Machine sequence logic, multiple instances vs one master

James Mcquade said:

Jzerb,

in any machine, and I mean any machine!
you have to have manual controls to reset the machine to the home position and clean it out or restart the operation.

what I was talking about was the following and maybe you understood.

if start and not go there
jsr seq 1
jsr seq 2
jsr seq 3
…
jsr seq 7
cycle end
wait for next start instruction.

if start pb and go there
jsr seq 2
jsr seq 3
jsr seq 4
…
cycle end
wait for next start instruction

as I said earlier, you must have manual logic to home the machine AND in the proper order to prevent you from tearing up the machine.

I saw a machine that cost 2.5 million tore to pieces when the company lost power and when power was restored, they hit the home button per the instructions. everything went home all at once and did $250k in damage and took 9 months to rebuild. the programmers were fired by the oem and the oem was not happy having to pay the repair costs and lost revenue bill.

james

Click to expand...

so what i have come up with, and it seems to be working thus far is this.

you have setpoints a,b,c,d,e for vertical machine movement.
you have three different buttons on the HMI, for three different sequences.
i have three different step indexes for each sequence. if youre in one sequence you cannot start another and other safety interlocks etc.

operator hits button for sequence 1. sequence 1 starts, goes to setpoints a,b and is then complete.

operator hits button 2 for sequence 2. sequence 2 starts, goes to setpoint b and is then complete.

operator hits button 3 for sequence 3. sequence 3 starts, goes to setpoints c,d,b,a and is then complete.

i figured overall the easiest way, for my programming skill level, was to do it that way. I have seen it done with the JSR breakup as you mentioned, i even have an older piece of code from a machine done years ago that was programmed by an outside vendor that uses that method, and as much as i liked it i couldnt seem to follow it as easily. Then again, i guess its always easier to follow your own written code.

if there is an issue within any sequence, someone with super user access to the HMI has to log in, reset the step index for the cycle then hit a home button to bring machine to a known position before attempting to start any other sequence.

Experience is the best teacher and we all learn as we do more.
we also develop our own programming methods.

remember who your best friend / worst enemy is... Maintenance
a well documented program that is written in a way that maintenance can easily followed and trouble shoot is priceless. when they call you for help, they do have a problem.

a program that you wrote in 50 rungs instead of 200 that only you can understand is worthless. when it breaks down, maintenance cannot trouble shoot the program because its to complex. the machine is down, production suffers, management hears about it, your boss hears about it, and you are the scape goat who has to reprogram the machine a second time if you are not fired first. only this time, the program has to be approved by maintenance !

Don't laugh, it happens more than you think.

james

James Mcquade said:

Experience is the best teacher and we all learn as we do more.
we also develop our own programming methods.

remember who your best friend / worst enemy is... Maintenance
a well documented program that is written in a way that maintenance can easily followed and trouble shoot is priceless. when they call you for help, they do have a problem.

a program that you wrote in 50 rungs instead of 200 that only you can understand is worthless. when it breaks down, maintenance cannot trouble shoot the program because its to complex. the machine is down, production suffers, management hears about it, your boss hears about it, and you are the scape goat who has to reprogram the machine a second time if you are not fired first. only this time, the program has to be approved by maintenance !

Don't laugh, it happens more than you think.

james

Click to expand...

oh im sure thats no laughing matter. even more id be willing to bet there have been cases where people have failed, been fired, a new hire comes in and fails just as bad if not worse at their attempt.

i do agree with the maintenance being the most important people to look at the program in regards to how you write it. which is why if i have to do something in twice as many steps to make it clearer to a maintenance person i have no qualm with it.

glad we are on the same page.

I have run into several people who think that is the stupidest thing they ever heard (mechanical designer and former engineering manager). the designer also said I was to safety minded and loosen up (NOT ever going to happen !)
my sons work here during the summer and I want them to be safe along with everyone else! be smart, work safely, go home, and return tomorrow !

james