GUARDSCAN BPU 4 BLANKING PROGRAMMING UNIT TECHNICAL MANUAL 343233-01 English WARNING Guardscan photo-electric safety systems are intended to protect operators working at or near dangerous machinery. They can only perform this function if they are correctly fitted to a suitable machine. It is essential that the full contents of this manual and all the authoritative documents referred to herein are fully understood before any attempt at installation is made. If in doubt contact your authorised Guardscan distributor. IMPORTANT This manual must accompany the product throughout its working life. Those persons responsible for the product must ensure that all persons involved in the installation, commissioning, operation, maintenance and servicing of the product have access to all the information supplied by the manufacturers of the machine and its safety system.
Guardscan photo-electric safety systems are intended to protectoperators working at or near dangerous machinery. They canonly perform this function if they are correctly fitted to a suitablemachine. It is essential that the full contents of this manual andall the authoritative documents referred to herein are fullyunderstood before any attempt at installation is made. If in doubtcontact your authorised Guardscan distributor.
IMPORTANT
This manual must accompany the product throughout its workinglife. Those persons responsible for the product must ensure thatall persons involved in the installation, commissioning, operation,maintenance and servicing of the product have access to all theinformation supplied by the manufacturers of the machine and itssafety system.
2
Guardscan Light Curtain Products are maufactured by:
1.1 GENERAL1.2 TYPES OF BLANKING1.3 IMPLICATIONS OF BLANKING
2. BPU 4 PROGRAMMING UNIT
2.1 UNIT DESCRIPTION2.2 PROGRAMMING INSTRUCTIONS2.3 IMPORTANT CONSIDERATIONS
3. MANAGEMENT ISSUES
3.1 BLANKING TEST PROCEDURE3.2 DETECTION CAPABILITY - TEST AND INDICATION3.3 CHANGE OF OPERATING PARAMETERS
4
Figure 1
1. INTRODUCTION
1.1 GENERAL
WARNING
Incorrect use of blanking and/or failureto correctly address the implications ofblanking on the management of a machine,is potentially very dangerous. It is thereforevital that the requirements for the use ofblanking specified in this manual are fullyunderstood and complied with.
The Guardscan BPU 4 unit is used to programthe blanking function of a Guardscan lightcurtain which is equipped with this feature.This includes the GS 140 range of lightcurtains. Blanking originated in the U.S.A.but has since been generally adopted bymanufacturers and users of light curtainsworldwide.
Blanking is sometimes confused with otherlight curtain related functions, for examplemuting, and therefore it helps to start with anexplanation of exactly what blanking is.
First consider the normal operation of a lightcurtain without blanking. A light curtaintypically consists of a grid of parallel beamsof infra-red light, each beam consisting of anemitter device at one end and a receiver deviceat the other (see Figure 1).
If any single beam is obscured, the lightcurtain will generate a stop signal.
Emitter Unit Receiver Unit
Light Curtain
5
Figure 2
IS ANY BEAMOBSCURED ? YESNO
STOPMACHINE
DONOTHING
CHECKCURTAIN
CHECKCURTAIN
IS CURTAINSTATE
ACCEPTABLE?NOYES
STOPMACHINE
DONOTHING
COMPARE WITHPROGRAMMED
REQUIREMENTS
The decision process of the light curtain is arelatively simple one as shown in Figure 2.
Now consider the operation of a light curtainwith blanking . A light curtain with blanking isable to:
(a) determine the state of each individual beamof its curtain(b) compare this information with previouslyprogrammed requirements(c) based on this comparison, decide whetherto send a stop signal to the machine.
The light curtain decision process is now amore complex one as shown in Figure 3.
Figure 3
Blanking therefore modifies the basic instinctof the light curtain to stop the machine whenany beam is obscured, and makes its responseconditional.
Safe use of this modified behaviour obviouslymakes special demands on the design of thelight curtain but equally important demandsare made on the installation, programming,operation and maintenance of the machine/light curtain combination.
Notice that the light curtain can only considerthe question:
'Has this state of the curtain been programmedas acceptable?'
It cannot consider the question:
'Is this a safe state for the curtain to be in?'
This is the responsibility of all those involved inthe use of the machine and can only be achievedwith careful consideration of all the implicationsof the use of blanking as described in this manualand careful analysis of the application.
6
1.2 TYPES OF BLANKING
1.2.1 GENERAL
There are basically two types of blanking:fixed and floating. The two types can be usedindependently or in combination. Theoperation, purpose and implications ofindependent and combined use are consideredbelow.
1.2.2 FIXED BLANKING
In fixed blanking, one or more selected beams,at particular positions in the curtain, are allowedto be obscured without a stop signal beinggenerated.
Note: The behaviour of a fixed blankedbeam can be further modified by the useof fixed and floating blanking incombination. This is explained in section1.2.4.
Fixed blanking is used where correctpositioning of the light curtain dictates thatsome necessary fixtures on a machine, forexample sheet supports on a press brake, willobscure some beams during normal operation.
These beams can be selected for fixed blankingso that the presence of the fixture does notcause the curtain to send a stop signal and themachine can be used normally.The curtainignores the obstruction.
In the Guardscan GS 140 light curtain, oncea beam has been specified as 'fixed blanked'it is monitored in 'opposite mode'. If a fixedblanked beam becomes unobscured, the lightcurtain will generate a stop signal, just as if anormal, non-blanked beam had beenobscured.
If a fixed blanked beam is not monitored in thisway, removal of the fixture would leave anunprotected area in the curtain.
In the Guardscan GS 140 system theprogramming of fixed blanked beams isachieved by means of a learning function.
Using the BPU 4, the light curtain is instructedto learn the state of the curtain, i.e. whichbeams are clear and which are obscured. Thisstate is recorded in non-volatile memory. Forthis reason fixed blanking is also referrred toas learned blanking later in this manual.
After programming, the current state of thecurtain is continually compared with therecorded state and any deviations will result ina stop signal being generated.
7
CISABNOITCETEDYTILIBAPAC
GNITAOLFFOEPYTDESUGNIKNALB
MAEB1 MAEB2
mm41 mm3 mm11
mm03 mm5 mm12
mm07 mm83 mm88
1.2.3 FLOATING BLANKING
Floating blanking allows a number of beams,usually one or two, to be obscured without astop signal being generated. The term floatingblanking is used because an obstruction canmove or 'float' within the detection zonewithout a stop signal being generated,providing that the obstruction does not obscuremore than the specified number of beams.
Floating blanking is used to allow anobstruction to move within the detectionzone, for example where flexible cables orpipes pass through the detection zone and canmove whilst the machine is operating.
The Guardscan GS 140 light curtain can beprogrammed for 1 beam floating blanking or2 beam floating blanking.
The maximum size of object which will beignored by the curtain, at any range, is givenin Table 1.
Table 1 - Ignored object diameter andignored movement of fixed blanked object
1.2.4 FIXED AND FLOATING BLANKING IN COMBINATION
When fixed and floating blanking are used incombination the floating blanking modifiesthe fixed blanking. Recall that floating blanking,used independently, allows a number of beamsto be blocked without generating a stopsignal. It allows a number of beams whichwould normally need to be clear to beobscured. In other words, it allows a numberof curtain discrepancies.
This is how floating blanking works with fixedblanking.When a light curtain has beenprogrammed for fixed blanking, some beamsneed to be clear and all other beams need tobe obscured, otherwise a stop signal will begenerated. The floating blanking allows anumber of curtain discrepancies. So, beamswhich would normally need to be clear can beobscured and beams which would normallyneed to be obscured can be clear.
In the case of the Guardscan GS 140 lightcurtains the maximum number of allowedcurtain discrepancies can be set at 1 or 2.
This would allow a fixed blanked object, forexample feedstock, to move slightly duringmachine operation. The maximum allowablemovement of a fixed blanked object withfloating blanking is given in Table 1.
8
NOITCETEDCISABYTILIBAPAC I,TNEMERCNI
mm41 mm9
mm03 mm71
mm07 mm05
1.3 IMPLICATIONS OF BLANKING
1.3.1 EFFECT OF BLANKING ON DETECTION CAPABILITY
Blanking of any kind increases the detectioncapability of a light curtain. The detectioncapability of a light curtain is the smallestdiameter of opaque object which the systemcan reliably detect.
Note: An increase in detection capabilityis not an improvement. It means that thecurtain is less sensitive to intrusions.
The basic detection capability, Db, of an
unblanked Guardscan GS 140 light curtain ismarked on the label fitted to each unit and willbe 14mm, 30mm or 70mm.
The effective detection capability, De, of
the light curtain which is blanked can becalculated using the following formula:
Formula 1: De = D
b + I (N
fx + N
ft)
where:I = beam increment (see Table 2)N
fx = number of beams in largest
contiguous block of fixed blanked beams
Nft
= number of floating blanked beams
Table 2
Note: Read sections 1.3.2 and 1.3.3 forguidance before using this formula.
1.3.2 EFFECT OF BLANKING ON SEPARATION DISTANCE
As previously explained, the use of any type ofblanking increases the detection capability.Detection capability is one of a number offactors used to calculate the separation distance,i.e. the distance at which the light curtain ispositioned from the dangerous parts of themachine. (See the light curtain manual for furtherdetails).
Normally, the greater the detection capability thegreater the separation distance, all other factorsbeing equal. Certainly, the use of floating blankingalways requires an increase in separation distance.
With detection capabilities of more than 70mmsection 6.1.4 of EN999 applies. Additional riskshave to be considered, e.g. creeping underneaththe lowest beam, reaching over the highest beamor in between beams. Moreover recommendedpositions of highest and lowest beam are given.
However, when using fixed blanking, althoughfixed blanking always increases the detectioncapability of the light curtain, it is not alwaysnecessary to increase the separation distance.This depends entirely on the nature of theobstruction.
Figures 4 and 5 show two obstructionpossibilities: complete obstruction andincomplete obstruction.
In the case of incomplete obstruction it ispossible for a person to gain access to thedangerous parts, between and on either side ofthe obstructions, through the area which wouldhave been covered by the fixed blanked beams.
9Figure 5 Complete obstruction
Figure 4 Incomplete obstruction
Figure 6 Combined obstruction
Therefore, in the case of incompleteobstruction, the effective detection capabilityhas been increased and the separation distancemust be calculated using this increased value.
In the case of complete obstruction, it is notpossible for a person to gain access to thedangerous parts of the machine through the areaof the curtain which would have been coveredby the fixed blanked beams. When the lightcurtain/obstruction is considered as a whole, thedetection capability in the unobscured areas ofthe curtain is not effectively increased.
Therefore, the separation distance can becalculated using the basic detection capabilityvalue.
It is important that an obstruction originallyconsidered as complete is not modified at alater date such that the use of the basicdetection capability value is no longer valid. Ifthis cannot be assured, it is recommended thatthe application is treated as an incompleteobstruction from the outset and the separationdistance calculated accordingly.
Note: Any gaps between a completeobstruction and the light curtain unitsmust not exceed the values recommendedin EN294.
Figure 6 shows a combined obstruction where,due to the shape of the obstruction, part of thecurtain is completely obstructed and part ofthe curtain is incompletely obstructed. In thiscase the complete and incomplete parts of theobstruction should be treated separately.
In all cases, if the obstruction is removed, theopposite mode monitoring will take effect andwill cause a stop signal to be generated.
Fixedblankedbeamsincomplete
complete
Basic detection capabilityapplies here
FixedBlankedBeams
Dotted line showseffective detectioncapability near obstruction
Basic detection capabilityapplies here
Fixedblankedbeams
Basic detection capabilityapplies here
10
CISABNOITCETEDYTILIBAPAC
MAEB1GNITAOLF
MAEB2GNITAOLF
mm41 mm32 mm23
mm03 mm74 mm46
mm07 mm021 mm071
Table 3
1.3.3 CALCULATION OF EFFECTIVE DETECTION CAPABILITY
The effective detection capability to be usedfor the purpose of calculating the separationdistance can be determined as follows:
Case 1Fixed blanking with complete obstruction:
Basic detection capability applies.
Case 2Fixed blanking with incomplete obstruction:
Formula 1 applies.
Case 31 or 2 beam floating blanking only:
Formula 1 applies (see Table 3 below).
Case 4Fixed blanking with 1 or 2 beam floatingblanking and complete obstruction:
Formula 1 applies with Nfx = 0.
Case 5Fixed blanking with 1 or 2 beam floatingblanking and incomplete obstruction:
Formula 1 applies.
Note: If there are a number of obstructionsin the same curtain the above calculationmust be made for each obstruction andthe largest value found should be used inthe calculation of separation distance.
Full details of the calculation of separationdistance can be found in the technical manualfor the light curtain and in the Europeanstandard EN999.
For cases 2 and 5 above, if the number ofbeams which are fixed blanked (Nfx) is notclear the following procedure can be used:
1. Measure the largest obstruction, where itobscures the curtain.2.Divide the measurement by the appropriateincrement, I, shown in Table 2.3. Add 0.25 to the answer then round up tothe next integer.4. Use this value for the term Nfx.
Example: A vertical light curtain with a basicdetection capability of 30mm is incompletelyobstructed by horizontal sheet supports withsection 48mm x 48mm.
The value of I for a curtain with basicdetection capability of 30mm is 17mm(from Table 2).
48 divided by 17 gives 2.82
Adding 0.25 gives 3.07
Rounding up to next integer gives 4
Using Nfx = 4 in Formula 1 gives:
De = 30 + 17 (4 + 0)
De = 98mm
Use this value for detection capability whencalculating separation distance.
11
Figure 7 Figure 8
2. BPU 4
2.1 UNIT DESCRIPTION
The programming unit Guardscan BPU 4 isrequired to program the blanking function ofa Guardscan GS 140 system.
The BPU 4 unit is connected in-line betweenthe receiver unit and the machine as shown inFigure 7.
The BPU 4 has five indicators and twobuttons. The front panel of the BPU 4 isshown in Figure 8.Four of the indicators are associated with thefour types of blanking:
No BlankingLearned (Fixed) Blanking1 Beam Floating Blanking2 Beam Floating Blanking
Because these can be used in combinationthere are six possible programmed modes:
No BlankingLearned (Fixed) Blanking1 Beam Floating Blanking2 Beam Floating BlankingLearned with 1 Beam Floating BlankingLearned with 2 Beam Floating Blanking
Receiver Unitwith
Connector
Programming Unit
To Machine
No Blanking
Learned Blanking
Floating 1
Floating 2
Confirm
BPU 3
A B
BPU 4
12
START
Step 1 Step 2 Step 3 Step 4
BPU 2
No Blanking
Learned Blanking
Floating 1
Floating 2
Confirm
BPU 3
A B
No Blanking
Learned Blanking
Floating 1
Floating 2
Confirm
BPU 3
A B
No Blanking
Learned Blanking
Floating 1
Floating 2
Confirm
BPU 3
A B
2.2 PROGRAMMING INSTRUCTIONS
The basic programming sequence is illustrated and described below:
1. Connect the programming unit in-line withthe receiver unit. All the mode indicators willcome ON with the current mode indicator(s)flashing.
2. To enter programming mode, press buttonsA and B together for 3 seconds. The modeindicators will go OFF.
3. After a short period the confirm indicatorwill come ON and then go OFF. Button Bmust be pressed within 3 seconds of theconfirm indicator coming ON.
4. If steps 2 and 3 are followed correctly theindicators for the current mode will be ONsteady, together with the confirm LED.
Pressing button A repeatedly will cycle theindicators forward through the possibleblanking modes and illuminate the confirmLED.
BPU 4 BPU 4 BPU 4
No Blanking
Learned Blanking
Floating 1
Floating 2
Confirm
BPU 4
A B
13
FINISH
Step 5 Step 6 Step 7
7. After a short period, providing the curtainis in an acceptable state, the outputs will comeON. The system is now in the initial state.Disconnect the programming unit from thelight curtain.
Figure 9
No Blanking
Learned Blanking
Floating 1
Floating 2
Confirm
BPU 3
A B
No Blanking
Learned Blanking
Floating 1
Floating 2
Confirm
BPU 3
A B
KEY:
= OFF
= ON
= Flashing
5. To program a particular mode, press buttonB and the desired mode indicator will comeON.
6. Once the selected mode has beenprogrammed all the other indicators will comeON steady and the programmed modeindicators will flash.
BPU 4 BPU 4 BPU 4
No Blanking
Learned Blanking
Floating 1
Floating 2
Confirm
BPU 4
A B
14
2.3 OPERATING CONSIDERATIONS
2.3.1 BPU 4 OPERATION
The following points should be observedwhen using the BPU 4.
1. Beam 1, the beam nearest the connector endof the emitter and receiver units, cannot beblanked in any way. If beam 1 is obscured, theoutputs will go OFF.
2.When the BPU 4 unit is attached to the lightcurtain initially, check that all the modeindicators illuminate.
3.Once programming mode has been entered,if no buttons are pressed for a period of tenseconds, programming will automaticallyabort and the previous programmed modewill be resumed. Similarly if an inappropriatesequence of button operations is performedthe programming will automatically abort.Automatic aborting will be indicated by all themode indicators illuminating for a period offive seconds.
4. The machine cannot be operated with theBPU 4 connected to the light curtain. It isrecommended that the BPU 4 unit is held bya responsible person when not in use.
5. If no beams are obstructed, learned blankingwill not program. If the selected mode islearned blanking or includes learned blanking,the light curtain will default to the selectedmode minus learned blanking. For example iflearned blankng only is selected, the lightcurtain will default to no blanking; if learnedblanking with 2 beam floating blanking isselected the light curtain will default to 2 beamfloating blanking only.
6. If the light curtain is in test mode (indicatedby the red indicator on the emitter unit beinglit steady) the programming unit will notfunction.
7. If the communication link between the lightcurtain and the BPU 4 unit is not functioningall the mode indicators will flash whilst theBPU 4 is connected.
2.3.2 CURTAIN OPERATION
When a light curtain is programmed for blankingof any type, the yellow indicator on the lightcurtain receiver unit will be lit steady.
15
3. MANAGEMENT ISSUES
3.1 BLANKING TEST PROCEDURE
Immediately prior to programming the lightcurtain for learned (fixed) blanking (with orwithout floating blanking) it is essential that thelight curtain is tested as follows:
1. With the light curtain in its intended positionon the machine but with no obstruction inplace, program the light curtain for 'Noblanking'. Check that all the indicators of theBPU 4 unit illuminate when the programmingunit is initially attached to the light curtain.Afaulty indicator could lead to programming ofthe wrong mode.
If any indicator does not illuminate, DO NOTUSE THE PROGRAMMING UNITUNTIL IT HAS BEEN REPAIRED.
2. Perform the daily test on the light curtainsystem, as detailed in the light curtain technicalmanual, using the test piece supplied with thelight curtain (i.e. the test piece with a diameterwhich is the same as the detection capabilitymarked on the light curtain unit labels).
If this test fails DO NOT USE FIXEDBLANKING UNTIL THE LIGHTCURTAIN HAS BEEN REPAIRED.
3. If the test is passed, without moving the lightcurtain, fit the obstructions in place andprogram the desired blanking mode.
This test ensures that faulty beams, whichmay not be obscured by the obstruction, arenot inadvertently blanked.
3.2 DETECTION CAPABILITY -TEST AND INDICATION
When blanking is in use the detection capabilitycan be affected such that the detectioncapability marked on the light curtain units isnot correct. This also means that the test piecesupplied with the light curtain is no longersuitable for performing the daily tests.
Previous sections of this manual describehow to determine the effective detectioncapability for any blanking situation.
A test piece will need to be obtained orproduced to suit the effective detectioncapability, in order to perform the daily tests.
Also it is recommended that the currenteffective detection capability of a system berecorded and clearly displayed at the machine.
3.3 CHANGE OF OPERATINGPARAMETERS
If any operating parameter relating to theguard or the machine is changed, i.e. theobstruction removed or the guard repositionedit is essential to ensure that the blanking testprocedure specified in section 3.1 is carriedout.
