Partnership creates perfect canister

Edited by the Engineeringtalk editorial team Oct 25, 2002

A four-way partnership has produced a cost-effective 12-station assembly unit, to create a finished, leak-proof, polypropylene anaesthetic canister.

A four-way partnership between machine builder, Werner Engineering Systems, its customer, weld systems supplier Telsonic together with end user Molecular Products, and SMC Pneumatics, has produced a cost-effective 12-station assembly unit, to create a finished, leak-proof, polypropylene anaesthetic canister.

The brief was for the machine to assemble a six-part assembly to create a finished canister.

The machine would then be incorporated into Molecular Products soda lime dispensing system.

The canisters containing soda lime, and two foam filters, are used in hospital operating theatres, to filter carbon dioxide out of the anaesthetic machine breathing circuit.

Therefore, integrity of the canister is vital.

The project brought together the skills of all four companies, Telsonic with their expertise in welding technology, Molecular Products provided the knowhow for the controls and programming, which left Werner to concentrate on all aspects of design and build, with SMC providing cost effective pneumatic solutions.

"The whole project was completed in 16 intensive weeks", enthuses David Norton, Sales Director of Werner Engineering, "This time frame was achieved by Molecular Products introducing a two-wire ASi (fieldbus) system into the equation, this made economical and design sense due to the high amount of inputs and outputs required.

By using this system, savings were made on labour costs and, as a bonus, it gave the whole project an aesthetically pleasing look".

The ASi system controls 29 pneumatic actuators and an electric cam index box, which drives the rotary system.

The machine achieves up to a 10ppm cycle time, which is reduced to 6ppm if the pressure test station cycles.

After assembling two pads and filling, with a measured quantity of soda lime, (stations 1 to 9) the machine places and ultrasonically welds a lid into position.

This type of welding on soft polypropylene, although fast and cost-effective, is a difficult process, and the shrinkage rate is poor.

After the welding process, at station 10, a 10s pressure test takes place, at 2.5lb/in2, to check weld integrity.

If pressure decay is detected (at around 10% or below) a signal is sent via the plc and the canister is rejected at the final station (12).

Station 11 positions a transit cover over the inlet and outlets, which are then transported via a conveyor, incorporating pneumatic escapement and guided cylinders, from the machine to a finished part area.

In addition, because of the corrosive properties of soda lime hard anodised aluminium and stainless steel was used throughout.

From SMC's perspective, Area Sales Manager, Russell Lotinga, who was involved with the project, from the start, says, "It was a challenge, but the two-wire system was certainly the way to go, considering the amount of cylinders and sensors", he continues, "We carried out a cost saving exercise at the beginning, comparing two-wire ASI with a conventional system - with the two-wire bus, the parts were slightly more expensive, but the labour costs savings were tremendous".

David Norton concludes, "The four way partnership has worked extremely well for all parties.

We will certainly be using the ASI system again, because of the cost effective benefits, which, of course, can be passed on to our customers".