I need to build a pick and place device using two pneumatic cylinders, one for the horisontal and one for the vertical movement. Vacuum will be used to pick up the plastic parts; typically 7.0 mm diameter x 1.6 mm thick. I also want to use normal limit switches at the end of each stroke, not magnetic reed switches.
Can some one help me with the design of a basic circuit please?
The device will be used as a good visual display of electrical and pneumatic utilisation.
Thanks,
Dave Pretorius.
It's not clear what you have to do. I suppose it's about this sequence:
vertical up
horizontal right
vertical down
pick object with vacuum
vertical up
horizontal left
vertical down
release objet (stop vacuum)
end of sequence
So you just have two pusbuttons to control the system: one is called "reset to start position" and the other is "do picking sequence". Is this correct?
All this must be done with a relay logic?
Yes, you are correct, sorry for not givving all the details. Yes I would like to use relays only as I have no experience using a PLC.
The control circuit can be in any voltage. I will buy all the relays, timers etc. You just say what I need.
It's non so easy ... a simple PLC with few I/O would be the best solution.
Anyway, here is I/O table:
Code:
Inputs
------
FU ........ up switch (pressed when arm is up)
FD ........ down switch
FL ........ left switch
FR ........ right switch
PR ........ reset pushbutton
PC ........ start-cycle pushbutton
Outputs
-------
VU ........ up valve (moves arm up)
VD ........ down valve (moves arm down)
VL ........ left valve (moves arm left)
VR ........ right valve (moves arm right)
VV ........ vacuum valve
Here are the movement statuses
Code:
5
<---------------------------
| ------------------->| ^
| ^ 2 | |
| | | |
6| |1 3| |4
| | | |
v | v |
End Pick
Start
Here is a starting poi for the program.
K1, K2, ... are relays, each one is a memory of a movement state
Code:
Movement (1)
PC FD FC K2
---| |---| |---| |-+-|/|------(K1)
|
K1 |
---| |-------------+
Movement (2)
FU K3
---| |-------------+-|/|------(K2)
|
K2 |
---| |-------------+
...
where -| |- in an NO contact, -|/|- is an NC contact