VC sensors for bending machines (press brake machines)

3.1   Measure Angle > 120 degrees

Try to mount your sensor perpendicular to your machine. Especially at large plate angles like 120 - 180 degrees (flat plate), the die reflected the laser line to the plate (also the other way around) and you get a double laser line, if the sensor is not mounted perpendicular. This more or less close double line biased the result angle.

Put a mirror on the die and check if you have a double laser line on the die. Try to improve the sensor mounting so that the reflected line is on identical position as the original line.

If the bend angle is smaller than 120 degrees this effect becomes less important, as the reflection is not that strong any more.

4.1   Manual detection of mounting position

Try to determine the values X, R and Angle of both sensors as well as possible and use it as an input for the press brake controller. See drawings in chapter Recommended mounting positions for the position of X, R and Angle.

Then make a test bending to 90,0 degrees.

Measure the result angle with a separate tool at the same position as the laser measure the plate. If the result is for example 91,0 degrees you have to reduce your mounting angle settings of 1 degree.

For example Front sensor: original -30,0 degrees becomes -30,0 - 1,0 = -31,0 degrees for the new settings. Then bend again. The result angle should be now 90,0 degrees.

The parameters X- and R-position are not that critical. An accuracy of 0,5mm is sufficient. Both parameters refers to the centre of the laser beam lens. Please have a look at the technical drawings.

4.2   Automatic detection of mounting position

We recommend to use the MDT (mounting detection tool) in order to get the accurate mounting position of both sensors (X, R and Angle). Additionally with this tool, you can check, if every sensor works correctly.

Maybe your press brake controller has already implemented the automatic detection of the sensor mounting position X, R and Angle. Please ask your vendor.

If not, you can use the our VC Tools for detecting the parameters X, R and Angle: Angle Measure Tool

Or use the VC Update-Tool (repeat it for every sensor).

VC Press Break Mounting Detection Tool

Do the following steps:

1. mount in front of the laser beam the VC Press Break Mounting Detection Tool (MDT) from Vision Components (VK000563 / VC PB-MDT)
2. select “Sensor Mounting Position” at your controller or our VC Tools and start the measuring. Maybe repeat it in order to see if the values are stable
3. check if Phi from the output string is in the range 135,0 +/- 0.3 degrees. Then the sensor works fine. Otherwise check if the sensor can’t see the full range of the MDT. See later in this chapter
4. transfer the values (X, R and Angle) to your press brake controller. Maybe you have to add an offset to R. See later in this chapter.
5. do it for both sensors (front and back sensor IP)

Take care of the correct reference plane. It has to be the same as for your V-Die height. If you use an Adapter block(60 x 60 x 20), then set the correct offset (Adapter Height) at your controller OR add the offset to the value R: R_controller = R_measured + Adapter_Height, e.g. R_controller = -40+20=-20.

In order to get stable results, please take care that the sensor sees both regions (MDT_LenLine0_MM and MDT_LenLine1_MM) completely (full selected length). For our recommended mounting positions V6-V70 and V6-V160 it is already the case.

If you cannot use the 13 x 20 mm sliding block, you can develop your own adapter block that fits to your machine.

6.1   Mounting Position for dies V6 – V70 (recommended)

6.2   Mounting Position for dies V6 – V160

6.3   Mounting Position for dies V60 – V200

11.1   Sensor Initialisation

Send once after sensor start up (initialisation) the following parameters (for a clear defined start):

1. Product Parameter (CMD_RECEIVE_PRODUCT_DATA - ID 40):

         AdjustSensorRoi = 2 # or 1 for max. speed
   
         J00_ProductType = 0
         J01_ProductType = 0
         J02_ProductType = 0
         J03_ProductType = 0
   
        J00_LineAlgoMode = 2
   J00_MaxLineDisBestFit = 1.0
      J00_BestLineFilter = 100
     J00_HistoLineFilter = 1
              J00_PhiMin = 0.0
   

2. Sensor Parameters (CMD_RECEIVE_SENSOR_DATA - ID 43):

             DataMode = 8
             NbrLines = 0
          ShutterTime = 50
              GainVal = 0
            LaserMode = 1
            RlcThresh = 10
          LaserSelect = 0
             OptWidth = 8
             MinWidth = 2
             MaxWidth = 30
      SpeckleFilterDx = 5
      SpeckleFilterDy = 3
      LaserMaskFilter = 31
      ReflexionFilter = -1
            ROI_X_PIX = 0
            ROI_Y_PIX = 0
           ROI_DX_PIX = 1408
           ROI_DY_PIX = 1080
        AdjustSenHmax = 0
          TriggerMode = -1
       TriggerDelayNs = 0
         ExposureMode = 1
       AutoShutterVal = 128
    AutoShutterFilter = 0
       AutoShutterMin = 1
       AutoShutterMax = 100
          AutoGainMin = 0
          AutoGainMax = 300
       DoubleShutter1 = 5
       DoubleShutter2 = 20
       TripleShutter3 = 100
       EthernetPackNr = 1
       AutoTriggerFPS = 50.0 # or 100 for 100 frames (angles) per second
     AutoTriggerError = 0
   EthernetSendNoWait = 1
         MedianFilter = 7
            SensorLUT = 0
    TransferAllPos_MM = 0
   

11.2   Angle measurement

If you want to measure angles send the following parameters:

1. Product Parameter (CMD_RECEIVE_PRODUCT_DATA - ID 40):

           J00_ProductType = 1
             J00_PolygonNr = 2
   J00_PolygonPoint_X00_MM = -500.0
   J00_PolygonPoint_Z00_MM =    0.0
   J00_PolygonPoint_X01_MM =  500.0
   J00_PolygonPoint_Z01_MM =  500.0
   

2. Sensor Parameters (CMD_RECEIVE_SENSOR_DATA - ID 43):

   DataMode = 8
   NbrLines = -1
   

You will permanently get a result strings like:

JOB 0.0001: Phi=156.36 Cx=00.4011 Cy=-0.9161 B=-0104.19 LAlgo=2 Points=0501 DetLen=042.6 Filter=100 dPhi=0.03 Error=0 Sh=0012us Gain=000 TimeStamp=0000006468167ms

For accuracy reason ignore the first 5-10 angles after a new plate or ROI is defined, as the auto exposure takes some images for adaption.

11.3   Stop angle measurement

If you want to stop measure angles send the following parameters:

1. Sensor Parameters (CMD_RECEIVE_SENSOR_DATA - ID 43):

   NbrLines = 0
   
   OR
   
   Use the "STOP" command (CMD_STOP 0).
   

Later we will adapt the ROI (region of interest) parameter that it fits to the V-die. See following chapter.

J00_PolygonPoint_X00_MM = -500.0
J00_PolygonPoint_Z00_MM =    0.0
J00_PolygonPoint_X01_MM =  500.0
J00_PolygonPoint_Z01_MM =  500.0

For that you have to know the mounting position (R, X and Angle) of the individual sensor.

12.1   Measure X, R and Angle with the MDT (ProductType 1002)

Before you start the detection, please mount in front of the laser beam the VC Press Break Mounting Detection Tool from Vision Components (VK000563 / VC PB-MDT (mounting detection tool).

Please have a look at chapter Automatic detection of mounting position.

For an easy detection of the MDT (mounting detection tool) use the following parameters.

Measure the MDT at least 10 times in order to give the auto shutter mode time to fit the laser brightness.

Then you can use the output values.

12.1.2   Sensor result output of the MDT detection (ProductType 1002)

Front Sensor:

JOB 0.1002: Position=FRONT  R=-61.3  X=-100.3  Angle=-28.04 [-20.0..-50.0]  xC=003.2 yC=153.9 Phi=134.95 Error=0 Sh=0033us Gain=000 TimeStamp=0000008748009ms

Back Sensor:

JOB 0.1002: Position=BACK   R=-61.4  X=0101.5  Angle=030.77 [ 20.0.. 50.0]  xC=003.1 yC=154.5 Phi=134.93 Error=0 Sh=0033us Gain=000 TimeStamp=0000008849994ms

Description of MDT:

L:     laser beam centre (0|0)
Angle: angle of the scanner
LenX:  x distance of the scanner to the centre of the MDT tool
S:     cross point of line Line[0] and the perpendicular line LS
C:     cross point of die line (Line[0]) and angle line (Line[1])
LenBA: width of the MDT tool

Output:

R     = length of distance BS
X     = x distance from Point L (position (0|0)) and centre of MDT tool
Angle = sensor mounting angle
Phi   = angle of the MDT (135,0 +/- 0.2 degrees)

Maybe display the Phi value (front and back) in order to see if the sensor works fine.

12.2   Measure the Angle in a rectangle ROI (ProductType 1)

12.2.1   Calculating the ROI (ProductType 1 - rectangle ROI)

• NMZ = None measure zone [mm]
• LML = Laser measure length [mm]
• DieX = DieWidth / 2
• DieY = DieHeight (from reference line R = 0)

	Back Sensor (Angle > 0, DieX > 0)	Front Sensor (Angle < 0, DieX < 0)
	Len1 = (NMZ) / cos(Angle) Len2 = (NMZ + LML) / cos(Angle)	Len1 = (NMZ) / cos(Angle) Len2 = (NMZ + LML) / cos(Angle)
P0x	DieX + Len2	DieX - Len2
P0y	DieY	DieY
P1x	DieX - LML * cos(Angle)	DieX + LML * cos(Angle)
P1y	DieY + Len2 / tan(Angle) - LML * sin(Angle)	DieY - Len2 / tan(Angle) + LML * sin(Angle)

JOB 0.0001: Phi=156.36 Cx=00.4011 Cy=-0.9161 B=-0104.19 LAlgo=2 Points=0501 DetLen=042.6 Filter=100 dPhi=0.03 Error=0 Sh=0012us Gain=000 TimeStamp=0000006468167ms


Job:                job number followed by ProductType
Phi:                measured line angle [°]
Cx, Cy, B:          general straight line equation
LAlgo:              line algorithm mode (2 = combination of hough and best line)
Points:             detected laser points
DetLen:             measured line length [mm]
Filter:             use x% of the closest detection points to the line for best line calculation
dPhi:               expected angle accuracy
Error:              error number
Sh:                 used shutter time [µs]
Gain:               used gain value
TimeStamp:          image acquisition time since camera power on [ms]

12.3   Optional - Measure Angle in polygon ROI (ProductType 1)

12.3.1   Calculating the ROI (ProductType 1 - polygon ROI)

• NMZ = None measure zone [mm]
• LML = Laser measure length [mm]
• Len = (W + NMZ + LML) / cos(22.5°)

	Back Sensor (Angle > 0, DieX > 0)	Front Sensor (Angle < 0, DieX < 0)
P0x	DieX + NMZ	DieX - NMZ
P0y	DieY	DieY
P1x	DieX + Len	DieX - Len
P1y	DieY	DieY
P2x	DieX + Len * cos(45°)	DieX - Len * cos(45°)
P2y	DieY + Len * cos(45°)	DieY + Len * cos(45°)
P3x	DieX - W	DieX + W
P3y	DieY + Len	DieY + Len
P4x	DieX - W	DieX + W
P4y	DieY + NMZ + W	DieY + NMZ + W

JOB 0.0001: Phi=156.36 Cx=00.4011 Cy=-0.9161 B=-0104.19 LAlgo=2 Points=0501 DetLen=042.6 Filter=100 dPhi=0.03 Error=0 Sh=0012us Gain=000 TimeStamp=0000006468167ms


Job:                job number followed by ProductType
Phi:                measured line angle [°]
Cx, Cy, B:          general straight line equation
LAlgo:              line algorithm mode (2 = combination of hough and best line)
Points:             detected laser points
DetLen:             measured line length [mm]
Filter:             use x% of the closest detection points to the line for best line calculation
dPhi:               expected angle accuracy
Error:              error number
Sh:                 used shutter time [µs]
Gain:               used gain value
TimeStamp:          image acquisition time since camera power on [ms]

12.4   Converting Machine Coordinates to Sensor Coordinates

You will need the mounting values R, X and Angle of the individual sensor.

x = MachineX - X
y = MachineY - R

// rotation matrix from machine coordinates (centre of die holder) to sensor coordinates
SensorX =  cos(Angle) * x +  sin(Angle) * y
SensorY =  -sin(Angle) * x + cos(Angle) * y

Example Values (rectangle ROI):

P = Machine Coordinate Points

S = Sensor Coordinate Points

See chapter Angle Measurement for calculation.

Back: DieHeight=65.00 DieWidth=80.00 LML=30.00 NMZ=3.00 X=110.00 R=-40.00 Angle=23.40 → P0x=75.96 P0y=65.00 P1x=12.47 P1y=136.18 S0x=10.46 S0y=109.88 S1x=-19.54 S1y=200.42

Front: DieHeight=65.00 DieWidth=80.00 LML=30.00 NMZ=3.00 X=-105.00 R=-40.00 Angle=-22.40 → P0x=-75.69 P0y=65.00 P1x=-12.26 P1y=140.17 S0x=-12.92 S0y=108.25 S1x=17.08 S1y=201.91

12.5   Calculate Plate Angle

Plate Angle could be measured in range [0° .. 240°], typical [30° .. 180°]. 180° is a flat plate.

if X_Front < 0 AND X_Back > 0: # mounting both sensor cables right (recommended way)
PlateAngle = –(SensorAngleFront – MountingAngleFront) + (SensorAngleBack - MountingAngleBack)

if X_Front > 0 AND X_Back < 0: # mounting both sensor cables left
PlateAngle = (SensorAngleFront – MountingAngleFront) - (SensorAngleBack - MountingAngleBack)

if X_Front < 0 AND X_Back < 0: # mounting front sensor cable right, back sensor cable left
PlateAngle = –(SensorAngleFront – MountingAngleFront) - (SensorAngleBack – MountingAngleBack) + 180

if X_Front > 0 AND X_Back > 0: # mounting front sensor cable left, back sensor cable right
PlateAngle = (SensorAngleFront – MountingAngleFront) + (SensorAngleBack – MountingAngleBack) - 180

if PlateAngle < 0: PlateAngle + 360
if PlateAngle > 240: PlateAngle - 180

if X_Front < 0: PlateAngle = -2 * (SensorAngleFront – MountingAngleFront) + 180
else: PlateAngle = 2 * (SensorAngleFront – MountingAngleFront) - 180

if PlateAngle < 0: PlateAngle + 360
if PlateAngle > 240: PlateAngle - 180

if X_Back > 0: PlateAngle = 2 * (SensorAngleBack – MountingAngleBack) - 180
else: PlateAngle = -2 * (SensorAngleBack – MountingAngleBack) + 180

if PlateAngle < 0: PlateAngle + 360
if PlateAngle > 240: PlateAngle - 180

15.1   Angle accuracy

In any case of angle accuracy problems, please do the following steps:

• Carefully clean both glasses of the sensors. Do not make any scratches on the surface.
• Check with the MDT (mounting detection tool) if both sensors work correct. See chapter Angle Measurement Test. Take care, that the laser and the field of view of the sensor is not blocked by any mechanical parts. Then Phi should be in the range 135,0 +/- 0.3 degrees.

Now both sensors are fine. The problem must be in the settings. Please check your controller settings:

• Are the values for X, R and Angle correct transferred to your controller (including sign)?
• Did you use an MDT Adapter and did you set the correct Adapter Offset at your controller? See chapter Automatic detection of mounting position with the MDT.
• Is the correct V-Die selected?
• Could both sensors see the plate (laser and field of view of the sensor is not blocked).
• Is the plate long enough for the selected laser measure length (LML)?
• Some controller needs the correct settings of the sensor mounting position (cables right or left).
• Inaccurate angles

15.2   Constant Angle Offset

If you always have a constant plate angle result offset, than change the value of the mounting “Angle” at your controller. If the result is 91,0 degrees (open angle, instead of 90,0 degrees) you have to decrease your mounting angle settings of 1,0 degree. For example Front sensor: original -30,0 degrees becomes -30,0 - 1,0 = -31,0 degrees as a new setting. Then bend again. The result angle should be now 90,0 degrees.

15.3   Communication Error

In an industrial environment take care of the electromagnetic compatibility (EMC). Use Ethernet cables which are at least Cat5e and well shielded.

15.4   Unstable angle results

The main challenge is the measurement of the spring back angle. If the results are unstable, try to improve the controller settings for the spring back angle calculation.

15.5   Bad angle results using only one sensor

When the plate part is unbalanced, it will inevitably fall on one side, in that case we advise using strain gauges.

15.6   Mechanical sensor crash

Check the accuracy of the sensor with the MDT (mounting detection tool). Phi should be in the range 135,0 +/- 0.3 degrees. If not, change the sensor and don’t forget to adapt the IP address of the new sensor.

15.7   Can’t get the values (X, R, Angle) of the MDT (mounting detection tool) or Error -4000

Check if the sensor has at least version 1.9.7.