Light Curtain Tripped

SMOKE · Sep 30, 2009

I have a pick and place that moves through a light curtain.
The operator places his parts on the table and then is required to put his hands on double palm buttons.
At that point the light curtain will mute and the table will travel into the robot cell.
If he removes his hand/s from 1 or both buttons the light curtain will trip.
What in your opinions would be the proper way to recover from this situation?

leitmotif · Sep 30, 2009

Pull part back out and try again?

Best answer I can give with limited info.
Would helpto at least know what machine does.
Dan Bentler

Rich1955 · Sep 30, 2009

As the first operator is holding down the buttons can a second operator touch the machine??????????

leitmotif · Sep 30, 2009

Well from the limited info
yes a second person could put a hand thru the curtain and get munched while operator has the two hand controls circuit satisfied and overriding curtain.

Dan Bentler

rigicon · Sep 30, 2009

does the table move in and then the robot start to pick and place or is the robot synchronised with the table movement?
Can you have 2 sets of light guards or can you use "blanking" instead of muting on the light guards so that only the correctly placed parts and nothing else will satisfy the Cat 4(human safety) circuit.
Maybe a safety camera is another add on option.
2 hand start is ok if only one operator but the other month someone was killed in poland in an injection moulding machine they had wired 2 hand starts on oposite sides of the machine. Be careful out there...

SMOKE · Sep 30, 2009

As the first operator is holding down the buttons can a second operator touch the machine??????????

Yes one could touch it.

Well from the limited info
yes a second person could put a hand thru the curtain and get munched while operator has the two hand controls circuit satisfied and overriding curtain.

Yes. I have made that point myself. Management says the operator is close enough to be aware of anyone (I know)

Actually there is a loading table in front of the LC and for someone to get through it the would have to climb up on the table.

The is a chance of the movable table pinching someone when it comes back. We are going to put on a safety bumper.

leitmotif · Sep 30, 2009

leitmotif said:
well from the limited info
yes a second person could put a hand thru the curtain and get munched while operator has the two hand controls circuit satisfied and overriding curtain.

Dan bentler

what does this machine do

504bloke · Sep 30, 2009

SMOKE said:
Yes one could touch it.

Yes. I have made that point myself. Management says the operator is close enough to be aware of anyone (I know)

Actually there is a loading table in front of the LC and for someone to get through it the would have to climb up on the table.

The is a chance of the movable table pinching someone when it comes back. We are going to put on a safety bumper.

From your description and what you have said here in the UK this would be considered unsafe. You (Thats Meaning "Managment") cannot rely on an operator an operator being aware of it (ie seeing someone).

SMOKE · Sep 30, 2009

what does this machine do

Crimps, or punches, or copes, or does a plasma cut on 25lbs to 300 lbs of steel.

From your description and what you have said here in the UK this would be considered unsafe. You (Thats Meaning "Managment") cannot rely on an operator an operator being aware of it (ie seeing someone).

I am with you ... but, The only direct access to the hazard is through the guy on the buttons unless you jump up on the table.

leitmotif · Oct 1, 2009

SMOKE said:
Crimps, or punches, or copes, or does a plasma cut on 25lbs to 300 lbs of steel.

I am with you ... but, The only direct access to the hazard is through the guy on the buttons unless you jump up on the table.

Combination press (brake punch) and plasma cutter huh - sounds like a neat machine.

Could it be possible sequence is
1. Operator presses two hand controls
2. Curtain is bypassed to allow raw stock thru
3. After stock is thru curtain resets
4. With curtain reset the punch etc or plasma is allowed to operate
5. Then if curtain is broke or two hand released machine stops?

Thinking on many machine setups I have seen where there is an infeed roll setup sawmills steel mills etc it is theoretically possible for someone to crawl up on the rolls and get into point of operation but the roll case itself is considered adequate. Would have to see machine in operation to adequately assess hazard. Photo would be neat if just for my curiosity.
Dan Bentler

Rich1955 · Oct 1, 2009

I would move the light curtain so that the operator passes the stock thru the curtain and locks out the robot.

shooter · Oct 2, 2009

Make a fence the operator pulls down, this way nobody can be in the danger zone, and the operator does not have to push buttons on a specific time, but can walk away, or do something else.

geoplc · Oct 2, 2009

We have several machines which I believe may be simlar to you operation. Ours work as such:
1. op loads fixture, holds buttons, light curtain is NOT muted.
2. When the table, PNP, etc reaches a midpoint or the endpoint of its travel (a point at which you can no longer reach the danger area), the op can release buttons. The position switches should be forced guided contacts and used with redundant switches. For more safety they can be tied to a safety relay which monitors both switch conditions.
3. At this point the the light curtain is muted.
4. Once the safety switches are no longer made the light curtain is active (ie. table,PNP traveling from robot to operator.

The key is the distance from the point of danger to the operator. The Banner Engineering web page has plenty of useful info.

TheStarr · Oct 2, 2009

I have never been a fan of the operator having to keep their hands on the buttons/switches. It never seems to be user friendly or safe.

I would have two curtains: Operator-to-table (A), Table-to-machine (B).

The palm switches would start the transfer sequence.

Curtain B would mute. Curtain A would activate. Table would transfer.

This way they just hit the switches and it locks down the machine while in motion.

You could have 20 people there and no one is getting past curtain A.

Recently, at a business near by, an Operator cycled a press with palm switches and no light curtain, it crushed a techs hand which had to be amputated half way up to the elbow.

Not something I ever want to happen on a machine I designed!

Light Curtain Tripped

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