In the history of every company, there are milestones that have a decisive influence on further development. At BMR elektrischer und elektronischer Gerätebau from Schwabach, this was the start of the production of frequency inverters in 1990. The new product area benefited from the company's experience in electronics production and the development of its own electronic control systems. Today, the company specializes in the development and manufacture of static frequency inverters for motor spindles in the power range from 150 VA to 3.6 kVA and for speeds of up to 240,000 rpm, for both high-voltage and low-voltage types. The SFU0303 frequency inverter is specially designed for use in modern machining centers and is currently being used by IPTE, a manufacturer of complex production systems for the electronics industry, in the field of depaneling.

BMR has been manufacturing the frequency inverter model since 2009 and has continuously optimized it and adapted it to current requirements ever since. Of course, this applies in particular to Industry 4.0. There is hardly any other sector in which the transformation of technologies can be better demonstrated than in electronics.

SFU0303 with backup inverter. © BMR

Always good for tension
The sophisticated control process is the key to controlling the spindles in all speed and load ranges. High torques can be achieved on the spindle even at low speeds. In addition, the control can be set so that the spindle remains very cool when idling and still allows a strong feed during load jumps. The sinusoidal output voltage is generated via pulse width modulation at 28 kHz and a variable regulated DC link voltage. This guarantees high control efficiency with low losses and minimal heat generation in the spindle. In all power ranges, the DC link always provides exactly the voltage required for the required power or speed. This makes it possible to operate low-voltage spindles without an additional external sine filter. The risk of the spindle heating up is prevented. The operation of asynchronous and synchronous (BLDC) spindles is a matter of course and can be achieved by simply changing the active spindle parameter set.

Since 2016, the SFU0303 has also been available in combination with a new, proprietary dressing system or as a process monitoring system in the Dressview 0303 version or in a reduced version as Dressview Lite.

High cycle times in depaneling

IPTE Germany in Heroldsberg develops and manufactures test and production equipment for the Systems, Assembly and Test divisions. The BMR frequency inverters have been used in the field of depaneling for many years. Depaneling is the separation of several panels produced at the same time.

SFU-0303 and SFU0303-DressView Lite in two-spindle operation. © BMR

In addition to maximum reliability, a decisive criterion for the product selection was the simple remote control of the spindle parameters via a standard interface to ensure smooth multi-spindle operation. When switching between the spindles, the corresponding parameter set is always selected automatically. The integrated high-performance brake chopper enables high cycle rates, as not only steep acceleration ramps but also steep braking ramps can be realized. In a global benchmark test for depaneling machines in 2016, one of these routers also achieved first place thanks to the performance of the frequency inverters used. "The SFU0303 is a key component in our machines and helps us to take a leading role in the market with our machines," says Mathias Schönlein, Product Manager for Depaneling machines at IPTE Germany. "I am particularly impressed by the powerful control and the excellent control characteristics. It has proven itself extremely well as a drive for our spindles."

The versatility in parameterization and the large number of interfaces enable easy integration into the application. In addition to the six digital and two analog inputs, six relays and two analog outputs are available to the user in any configuration. The "Variolast" function ensures convenient tool monitoring. The current status of the inverter and spindle is displayed in plain text on a 3-line LCD. The SFU-Communicator communication module also provides the option of connection to most industrial and fieldbus systems.

As standard, the frequency inverter is installed in the SSE housing variant for control cabinet installation. In addition, a variant for table-top operation and for installation in a 19" rack is also available. In the compact SSE version, the housing is chip-proof with an external heat sink and can also be used in dusty environments. Chips and other dirt can no longer penetrate the system. Cooling is actively supported by a temperature-controlled fan.

Retrofit saves costs

At IPTE, the classic BMR frequency inverter not only demonstrates its performance in modern machining centers. It is supplied as a connection- and function-compatible replacement device for its predecessor versions and thus enables the continued operation of older CAD-CAM systems, for example. This is because replacing the entire electronics is usually a costly undertaking.

IPTE is currently successively retrofitting all old machines with compatible 0303 series inverters in the event of repairs. Thanks to the flexibility of the configuration, they can be seamlessly integrated into the existing machines and adapted to the old parameterization. This makes it possible for IPTE to keep the machines in use worldwide in operation cost-effectively and at the same time upgrade them to modern inverter technology.

Dipl.-Ing. Frank Buchholz, Development BMR and Silke Brügel, freelance journalist / am