Gambit

You have the wrong idea over OPC. OPC servers (usually a PC) have the driver for the different PLC types. Sot here will be many that support the FX series and the S7. This data is then available for OPC Clients (like SCADA).  Depending on the the client you could then exchange Data between them. Having said that OPC UA is a new standard of OPC which is also available on the PLC hardware level but found in the larger system. For Mitsubishi that would be the iQ-R. But for most systems that is only server and mot client. Also be aware that OPC is not a deterministic network!!! If you still would like to connect these two PLC via OPC you could use something like IBH  https://www.hannovermesse.de/product/ibh-link-ua/207879/A240351 Which supports not OPC Server as Client and has drivers for Siemens and Mitsubishi. Problem is that your FX3 series is not supported. You would have to upgrade it to an FX5 series. Alternatively you could use another network or even easier is to put an HMI Like a Mitsubishi GOT on top which can communicate with both PLC Types and also has the ability to setup exchange of Data between them.  

you can use any Timer you would like. I would use labels and not care which used but....  In your PLC parameters devices TAB you can create more if needed. The  Device/Label Automatic Assign Setting labels are those  used for the compiler. So those are the ones you cannot use yourself. But you can change the settings if you like

In that case i would contact your Mitsubishi Rep.

Your module should be fine. IS the module in the first slot of your Rack after the CPU ?  

Looks Like your QJ71C24N module is to old. Which version is it? you can find out via system diagnostics  

There is nog program ion the PLC because of the battery. There is nothing wrong with the PLC. If you can get the program from the manufacturer of the cutting machine then all you have to do is download the program. If not you'll have to write the program yourself. e-learning courses  

There will be a description in the OPC server you use. But all you have to do is setup the IP adress and define an SLMP port with a port number.  

All you have to do is clear the PLC. (initialise) Online => CPU memory operation => initialization 

FYI -- If you have V1.060 of GX Works 3 you can now also update the firmware of the CPU  via the software. It's now also possible to update the special modules 

Looks like your CPU might be to old. You should update your firmware. (which firmware do you have) Latest version is V14: https://www.mitsubishielectric.com/dl/fa/software/update/plcr/0000000109/r00_r01_02_cpu_14.zip    

ehm any reason Why you like to work with GX Developer if you have GX Works 2 ??? Anyway I guess you would read the program but you would loose all comments and such if it was downloaded with GX Works 2 at all. Also things like Structured text will be now the compiled code Also  a password maybe in the PLC preventing you from uploading it.        

110 Ohm 1/2W

I don't think there are any for free. But if you want to make something yourself you only need to create the SLMP driver which is in the manual.

By default it will start with one but you can change this in the settings: GOT => enviromental =>screen switching /window.... Scroll down to the other settings and select ...Specify the screen no...... and  enter 10 at the end    

There are many ways to get this  data. My question was more what do you want to do with it. (excel vb c# ...) As for a protocol you van use SLMP/MC protocol or modbus or you can make one of yourself.