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Robot safety considerations in small shop?

Garwood

Diamond
Joined
Oct 10, 2009
Location
Oregon
In a 1 to 3 man shop setting with a robot tending a vertical machining center what kind of safeties need to be in place? Are there alternatives to mechanical guarding such as light curtains?
 
SICK makes laser area sensors that can be used. You are required to protect from 1' to 5' in height from the floor if the robot is floor mounted (I need to verify this again, some things changed with the latest revision to the code and I'm now thinking this is one of them - We run ours from 120 mm to 2500 mm for a floor mounted application). Long light curtains are expensive (very).

Also, the area required for light curtains is going to be more than for a fence as you have to account for the reaction time of the light curtains and controls vs. robot maximum available speed and work envelope. I.E. If you ran through the light curtain as fast as you can go, the robot has to be stopped before you could reach its work envelope. That requires extra distance (considerable) between the curtain and the robot work envelope. I highly recommend that a mechanical barrier with a locking door switch be used. The minimum distance is based on the size of the opening for barriers. Also, for the door, it cannot be allowed to close with someone inside. For many of ours, we utilize LOTO and put a chain with lock-out lock around the door so it cannot be closed. In other instances, we use a spring-loaded pin with a lock hole. You can't allow anyone into the cell without a dead-man switch in hand, or the system locked out.
 
I have only dealt with one Robot... So im no Way an expert. Our Robot sat inside a cage with doors on both sides. We bought ours from Motoman, so basically is was built to our liking and im pretty sure everything was refurbed. Still... It ran well... Robot would weld inside the enclosure on a rotary work table. At the operator side there was a light bar and a divider to shield the arc from the operator. Once you loaded the fixtures you you prompt the machine that you were ready. If the machine was done welding it would rotate the table as soon as youd hit the button. Break the light curtain while the table moved and it shut down the servos. Beyond Estops the only other saftey i remember was the break away on the head. If I remember correctly, you could adjust air pressure on a saftey switch at the robots furthest most axsis. If you hit the head harder than the set pressure it kicks off the servos.
At least for welding You want to be able to get right in with the robot to see how its welding when its running. maybe not as important in your application.
Good luck and Congratulations
 
Just to echo above. Perimeter fencing with no holes. Gate switch tied into estop circuit. Nobody gets inside the gate without a lock on the servo disconnect for fixing faults or holding the teach pendant (contains the deadman switch) in a jog-speed setting for teaching and jogging. Adding an interface in the fence for a human to load and unload parts is big $ because of all the safety considerations.
 
We use a perimiter fence, in conjunction with a Fortress brand key-access door gate, with an emergency-release latch, in case someone was to be inside when the door was closed. From the inside, there's a red handle on the gate latch that opens the door and puts the cell in an E-stop state. We also have a standing policy, complete with placard on the gate, that anyone caught inside the cell without an interlock key for the gate gets an immideate suspension.

www.fortressinterlocks.com | Products | amGard pro safety switches | Product range
 
Sounds like possibly an application for a robot like Baxter. I saw one at at trade show and my first thought was that a 3D printer was the perfect accessory for it. You' print the gripper you need to handle a part. If it wears out just print another.
 








 
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