Question

Homework 5 (Work Cell Safety)

1) Explain the operation of the Safety (Light) Curtain.

2) Explain the role of 'three safety zones' in robot work cells?

3) In your opinion, what is the difference between safety and security?

Note: I need those questions to be typed in a Word Document

Answer 1

Safety Light Curtains:

Before going into the operation of the safety light curtains let me first explain what is a safety light curtain. Safety light curtain is an opto electronic device used to prevent personnel from heavy, harmful moving machineries. Normally personnels working near heavy machineries like Winders, Pressers, Palletisers etc. are prone to injuries by accidental contact with those machines. In order to prevent these accidents, a barrier is required to isolate the personnel and the machineries. In most cases a physical barrier such as sliding gates, pullback restraints are not applicable due to several constraints.

Safety light curtains will be a perfect alternate solution to all those physical barriers. Since it operates with light as medium, it can be applicable in all places and equipments and does not cause any disturbance to the normal working of the equipments.

a) Operation of Safety Light Curtain:

The basic principle of operation of Safety light curtain is Photoelectric coupler. ie It consists of a Photo electric emitter and a photo electric detector. the photo electric emitter is also known as the transmitter and the photo electric detecter is also known as the receiver.

Safety light Curtains consists of a series of array of photoelectric emitter and detectors arranged opposite to each other. Each pair of photo electric transmitter and receiver is synchronised to each other so that transmitter projects a beam of light into the receiver continuously.

When an opaque object interrupts either one or more beam of light falling on the receiver, the control logic circuit of the safety light curtain then sends a stop signal to the moving machinery. thereby halting the working of the machine and also preventing the accidental injury to the object which gets into the machinery accidentally.

In order to make this process more safety, the receiver and the transmitter are modulated and pulsed at a specific frequency and are so designed to detect only the specific pulse and frequency designated for them. Thereby enhancing the safety of the system.

These array of opto couplers (ie transmitter and receiver) are placed around the moving machinery which has the potential to cause damage to the personnel working near them.

b) Three Zones of Safety:

AS per the US National Bureau of standards, Three safety zones are being defined around a typical robot work cell. Let me first state all those three safety zones,

1. The Perimeter:

The work envelope which is found outside of the robot but within the perimeter boundary limits of the robot is known as the first safety zone.

The Role of this zone is to keep the personnel or the worker out of the work area and to keep all tjose hurling objects inside the Work area. also the perimeter barrier should be provided with interlocked gates or with a system which wil shut down the operation of the whole system in case of any intrusion.

2.Position Work Envelope:

The zone within the perimeter is known as the second safety zone.

The role of this zone is to transit parts , tools and other objects between the worker and the robot, which are needed for the operation of the system.

3. Robot Work Envelope:

The zone fo contact which is available immediately adjacent to the robot's arm is the third safety zone.

The role of this third zone is to make the robot accessible during training or maintenance of robots.

C) Safety and Security:

According to my opinion, Safety means the condition of being protected from damage or danger

whereas Security refers to taking any preventive measures to avoid any harm or damage to lives or belongings.

In other Words, Safety results as an outcome of security. (ie once we are provided with security then we are safety)

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