Manufacturing Rotors & Stators Without Punching Tools, Using Laser Cutting

In today’s world, you could be forgiven for thinking that electrical machines, motors and generators are being reinvented.

Energy efficiency, electromobility or having to adapt specifications to a particular application all present new challenges in the development of electrical machines.

Developers have new ideas as to how the perfect design for a particular application should look and the production department does not have the tools to make a prototype from these ideas.

But it is not only creating prototypes but also low volume production that causes headaches in manufacturing. Special electrical machines which are adapted to the application are often not produced in high volumes.

You can easily manufacture many of the components of an electrical machine without using tools for high-volume production. For example, you can use turning or milling to produce one-off components without any problem.

Thin parts manufactured to a high degree of precision…

Components manufactured without using tools…

But there is a lot of expertise in the design of rotors and stators. They are constructed from several hundred individual sheets. The sheets are punched in the traditional manner. There is also no doubt that volume production is the most economical method of production.

To achieve higher volumes in order to make the tool worthwhile, the motors are built into the modular construction system, so that as many motors as possible can be used for the same tool. This is not a good solution for having the optimum motor! Developers and the manufacturers would also like more freedom when working with low volume production.

When manufacturing punching tools, the cost and time factors do not fit with low volume production. Everyone tries to reduce the time and costs of low volume production with simple pattern tools, or with single-use stamping machines. But these technologies also significantly reduce the flexibility of the system.

The tendency for electric motors is moving towards thinner sheets. In extreme cases, sheets are used at a thickness of 0.1 or 0.2 mm, the standard today is 0.5 mm. This requires high-quality punching tools. If the design is decided and the volume is high enough, then this justifies the investment. If another change is required later, then it becomes expensive.
So the question is, at what point is a punching tool worthwhile, or how can you manufacture at low volumes economically, without using tools? Tools are expensive and they take time to manufacture.

Tool-free production is of particular interest during the development phase. A lot can be simulated on the computer but there is nothing like an actual trial! It is extremely beneficial if you can quickly implement new ideas and test them out.

But how can we manufacture a few electrical sheets to a high level of precision without a punching tool?

This is where laser technology comes into its own.

The perfect choice: convert the technical drawing to a machine program, place the sheet on the machine and cut with the laser.

There are lots of laser cutting machines on the market, but most of them do not achieve the required quality with electrical sheets. Geometrical accuracy is not enough and the cut edges are not free of burrs.

So what is the difference between laser cutting and laser cutting?
There is no single laser cutting machine that can do everything! Most laser cutting machines on the market are designed for standard sheet processing. They are designed for sheets which are 1 mm to 20 mm thick and an accuracy in the range of +/-0.2 mm is usually sufficient. It is standard practice to deburr the sheets after laser cutting.

Processes which have been acceptable in sheet processing in the past are no longer sufficient for the manufacture of electrical sheets. The sheets must be free from burrs when cut. The insulating layer on both sides means that it is not possible to machine the sheet afterwards. The accuracies required are in tolerance classes IT7 / IT8 which is only a few hundredths of a millimetre.

The laser cutting machine must be able to achieve this over the entire working range. Material thicknesses are below 1 mm which also puts special demands on the design of laser equipment.

The complete concept of the machine with the implemented laser technology must be designed for thin parts, which are manufactured to a high degree of precision with a high dynamic response.

The special requirements for electrical sheets mean that you need special laser cutting machines!

There are more and more specialists who are successfully working on the subject of laser cutting electrical sheets. This means that all the designs considered by the developer can be implemented and the motor can be tested quickly. If the result is still not satisfactory, new drawings are produced, the part is laser cut and then the new motor is ready for testing, all in a short period of time. When producing at low volumes, you can reduce costs and delivery times by using a production method, which doesn’t require tools. Changes can be easily incorporated, no need to alter the tool. This applies to both small and large motors, for different material thicknesses and different coatings.

Complete flexibility is enjoyed when manufacturing rotor and stator sheets…


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