Welding Robot - fischertechnik Computing Starter Pack Begleitheft

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4.4 Welding Robot (see assembly instructions page 21)
Task 1:
The robot should attach the lid on a metal housing at three different posi-
tions with a welding point. The welding electrodes are simulated by a lens
tip lamp, and the three positions on metal housing by yellow blocks.
The robot should move to three different positions one after another and
weld at each one. Then it should return to its starting position and start
again from the beginning.
Because the robot also has to operate independent of the PC in download
mode, it should be possible to trigger a reset via the E8 pushbutton, i.e.,
restart the program from the beginning after pressing and releasing the
pushbutton.
Programming Tips:
x
First move the robot to its starting position (press M1 left until E1).
x
Move then to position 1. Use the POSITION block for this, and count the
impulses at Input E2. You must experiment to see how many counter
impulses are required until the position is reached. The best is to use
the parameter EA as the result in the POSITION block. Then you can
continually change the value on the TERMINAL.
x
Write a subprogram "Weld" for the welding procedure. Switch on the
lens tip lamp (M2) in this subprogram and then switch it off again im-
mediately. Repeat this procedure a few times by programming a loop
and counting a variable VAR1 until the value is 20, for example. Then
exit the subprogram. Don't forget to reset the variable to zero first
(ASSIGNMENT block).
x
Do the same with positions 2 and 3. Use the parameters EB and EC as
results in the Position blocks.
x
Of course, you use the RESET block for the reset, which you place on the
work sheet without a connection to the other blocks (formula entered in
the dialog box: E8).
x
Test the program in online mode until you have set all positions on
the TERMINAL correctly. Then load it onto the interface (Run –
Download), and run it in download mode. It functions there
exactly as in online mode. However, you cannot change the terminal
18
The workshop already mentioned has
now also purchased a welding robot.
Because the owner was so happy
about the way you programmed his
stamping press recently, he also asked
you to get his welding robot running.
First assemble the model according to
the instructions.
parameters anymore, because the interface no longer has a connection
to the computer (i.e., you can change them on the screen, but the robot
will not react to the changes anymore).
x
Don't forget that to return to online mode after a download, you must
interrupt the power supply to the Intelligent Interface for approx. three
seconds.
x You can find the ready-to-run project here under Welding robot 1.mdl.
The program for the welding robot is not especially large. But imagine that
the robot arm would move up and down as well as forward and back in ad-
dition to in a circle. If the robot would move to every position with a sepa-
rate POSITION block as in the example project, and if the robot moved not
only to three, but to more positions, the program would become very large.
When programs become too large, they no longer function in download
mode at some point. Additionally, it is not very elegant to call the "Weld"
subprogram three times. Consequently, we are going to design the program
completely differently in the way that real pros do.
Task 2:
Design the program, so that the fewest number of blocks are required and
the "Weld" subprogram only appears once in the flowchart.
Programming Tips:
x
Before you get started, it can be helpful to read through Chapter 10.4
"Saving Function Blocks – More Efficient Programming in LLWin". Then
you will have a good idea of the solution. Our program will even be-
come simpler.
x
You control the actions of the robot using the variable VAR3. The variable
is raised by one after each action. The robot should do the following in
order:
Value of VAR3 Action
0 Move to starting position
1 Move to position 1
2 Weld
3 Move to position 2
4 Weld
5 Move to position 3
6 Weld