Rules based systems (algorithm) are harder to program and I have seen post on here with people saying there is no real difference in defect detection.
Image based systems are much easier and intutitive to program.
If you are doing 1 million cell phones and you know the product wont change then the Rules based may be for you. If you are doing lower volume higher mix then I think you will find that Image based system is probably a better fit.
Best way to determine is pick a couple of each and ask for a local demo. Bring in the requested cad and 1 good board and 1 board with defects. Have the companies program and then run both boards.
This will give you an idea of how it will fit your paticular need.
I have programmed one of each. The rules-based machine is about 6 years older than the model-based system, so It's probably not a fair comparison, but I prefer the model-based system by far. The model-based machine gives you a lot more flexibility and is easier to program. I programmed the rules-based machine for 5 years and have only been programming the model based machine for 1 year and I have a far greater understanding of the programming of this machine.
Which companies are you talking about? There are now 2 that have left the industry... Orbotec announced a couple of months ago and Agilent was announced today on evertiq.com
With that said, We have been using the Yestech AOI systems for a while now and they work well for us, just to throw a name out there. The operation of the system is very user friendly for us and we typically get programming done quickly, about 45 minutes per side.
AOI - Algorithms or Comparators| 15 February, 2009
This is the age old question on AOI. Fortunately, the answer hasn't changed much over the years. It really depends on your business...period. A high-mix low-to-mid volume manufacturer, will need to concentrate on equipment that may be progammed very easily, with very quick debug time from assembly to assembly. These attributes are typical of comparison based systems.
Higher volume manufacturers, we are talking tens of thousands of assemblies per production run, may opt for algorithm based systems. These systems are inherently more accurate than comparison based systems, but they are difficult to program and require more technical expertise at the helm.
We are a low volume high mix manufacturer. When we did our equipment evaluation, we looked at some of the higher end algorithm based machines, but determined that we simply did not have the time or resources to program these systems for our typical batch sizes. Our consultant steered us toward comparison based systems. In doing our research, we found that there were really only two vendors that were suitable for hig-mix low-to-mid volulme application: Yestech and Mirtec. We brought both systems in for evaluation.
We found that the Yestech programmed very easily, but the debug process took longer than expected, and there were several defects that were not caught right up front. This was alarming. We also ran the same boards through the machine several times and kept getting inconsistent results. The biggest advantage with Yestech was the price. They are by far the most inexpensive machine out there, but the performance was not the best.
The Mirtec machine also programmed very easily. My team and I thought that the Mirtec machine, however, was more simple to operate especially when reviewing defects. The debug time was also much faster and the machine caught every one of our defects on the first pass, as well as a cracked component which my team was not aware of. Lastly, when we ran the same boards through the machine, we got consistent inspection results as advertised. Mirtec is more expensive, but we felt that it was well worth the money based on the performance of the equipment.
Needles to say, we selected Mirtec. We now have six machines and our production quality has improved dramatically. The standard SPC software package has been a great tool in helping us resolve many of our process issues.