Automated assembly system fabricates sensors

MacGregor Welding Systems' latest automated assembly system is designed to fabricate miniature sensor modules for use in analyser equipment.

MacGregor Welding Systems' latest automated assembly system is designed to fabricate miniature sensor modules for use in analyser equipment.

It takes individual component parts and assembles them completely automatically - a process which involves the precision welding of metallic connector ribbons onto small pins.

The system makes extensive use of Festo electrical and pneumatic actuators, including two electrical mini slide units with matching controllers, which are fed with position feedback data to ensure high-accuracy assembly and precision micro welding.

Based in Mildenhall, Suffolk, MacGregor Welding Systems designs and manufactures a wide range of micro resistance and pulsed micro arc equipment, which is used in diverse industrial manufacturing applications.

Founded in the late 1970s, it initially concentrated on the development and manufacture of pulsed micro arc welding torches and precision resistance welding heads and power supplies.

These are typically used by customers in the medical, aerospace and automotive industries to perform high-reliability joining and interconnection of electronic components and sub-assemblies.

In recent years, MacGregor Welding Systems has expanded the Systems Engineering side of its business significantly, and nowadays produces a considerable number of application and customer-specific assembly machines.

Most recently, the company has seen a dramatic increase in systems sales following the recent introduction of RoHS legislation, which has created an upsurge of interest in micro joining techniques as the electronic industry moves to lead-free components and manufacturing processes.

MacGregor Welding Systems' latest component assembly machine fully automates the production of miniature sensor modules.

The multi-stage process involves precision assembly of various small parts - including the fitting and lubrication of O-rings and final moulding insertion - as well as welding two strips of metallic ribbons onto a pair of small pins on the sensor module, and onto a connector block.

The company chose to base the machine predominantly on Festo pneumatic and electrical actuators, using SLTE electrical mini slides and associated SFC-DC motor controllers for two of the most demanding parts of the system, which require exceptionally high positional accuracy.

According to Graham MacGregor, Managing Director of MacGregor Welding Systems, "We elected to use Festo SLTE mini slides primarily because they provide a complete, ready-to-run positioning solution".

"The slides incorporate their own miniature motors, which simplifies system integration and makes them very cost-effective, and the supplied control software is extremely easy to use".

One of the mini slides is associated with the initial product assembly stages, the other with the welding stage.

The welding process uses a technique known as micro resistance welding, which involves passing a short-duration, high-current pulse through the materials to be joined, while accurately controlling applied force.

The welding head module provides up to 10mm of dynamic movement, and is driven into position by the SLTE mini slide.

A compression transducer provides feedback to the control system, which triggers the welding power supply to deliver a pulse of current when the weld electrodes are in the correct position.

The weld head can accommodate a force in the range 2 to 70N, and the current pulse - up to 1000A - is typically limited to between 5 and 50ms.

The welding process involves far less thermal energy than a conventional solder joint, making it ideal for heat-sensitive components, and provides a much faster means of securing consistent, high-integrity electrical connections.

The automated assembly machine was recently installed at the customer's premises, where it is currently undergoing evaluation prior to production ramp up.

It is understood to be performing impeccably - so much so that a second machine has just been ordered - and the customer is said to be delighted that such a small footprint system can provide such a high throughput solution.

Back to top