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Exercise 7

Conveyors

EXERCISE OBJECTIVE

In this exercise, you will be introduced to conveyors. You will learn to use the BeltConveyor, Model 5210. You will also learn to use the If-Else-Endif and While-Repeattask commands

In the Procedure section, you will experiment with the various features of the BeltConveyor, and you will detect these objects with a limit switch mounted on theconveyor chassis. You will use the TTL outputs of the Robot Controller to remotelycontrol the Belt Conveyor.

DISCUSSION

Conveyor systems are needed when components or material must be moved fromone station to another one along a fixed path. Most conveyor systems use anelectrical or hydraulic power source to move their loads. However, when the receiverstation is lower than that of the sender, the force of gravity is often used as powersource.

The most common types of conveyors are roller, belt and chain.

Roller conveyors are popular in manufacturing. Tubes orrollers, over which the material flows, are connected to twoends of a fixed frame. They can use the force of gravity or bedriven by mechanisms.

Belt conveyors are another automated way to move materials.The belt moves in a continuous loop with the top half carrying the load to the nextstation, and the bottom half returning to its starting point. You have seen belt-typeconveyors at the checkout counter of supermarkets and airport security checkpoints.

Chain conveyors loop chains around sprockets at the ends of their pathways. Theyoperate in the same way as bicycle chains. However, they use powered sprocketsrather than manual force to drive the chain along channels supporting the flexiblechain sections.

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Belt Conveyor

The Belt Conveyor of your training system is shown in Figure 7-1. It can be operatedeither by switches mounted on the control panel, or by control signals applied to itsTTL inputs. The control signals are provided by the TTL outputs of the RobotController.

Figure 7-1. Belt Conveyor, Model 5210.

The control panel of the Belt Conveyor is shown in Figure 7-2. As the figure shows,the operating parameters that can be controlled from the control panel are the speed(SPEED), logic level of the TTL input (STOP) at which the conveyor stops, motorengage/disengage (MOTOR), and belt direction (DIRECTION).

Figure 7-2. Control panel of the Belt Conveyor.

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Speed

The SPEED potentiometer controls the speed of the belt from Slow to Fast. At theSlow position, the belt of the conveyor is stopped.

Stop

The Logic switch is used to select the TTL level required at the input Stop toremotely stop the conveyor. When the Logic switch is set at High, the conveyor stopson a high level. Conversely, when the Logic switch is set at Low, it stops on a lowlevel.

Motor

The Motor switch is used to select between three operating modes:

Engage: In this mode, the motor of the Belt Conveyor is torqued and the conveyorruns if the settings of the Stop section correspond to a run condition. If thesettings of the Stop section correspond to a stop condition the motor is stoppedbut remains torqued.Disengage: In this mode, the motor is stopped and freed (not torqued).Ext.: The operation is controlled remotely by a signal applied to the Ext. Input.When the level of the Ext. Input is high, the conveyor operates as in the Engagemode. Conversely, when the level is low, it operates as in the Disengage mode.

Direction

The Direction switch is used to select between three operating modes:

Forward: In this mode, the belt of the conveyor goes from right to left (when facingthe control panel).Reverse: In this mode, the belt of the conveyor goes from left to right.Ext.: The operation is remotely controlled by a signal applied to the Ext. Input.When the level of the Ext. Input is high, the direction of the belt is in the Forwardmode. Conversely, when the level is low, it is in the Reverse mode.

Limit Switch

The Belt Conveyor is provided with a limit switch to detect the presence of parts onthe belt. The limit switch is movable, and there are several sets of mounting positionsfound along both sides of the conveyor chassis.

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Task Commands

In this exercise, you will be introduced to the If - Else - Endif and While - Repeat taskcommands.

If - Else - Endif

If: This command evaluates an expression. If the expression is true, theexecution of the task program continues normally on the next instruction line.If the expression is false, the execution continues after the next Else statement(if used) or Endif statement. The syntax and the parameters associated withthe If command are as follows: IF <expression>. Example: IF INPUT(1) =HIGH

Else: This command indicates the end of the instruction lines that areexecuted when the previous If statement has evaluated a true condition. Theinstruction lines that follow the Else statement are executed only when theprevious If statement has evaluated a false condition.

Endif: This command indicates the end of an If-Else-Endif block of codes andexecution continues on the next instruction line. For each If command theremust be one matching Endif statement. If there are multiple nested Ifstatements, each statement must have a matching Endif statement.

While - Repeat

While: This command evaluates an expression. If the expression is true, thenext instruction lines are executed up to the Repeat command. When theRepeat command is reached, the execution is returned to the While commandwhere the expression will be evaluated repeatedly until the expression fails.The syntax and the parameters associated with the While command are asfollows: WHILE <expression>. Example: WHILE INPUT(1) = HIGH.

Procedure Summary

In the first part of the exercise, Set-up, you will install and connect the equipment.

In the second part, Direct Control of the Belt Conveyor, you will operate the conveyorusing the switches on the control panel.

In the third part, Remote Control of the Belt Conveyor, you will experiment with theremote control of the Belt Conveyor. You will control the operation from theController Status window of Robotics.

In the fourth part, Additional Experiment - Simulation of a Quality Control Station, youwill create a program that simulates a quality control station using the Gravity Feederand the Belt Conveyor. You will create the position points using the Hand-HeldTerminal and you will use Robotics to create the task program.

In the last part of the exercise, Shutdown Procedure, you will shut down the system.

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EQUIPMENT REQUIRED

Refer to the Equipment Utilization Chart, in Appendix A of this manual, to obtain thelist of equipment required to perform this exercise.

PROCEDURE

CAUTION!

When you work with moving equipment, make sure you are not wearing

anything that might get caught, such as a tie or jewelry. If your hair is

long, tie it out of the way.

Set-up

G 1. Install the Servo Robot and the Belt Conveyor as shown on Figure 7-3.

Note: Refer to the Equipment Layout shown in Figure E-1 inAppendix E.

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Figure 7-3. Location of the equipment on the Work Surfaces.

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G 2. Make sure the limit switch of the Belt Conveyor is located as shown inFigure 7-4. Relocate if necessary.

Figure 7-4. Location of the limit switch on the Belt Conveyor.

G 3. Make sure that the emergency stop button is released (in the up position)and easily accessible.

G 4. Connect the equipment as shown in Appendix B. Refer to the User Guideof your training system for detailed instructions.

Connect the Belt Conveyor to an AC power source.

Direct Control of the Belt Conveyor

G 5. On the control panel of the Belt Conveyor, set the controls as follows:

SPEED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FASTLOGIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LOWMOTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DISENGAGEDIRECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . REVERSE

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Turn the power on using the switch located on the left side of the controlpanel.

G 6. Set the MOTOR switch at ENGAGE to start the motor.

Familiarize yourself with the operation of the Belt Conveyor using theSPEED, LOGIC, MOTOR and DIRECTION controls.

Place a film canister on the conveyor and observe its movement whileoperating each control.

G 7. Indicate in Table 7-1 if the Belt Conveyor is stopped or running for eachcombination shown.

STOPMOTOR

SWITCH

POSITION

BELT

CONVEYOR

OPERATIONLOGIC SWITCH

POSITION

INPUT LEVEL

(TTL)

High

High1Engage

Disengage

Low2Engage

Disengage

Low

HighEngage

Disengage

LowEngage

Disengage

1 The default level of the TTL inputs is high.2 Short-circuit the input with a lead to set the level at low.

Table 7-1. Direct control of the Belt Conveyor.

G 8. Once your experiment is completed, turn off the power of the Belt Conveyorusing the switch located on the left side of the control panel.

Remote Control of the Belt Conveyor

G 9. On the control panel of the Belt Conveyor, set the controls as follows:

SPEED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FASTLOGIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . HIGHMOTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . EXT.DIRECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . EXT.

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G 10. Connect TTL output 1 of the Robot Controller to the Stop Input of the BeltConveyor as shown in Figure 7-5.

Figure 7-5. TTL input/output connection diagram.

Connect the common terminal of TTL output 1 to the common terminalof the Stop Input on the Belt Conveyor.

Connect TTL output 2 to the Motor Ext. Input of the Belt Conveyor.

Note: Since the common terminals are linked in the BeltConveyor and Robot Controller, it is not required to connectthe common terminal of the Direction Ext. Input and MotorExt. Input.

Connect TTL output 3 to the Direction Ext. Input of the Belt Conveyor.

G 11. Turn the Belt Conveyor and Robot Controller on.

G 12. Launch Robotics.

G 13. Open the Controller Status window by selecting Controller Status in theWindow menu.

G 14. Click the appropriate LEDs for controlling the level of the TTL outputs todetermine if the Belt Conveyor is stopped or running for thecombinations shown in Table 7-2.

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STOPMOTOR

EXT. INPUT

LEVEL (TTL)

BELT

CONVEYOR

OPERATIONLOGIC SWITCH

POSITION

INPUT LEVEL

(TTL)

High

HighLow

High

LowLow

High

Low

HighLow

High

LowLow

High

Table 7-2. Remote control of the Belt Conveyor.

G 15. Set a combination for which the conveyor is running, and determine if thebelt is in the Forward or Reverse mode when the level of the DirectionExt. Input is high.

G 16. Once your experiment is completed, turn off the Belt Conveyor.

Remove the leads connected on the front panel of the Robot Controller.

Additional Experiment - Simulation of a Quality Control Station

Program Description

You will create a task program which is a section of a more complex productionprocess. In this program, a robot picks production parts and transfers them viaa belt conveyor to a quality control station for examination. If a part is alreadypresent at the quality control station, the robot transfers the parts in a temporarycontainer.

You will use the Gravity Feeder to feed the Servo Robot with parts, and the BeltConveyor to move the parts to the quality control station. You will use the limitswitches mounted on the Gravity Feeder and Belt Conveyor to detect thepresence of parts, and you will use a TTL output of the Robot Controller to controlthe operation of the Belt Conveyor.

You will also use the task commands If and While to determine which actions toperform.

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Program Flow Chart

The flow chart for this program is shown in Figure 7-6.

Figure 7-6. Flow chart for the quality control station program.

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Suggested Connections

When many input/output connections are required by a program, it is of goodpractice to use a table where all connections are grouped. Table 7-3 shows thesuggested connections for the quality control station program.

EXTERNAL DEVICESROBOT CONTROLLER

TTL INPUT TTL OUTPUT

Gravity FeederLimit SwitchNO contact

1

Belt Conveyor

Limit SwitchNC contact

2

Limit SwitchNO contact

3

Stop

TTL input1

Table 7-3. Input/output connection table.

Program Set-up

G 17. Install the Gravity Feeder and metallic can as shown in Figure 7-3.

G 18. Fill the Gravity Feeder with 2 parts.

G 19. Make the connections shown in Figure 7-7.

Note: Since the connection table shown in Figure 7-1 andconnection diagram shown in Figure 7-7 contain the sameinformation, both methods can be used to illustrate theconnections.

G 20. On the control panel of the Belt Conveyor, set the controls as follows:

SPEED . . . . . . . . . . . . . . middle position between SLOW and FASTLOGIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . HIGHMOTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ENGAGEDIRECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . REVERSE

Turn the power on using the switch located on the left side of the controlpanel.

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Figure 7-7. TTL input/output connection diagram.

G 21. Execute a hard home positioning.

Note: In this part of the exercise, you will save the position pointsusing the Hand-Held Terminal. Once all position points requiredby the program are saved, you will transfer them in the TaskEditor window of Robotics where they will be associated with taskcommands to create a task program.

Creation of the Position Points

G 22. Using the Hand-Held Terminal, pick a part from the Gravity Feeder andplace it in the detection zone (shown in Figure 7-4) of the Belt Conveyor.Save all required points as PCONV01 to PCONV__. Do not forget to reducethe speed when necessary.

G 23. Using the Hand-Held Terminal, pick a part from the Gravity Feeder and dropit in the metallic can. Save all required points as PCONT01 to PCONT__.Do not forget to reduce the speed when necessary.

G 24. Once your points are saved, select Online in the Robot menu of Roboticsto transfer the control to Robotics.

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Writing of the Task Program

G 25. Select New Task Editor in the sub-menu Upload to of the Robot menu ofRobotics to transfer the points in the Task Editor window.

In the Program Information window, enter your name in the Author field andthe date in the Date field, then click the OK button.

G 26. Enter the HOME command in the Task Editor window to execute the step[Home positioning] in the flow chart shown in Figure 7-6.

Note: The expressions shown in brackets correspond to the stepsin the flow chart of the program.

G 27. Enter the OUTPUT(1) HIGH instruction to execute the step [Stop theconveyor].

This will ensure that the conveyor is stopped at the beginning of theprogram (as determined by the position of the Logic switch on the controlpanel of the Belt Conveyor).

G 28. Enter the WHILE INPUT(1) = LOW instruction to execute the step [Part inthe feeder?].

The instruction lines that follow will be repeated as long as the statement istrue. If the statement is false, the program will continue with the instructionline that follows the associated REPEAT command.

G 29. Enter the IF INPUT(2) = LOW instruction to execute the step [Part at thequality control station?].

If the statement is true, the program will continue on the next instruction line.If the statement is false, the program will continue with the instruction linethat follows the ELSE command.

G 30. Transfer the position points named PCONV01 to PCONV__ from the rightto the left column of the Task Editor window to execute the step [Pick a partfrom the feeder and place it on the conveyor].

Note: Press the Ctrl key during the dragging to automatically addthe MOVETO command to each point.

G 31. Enter the WHILE INPUT(3) = HIGH instruction to execute the step [Part atthe quality control station?].

As long as the statement is true, the instruction lines between the WHILEand associated REPEAT commands will be repeated. If the statement is

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false, the program will continue with the instruction line that follows theassociated REPEAT command.

G 32. Enter the OUTPUT(1) LOW instruction to execute the step [Start theconveyor].

G 33. Enter the REPEAT command to return the execution of the program to theassociated WHILE command (WHILE INPUT(3) = HIGH).

G 34. Enter the OUTPUT(1) HIGH instruction to execute the step [Stop theconveyor].

G 35. Enter the HOME command to execute the step [Home positioning].

G 36. Enter the ELSE command.

If the statement IF INPUT(2) = LOW is false the program will continue withthe instruction line that follows the ELSE command.

G 37. Transfer the position points named PCONT01 to PCONT__ from the rightto the left column of the Task Editor window to execute the step [Pick a partfrom the feeder and place it in the container].

G 38. Enter the HOME command to execute the step [Home positioning].

G 39. Enter the ENDIF command to indicate the end of the IF INPUT(2) = LOWinstruction.

The execution of the program will continue with the next instruction line.

G 40. Enter the REPEAT command to return the execution of the program to theassociated WHILE command (WHILE INPUT(1) = LOW).

G 41. Enter the END command to execute the step [End]. This will end theexecution of the task program.

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Formatting the Task Program

G 42. Format your task program as shown to facilitate the reading.

0001 HOME0002 OUTPUT(1) HIGH0003 WHILE INPUT(1) = LOW0004 IF INPUT(2) = LOW0005 MOVETO PCONV010006 MOVETO PCONV02 (*) ...

MOVETO PCONV__WHILE INPUT(3) = HIGH

OUTPUT(1) LOW REPEATOUTPUT(1) HIGHHOME

ELSEMOVETO PCONT01MOVETO PCONT02...MOVETO PCONT__HOME

ENDIFREPEATEND

(*) From this line, the line numbers depend on the number of pointssaved.

Note: You will learn in the next exercises how to addcommentaries to the instruction lines to facilitate theunderstanding of the program.

G 43. Save your program as EXE_7_A.

Program Testing

G 44. Fill your Gravity Feeder with two parts.

G 45. Execute your program.

G 46. Did the Servo Robot place the first part on the Belt Conveyor and thesecond one in the metallic can, then stop at the home position? If not, verifyyour program, and ask your instructor if necessary.

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G 47. Remove the parts from the Belt Conveyor and metallic can, then fill yourGravity Feeder with five parts.

G 48. Execute your program.

While the Servo Robot is moving to the metallic can to drop the second part,remove the part from the belt conveyor (manually).

G 49. Did the Servo Robot place the third part on the Belt Conveyor to feed thequality control station, then the fourth and fifth parts in the metallic can? Ifnot, verify your program, and ask your instructor if necessary.

G 50. What will happen if the program is launched without parts in the GravityFeeder? Explain.

Shutdown Procedure

G 51. Make sure that there is nothing inside the gripper.

G 52. Clear the area around the Servo Robot so that it will not hit anything whenit moves.

G 53. Execute a hard home positioning.

G 54. Turn off the Robot Controller and Belt Conveyor by setting their powerswitch at the O (off) position.

G 55. Disconnect the system and return the equipment to its storage location.

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CONCLUSION

In this exercise, you were introduced to conveyors. You learned that the conveyorof your training system is a belt conveyor, one of the most common types ofconveyors. You learned to control the Belt Conveyor from the control panel andremotely using the TTL outputs of the Robot Controller.

To obtain precise movements and facilitate the programming, you have used theHand-Held Terminal to create the position points and Robotics to program.

REVIEW QUESTIONS

1. Name three types of conveyors.

2. Describe the required settings for the Belt Conveyor to run in the reversedirection (direct control).

3. Name three parameters that can be remotely controlled on the Belt Conveyor.

4. To program the Simulation of a Quality Control Station, explain why it is best touse the Hand-Held Terminal to create the position points.

5. What is the use of the Else command in a If-Else-Endif block of codes?