VFD/DRO problem

T

tstr

Registered
Registered
Joined
Mar 24, 2024
Messages
7
I have added a VFD to my Chinese 14x40 lathe, but ran into a problem with the DRO. When starting the lathe, the numbers on the DRO also start to run. From what I can see, there doesn't seem to be any electrical connections from the DRO to the lathes electrical box, only cables coming to it are the X- and Y-axis data cables and the 230V power cable that is connected to the wall. The DRO numbers stay put when the spindle is not moving but as soon as I start the motor the numbers begin to run.
The electrician that has been giving me some pointers for the installation thought that the VFD may be interferring with the data cables, but at least according to the Aliexpress brochure the VFD should have a built-in EMC-filter. Any ideas what could be the issue and how to fix it?
 
tstr said:
I have added a VFD to my Chinese 14x40 lathe, but ran into a problem with the DRO. When starting the lathe, the numbers on the DRO also start to run. From what I can see, there doesn't seem to be any electrical connections from the DRO to the lathes electrical box, only cables coming to it are the X- and Y-axis data cables and the 230V power cable that is connected to the wall. The DRO numbers stay put when the spindle is not moving but as soon as I start the motor the numbers begin to run.
The electrician that has been giving me some pointers for the installation thought that the VFD may be interferring with the data cables, but at least according to the Aliexpress brochure the VFD should have a built-in EMC-filter. Any ideas what could be the issue and how to fix it?
Click to expand...
so obviously it is interfering.
Do the cables for the DRO have metal shielding?
Are the VFD and DRO near each other. Try moving the DRO head to another area.

Can you show us pictures of your setup? I think most of us would like to know if there's a crosstalk issue, a frequency issue.
And we would need to see the cables how and where they run, the proximity of things to each other, etc.

edit: And welcome aboard HM.
 
Issues like this often require some experimentation. You might try separating cables as far as possible.
Are the units fed from the same power outlet? Sometimes using two different outlets can solve the problem.
Also, trying some ferrite snap-on noise suppressors on the power cabling can often help, as well as making some shield
with aluminum foil on one or both power cords.
Make sure the lathe is well grounded.
Plenty of online info is available- search "EMI interference, causes and solutions"
 
woodchucker said:
so obviously it is interfering.
Do the cables for the DRO have metal shielding?
Are the VFD and DRO near each other. Try moving the DRO head to another area.

Can you show us pictures of your setup? I think most of us would like to know if there's a crosstalk issue, a frequency issue.
And we would need to see the cables how and where they run, the proximity of things to each other, etc.

edit: And welcome aboard HM.
Click to expand...
Now that you said it, the cables do run quite close the VFD but there is not very much to do about that.
Here is the picture of the setup:
vfd.PNG
 
markba633csi said:
Issues like this often require some experimentation. You might try separating cables as far as possible.
Are the units fed from the same power outlet? Sometimes using two different outlets can solve the problem.
Also, trying some ferrite snap-on noise suppressors on the power cabling can often help, as well as making some shield
with aluminum foil on one or both power cords.
Make sure the lathe is well grounded.
Plenty of online info is available- search "EMI interference, causes and solutions"
Click to expand...
Two different power outlets, the VFD is powered by a 400V 3-phase socket and the DRO by a 230V socket.
How do the ferrite suppressors work, I just clip them on the data cables near the DRO, do I need to add them somewhere else?
 
Like I said, experimentation is required. The solution is sometimes the least convenient.
You can try ferrite suppressors on any and all of the cabling. You might even need an additional noise filter for the DRO. Corcom makes various
sizes of those.
Usually the noise is transmitted thru the power cables but it can also be carried thru the air.
Painful as it is, you may need to move the VFD to another location off the lathe. On the back wall perhaps.
 
Mark is, as usual on these topics, correct. Experimentation is necessary.

I'd start by rerouting that power cord to the DRO. Get it as far away from the VFD and it's associated wires as possible.

Typically VFDs are placed inside metal cabinets. Oil, swarf and chips are not friendly to VFDs. Those metal cabinets also provide additional EMI/noise shielding that is not present having the VFD exposed on the back of the machine.
 
so what everyone said above.

I mentioned moving the DRO head, because I thought it would be the easiest to move and it looks like it is.
For testing, take the head of the dro off the mount, move it to the tailstock end for testing, re-route the cables away from the VFD.
plug the DRO into an extension off another outlet further away. move as many DRO cables away from the VFD and it's cables as possible.
Give it a test.

if things work, start working it out and figuring out what you need to do to move things around. Does that DRO head really need to mount near the VFD... ??? That's all I have to say. The rest is the other guys, they are the electronic experts... I like the think I'm the KISS guy. (keep it simple stupid)
 
If there is EMC filtering inside the VFD then it is very minimal filtering. Effective EMC filters are fairly large, probably at least the volume of your VFD if you filter both the input and output of the VFD. Along with experimenting as suggested above, moving the VFD to a metal enclosure a little bit remote to the DRO / lathe and putting EMC filters on the input and output lines of the VFD, very close to the VFD and inside the same enclosure should help a great deal. My VFD of my CNC mill (5 meters away) was messing with the DRO of my lathe (but not with the mills own encoder feedback). For a while I would just not run anything on the mill if I wanted the DRO on the lathe to work. I added a better input EMC filter to the mill VFD and that did the trick. It already had a good output filter.

I usually take the "kill it dead" approach to these noise generators (VFDs) and block the noise at its source.
 
Yep, will have to experiment. Separating the power cables did help somewhat, the numbers are still running but not as fast. I will probably first try the woodchuckers advice with moving the DRO to tailstock end and if that doesn't fix the issue the I will have to try the noise suppressors. Hopefully those will fix it because moving the VFD would not work very well as I can't start/stop the lathe anywhere but on the VFD control panel that has only a 1 meter cable, which is the reason the VFD was mounted on the back of the electric box.
 
You must log in or register to reply here.
Back
Top