Telsonic UK welds Siemens panel to IP54 rating

Telsonic has provided an IP54-rated welded joint on a Siemens inverter operator panel incorporating sensitive electronics.

The Siemens plant in Congleton manufactures a range of components and solutions for drives and motion control.

Engineers here were considering the use of ultrasonic welding on an operator panel for a variable-speed motor drive, but required re-assurance that vibrations generated by the process would not damage the internal electronics.

The Siemens operator panel, at the production stage where the welding must take place, comprises of three main components: polycarbonate front and rear housings and a PCB.

The assembly and subsequent welding of the rear housing to the front housing secure the PCB within the assembly.

If ultrasonic welding was to be used as the joining method it was essential that the energy was directed into the joint and not allowed to dissipate into the features that retain the PCB within the assembly.

These stringent application requirements were reviewed by Telsonic UK and the proposed solution focused on an efficient joint design.

Telsonic worked closely with Siemens engineers to design and create an 'energy director' joint as an integral part of the moulded-case features, to create a finished closure that would achieve the required welding specifications and at the same time eliminate any possibilities of damaging the electronic components on the PCB.

In this application, the 'energy director' joint required only 600 Joules (Ws) of energy to achieve the weld, as opposed to around 1,000 Joules, which would have been required with a more traditional hermetic weld-seal joint.

Having designed the joint configuration, tested the welding parameters and established the cycle time of 0.55 seconds, Telsonic then designed and built the production machine for Siemens.

The Telsonic production system for the application is based around a 20Khz, 3kw USP3000P ultrasonic welding system, complete with electronic proportional pneumatic control and a linear encoder, a configuration that allows the weld collapse height to be precisely measured.

This, together with the reduction of 40 per cent in the energy required to achieve the weld, guarantees that no excess energy is transmitted to other areas of the casing or PCB.

The Telsonic machine is also to be configured to produce two variants of the operator panel, with the system storing the welding parameters for both product types.

Parts are manually loaded to a precision welding fixture incorporated within a drawer mechanism.

An array of sensors incorporated within the machine tooling is then used to verify that each of the individual parts has been correctly loaded before the welding process takes place.

The system has been configured to ensure that the welding process does not take place before a barcode is allocated to the part.

The system logic also eliminates the possibility of the same assembly being welded twice by mistake.

The weld delivery result for each cycle is monitored by process-control weld limits set within the MPS4 controller and subsequently included in the data string output to the Siemens system.

Warning indicators and an operator panel allow clear and intuitive operation.

The system is guarded with an extruded aluminium frame and polycarbonate infill panels, for safe operation.

This system also provides full process traceability.

The Telsonic machine interfaces seamlessly with Siemens' own hardware and bespoke internal quality IT application.

The individual-component barcode details, scanned prior to welding, are stored alongside weld-result parameters, selected by Siemens and logged from the welding operation together with the time and date.

At the end of each cycle this information is passed from the Telsonic MPS4 Weld Controller to the Siemens bench-top controller, which comprises of an operator-screen interface and PLC with Siemens application software, specifically designed to link to their SQL system.

Five levels of password protection are available within the MPS4 controller to ensure that only trained and qualified individuals can adjust weld set up, data-set storage, initialisation settings and process-control parameters.

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