LukeMachineElements1 (Customer) asked a question.
Need Photoelectric Sensor to Detect the Side of a Material
I need a sensor to detect the side of a 3/8" wide plate. The sensing area is 32" long. I wanted to use a retroreflective or throughbeam photoelectric sensor for this. I was wondering if anything special needs to be used since the object is relatively thin.
I believe you will need to add some details of the process to get pertinent information.
Maybe call AD directly for application help
As Tom@Pton mentioned, more details are needed to select a photo sensor, such as environment, mounting options and distances, sensing distance, beam widths, object material to detect, etc. And personal preference and/or experience with machine using other sensors play a pert. In one application, we used a sensor that operated fine and met all the specs, however machine operation and material (mis) handling caused sensor mis-alignment. In one product line, we used the thru-beam fork sensors with great success. There are also other object-sensing sensors, besides photo sensors, that may meet your needs. If the material is opaque, material thickness should not matter for thru-beam, as long as it blocks the light. If the thin material is "wavy", then this could cause the retroreflective sensor to mal-function. In one application sensing translucent material, we used a photo sensor with adjustable sensitivity to detect the change in light. This worked very well. However, at some point the adjustment got changed somehow? When looking at "environment", besides dust, vibration, shock, etc., also look at the people environment.
Through beam is the better choice here. You get a tighter beam and more reliable detection over 32 inches. Retroreflective sensors tend to spread the beam too much for a thin target. Go with something that has a small beam diameter. Standard through beam sensors are often around 0.2 to 0.4 inches, which could be risky with a 3/8 inch target. A fiber optic through beam setup can get the beam down to just a few millimeters, which would be a lot safer. Also, make sure it’s actually rated for a 32 inch range. A lot of standard fiber optic sensors only work reliably over a few feet. I’d look at a long range fiber optic pair or a laser through beam sensor if you need a really tight spot at that distance.
Alignment is another thing to watch. At 32 inches, even a small amount of misalignment can cause you to miss a thin edge. A laser with a visible beam can make setup a lot easier.
So for clarity on this matter, the sensor needs to reliably shoot across 32" of distance, and have a detection area for the beam size that fits within 3/8" vertical space anywhere across that 32" of space as a part goes by?
I should have clarified this sensor will monitor the operator placing a part in the machine. The part is a long disk about 14"OD 3/8" THK. The 32" distance is the range I need to get the sensors out of the way. As suggested, I've looked into through beam. The QM series looks good. I think the adjustments can help out the installation process. They also have shutters (STQM0) available for the through beam. I wonder how well those work.
This sensor is mainly for seeing if the part is in place, not safety or overtravel. The main goal is to get it a distance from the loading area.
Yes, that clears up some things for me. There are many specs to evaluate There are multiple sensors that can meet your 3/8" space and 32" range. For example, the FKLD (receiver) and FKLH (emitter), is a class 1 red laser thru-beam sensor with a range of 0.05-50m. And estimating from the graph, the light spot diameter, at ~1m (>32"), is <5mm (<1/4"). The emitter and receiver must be aligned and maintain alignment during operation. If this is a problem, perhaps sensing the material could be done from above, or below, the conveyor. I was looking at the thru-beam sensor because, with the retro-reflective sensor, the part must maintain a perpendicular-reflecting surface. If the plates are set on the conveyor in a random position, the parts will not provide consistent reflective surfaces. Tech support can provide various possible sensors.
It seems there are a good number of through beam options that have tighter beams. I was originally having the sensor be above/below the part but we are trying to keep it away from the loading area. I was talking with the engineer designing the mounts. We came up with the idea of mounting the transmitter/reciever at an angle. This way there is more of the plate to block the sensor. I was shying away from it at first but I'm not sure if there's any reason the beams need to be at 90 degree increments.
It sounds like you are making progress. Yes, you can mount a thru-beam photo sensor where the beam is not perpendicular to the side of the moving object. As long as all the light is blocked when the part is in the beam path, and the light can hit the receiver when the part has moved past the beam path. There are sensors (diffuse, ultra-sonic, radar, etc.) that rely on the beam reflecting off of the object, and this is where the reflective angle is critical. Your sensor must have a narrow beam such that the object blocks all the light that could reach the receiver. But as you say, there are a number of sensors with narrow beam diameters less than the thickness of your part. And with narrow beam diameters, emitter/receiver alignment is critical. If you cannot mount emitter/receiver above and below because the part may be placed on the conveyor where it will not block the beam, a light grid bar set could be used.