rsdoran
Lifetime Supporting Member
In an earlier thread I was struggling to learn about all the above to combine 7 Toshiba G7 drives with a Horner (www.heapg.com) OCS250 and a 450 DNET module.
I have had alot of time to work with all 3, I even have it all working in a sense.
What I have
A machine that will use 7 .5HP motors with Toshiba G7 drives to position "stands" to straighten metal. There is a 40 to 1 gearbox the motor mounts to which is dual shaft, a 1000 ppr line driver encoder is attached to one shaft and the other will turn the 2" 8 thread per inch screw that positions the "stands.
The encoder feeds to an ASD Multicom card that is an addon card for the G7 drive. This same card connects Devicenet.
The PLC is a Horner OCS250 with a 450 Devicenet master module attached. I have configured it successfully to work with the Toshiba drives using 8 bytes consumed and 8 bytes produced. With this bytes I have 16 inputs, 16 outputs, 3 words to send data and 3 words to get data. The only data I have sent so far has been frequency reference for speed. The data I recieve is Actual speed (in hz) and Motor Counter Data (matches encoder pulses but is in integer format).
Using what I have I ran into a problem with the Motor count data, the drive is difficult to stop precisely as it is so may overtravel. This is a problem at times, like going to zero to home it. The Motor Count data shifts from -32767 to 32767 if I overtravel when going to 0(home) which makes it go back to high speed and to find home again. Since this is integer data from the drive I have not figured out an algorithm to know when the drive has overtraveled (BUT read on I dont think it will mattter).
My travel distance is only 4 inches in this application so with the encoder/motor count data plus the info about how far the screw will turn per revolution I calculated I could easily travel 8 inches with the data as is, I also determined I only needed to travel 4 inches. Plenty of room to eliminate the overtravel issue.
BUT
This system WILL NOT WORK.
The first clue I got was when I did a position, as is the device is not accurate enough, the big issue being when I goto home (note: I dont have to use 0.00 for home, it can be 1.00). It is never precise, it may be .00125 or -.00125 or whatever off. This means if they shut off the machine that number will change to 0.0000 which will move the stand by that much each time it happens. May not sound like a lot but I am willing to bet this alone would create a scenario to have to reset/readjust the system ever week or so...ie way more than it should ever need.
The other issue is if it loses power while in position. I lose motor count data...ie encoder/position, its now at 0. The only way to reset it is manual move all stands to home then shutdown and restart the machine. Since the motors arent precise this will mean that home is now something besides 1.00.
I have built the panel for this system but as is I see no way to make this work for what is needed even though the application is simple.
I have been told not to worry about this stuff now! Shouldnt you learn if what you have will work before you build panels and install it?
Guess thats my only question. Thanks for taking the time to read this.
Special thanks to Steve Bailey for the help with the PLC and the math for the screw. There are many others that offered help when I needed in and I want to thank them all very much. Special thanks to Eric Nelson and Peter Nachtwey.
I have had alot of time to work with all 3, I even have it all working in a sense.
What I have
A machine that will use 7 .5HP motors with Toshiba G7 drives to position "stands" to straighten metal. There is a 40 to 1 gearbox the motor mounts to which is dual shaft, a 1000 ppr line driver encoder is attached to one shaft and the other will turn the 2" 8 thread per inch screw that positions the "stands.
The encoder feeds to an ASD Multicom card that is an addon card for the G7 drive. This same card connects Devicenet.
The PLC is a Horner OCS250 with a 450 Devicenet master module attached. I have configured it successfully to work with the Toshiba drives using 8 bytes consumed and 8 bytes produced. With this bytes I have 16 inputs, 16 outputs, 3 words to send data and 3 words to get data. The only data I have sent so far has been frequency reference for speed. The data I recieve is Actual speed (in hz) and Motor Counter Data (matches encoder pulses but is in integer format).
Using what I have I ran into a problem with the Motor count data, the drive is difficult to stop precisely as it is so may overtravel. This is a problem at times, like going to zero to home it. The Motor Count data shifts from -32767 to 32767 if I overtravel when going to 0(home) which makes it go back to high speed and to find home again. Since this is integer data from the drive I have not figured out an algorithm to know when the drive has overtraveled (BUT read on I dont think it will mattter).
My travel distance is only 4 inches in this application so with the encoder/motor count data plus the info about how far the screw will turn per revolution I calculated I could easily travel 8 inches with the data as is, I also determined I only needed to travel 4 inches. Plenty of room to eliminate the overtravel issue.
BUT
This system WILL NOT WORK.
The first clue I got was when I did a position, as is the device is not accurate enough, the big issue being when I goto home (note: I dont have to use 0.00 for home, it can be 1.00). It is never precise, it may be .00125 or -.00125 or whatever off. This means if they shut off the machine that number will change to 0.0000 which will move the stand by that much each time it happens. May not sound like a lot but I am willing to bet this alone would create a scenario to have to reset/readjust the system ever week or so...ie way more than it should ever need.
The other issue is if it loses power while in position. I lose motor count data...ie encoder/position, its now at 0. The only way to reset it is manual move all stands to home then shutdown and restart the machine. Since the motors arent precise this will mean that home is now something besides 1.00.
I have built the panel for this system but as is I see no way to make this work for what is needed even though the application is simple.
I have been told not to worry about this stuff now! Shouldnt you learn if what you have will work before you build panels and install it?
Guess thats my only question. Thanks for taking the time to read this.
Special thanks to Steve Bailey for the help with the PLC and the math for the screw. There are many others that offered help when I needed in and I want to thank them all very much. Special thanks to Eric Nelson and Peter Nachtwey.
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