"The mastery of chemistry has to go hand in hand with the process of mechanical engineering," Dr Bayer, inventor of polyurethane, the world's first two component polymeric system.

There are countless two-part reactive chemical systems that are essential to a vast number of manufacturing processes. These range from performance critical gluing and sealing on vehicle production lines to civil engineering projects. Such processes rely on the content of the two-part system being completely accurate. Imagine an airplane where the tail wing hasn't been safely attached and one can begin to see why accurate two-part mixing is truly mission critical.

As a result, TM Robotics, AMT and Failsafe Metering are working together to develop a groundbreaking method of using robots to dispense 100% accurately mixed two-part reactive chemicals. The work is being conducted in Failsafe Metering's R&D lab in Kettering. It uses a Shibuara Cartesian linear actuator supplied by TM Robotics as the robot 'guinea pig'. AMT is providing its integration expertise to ensure that the robot operates to its full potential.

The process being used, developed by Failsafe Metering, is based on the fundamental properties of a liquid under pressure. The liquid, in this case glue, is subjected to high pressure, becoming hydraulic, and producing its maximum density per unit volume. In this state, the liquid can then be uniformly divided into two precise, volumetric units to be electronically checked for accuracy.

The system starts with the simultaneous metering of a small dot of each liquid component. Every single dot is automatically qualified in terms of its minimum volumetric size (squeezed at high pressure to maximum density or maximum weight per minimum volume). This is where the biggest distinction between this system and a conventional two-part reactive chemical mixing system lies. In most processes, sampling some of the mix that has actually been produced is the only way to check the quantity of each fluid in the mix. For example, if resin is used when manufacturing a car, the only way to check the content of that glue, is to take the bumper of one of the cars and test the glue itself. Even when one does this, the test result only describes the glue content on the bumper that has been tested, not the entire production run. Using the Failsafe Metering system, all of the glue is be checked before it is applied, dot-by-dot.

After checking, the glue is rapidly fired forward towards, and combined within, a dispensing head, from which the output forms a shot or flow. The qualification process is then based on an electronic signal, which is generated when each dot is tested. The signal is sent to a meter, which will shut down the system if the mix is incorrect and prevent it from reaching the point of application. At present, the entire system is correct to two decimal points. For example, if you require a mixture of one part to fifty and you actually have 1/49.99 the process is stopped.

At this point, the glue mix is pumped through to the Cartesian linear actuator, which dispenses the glue smoothly into the application. This process is already being used on vehicle spoilers and in several different kinds of door sealing systems.

If at any point the process is stopped, the mix already in the process will still be used and will still be perfectly mixed. There is no possibility for contamination whatsoever because it is checked before it gets the dispensing head. In a regular system it would not be checked until the product was complete.

LaurencePenn, managing director of Failsafe Metering, had the idea for this new system while toying with a replica revolver. One evening, as he spun the barrel of the gun it occurred to him that, instead of sending a constant flow of liquid through the 'barrel' of a mixing system, he could 'machine gun' that liquid through. The result would be a series of discrete 'dots', which could each be measured.

"Using conventional methods it is perfectly possible for a product to make it all the way down the production line with no sealant on it at all. It could be, literally, held together by its component parts," said Penn. "This would not be possible with our system. When companies come to us talking about quality assurance methods like Six Sigma and asking for failure rates of 3.4 per million, I ask why the failure rate should be so high? With Failsafe Metering there need not be any failures."

"Automation by itself only increases the efficiency of a process," said Nigel Smith, managing director of TM Robotics. "It doesn't mean that the product being manufactured is of any higher quality. Unless the raw materials or quality assurance process is improved, a line of glue will always be a line of glue, with all the faults inherent in that. However, Failsafe Metering's process actually allows the end product to be improved. When combined with the innovation delivered by automation this represents a formidable proposition."

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Ref: TMR/0603/TS12/TS13/TS15/TS19