PLC driven cutter machine

Wefinish

Member
Join Date
Jul 2014
Location
New York
Posts
14
Hello everybody, first off I would like to say thank you to anybody who is willing to help me.

I have a project I've been thinking about for the last 15 years. I have many of the mechanical problems solved. About a year ago I began to delve into the Control end of the project and quickly learned how much I didn't know about this field.

I'll do my best to provide the details I see asked for in other posts. So here it goes.

About a year ago I bought the book by Jon Stenerson titled "fundamentals of programmable logic controllers, sensors, and communications”. This third edition book help me feel like this was something I could pull off. However now that I am to the point of making connections I'm afraid of ruining expensive electronics.

Machine description:
My machine will be using a single motor to drive a cutterhead roughly 6 feet down a track. It will do so using an acme threaded rod. Upon reaching the end the cutterhead will return to the point of origin and again turn around and repeat the cycle. At the start I would like the motor to ramp up to speed in two seconds then continue to travel to the far end where it will ramp down over two seconds, stop, Reverse rotation, ramp up and continue back to the point of origin at speed until that sensor is triggered. Although I don't know at this point how many of these cycles will be required, my best guess to start would be 200. So I anticipate using a counter to stop the machine when the cycles are completed. In the future possibly some sort of cutter depth detection. At this point I have not purchased any emergency stop devices, but I understand safety is first even though this is a garage project.

I'm sure there are other details I have left out. I will provide them as best I can.

Parts inventory:
Motor– Marathon electric model number MVC 56H17T5301B P
It's a 1/2 horse 230 volt single phase

Controller–Mitsubishi D700

PLC– unitronix jazz micro–OPLC JZ10 – 11 – R10

Switching power supply– SPD 2410

Proximity switches X 2– EI1204PPOPL Carlo Gavazzi
 
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Get a couple of hard wired limit switches to mount at the end of travel of your screw. Verify these switches with your ohmeter and wire them in series with your direction control relays to prevent overtravel and major breakage. You want to set these switches so that at full speed, the machine will stop fully before hitting the physical end of travel. These switches I like to be bolted down, not much adjustment. Operate the machine within the limits of your proximity switches, but protect your machine with hard wired overtravel limit switches wired into the direction control commands for a drive or contactor coils so that you can still operate in the opposite direction in order to correct an overtravel condition, but even a stuck PLC relay output welded on can no longer try to bend the ends of your screw and make awful noises as metal stretches and bolts snap...
 
One other thing, make sure you design it so that if you do hit a switch, you won't be able to coast past it and have the switch turn back on.
 
So this will go back to my ladder code correct? When this series circuit is opened I will need it to latch open. Is that right?
I don't expect a lot of inertia. The cutter is going to resist movement unless motor is pushing it.
 
No - your list makes more sense now. You had a 3 phase drive and a single phase motor. But now we see that the motoris 3 phase so at least that is fine.

Regarding the limit switches ... you can bring a contact back to the PLC but the switches must be able to stop the drive external from the PLC. This is for safety in case the program or PLC goes 'nuts'.
 
They do make limit switches that will stay tripped until manually reset. You could use them for the over-travel switches.
 
I would not use a phase converter - no need. If you have single-phase supply voltage, but a 3-phase motor, then simply buy a variable speed motor drive that uses 1-phase Input, but produces a 3-phase output.
Looking up your Mitsubishi D700 variable speed drive, the D700 model FR-D720S-025-NA would accept 230 volt 1-phase input power, but produce 230 volt 3-phase, 1/2 horspower output power.

See the chart on Page 3 for the D700 Input/Output voltages:
http://www.mewdevenezuela.com/productos/descargasProductos/PSG_Variable_Frequency_Drives_VFD.pdf
 
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The Mitsubishi D700 you listed should be able to take single phase in and drive the 3 phase motor. you need the complete p/n to verify this
 

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