UC 100 Not Respond On Mach3 After Plasma Piercing

[walkerthong]

Hi All, I am having some problem with UC100 motion controller. Below is my configuration.

Win 7 32 bit
Intel I3 6100
UC100 Motion Controller (V2.148) + PMDX 122 Interface Card
Neuron Lite THC Controller
Mach3 Version 3.043.066
PMX 105 Hypertherm Plasma

When normally jog and test run, no problem will occur. But when start to pierce by plasma, mach3 will show error as shown in photo provided below. This only happen when piercing thick material 15 and 16 mm by 105A consumables. When i using Finecut consumables to cut 1.5mm plate, no issue found. So far i did change a screen usb cable, new motion controller, relocated to less noise place and reinstalled whole software.

Also after UC100 motion controller not respond, mach3 will go into a lag status, need to close down and reopen then solve. UC 100 needs to replug in also.

Any help will be appreciated.

Thanks
Thong

[cncdrive]

This sounds like a serious noise issue coming from your plasma unit and effecting your computer and the UC100.
The thing that you have to replug the UC100 to the USB port in order to make it work again means that your computer's USB chipset got an error and gave up the communication and disconnected your UC100,
so you physically have to replug the USB connection to make the USB chipset to reestablish the communication with the device.

Generally speaking about plasma units, they are mostly generating lots of EMI noise and you can make that worse if things are not properly grounded.
For example an only 0.1 Ohms of resistance switching 100Ampers will produce a 10Volts voltage difference on that resistor. And let's say that resistor is your ground wire...

What you should do is to verify the grounding, make sure that everything is grounded to a single point called star ground point and make the ground wires as thick and short as possible.

However there are plasma units which themselves generating too much EMI noise which will be a problem even if your grounding is as optimal as possible.

What the problem with noise is that USB is ground referenced communication and this means that the PC and the USB device communication data is referenced to a common ground point, this point is the chassis ground potential of the computer, let's call this 0Volts.
When a noise effecting your computer ground, for example a plasma unit is switching high current then this tries to shift the ground point of the PC,
so the ground point will shift and for the USB communication to have no problem the ground of the UC100 also has to shift,
otherwise if the UC100 ground point will not shift together with the PC ground then the communication channels (D+ and D-) voltage levels will go out of range and that will cause the mentioned problem,
a serious communication error when the USB chipset will finally give up and make a disconnection.

The issue is that however the ground point of the PC and the ground point of the UC100 is electrically the same potential, because they are connected together via the USB cable's ground wire,
but every cables have an inductance and resistance, so if the PC ground point moves fast enough will cause a problem, because due to the cable's inductance and resistance the UC100 ground point can't move with infinite rate and there can be cases when it will lag behind, so the ground points will shift in voltage causing the problem.

What you could do is:

1.) Try to elliminate the noise or at least reduce it to a level when it will cause no more problems.
2.) Try to connect a thick wire (>0.5mm^2 and as short as possible) between the PC chassis (ground) and one screw of the UC100 (ground), that will make a lower impedance link between the PC and the UC100 which will help the UC100 to follow the ground shifts better, so most of the noise will be converted from differential to common mode and so they will not cause any more problems.
3.) Use one of our ethernet controllers instead of the USB ones. Ethernet is isolated communication, so there are no common ground points and so this kind of issue will not happen with an ethernet controller. We generally advice to use ethernet controllers only on plasma cutters, because they are powerful noisy devices.

[walkerthong]

Good day admin,
First of all , sorry for unable to upload the photo , the error is UC 100 not respond, Please check the connection and restart the Mach3. Thanks for such detailed explanation and solution, i will try to work out with your solution.
Also, i would like some opinion from admin, is that any effect to reduce noise to UC 100 if i install a EMI filter on pc power plug ?
I noticed that my machine grounding wire is too long and thin as 6mm only. Also, raw voltage is used by my THC instead of divided voltage. (I am guessing these cause noise issue)
I could not use ethernet controller as my thc already use ethernet connection.

[Gary Campbell]

Plasma is almost always problematic. Some brands more so than others. I would suggest that you hook up an oscilloscope to the equipment ground, the usb ground, and any other low voltage terminals you can get. Hopefully you can acquire one that records, although it sounds like you wont have to record very long.

Once you find where the EMI is and what causes it, you can try numerous filters to eliminate the problem.

[walkerthong]

Good day Gary,
Thanks so much for advice. I will track down the source use your method.

[cncdrive]

Good day to you too.

Yes, the UC100 gives the "Not respond" message if the communication was cut, so that message is exactly what I thought about.

Gary is right that with measuring the noise and knowing the frequency domain you could try to install a suitable filter.

Your THC using Ethernet should not be a problem in using ethernet also for the motion controller.
Ethernet is not a point to point communication (like how USB is), so even if you have only one ethernet connector on the computer you could add an ethernet router with more ethernet ports and then set it up and connect more than one ethernet devices.
However you should ask the NeuronTHC guys about this first to make sure it will work.
The UCCNC and our motion controllers can handle it without problems, the controllers can get their IP addresses even with DHCP, so setting up the router to work as a DHCP server is probably then the easiest solution, so the ethernet router can give the devices dynamic IP addresses, just like when you have a home LAN network, the router can produce and assign the IP addresses to several computers, the motion controllers work the same, they can work with DHCP and can get the IP addresses dynamically from the DHCP server, just enable the DHCP option with our Utility tool which you can find in the UCCNC/Util folder and enable DHCP in the router, or if you running Mach3 then it installs in the Mach3/Plugins/CNCdrive_Util folder.

Or you could set a fixed IP in the route table of the router and connect from the PC side via that.

[walkerthong]

Good day cncdrive admin,
My problem solved ! i changed a new earthing rod with short and thick wire, connect uc100 ground with pc chassis ground and changed to divider voltage, so far no more problem. Great thanks. Appreciated.
Thong

[walkerthong]

Hi CNCdrive admin,
I am also having problem when sometimes my machine Y axis, using stepper Yako driver, only Y1 axis able to move, Y2 cannot move and cause gantry twisted. After restart PC, it will not happen. Any advice ?