Hi there, once again I am addressing a question for you, guys.
I have a robot Agilus 10 KRC4 with variable frequency drive, that is VFD Sunfar E550 and Beckhoff PLC EK1100 with one module of 16-channel digital input& output. There is no analog outputs unfortunately. I attached a photo of inputs for VFD.
Now, I am wondering how can I control my spindle velocity through any command in my program as it implemented in CNC. without an analog module. May I do it via connecting wires to RS+ and RS- with PL? For what purpose X4 and RS inputs is? I know that X4 is a digital but maybe there is a way to put one frequency on it, is there?
Really, appreciate your help
Possibilites to chage spindle velocity by VFD
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Aleks_Tarasov -
March 2, 2018 at 3:19 PM -
Thread is marked as Resolved.
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That depends entirely on the VFD. What does the VFD require for speed control? You're going to have to read your VFD's documentation in detail.
If the VFD can accept a multi-bit binary input for speed control, then the solution is simple.
If the VFD will only accept analog voltage input, you're more or less out of luck. There is a crude method for generating an analog output by using a hand-built R/C circuit and issuing a train of pulses from the output, but unless you're an experienced electronics person it's easy to get wrong and fry something. Plus it probably wouldn't be very stable.
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KRC4 does not support RS232, RS422, RS485 so this wont work.
Soooo, by far the simplest and cheapest option is to just add an analog output module.
You already have EK1100 and if the ONLY other modules are EL1809 and EL2809, then there will be space to add this even when the I/O are inside KRC4 compact controller. Otherwise add external analog module. -
That depends entirely on the VFD. What does the VFD require for speed control? You're going to have to read your VFD's documentation in detail.If the VFD can accept a multi-bit binary input for speed control, then the solution is simple.
If the VFD will only accept analog voltage input, you're more or less out of luck. There is a crude method for generating an analog output by using a hand-built R/C circuit and issuing a train of pulses from the output, but unless you're an experienced electronics person it's easy to get wrong and fry something. Plus it probably wouldn't be very stable.
Thanks for answering!As for our purposes, it would be enough to have at least two or three variants of rpm for spindle.
Could you please explain in details what it means "multi-bit binary input for speed control"? Is it the same as on the screenshots? I just don't catch how can digital input of VFD change frequency. -
Thank you as well, panic mode!
As I know there must be a library for WorkVisual for this type of module in order to map outputs. Where can I get it? -
i am not sure i follow... please don't make me think more than needed
most VFD will allow you to select speed using few fixed preset (selectable by VFD inputs).
if that is good enough for you, just wire few outputs from your KRC to VFD inputs, and make needed configuration on VFD and in robot.You already mentioned that your KRC uses Beckhoff I/O.
You can get the needed description files from Beckhoff or from download section of this forum.Mapping IO in WoV is explained in WoV help and WoV manual.
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We have this scheme of wiring buttons for controlling start and stop spindle. Am I right that from it the only free terminal for adjusting speed is X4? If yes so it seems to me that I could only set two values for a speed in one direction. That is for X1 and for X4. Correct me please!
Many thanks in advance -
[size=small]i would lie to suggest reading READ FIRST and making sure that question contains [/size][size=small]optimal [/size][size=small]info (not too much, not too little,... should be just right). [/size]
[size=1em]Note: i get tired explaining how to read or how to ask questions. by the time topic finally gets to something usable, i may have already lost the interest. my goal is not to help ONE person. i would like to help MANY and make sure that each topic is CONCISE and USEFUL to others - otherwise there is slim chance that i may still be interested in participating. (only then it is fair to tell someone to "read/search forum" so i don't have to repeat myself). [/size]
Back to your questions:
[size=1em]you are correct... using that setup you can only have two speeds (unlike analogs, digital signal can only have two values).[/size]
[size=1em]note: [/size]
[size=1em]- you still did not mention how many speeds would be ok for your needs. [/size]
[size=1em]- are they specific speeds or you just need ability to change it over some range?[/size]
[size=small]-[/size][size=1em]what range? [/size]
[size=1em]- are there any other devices in the system? (maybe they can talk to VFD)[/size]
[size=1em]- etc.[/size] -
OK, I'll get to the point, sorry for not following some rules.
- the issue was setting the whole range of a frequency/speed that allowing VFD. Not important what a range, cause it would be a particular case. Let it be for example from 10 Hz to 350 Hz.
- no, there isn't any devices as I am concerned
Anyway, I've figured out from the manual that X1-X4 terminals have settings which allows user to set a step in order to send impulses having added/subtracted to current frequency.
Quote from the manual "When the UP is effective, the frequency increases and when DW is effective, the frequency decreases."
Finally the decision is
- buying an analog output module
- playing with digital input of PLC and multifunctional terminals of VFD
- "using a hand-built R/C circuit and issuing a train of pulses from the output, but unless you're an experienced electronics person it's easy to get wrong and fry something"
I think if someone had other VFD it should be something similar. It is a common view of a question, I hope it will be useful for someone.
Thanks to you, men! -
[size=small]350Hz? are you really sure that is a good idea? forcing motor a bit over the limit ok but you are talking 700% of what motor is designed for...[/size]
[size=2]also the low speeds are problem. you probably don't want to go below 10-15 Hz or so unless there is external forced air cooling (even if motor has fan, it will do nothing at such low speed). may want to check that with motor manufacturer first.[/size][size=small]but you decided on solution so - good.[/size]
[size=small][/size]
[size=small]Btw. there [/size][size=small]are always many ways to get the job done.[/size][size=2]since you have digital outputs, one possibility could be to use those outputs and make basic ADC using resistors. This is quite ok for 3-4 bits. [/size]
[size=2]4 bits would give you total of 2^4=16 steps or value range 0-15 or speed increments of about [/size][size=small]6% or so.[/size]
[size=small]someone could also consider only range 40-100% to be useful and have finer steps within that range.[/size]
[size=small][/size]
[size=small][/size] -
Yes, there is air cooling. We have HSD spindle "ET65-08" with a range from 3000 to 24000 rpm and maximum frequency 400 Hz. I calculated that a minimal frequency for my HSD Spindle ET65-08 is 50 Hz (f=p*n1/60). You are right that 10 Hz isn't enough. But based on that data from passport I suggest that 350 Hz would not harm anything.
Your idea with ADC sounds good and interesting! I haven't even thought about. Probably, there would be useful to apply Arduino or another microcontroller! I'm glad, because Arduino is my little hobby now! Thanks! -
[size=2]many people never looked up "gigo principle"
it is much easier to think of solution when boundaries are set.
this is why i keep on pushing for specs and details when asking for help.
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