limit switch

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ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
I need to detect the presence or lack of, a bag in a process that fills paper bags with 50 lbs of product. Both sides of the bag must be sensed for proper placement before the bag is clamped, opened and filled. OEM mechanical switches are now $300, up from $80 and only last 2-3 months. Sensing distance is about ?" with a max of 3/4" allowed. I experimented with photo electric without success. Any suggestions?
 
I am assuming this a fill and stitch type machine like a Doughboy, right?
Would a proximity switch work on the application?
Was the photo eye a through beam or retro reflective or something else?

I am trying to regenerate the part of my mind that used to design and work on packaging equipment a long time ago in a far away place.

I'll let you know if I come up with something else.
 
ptonsparky said:
I need to detect the presence or lack of, a bag in a process that fills paper bags with 50 lbs of product. Both sides of the bag must be sensed for proper placement before the bag is clamped, opened and filled. OEM mechanical switches are now $300, up from $80 and only last 2-3 months. Sensing distance is about ?" with a max of 3/4" allowed. I experimented with photo electric without success. Any suggestions?
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Capacitive proximity switch. Just don't get shocked by the price.
Even that will be limited, because if the bag is partially open and "makes" both capacitance sensor, you can still gat a valid signal and spill the goods. OR (optical recognition) is the sure way to, but that will be even more expensive than the 2 cap's.
 
Prox will work with some field modification of the existing limit switch body. I just need the plunger to activate the prox. Won't need the switch itself.

Capacitive are a thought although it would require the largest diameter and I hate to modifiy a machine to find out they work only most of the time.

Can't use the through beam and the reflective I tried had to great a range. Interesting that it would sense the print as I moved the target left/right in front of the beam. Stuff you learn by accident.

Price is not to much of problem as long as it works.
 
So I take it your trying to beat the $300 price tag from the OEM. Without a visual, its tough to say. $300 for an industrial switch doesn't sound bad to me considering the time and effort trying to re-engineer an already running process.
 
Doughboy is a manufacturer of a form, fill and sew bagging machine. they are in Wisconson I think.

The photo eyes reading print is interesting. I worked on a prototype machine that would take 2 sheets of polyethylene, line them up, heat seal and fill. The way the sheets lined up was a black mark on both sheets. The prox switch would read the black mark to ensure the correct location.

Good luck
 
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