Âť D e s i g n N o tes
Edited by: Mike Santora • Associate Editor
as elta Robot e Omron D th g in w s ie d o V ping meth erent stop it uses diff d n stop a mergency between e curtain). stop (light protective
How using a programmable safety rated controller can increase the life of your machine How do you stop your car as you approach a red light? Is it a gentle release of the gas pedal so it can coast, slamming on the brakes or somewhere in between? With both methods, each way of stopping has a practical purpose. Most people like to glide to a stop. It’s easier on the passengers and it saves on gas and brake pads. However, sometimes you have to stop the car as soon as possible. The same is true with machines. For engineers there are other practical considerations when designing an emergency stop system than the obvious primary function. A normal stop allows the machine to glide to a smooth stop at the end of a sequence. In most cases, this will be done by a signal sent 42
DESIGN WORLD
Design Notes 7-15_Vs3a.LL.MD.indd 42
July 2015
to the machine to let it know it should finish its task. The signal can be sent by the operator, usually with a black pushbutton. For times when an operator needs to deliberately stop the machine as quick and safe as possible, an emergency stop is used. This type of stop is performed using a red mushroom shaped device with a yellow background. Machines require at least one category 0 emergency stop, which is the immediate removal of power. On occasion though, the removal of power creates more hazards, so category 1 emergency stops may be suitable for additional emergency stop buttons. This is a controlled stop before the power is removed.
www.designworldonline.com
7/1/15 9:44 AM