I have a small application in which a PLC controls a conveyor system moving pallets around from automated stores and AGV's etc.
Before the pallets are permitted into an automated area they must be gauged to ensure no overhangs on the 5 sides. Photocells have been tried in the past with varying degrees of success.
Is there any other way of gauging the pallets more reliabily.

Regards

Mark Loveland

 

Mark,

Some proximity switches are available that read pallets fairly well. Omron has one that works, I don't recall the part number but I suppose I could get it for you if you are interested. You may try a relatively small one.... say 18mm placed along the edges you wish to detect the over hang but are your pallets built that precise? Most pallet builders are pretty sloppy on dimensional characteristics that I've seen. We used a 30mm to detect a pallet being present for a ABB robot pick and place unit but the pallet
variance sometimes gave us problems because the board we picked up on would not always be where the majority of them had the board fastened.......

Sid Roberts

 

Sick Optic http://www.sickoptic.com/ make a variety of infrared sensors which may be suitable for your purpose. Or what about a simple gauging tool using swing doors and limit switches.

 

According to the accuracy requirements, you can purchase analog ultrasonic sensors for less than $300 from Migatron. Wenglor and Balluff have laser
analog sensors that cost a bit more but can be as accurate as you desire.
Gene Wilkins

 

Hi Mark,

I was thinking maybe light curtains, but Trevor's idea seems like an ideal solution. Give the "defective" pallet a monitored object to "crash into" BEFORE it gets to the object you're trying to protect. At the entrances to "low clearance" areas, that's exactly how some facilities warn the drivers of tall trucks to stop.... BEFORE they "wedge" themselves into a place they don't fit ;o) Even simply a low-force rotary limit switch, or "wobble-stick" limit switch might do the trick, with no additional components.

Regards,

- Eric Nelson
[email protected]
Controls/Software
Packaging Associates Automation Inc. [email protected]
Rockaway, NJ, USA