MFDC controllers

Medium Frequency Direct Current

Conventional spot welding processes relied for the first hundred years of its life on AC power supplies. These controls and transformers are cheap, and the process bonded most of the world’s car bodies until the 1990’s.

With the advent of automation and in particular, the use of aluminium in auto manufacturing, more reliable processes were in demand.

At the same time, reliable high power, high speed switching devices known as IGBT’s became available, and MFDC was born.

The process uses 1000Hz, making transformers much smaller, and then rectifies the welding current, allowing use of long electrode arms and high currents with none of the enormous induction losses associated with AC.

Weld times can be controlled to 1/1000 of a second instead of 1/50, and the process is inherently stable, improving consistency and weld reliability.

The range of communication protocols available in the modern world is wide, but the Sunke range can cope with all. For parameter programming, RS232, RS422, RS485, Modbus and Ethernet are all possible, while for I/O control Profinet, Profibus, Devicenet and CC-link are added into the mix. In short, the Sunke range can talk to any customer’s required protocol.

Weld controls operating in the robotic sphere in the 21st century automotive industry have to work with the highly sophisticated IT systems in use around the world. Modern car manufacturing lines can produce a complete, fully welded, body in white every 40 seconds, meaning that any weld failure can cause very high production on-costs.

It’s essential, therefore, that every weld have its own weld programme. If not, changing parameters for one failing weld can cause failures to ripple down to other welds. With a single weld programme for each weld, parameters can be monitored and changed with no affect on other welds on the same component, reducing the risk of weld failures, and simplifying fault finding.

It’s also essential to be able to make the controls fit the different physical needs of a wide variety of customers. For this reason, Sunke offers customisation services for large users, enabling the physical layout and external connections (comms, air, water etc) to be matched to existing standards as well as working with new standards for new projects.

Uniquely, Sunke is able to offer both the more conventional Medium Frequency DC controls and the latest Variable Frequency (MFAC) designs. This concept offers cost savings, both capital and operational, as well as weld quality improvements. For more information, see the link below.

In short, Sunke has the ability to do whatever customers need, as well as having service centres in both the EU and the USA.

While robotics become ever more widely used in automotive plants, there is still a place for manual welding guns. In lower volume plants, or where customisation means a wider variety of lower volume components as part of a model range, manual weld guns still offer many advantages.

It’s critical, therefore, that despite lower levels of automation, quality control can still be rigidly maintained. The old style AC weld controls, with the ability to change weld times by only around 10% at a time, don’t offer the levels of accuracy and repeatability required in a modern manufacturing environment.

It’s also essential to be able to make the controls fit the different physical needs of a wide variety of customers. For this reason, Sunke offers customisation services for large users, enabling the physical layout and external connections (comms, air, water etc) to be matched to existing standards as well as working with new standards for new projects.

Uniquely, Sunke is able to offer both the more conventional Medium Frequency DC controls and the latest Variable Frequency (MFAC) designs. This concept offers cost savings, both capital and operational, as well as weld quality improvements. For more information, see the link below.

In short, Sunke has the ability to do whatever customers need, as well as having service centres in both the EU and the USA.

Normal spot and projection welding still have an important place in production industries around the world. Spot welding stitches together white goods, air conditioning ducting, computer frames, steel radiators and so many more components which hide their structure under a skin which is all the consumer sees.

A process like nut welding is crucial to high volume industries, with its ability to fasten nuts from small M4 to large M12 in a very rapid production process. This process is enhanced by Sunke’s 21st century control systems, which can speed up production while still maintaining quality and feeding data back to systems managers.

Any spot welding process using zinc coated materials is improved with the use of medium frequency processes, reducing tip stick, lengthening tip life and optimising weld quality.

Welding aluminium used to be regarded as a specialist process, but with Sunke’s MFDC and MFAC weld control systems, very high power welders can still be operated from normal industrial power supplies, and good quality maintained in a normal industrial environment. This is a rapid change from conventional AC systems, which made consistent high quality welding of aluminium very difficult.

It’s critical, therefore, that despite lower levels of automation, quality control can still be rigidly maintained. The old style AC weld controls, with the ability to change weld times by only around 10% at a time, don’t offer the levels of accuracy and repeatability required in a modern manufacturing environment.

Medium Frequency DC (MFDC) welding uses a transformer normally operating at 1000Hz (up to 10000Hz is possible), being driven by a welding control able to work in mill-second intervals, and provide very accurate digital control of welding current. The transformer is expensive, as it has two or more large wafer diodes, requiring very accurate assembly, and having a limited life.

Sunke’s development of this process came from the desire to replicate the welding benefits of MFDC, reduce the equipment costs, reduce power consumption and improve weld quality, all the Holy Grails of spot welding.

With MFAC, all these can be obtained.

Equipment costs are reduced as a conventional AC transformer is used. A 3-phase mains input is chopped up to provide a controllable AC waveform, the frequency of which can be varied.

The use of a 3-phase supply reduces energy costs (from actual customer test data) by an expected 15%, substantial in these days of energy reduction and carbon offset requirements.

Weld quality is improved, in particular reducing splash and allowing maintained weld quality from reduced weld energy settings. The system produces good results of hard to weld materials, such as boron coated steels.

Sunke is working with PWRWP and the Welding Institute to produce long term test data which is expected to confirm the energy savings and quality gains.

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