Machine vision in 3D
In a recent issue of Control Engineering Europe we have an article about a new machine vision product called "Optigo" that inspects—and measures—manufactured parts in three dimensions. The camera, which is made by a start-up company called CogniTens, has been making the rounds of European trade shows.
In a recent issue of Control Engineering Europe we have an article about a new machine vision product called 'Optigo' that inspects-and measures-manufactured parts in three dimensions.
The camera, which is made by a start-up company called CogniTens, has been making the rounds of European trade shows. Needless to say, it has caught the attention of aerospace and automobile manufacturers. For anybody who makes quantities of metal parts in various shapes and sizes and wants to measure them with precision, this may be the answer.
Optigo captures three separate stereo images, triangulates them, and calculates height, width, and depth measurements to within a hundred microns. In some cases its makers claim it can measure down to 30 microns. R&D developers dream about pushing the limit to 10 microns.
On the factory floor
The device was designed for operation right on the factory floor. It basically performs the same function as a co-ordinate measuring machine (CMM), except it can measure hundreds of thousands of points simultaneously and doesn't need to operate in a special environment.
Of course, it would take you some time to check a computer listing of the x, y, and z positions of 200,000 points, and the CogniTens people realise that. They have come up with a clever alternative: to transfer the acquired image to a CAD program, compare it with the original design, and produce a colour image indicating the differences. In our article we give an interesting example of this: a sequence of automobile doors going out of spec.
The area of interest turns yellow, then red as the surface becomes more uneven with subsequent product coming down the line.
Other automobile parts, such as crankshafts, can be rotated and imaged from all sides. The visualisation software shows the operator where excess metal must be re-moved. and, just as importantly, it shows where material may be missing. Why spend time machining a part if deficiencies in other areas will require it to be scrapped? Optigo may help managers make these kinds of decisions.
To replace CMMs?
CMMs are highly accurate mechanical beasts, and they can handle a range of different sizes and shapes, but they take up a lot of space and require special controlled environments for operation. You won't see them on-line, inspecting parts passing down the conveyor belt. And you won't see them inspecting more than a few dozen points, which means some critical surfaces may go unverified.
Any non-contact method of dimension measurement will obviously have its advantages for a manufacturing environment. There have been a few successful ones based on optical techniques such as Moire patterns, laser trackers, and photogrammetry. Perhaps further development will make these techniques more proficient and easier to use.
But for now you might be interested in what the CogniTens people are doing, and in case you're not one of our 30,000 readers in Europe, we've made the article available to you on our web site. You can find it at www.controleng.com/archives/2001/ctl0402.01/e0104p23.htm
Michael Babb, European editor firstname.lastname@example.org
Multibarriers to the rescue
Fieldbus, be it the Profibus PA or Fieldbus Foundation variety, has not enjoyed a warm reception in many European chemical industries.
The industry appreciates the value of digital technology. But there's a general malaise about the way fieldbuses are configured.
Most of Europe, and especially Germany and the Benelux countries, follows the intrinsic safety approach, and although the buses were designed from the ground up to operate in hazardous zones, power limitations prevent the full deployment enjoyed in non-hazardous areas. What good is a branch line if you can only attach 3 or 4 instruments to it?
With the help of some new 'multibarrier' equipment from ABB and 'binary boxes' from Bürkert, there is a very clever 2-wire solution that takes advantage of the relationship, and difference, between EEx(e) and EEx(i) safety specifications.
It gets a bit complicated but we have plenty of diagrams to guide you through it, and you can see the article -which was written by an end user in The Netherlands-on the web at