calculating parts per minute using S7 300 and a positioning cam

Join Date
Dec 2003
Location
english living in france
Posts
6
Hi All,
Could anyone give me some pointers of how to calculate the parts per min, on a simple semi auto machine, using S7 300 PLC and a positioning cam for input info.
I have a programme but it blocks from time to time?????? :(
 
kevin churchill said:
I have a programme but it blocks from time to time?????? :(

Kevin

That would be a good starting point, why don't you post your program here, or a screen shot of the relevant part of the program and we might be able to give you ideas on how to improve your current program.

The basic idea would be to just use a counter and a timer (1 minute) when the 1 minute is up, move the current count value to another location for 'storage', reset the counter and timer and away you go.

Just remember that the current counter value (CV) is in HEX, so you will have to move it to a DB area declared as INT.

Paul

P.S I see you are living in France, that's not a bad place to be an Englishman at the moment, but I think Australia would be better!
 
Paul,
Thank you for your reply, you will find attached a copy of the programme in question, I would very much like your thoughts on this.
Best regards, Kevin.

PS. Australia may be better, but can they play rugby "i think not"
 
Hi again Paul,
Just want to add that the program in my attachment of the last post works, but When I send the result to my siemens touch panel display, it only display's my parts per min, every min, as I now have my timer set at 1 min.
I have tried to play with the timer times but then I just get silly results.
I just can't get the damn thing to constantly display the actual PPM in real time without waiting for one min befor sending data to my display.
So I wonder, how do I get S7 to calculate the time it takes the cam to turn 360 degrees to 0, then calculate how many parts I have produced in this time and constantly display the results in real time on my display, updating every 360 degrees.
Please forgive me if maybe I have over complicated things as I know the secret to good programing is keep it clean keep it simple.
I am sure there is a way of doing this, could you or anybody else out there please offer some guidence.
yours most sincerely Kevin.
 
I'm not familiar with your brand PLC (only use AD), but here is my two cents worth. If the cam is one for one, ie one revolution for one part out, why not time the revolution and divide 60 by it. One revolution in 10 seconds. Divide 60(sec)/10(sec)=6ppm(God I hope math is right). I just did a project something like this on a paper folder, but couldn't time revolutions since there are too many variables involved. Like length of sheet, length of vacuum, drag of sheet. I finally counted sheets for 15 sec and then did math...seems to work great except for the 15 sec lag for display update. But this display was just a bonus for the operator to say "HEY, MY FOLDER IS RUNNING FASTER THAN YOUR FOLDER."

Dale
 
Kevin

You say the program that you attached works, that is good.

I had a quick look at the attachment yesterday, but due to having too much work on I didn't have time to have a good look at it.

What you want is to be able to display the 'current' speed of the machine in parts per minute, so if the first revolution of the cam takes 10 seconds then you display will read 6 PPM, if the machine then speeds up and the cam take 5 seconds for one revolution then your display will update and show 12 PPM. Is that correct or do you want to show an average speed in PPM?

As Dale stated he recently done a project like this. Here is the thread on Ron's Forum started by Dale it might be worth having a read of that to help you out.

If you let us know exactly what you want to display, then we can offer advice.

Paul
 

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