Motion co-ordinators use CAN for can inspection

A revolutionary new can inspection machine offers exceptional programming flexibility and low maintenance costs through the use of a Trio Motion Technology motion co-ordinator.

A revolutionary new can inspection machine offers exceptional programming flexibility and low maintenance costs through the use of a Trio Motion Technology motion co-ordinator.

The X-Seam double seam analyser from Sencon uses X-ray technology to inspect the vital joint between food or beverage can ends and sides.

Failures here could mean that filled cans might be exposed to contamination, leak or even burst.

In the constant search for ever higher quality, leading companies are investing in new methods of testing and improving can integrity.

Traditionally, manufacturers take samples from the can filling line, remove the contents and cut open the can to inspect seam dimensions.

Disadvantages of this method are the time taken to perform each test, the profile damage and deformation - which may be caused by the action of cutting through the seam, and the great difficulty in measuring very small deviations from the norm which may be exaggerated by operator error.

Manual testing is known to have a relatively poor "R and R" (repeatability and reproducibility) rating, meaning that there will be little accurate repeatability of results between different operators and even between results from the same operator over time.

The new Sencon X-Seam analyser eliminates the need to perform manual, destructive testing by using X-rays to generate images of the filled can at a number of points around the seam.

A sophisticated image processor then measures each critical point and produces a report based upon predetermined standards.

Typically, measurements are made to 0.001mm and have excellent "R and R" standards of better than 20%.

As the can is not damaged by the process, it may be returned to the production line.

Sencon's machine will perform tests on 18 cans in around 21min, where the manual method could take more than 2h.

"When we designed this new machine", commented Mark Tredinnick, Sencon's Project Development Manager, "We had a number of major concerns in mind.

The first, naturally with an X-ray machine, was absolute safety of operation.

Then there was high precision of measurement and complete reliability, plus the ability to change PC operating systems as future versions become available, without impacting on the mechanical control system.

We decided to make the X-Seam effectively in two parts, the mechanical systems and X-ray equipment as one unit, and the computer control and analysing systems as a second unit.

By separating can conveying, handling and measurement from the analysis side, we were able to develop a very complex machine in record time".

Sencon chose an MC202 motion co-ordinator, two CAN 16-I/O modules and one CAN analogue input module from Trio Motion Technology to control the entire mechanical elements of the X-Seam analyser.

These consist of input and output can conveyors, a vacuum lift mechanism which moves cans from the input conveyor to the measuring point and removes them to the other conveyor, and a chuck assembly which clamps the can firmly and moves it to the X-ray generator head.

During measurement, the chuck assembly rotates to four preset positions, providing four images of each can seam for analysis.

The chuck is rotated by a stepper motor sourced through sister company, Sencon in Chicago, to provide a degree of component commonality between different machines.

A second stepper motor drives the ball screw to move the chuck into position.

All other movements, including vacuum pickup and can transfer, are actuated pneumatically using limit switches and controlled by the MC202.

The whole assembly is therefore completely "stand-alone", needing only a start signal to begin operation and an indication of how many cans are to be tested.

Both of these signals come from the inbuilt computer which is equipped with a colour touch screen for easy operator interaction.

This computer stores test programs which may be called up and downloaded to the MC202 through a serial link.

Usually, however, the operator will only need to enter batch data and touch the procedure name.

The X-Seam analyser will then step through its pre-programmed routine, storing data and images of the tested cans for later analysis.

Communications facilities are provided for uploading this material to a network or supervisory computer.

External lights provide indication of the need for operator attendance where required, freeing them from continuous supervision during test procedures.

"The Trio controller was ideally suited to this machine", said Mark Tredinnick.

"It is small and easily installed on a standard DIN rail alongside the three I/O modules.

We had very little previous experience of this type of system, but there was no difficulty in programming the controller, using the standard Trio Basic language and the Motion Perfect software".

"The development team were impressed that the software was free, and found the support available was very good.

By adopting a modular approach, isolating the mechanical system from PC data collection, we have been able to make the working elements independent of the computer.

If, for instance, we need to change from Windows NT to any other operating system, then we simply reprogram or install a different PC without affecting the programming of the MC202.

Servicing, too, is much easier.

As all connections between the Trio modules and the machine are by standard connectors, we could change a unit very quickly in the field.

There would be no need for an extensive rebuild and full test of the system".

"In fact, of course, that's a theoretical advantage because we have not needed to change any units.

They have proven very reliable and perform so well that we are now using Trio motion co-ordinators in other Sencon can inspection systems".

The MC202 is a two-axis controller with a third axis available in software for the generation of complex motion profiles using virtual axis summing.

The co-ordinator employs 32bit DSP technology and is equipped with an RS232 channel, a TTL serial channel and one CAN channel as standard.

Up to 256 external I/O channels and up to 32 analogue input channels can be provided using CAN 16-I/O and CAN analogue input modules.

Facilities exist for connection to a Trio Membrane Keypad on a fibre-optic link.

The MC202 is one of a wide range of motion co-ordinators from Trio Motion Technology, including the six-axis MC206 and the new 24-axis MC224 with the ability to work in Sercos systems.

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