping system can be retrofitted on Series 500 starting with Edition 2. It achieves a high repeat accuracy and can transmit high torques. Additionally, fast workpiece changes are possible and workpieces can be set up while the machine is operating.

Already Industry 4.0-capable

Preventing defects is one of the central components of Lean Production, since defects result in wasted resources. This has nothing to do with Industry 4.0, but is a prerequisite for it.

Ultra-fast spindle clamping assures higher productivity and competitiveness as well as faster amortization. This can only be assured through sensors and electronics. Furthermore, it must be possible to operate the production equipment – without operators – around the clock, and rectify shutdowns and problems in the shortest possible time. Facts and data are indispensable to eliminate the causes and prevent future shutdowns. This means that a data logger and a data history are needed.

Rotary tables from pL LEHMANN come with a blackBOX as well as a watertight USB port. Data can be read out using a commercially available USB stick or via Bluetooth in the case of a problem and sent via e-mail to pL LEHMANN or a representative in your country. In this way, the causes of problems can be identified and eliminated faster. On the other hand, LEDs visualize the state of the machine at all times and indicate when, for instance, maintenance is due. Further support is offered in the form of an Ethernet interface, a web server as well as PC software, which allows trained maintenance technicians to perform evaluations and analyses independently. In this way, productivity is increased while the fault rate and frequency of breakdowns are reduced. Fast. Independent. Purposeful. Simply lean.

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