Datalogic SG4 BASE safety light curtains are an excellent choice! Anyone who works with and on machines, automated systems or robots is often not aware of the dangers involved. The potential impact on the health of all users can be devastating. As is so often the case, prevention is the best protection! The right safety technology is needed here. Here you can find out why safety light curtains are the ideal solution, which important selection criteria and installation instructions you should take into account and why you should choose the Datalogic SG4 BASE series.
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In many manufacturing processesthere are machine hazards from which operators must be protected. A particularly high risk is posed by manual work and testing stations such as presses, cutting, bending and punching machines. Without appropriate protective measuresit can happen all too quickly that users come into contact with moving machine parts. The consequences: cuts, bruises, fractures, sprains or even worse. To prevent this from happening in the first place, reliable detection of fingers, hands and other limbs entering hazardous areas is essential. In this way, the shutdown of dangerous machine movements can be initiated automatically. Safety light curtains are an ideal solution for this!
Fig. 1: The risk of injury in manufacturing processes is very high.
Fig. 2: Safety light curtain - structure
Safety light curtains are one of a range of optoelectronic safety sensors. They consist of a transmitter and a receiver unit and are similar in their operating principle to throughbeam light barriers from the field of photoelectric sensors, which are used in particular for position detection.
A safety light curtain transmitter transmits a multitude of light beams at defined distances to the receiver module. This creates a virtual and very close-meshed barrier to demarcate or secure hazardous areas. As soon as fingers, hands or other limbs penetrate this barrier and interrupt the light beams, the hazardous movements can be automatically switched off.
Another important difference to standard light barriers is that safety light curtains, as safety sensors, have corresponding safety technology and/or features to prevent unexpected failures. For example, they have redundant OSSD outputs that pass on switching states to corresponding safety controllers or safety relay modules. OSSD is the abbreviation for the full name "Output Signal Switching Device". These outputs send out periodic test pulses to detect possible short circuits. In addition, safety light curtains have self-test functions that also counteract system failure.
Did you know that? It is not uncommon for safety light curtains and safety light grids to be misleadingly used as synonymous terms. This is a fallacy, however. Although outwardly they look very similar to each other, there are essential differences with regard to their characteristics and suitable areas of application.
One of the most significant differences is the resolution. While light curtains create a multitude of light beams at a small distance, light grids usually create only two to four light beams spaced at significantly larger distances.
This is due to the different purposes for which they are designed. While safety light curtains are used for finger and hand protection detection at hazardous locations, light grids are used for more extensive area protection, whereby body detection by means of fewer light beams is sufficient.
Fig. 3 Safeguarding hazardous points with a safety light curtain
Fig. 4 Area protection with safety light grid
Area safeguard are often relevant in logistics applications. In this context, muting is also an important requested feature, which makes it possible to bridge light grids for a short time in order, for example, to move pallets out of the hazardous area without bringing system processes to a standstill. Immediately after the pallet transport, the light grid is reactivated to detect persons entering the danger zone again.
Hazardous location safeguarding with light curtains does not require a muting function in most cases, as transporting materials out of the danger zone is rarely necessary here.
The selection of a suitable safety light curtain is very simple. You only need to consider these three to four selection criteria:
Describes the distance between the light beams. This defines which part of the body can be reliably detected.
2) Protection field height
Stands for the height of the area to be protected by the safety light curtain. This depends on the size of the accessible danger area.
3) Protection type
Provides information about the internal structure of the light curtain to safeguard against unexpected failures. A distinction is made in particular between type 2 and type 4 safety light curtains (rarely type 3).
The higher the type, the higher the Performance Level (PL) that can be met according to the DIN EN ISO 12849 standard.
Type 4 light curtains meet the requirements up to PLe.Nowadays, type 4 light curtains have established themselves as the standard and light curtains with lower types are increasingly being displaced from the market.
4) Range (optional)
Describes the maximum distance between transmitter and receiver. However, the maximum range of most safety light curtains is usually so large that it only plays a role in very few applications. Therefore, it is considered an optional criterion.
There are other design features in which safety light curtains can differ. These include, for example, an extremely narrow type or the elimination of a dead zone. However, these features are relevant for very few industrial applications. In most cases, the use of light curtains with standard functions is perfectly adequate.
Before safety light curtains can be used, it is important that they are first installed correctly and that their functionality is tested.
A very important point is to maintain the correct minimum distance between the light curtain and the hazardous location. The regulations for this are clearly defined in the standard DIN EN ISO 13855.
Light curtain safety distance - calculation formula:
S = K * (t1 + t2) + C
S = min. safety distance
K = approach speed
t1 = response time of the light curtain
t2 = response time of the machine until standstill
C = maximum distance of undetected movement behind light curtain
The following formulas are derived from this:
For light curtains with 14 mm resolution: S = 2,000 mm/s * (t1+t2)
For light curtains with 30 mm resolution: S = 2,000 mm/s * (t1+t2) + 128 mm
Fig. 5 - Light curtain safety distance: according to DIN EN ISO 13855, a minimum distance must be maintained.
When correctly installing a safety light curtain, it is imperative that limbs entering hazardous areas are detected without exception. The prerequisite for this is the correct selection of the appropriate protection field height so that it is not even possible to reach past the light curtain into the danger zone.
Furthermore, it must be ensured that no one can be present behind the light curtain unnoticed. If the safety distance in an application needs to be very large, the additional installation of a horizontal light curtain is essential.
Fig. 6: Installation at a low safety distance / Fig. 6.1: It must not be possible to reach past a safety light curtain.
Fig. 7: At a very high safety distance, the horizontal installation of a safety light curtain is required. / Fig. 7.1: An undetected stay behind the light curtain must not be possible.
Since the light beams transmitted by the light curtain are not visible, aligning the transmitter and receiver over longer distances can prove very difficult. Laser pointers mounted on the transmitter can help here.
Safety light curtains are designed to cause machines to be switched off as soon as the light beam transmitted by the transmitter cannot reach the receiver. However, this is a hindrance with strongly vibrating machines, as the vibration may cause the transmitter and receiver to be briefly offset from each other. Vibration-heavy applications therefore require the use of special vibration dampers to prevent false tripping.
To trust is good, to check is better. This also applies to safety light curtains! To verify correct functionality and reduce the risk of liability in the event of a malfunction, a daily function test of each safety light curtain is recommended.
For this purpose, a test rod is passed through the protection field to check the correct interruption of the light curtain beams. The test rod must have the diameter of the resolution of the relevant light curtain.
The Datalogic SG4 BASE family of light curtains are ideal for most industrial applications thanks to their basic features. They impress with the following features:
Safety doesn't need to be expensive! This also applies to light curtains. Expensive manufacturer models are often not necessary here, because most industrial applications can be fulfilled with solutions for basic requirements. The high-quality Datalogic SG BASE safety light curtains are more than able to meet these requirements. At Automation24 we go one step further: as an official partner of Datalogic and Datasensing, we are pleased to be able to offer you this range in our online shop at unique conditions even in these exceptional times.
Automation24 offers you type 4 safety light curtains from the SG BASE family for finger and hand protection up to a protection field height of 1,050 mm.
Corresponding safety sensor accessories in the form of test rods, laser pointers as alignment aids and vibration dampers are also available in the range.
Convincing features for your protection, everything from a single source at excellent delivery conditions and, last but not least, unbeatable prices - as you can see, there are plenty of reasons in favour of the Datalogic light curtains. Convince yourself today and save yourself and other users from serious injuries.
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