Prior to the purchase of your cutting/finishing machine certain specifications need to be considered. Speed, pressure, repeatability and accuracy, to mention only a few. However, one thing, which is often overlooked, is the kind of technology the machine uses to recognize marks on prints. In today’s market, you have the choice between camera-based and sensor-based optical recognition. People often tend to assume cameras are faster than sensors. Generally spoken, this is true, however, it is not the full story.
To avoid misunderstandings and to make sure you have a good overview, here is some detailed information about both technologies.
First, we would like to start with sensor-based optical recognition, as this is one of the precursor technologies, used to determine positions. Many people think all sensors of finishing machines work in similar ways. But this is not entirely correct. Primarily, sensors measure a level of contrast for the material and a level of contrast for the ink. This measurement helps the firmware to determine the edge of a mark, as well as the size of the registration mark. Multiple marks can then be pinpointed on a sheet or roll, giving the firmware the necessary coordinates of the print itself and possible deformations.
Now, here is where they differ from each other. The sensors themselves comprise different technologies. In the current market, there are two possible types. The first type is the infrared sensor, capable of sensing most accurately and quickly. However, this type of sensor has its flaws. One of them is related to certain types of protective laminates, such as UV laminates. This type of substrate is designed to absorb or reflect UV light and infrared is also absorbed by this material. Since the sensor uses infrared light to bounce off the measured surface, it tends to have difficulties recognizing any difference in contrast. Consequently, many of today’s finishing machines will have issues sensing the registration marks on these laminates.
Another issue with the sensor-based optical recognition could be the colour of the registration mark itself. The currently most often used colour of registration marks is red or hues of red. However, the different shades of red could have a lower contrast because the infrared sensor will consider the red registration mark to be white. Consequently, red registration marks on white shades of material will entail the registration mark to be sensed. Before, Summa also used these sensors in their machines, but we quickly realized its limitations would have an impact on future developments.
This is why Summa developed its own bespoke sensor technology, based on a white-light sensor which can detect a much wider range of colours. Moreover, issues with lamination, UV or otherwise, are reduced to an absolute minimum. One of the many benefits this technology offers is its capability to handle any type of print-related issues, such as overspray or missing nozzles, without loss of accuracy during the final cut.
Nonetheless, sensor technology, even with the best intentions, has its weaknesses. For instance, when using highly mirroring media, the usage of this technology could get a bit tricky. In spite of that, Summa offers a cost-effective solution to this, so by the end of the day, the job will be done equally good.
This brings us to our second technology, the camera-based one, which, by many, is considered to be truly high-tech. It works in a very different way compared to the sensors. It actually takes a picture of the registration mark. Moreover, the accompanying software on the computer will analyze the picture. This is necessary because the image needs to be translated towards data in terms of shape, size and position. It would be too heavy a job to perform this on the processing power of an integrated circuit within the machine. As the computer takes over all computational work, the machine itself is able to accurately and quickly go from one registration mark to another. All this results in a considerable increase in speed. No measurements are needed by moving the head back and forth. The camera simply goes to the markers and takes an image.
Speed is a significant benefit here, but it is by far not the only asset of the camera-based technology. Another one is the flexibility of having imaging filters, recognizing the marks instead of putting a physical item over the sensor. All this can be done within the software. The ease of use as to safeguarding this filter and the possibility to quickly change it are also important assets to this technology. This way, even difficult substrates, such as the mirror or reflective material, can be contour-cut easily and efficiently.
And if you thought this is it, here’s another advantage. With the camera-based technology, we are no longer limited to use only one type of registration mark. The right software enables us to recognize a multitude of shapes. Many types of Print&Cut workflows tend to use their own shape of registration mark. With the camera-based technology, it can be part of the workflow without having to adapt anything.
Here’s an example. Assuming you have a flatbed, which is constantly running, and your production need is growing steadily. Logically, you would add another flatbed. However, if you could dedicate your printed roll material to a roll-based cutter with a camera, able to sense the flatbed's marks, this would help reduce your flatbed’s burden at a fraction of the cost of a second machine. If we piqued your interest in this particular workflow, simply check Summa’s Twin workflow capabilities.
In fact, there is only one drawback to this technology. Unfortunately, it will not work on a Mac OS or Linux based operating system. You will still need to have a Windows-based system, connected to the machine to access the camera’s imagery for the analysis.
S Class 2 OPOS Cam Series - With camera technology
Exploding the myth
Before we end this explanatory article, there are some misunderstandings we would like to rectify as follows. A common question or remark would be that a camera could never be as accurate as a sensor or, vice versa, that a sensor could never be as accurate as a camera. We can safely state that both systems are similar in terms of accuracy. As a matter of fact, our experts, testing this matter for years, have never encountered that one technology would be less accurate than the other.
Secondly, related to our own PostNET barcode automation workflow, some might say “Camera’s are not able to use this workflow”. This is simply no longer true, since the current S Class 2 OPOS CAM units are able to use this workflow. Only older S Class 1 OPOS CAM models wouldn’t support this workflow, but all newer models do.
So, we hope the above article has been of interest to you and helped you to better understand the differences between both technologies.