"Tom Gardner" wrote in message
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snip

Everything I ever need a machine to do is simple. My target project
controls two hydraulic cylinders. The machine makes solid-fill end
brushes. One cylinder holds the cup in a die, the outer cylinder inserts a
bundle of wire, then the first cylinder goes to high pressure and pushes
the cup further into the die that crimps it. As it is now, there are 3
hydraulic valves, five limit switches and two palm switches in series.
Eight 3 to 4 pole-double throw relays and a 24VAC transformer is all that's
in the control box. This is fairly simple with a bit of trickiness. It
runs fine now but it seems like a good project to cut my teeth on while
eyeing more complex machines.

Are the two buttons in series to keep the operators 2 hands on the buttons
while the machine is running?

A nice way to do two hand trip control in a PLC.

Have a timer to start timing on these 2 conditions, button 1 is ON and
button 2 is OFF, OR button 1 is OFF and button 2 is ON. The timer may be
something like a half second or so. This timer rung will have a third
condition that holds it on, that is the timer is done and either button 1 or
button 2 is ON.

This prevents the operator from tying down a button and operating from just
1 button. Since the timer seals itself in if either button is ON, both
buttons must be released to reset the start condition.

Ok, the next rung would be if button 1 is ON and button 2 is ON and Timer is
not done, then start the sequence.

If the 2 hand trip control sequence is started the turn on clamp cylinder
low pressure.

If Clamp cylinder is extended to the clamp position, extend the insert wire
cylinder.

If wire insert cylinder extended then turn on high pressure to clamp
cylinder.

Dwell timer for high pressure?

if high pressure step complete then retract cylinders.

if cylinders retracted and buttons released then cycle reset.

The cycle start condition from the buttons will need to be in every rung
that causes motion so that when a button is released the cylinder stops.

Perhaps you could have it so that it remains in cycle unless both buttons
are released. That way if operator needs to he can release either button,
the motion will stop, but the sequence will continue once the operator holds
the other button again. This would sort of be like a jog mode allowing
operator to stop and continue the sequence.

Just some ideas.

RogerN