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  1. #205
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    Default Re: 2nd build - For a friend

    Quote Originally Posted by WhiteWolf View Post
    Which VFD do you have? I dont know as much as you two gentlemen, just starting to wrap my head around all this but it seems to me that the Hitachi WJ200 was designed to be ran remotely over an ethernet network according to the literature on the Addon card. I cannot imagine that their modbus implementation was not designed to give accurate and relevent feedback due to this design goal but i could be wrong.
    My post you quoted was just stating how most, if not all VFD retrieve current RPM via Modbus, whether its Ethernet or RS-485, and is very accurate. What I meant by waste of time is a waste of resources. If I set my RPM to S12000 Modbus will continually write (polling) this string to set frequency to 200hz. Now... if I set up Modbus for RPM monitoring, Modbus would send a read command string and the reply would be 200Hz. To me this seemed redundant and a waste of resources. Especially since if spindle comes under load and RPM was reduced the VFD is still going to return it's set frequency 200hz 12000rpm.

    Some of the higher end VFD's like Hitachi have Sensorless vector Control (SLV) and utilizes control algorithms for motor control. If you were able to set up and read from this address than it may be possible to see a drop in RPM, I really don't know for sure and would be interested in reading of someone who accomplished this. This still wouldn't be actual spindle rpm, the only way to achieve that is with additional hardware.

    Dan

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    Huanyang VFD and LS Industrial Systems VFD



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    Default Re: 2nd build - For a friend

    Quote Originally Posted by WhiteWolf View Post
    I cannot imagine that their modbus implementation was not designed to give accurate and relevent feedback due to this design goal but i could be wrong.
    WhiteWolf, I checked the manual of your WJ200 and it seems that in functionality it is very similar to my Bosch Rexroth EFC5610. It is also a Sensorless Vector Control type (yours called "SLV") and has the same monitoring possibilities and the responses are based on READING of values, not mirrored commands. In other words, the monitored ACTUAL frequency is the actual frequency output to your motor by the VFD. There is also a "speed arrival" flag (called Frequency Arrival Output on page 176 of your manual) which can be monitored if you want to skip the fixed dwell delay otherwise necessary.

    Like I said earlier, the RPM drop under load is not important because it should be handled by correct configuration of the VFD or the actual milling process. If your VFD is in sensorless vector control mode then the VFD will keep the RPM necessary for the load to keep a constant torque. You need to tune the VFD to your motor to get optimal functionality. Auto tuning might work, but in my case I had to adjust a few parameters manually. Unfortunately, I don't remember which of my parameters were incorrect after auto tuning, but it was not very difficult to get it right.

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    Default Re: 2nd build - For a friend

    LOL yes, and when READING these values it will read what you set your RPM to regardless. Just like I posted. So make sure you have VFD set up properly.

    Dan



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    Default Re: 2nd build - For a friend

    Quote Originally Posted by Dan911 View Post
    My post you quoted was just stating how most, if not all VFD retrieve current RPM via Modbus, whether its Ethernet or RS-485, and is very accurate. What I meant by waste of time is a waste of resources. If I set my RPM to S12000 Modbus will continually write (polling) this string to set frequency to 200hz. Now... if I set up Modbus for RPM monitoring, Modbus would send a read command string and the reply would be 200Hz. To me this seemed redundant and a waste of resources. Especially since if spindle comes under load and RPM was reduced the VFD is still going to return it's set frequency 200hz 12000rpm.

    Some of the higher end VFD's like Hitachi have Sensorless vector Control (SLV) and utilizes control algorithms for motor control. If you were able to set up and read from this address than it may be possible to see a drop in RPM, I really don't know for sure and would be interested in reading of someone who accomplished this. This still wouldn't be actual spindle rpm, the only way to achieve that is with additional hardware.

    Dan

    ****EDIT*****

    Huanyang VFD and LS Industrial Systems VFD
    I have a lot ahead of me in learning to setup my CNC, then learning to use it. But I am a programmer, once i wrap my head around all this and feel comfortable with the machine, I will start experimenting.



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    Default Re: 2nd build - For a friend

    WhiteWolf -

    I have a Hitachi WJ200- 022SF.

    I was reading the manual last night specifically looking for ways to interface/control it and there are several. The typical ones such as MODBUS, 0-10V, PLC (Hitachi calls this one Intelligent Terminal and it uses discrete logic level inputs), Pulse train, Analog current, and I think thats it. SOme are just speed setting with no feedback and MODBUS and PLC obviously polling type networks. From a non-programmer perspective of the DIY'er two options interest me; I could simply use 0-10V for speed control and I could monitor current with a display guage connected to the right terminal. I would rather monitor current than RPM since the VFD will always try to maintain a constant RPM and by monitoring current, it will tell me how hard its working to to do that. Can I monitor and display current output with MODBUS?

    Second, the Pulse train input option seems like the same signal type as step-and-direction signals?? Can someone confirm or refute? If it is, UCCNC can output Step-and-direction signal for spindle control. If that works and works better than 0-10V, (Gerry said his results using 0-10v control were unsatisfactory and he was leaning toward MODBUS) then that and the current display gauge would work well for me.

    The input specs for the Pulse train listed in the manual is 24vdc, 32KHz max.



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    Default Re: 2nd build - For a friend

    Quote Originally Posted by Dan911 View Post
    LOL yes, and when READING these values it will read what you set your RPM to regardless. Just like I posted. So make sure you have VFD set up properly.

    Dan
    LOL indeed. This is from page 176:

    Frequency Arrival Output - The frequency arrival signal, [FA1] or [FA2], is intended to indicate when the inverter output has reached (arrived at) the target frequency. You can adjust the timing of the leading and trailing edges of the signal via two parameters specified to acceleration and deceleration ramps, C042 and C043. Refer also to chapter 4.
    Explained in more details on page 258 and 259.

    Registers 1001 (hex) is the value (read only) of the output frequency (two bytes) and 100B (hex) is the actual frequency value. None of those are a mirrored value of register 0001 and 0002 (hex), which is a read/write type and which is the actual set frequency. So, if you read back the same value all the time then you read the wrong register. When you set the VFD to certain RPM you actually write to 0001 and 0002 but when the frequency is read back it should read 1001 and 1002 or 100B and 100C. Those values together with the Frequency Arrival Output indicate that you are up and running. I agree that reading back the set frequency is pointless, but actual frequency should NOT be the same unless the RPM is up at the set value.

    Note, that I don't have the WJ200, so the above is from the manual which means that I can be wrong, but that is the way my VFD works and from reading the manual of the WJ200, the way I see it, is that the Hitachi works basically the same way, except that I can read back RPM, not just frequency.

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    Default Re: 2nd build - For a friend

    (Gerry said his results using 0-10v control were unsatisfactory and he was leaning toward MODBUS)
    Actually I said that IF the 0-10V results were poor, I'd go the Modbus route. I still haven't hooked it up to try it. I still need to buy a bunch of electronics stuff, and I'm still trying to figure out what I need, so I can buy most of it at once.

    Gerry

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    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  8. #212
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    Default Re: 2nd build - For a friend

    Sorry. I misunderstood.

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2nd build - For a friend
2nd build - For a friend