shrink wrapper safety

[grey]

Hi,

We are adding about 9 eyes to our shrink wrapper to prevent people walking into the unit. It is an overhead Orion wrapper with a skid roller system about 6 ft wide and 30 feet long. Skids enter one end via fork lift truck , go to middle , get wrapped then roll to other end to fork lift. Both ends are open permitting people to walk or jump in. Sides are guarded with locked gates.

Existing plc is AB SLC 500 .

Any suggestions on how to place and program these eyes so that it will let skids get wrapped , but catch people trying to walk in ?

thx

grey

 

[Terry Woods]

Wow, that's a tough one...

At least, it's tough in that I can't think of any Photo-Eye that can differentiate between a pallet and an idiot.

The only thing I can think of is having the Fork-Truck driver control the infeed. That is, when a pallet is delivered for wrapping, the driver presses and holds a push button to disarm the Infeed Eye and roll the pallet in. The driver has to hold the push button until the pallet is beyond the eye. Same thing at the outfeed end.

BTW, you might consider using a light-fence... a guy could crawl under a single beam.

 

[seppoalanen]

Safety light curtains:
Banner, Sick etc. and muting photoeyes with them separates products and 'idiots'.

 

[Eric Nelson]

Yes, this is a safety issue... Use safety light curtains at each end. This should have been provided WITH the wrapper, but that's an issue you can discuss with the OEM...

You can MONITOR them with the PLC, but hardwire the curtains into the control circuit (i.e. the E-Stop circuit). Arrange it so muting the curtains must be done INTENTIONALLY.
IOW, don't just stick a toggle switch labeled "Muting ON-OFF" at each end...
No matter how much training you provide, the operators WILL leave it in the "OFF" position... utoh

As Terry said, require the machine operator to HOLD the button to mute the curtain. Also, put this mute button in a location where the operator has a clear view on the protected area. I don't see this as the forklift driver's responsibility. They shouldn't have hold a button AND drive at the same time. Plus, they have a limited view of the protected area with a skid of product directly in front of them anyway!...

If you don't have someone available that can hold the button, you may want to investigate something similar to the vehicle sensors used to sense cars at intersections. These will sense the presence of the forklift, but not people. These could be used to "latch" the muting circuit after the forklift operator initiates it. Once the forklift leaves the area, the curtain will automatically re-enable.

beerchug

-Eric

 

[gene]

gene

Another method (although I don't know about space or cost issues) would be to add a longer infeed track. The tow motor operator sets a load on track triggering cycle start eye. The load then travels along a series of eyes to the light curtain at entrance. Eyes and curtain must be tripped in sequence or wrapper will not start. There must be an operator station where one could manually operate the unit but it shoud be far enough away that operator could not be inside the wrapper and start it. A lock out/tagout should be on this panel also.

 

[rogerhollingsworth]

Detect the physical dimensions of the pallet, anything entering the area with less or greater dimensions will disable the system.
Although I have known a few ladies that could pass for a pallet but that’s another story.

Good Luck
Roger

 

[Pierre]

When feeded by a lift truck, have a 15 second delay to start the conveyor. Then follow the pallet in front of every photoeye in sequence, in the good order AND in time-passing-in-front. Very seldom, a human will match those criterias. Legs just don't block photoeye in the same manner a pallet would.

When the infeed is from the line... have an interlock from the lin tell your wrapper that it's feeding something. Match the same sequence and time to identify that it is indded looking just like a pallet.

Have your wrapper do its first rotation on very slow speed. This will clear the way and if it's going to hit a human being... it will at least do it softly

Install a "Tennis-racket" detection on the leaadin edge of the rotary arm.

Last but not least, if needed, fire the first idiot who walks in it. This should scare the others for a whyle.

Make certain that to start this wrapper you don't just get a signal from a photoeye, get a serie of signals from a serie of photoeye in exact sequence.

Replace all those photoeye with diffuse types and have your employees only wear black cloatings. (OK, this was a joke)

 

[rsdoran]

I am going to go out on a limb here and say I think he didnt explain the situation properly.

I deal with Lantech and Orion stretch (not shrink) wrappers daily. Stretch wrappers are those that wrap poly around pallets of materials, shrink wrappers normally involve heat.

From my dealings in the past with pallet wrappers it invovles a conveyor system for the pallet to move on, therefore it is unlikely for people to enter thru the conveyor path under normal circumstances, not to say they wont. Are these eyes to prevent people from entering from the sides of the wrapper? What exactly is the safety issue involved with wrapping pallets...unless this is a shrink wrap operation involving going thru a shrink tunnel?

 

[grey]

clarification



I should have said stretch wrapper , not shrink wrapper.

It is a large overhead Orion wrapper that revolves from upper support. The main danger is that the side supports are close to the rotating arm and these models I believe have been known to terminate intruders.

The sides of the 6 X 30 ft approx roller area is enclosed with guards. The ends are the concern for any people entering.

Thanks for all the replys and hope there is more.

Will let you know how we are progressing with placement and implementation of eyes.

How would a tennis-racket detection system work ? Will go surfing for that term now...

 

[Hootnholler]

Hey Grey,

Just to add my $.02... I have worked on a few stretch wrappers in my time... In my area, believe it or not, yellow and black tape on the floor, or a yellow border painted to any entry on a wrapper is sufficient. I've never been a big fan of that rule...

Someone had posted putting a longer conveyor setup on the wrapper. That is a great idea. You could setup a few photoeyes/throughbeams on the input conveyor, write a simple sequence with timers to try and keep the 'windows' as tight as possible as the conveyor moves along the pallet. What would make this idea a good one, is try to put a timer on the 'sensing' of the eye with the pallet. It will take a bit of time for the pallet to pass by the eye, then time the 'dead space' to the next eye, then time the second eye, etc... It would be hard for an 'idiot' to mimic the progress of a pallet, but I'll be darned if they aren't getting smarter....

Another setup is to have a 'light curtain' used to detect when the pallet is entered, but again, timed. Say, 2 seconds of the beam being broke, then have the operator hit a pushbutton away from the moving parts. Then, put a safety in there, where if the curtain beam is broke during the 'revolutions' of the wrapper, to stop immediately. Just set the curtains to make a 'blanket' outside the pallet area.

For a little chuckle, I did see one person think it would 'be cool' to be wrapped by a wrapper with a pallet. They stood next to the pallet while the turntable turned. The only problem was when the wrapper was about done and covered their face... (how do I breath??) yes, Darwin's theory is alive and kicking... but, the person he was trying to impress was a quick thinker and poked a hole through the plastic by their mouth, but given that plastic stretches, when their finger entered their mouth, they forgot about the 'gag reflex' every person has... I'll let your imagination go from there...

Hoot

P.S. the person that was wrapped was fired immediately...but they did let him get cleaned up.

 

[Terry Woods]

There is this process... it doesn't matter what the process is.

No one is allowed to be in the process area.

On two of the four sides of the process area there are physical restraints.

On the other two sides, there are no restraints. Those sides are OPEN!

Anybody is free to enter (at their own peril, of course).

Idiots are the bane of control programmers. No matter what you try to develop to out-smart them, they always seem to manage to come up with an incredibly creative way around it!

Since you can't stop wandering-idiots from wandering like idiots, you have to stop the process. In some cases that might not be such a bad response. In others, maybe the process can't be stopped once it's going.

As a general solution for either case, if the palleted material can take it, how about installing 1500KV Static Fences at either end? A Force-Field, as it were.

If they do manage to get through, and I'm sure they'll try, I don't think they'll be moving much. Have an automatic sweeper go through once in a while to sweep-out the remains.

Of course, the idiot might try to ride the pallet like "Mr. Toad's Wild Ride!"

In that case, whether he's conscious or not, he's gonna get wrapped... so, maybe you should just ship it. Besides, maybe he knew where that particular pallet was going to be shipped to and wanted to go there himself!

Sometimes you have to smile and give the idiots a few points for creativity!

Another option might be to enclose the entire area in a tunnel - a very dark and very spooky tunnel! Play sound effects from a haunted house! Leave a few body-parts laying around each end of the process.

??? Actung! Minen! ????

A REAL potential solution (spendy too!) is a vision-system. Anything that does NOT "look" like a loaded pallet causes a shut-down. In that case, odd-ball pallets that might not fit the programmed description would have to be loaded by means of an "Exception Handler". The operator, making sure he doesn't have any "riders", presses and holds a button to tell the processor to "allow this odd-ball in".

But then... what if there are two idiots working (wandering?) together?

 

[seppoalanen]

Hey Hootnholler,
I have done those wrapping maschines among others Appleton WI but also to European countyes and I agree with you. In Europe that Light Curtain is allmost necessary for the low.

We can put diffrent kind of safety systems and teach people trust them, not their own sense (understanding) and some day they will trust too much. We tell people "use safety classes" but don't do anything for the dust. We tell people "use hearing protector" but don't do anything the noice...etc...

Light Curtain with muting cells needs space 3 to 4 feet in product direction and some times there are not that space.
Anyhow that Rotary arm can kill. If I understand there are 50 kg filmroll at the end of 6 to 7 feet arm and it rotates ~1/second and stopping takes at last 1/2 round with VFD ramp and more without it becourse motor own brake is slowlyer.

 

[seppoalanen]

I understand that safety is 1'st. But some 'idiot' can go inside the machine with pallet and light curtain with muting cell can approve it.

 

[Hootnholler]

Hey Seppoalanen,

Hope your trip to Appleton wasn't too traumatic

I never realized that this was such a large wrapper. The ones I'm used to use about a 2 to 3 foot (1 meter, approximately) roller. I have worked on some larger applications, but they are almost always automated, with a lead in conveyor for such an incident... hence, the suggestion to use the 'logical sequence' to mimic a pallet, which is what they seem to use...

Grey, have you any other input on what your limitations are on this setup? I have seen quite a few great people on here with some great ideas on how to fix almost any solution... if you don't believe me, check out the contractor post I had

Hoot

 

[glaverty]

Since this is a safety application I think you would want to go with the light curtains as suggested by others. I doubt that whoever you are buying the sensors from would recommend photoeyes for a safety application.