[FrisscoCBR]

Okay, so this is my first post here.

Hello, i have a really big problem with what is thought to be interference from vfd, here i will explain how it is manifested.

First thing first, i created my cnc from basically scratch(see attached picture), most parts are 3d printed, only the base and the rails are metal, everything else is either MDF or PLA 3d printed plastic. I thought i would make a small cnc with a makita tool for milling, but as things progressed i created a cnc that is 2m long and 1m wide and a 1.5kw spindle on it.

The brain of the machine is an Arduino uno with a Protoneer CNC shield 3.0 on top of it and 3 A4988 drivers in it for X and 2 Y axis motors, i am using pretty small motors but planing to upgrade to 2.8A 57BYGH 2.1Nm steppers with TB6600 as a driver with power of 36v for the driver, this i have on the Z axis becuase the small motor could not lift the spindle becuase it weights 5kg.

I am using openbuilds control as a control software, and GRBL version 1.1h(latest one) .

Now that the description is done i can explaing the problem, the problem starts when the spindles VFD is turned on, i get noticable noise on my LCD screen and it is actually coming from the graphics cards of the control pc, the main problem is that whenever i turn on the vfd with the software the arduino gets stuck and would not respond untill i disconnect the usb and reconnect it and that happens every time, notihing else would work to get it out of that state.Without the VFD everthing runs smooth as it can be. I also get the unknown error code 31 from the software when that happens. The things that i already tried to fix this are as follows:

1.Installed EMI filter in front of the VFD
2.Seperated vfd from the rest of the controls(it is mounted on the wall in a metal box that is also grounded)
3.Grounded the base and everything metal from the machine
4.Unscrewed the connector on the spindle and connected the ground pin properly to the chasis, because a lot of spindles come without it connected, and mine was ons of that type
5.I am using shielded cable from the VFD to the motor and the shield is connected only to the ground terminal on the side of the VFD.
6.On/off switch between the VFD and the Arduino is connected via shielded cable and galvanically isolated via optocoupler.
7.All the motor power supplys and pc power supplys are grounded and the pc chassis is grounded properly.
8.Because the VFD is single phase powered and i have 3 phase power in my house, the VFD and the power supplys are using different phases.
9.All of the grounds are connected together to a single point.
10.All of the limit swithes are normally closed and galvanically isolated via optocupler as that is the best option.

The thing that i am trying now is that i am making a new proper ground point because the house is old and probably has junky ground connections, my grandfather made them himself who knows how, but i know that i have ground for sure in the house.

The one thing that leads me to believe that i have the bad ground is that when the VFD is of the voltage is 0 V between Ground and Neutral and 230 V between Live and Ground as it should be. BUT when i turn the VFD on i have around 4V AC between Ground and Neutral everywhere.

Also to mention is that i tried turning on the vfd via its own terminal with the control cable disconnected. Arduino is doing the same thing it freezes and i have to go through the whole process every time!

So my question is am i correct and is there any way to solve this?