Fanuc Robot Safety Concern

Good afternoon all,

I have an application where a robot picks up a part off a transfer stand inside a robot cage and loads a milling machine. We are looking at cutting a hole in the robot fence and adding 6 fixtures inside the cage, very close to the opening for operators to load, and for the robot to pick up. The opening in the fence will have light curtains on either side, and will "pause / hold" the Fanuc R30iA-controlled robot. When the light curtain clears, I can resume the robot program after a 3-5 second delay automatically w/o having anyone press any reset button.

Would this be considered "safe" in the manufacturing / robotic world? Am I allowed to do this, or are there other safety precautions I need to consider?

Thanks!!!

I'd say no.

There are regulations on the size of entries and reaching distances from these to the dangerous (moving) parts.

A light curtain can't be wired to a normal digital input that would execute a pause command. It would need to be wired to a dedicated safety relay/controller whose output would e-stop the robot, applying the brakes.

There are also issues with the auto-restart. Any machines I've seen with light curtains have to be manually reset via a physical touch before automatic operations resume.

@the_msp Ah okay, that makes more sense, probably safer that way.

What other way can I go about doing this? Unfortunately, I don't have space to pass a conveyor through the fence, nor can I add a slide to move in and out. I will probably have to come up with some mechanical fixture that will move the part into position safely without operators hand getting inside the cage at all. It seems very tricky to accomplish w/o putting my operators at risk for getting there hand hit by the robot.

Maybe I can create an opening for the part to drop in, then the bin closes, and the robot can grab the part.

I will think of some more ideas and post later; if anyone has any thoughts they can share on the fixture idea, that would be great.

Thanks,

Co-bot? Depending on your cycle times and of course the expense of a new 'bot...

nor can I add a slide to move in and out

Click to expand...

You can't have a slide that moves in and out but what about a slide (within the cell) that takes the parts from an intermediate danger zone (loading zone) to the robot pick up?

Maybe I can create an opening for the part to drop in, then the bin closes, and the robot can grab the part.

Click to expand...

A shuttle? Place the part, slide the (horizontal) hatch close, shuttle transfers part in - have two alternating between loaded and empty.

If you go for a horizontal door between the operator and harm, I've seen a few where a vertical pneumatic cylinder is used - with only gravity lowering the part (extending the piston) and low air pressure retracting the cylinder to open the door. With locks of course for E-stop conditions but with only gravity lowering the door the risk is reduced.

Have a look at the shuttle transfer at around 0:55 here: https://www.youtube.com/watch?v=Ga1rVYvxvu0

Obviously your shuttles will be much larger

Anytime you modify a safety system it would have to be re-certified to ensure it still meets its original safety standard. I believe even when replacing failed parts in a safety system, they need to be exact or equivalent replacements.

Alive15,


I've seen lots of cells for automotive parts where the operater breaks a light curtain to walk in, load up a fixture, then walk back out. Because autostart is a safety no-go, there is a reset button the operator presses once they are back to the safe zone. They do this over and over and over and over. This seems somewhat analogous to your system. One big gotcha though is that there are timing calculations that specify how far away from the danger zone the light curtains must be based on fast the system typical hand movement speeds. This is typically measured in feet, so that might be a problem for your setup.



They also use safety PLCs (Siemens), who can communicate safety to the robots over ethernet comms (profisafe over profinet). Fanuc robots are commonly used, but I don't know which specific robot controllers support the ethernet safety comms.

Could you use an area scanner? In my experience auto restart can be acceptable with an area scanner if a proper risk assessment is performed.

I would personally never use any sort of auto restart with light curtains. But of course there are exceptions to everything with proper engineering.

What about placing part in either a sliding drawer or on a rotating turntable? Part is loaded by operator - outside of cell - and then rotated /slid into position where robot can reach it. This would require I/O for robot for part present/in position. A pushbutton /light curtain would give an " operator clear" signal.
I won't repeat all the previously mentioned safety concerns. Any introduction of an operator's body/body part into the path of a robot will require all kinds of risk assessment and safety circuitry.
A "cobot" might be an intermediate step. An operator could safely load/present the part to the cobot which then passes it to the main robot. This would require some expense of time and money BUT you could eliminate the safety risk.

To the OP, does the robot have the DCS (Dual Check Safety) option? The list of methods to address this issue gets longer if it does.

The process should start with a risk assesment, then think about designing out the need for a safety circuit.

Using a safety circuit should be your last port of call.

You have light curtains on the robot side and light curtains on the operator side? GM standard was to put a light curtain for operator and light curtain for robot, if both were broken then the robot would emergency stop. I believe the inside light curtain for robot was auto resetting.

If an Operator goes in a light curtain though then it should never be auto resetting, if somebody asked me to do this, I'd want a document, and the safety sign off from an engineer.

@the_msp I don't believe I can use a shuttle method; I'm thinking of just having an operator place the part directly into the fixture where the robot can go pick it up once it sees part present.

@James42005 I'm not modifying a safety system, I'm adding another layer onto an existing on. I am thinking of tying the light curtains into the robot safety controller. I have R30iA controller, there is a safety board on here where you can plug in lines for e-stop, safety doors, etc. so I will utilize these points for my light curtain.

@mk42 You are right, I don't believe any of our other machines work like that either. But some machines have light curtains that are not used, but only when the robot is running. Once an operator enters the cell, all light curtains are immediately turned on.

@_Dock_ Yeah, this idea may work, I have a few keyence area scanners in other cells. The issue is, the area where the operator is loading the part is pretty much "open", anyone can walk into this area. But I'm sure if I program the area scanner correctly, then I can stop the robot anytime someone walks onto the platform to go load the part.

@ValeoBill This idea is great too, but we will only be loading from these fixtures for a small amount of time. Otherwise, for a long term solution, I would probably go with this option, seems really good.

@jstolaruk I believe so, its R30iA, theres a safety board with multiple contacts that can be used to tie e-stops, safety door switches, etc.

@janner_10 At the moment, I need to figure out the process, once I do that, then I can fill out our risk assessment document.

@rblunt No I haven't installed any light curtains at the moment. Yeah, I won't make it auto-reset. So even for much safer machines, you cannot have the light curtains auto-resetting? I would think on machines with little to no risk of injury, you could get away with it?

The hard-wired safety interlocks you describe are the standards that come with all robots. You will find DCS in the teach pendants menus if it has that option.

alive15 said:

What other way can I go about doing this? Unfortunately, I don't have space to pass a conveyor through the fence, nor can I add a slide to move in and out. I will probably have to come up with some mechanical fixture that will move the part into position safely without operators hand getting inside the cage at all. It seems very tricky to accomplish w/o putting my operators at risk for getting there hand hit by the robot.

Maybe I can create an opening for the part to drop in, then the bin closes, and the robot can grab the part.
Thanks,

Click to expand...

Can you move the fence further inside of the cell to make room for a conveyor to then work? Space is limited from outside the cell from what I understand, can we move the boundary inwards? Does the robot need to move within the full space you currently have? I know that you need to have a minimum distance from any part of the robot to a safety fence for the various moves.

I like your bin idea and have seen it work. Similar to a CD-ROM drive, an operator ejects the part next on some sort of horizontal slide through the poka-yoke, and pushes it back once the part is properly seated.

I think you should be able to do this loading from outside of the cell.