In this article, I am going to show you how to properly ground your CNC Construction Set.

A properly grounded machine will help reduce EMI and RFI, and result in a safer machine.

If you plan on adding CNC plasma operations to your CNC Construction Set, then then grounding is even more important.


Please note that this article also applies to the KRMx02, The same electronics are used in both the KRMx02 and the CNCCS. So all the below comments apply.

Star System

I will be using what is sometimes called the Star Grounding System. This means the CNCCS frame will become the common connection point for the various grounds such as PE, Plasma, EMI, and RFI.

Grounding Bar

I will be using the following grounding bar as the tie point on the frame.

You can get one here:

Grounding Bar Kit

Step 1

The 8020 frame components are anodized so the outside of the frame is not conductive.

Take some sandpaper and remove a small patch of the coating in the rear lower left of the frame as shown here.

This is where we will be attaching the grounding bar.

You can use a conductivity tester or meter to test the frame to make sure you got through the coating.

Step 2

Place a 2020mm series 6mm drop-in t-nut into the lowest slot at 1” and 3”, as shown here.

You can get some of these t-nuts here:

M6 T-nut for 2020

Step 3

Take an M6 x 10mm screw and attach one side of the ground bar kit to the frame, as shown here.

Step 4

Use a second M6 x 10mm screw to attach the other side of the ground bar to the frame.

Check continuity from the ground bar to the frame.

Initial Ground Connections

You will be connecting three wires from the bar to the rest of your machine.

I recommend at least 14 gauge stranded wire for these connections. 12 gauge would be better.

Layout Board AC Ground

With the layout board unplugged, remove the cover on the terminal block and loosen the clamp nut on the green ground wire.

Slip the end of one of the ground bar wires under the clamp as shown here.

Tighten and replace the cover on the terminal block.

If you want you can check continuity from the terminal to the ground bar.

CNCCS 48V Ground

Remove the cover on the G540 ground terminal block shown here.

Loosen the screw shown and attach one the ground bar wires here.

Tighten the screw and replace the cover.

Again check the continuity.

Important to anyone not using a G540 Driver

Note the G540 has a common ground and negative DC voltage. If you are not using the G540 as a motor driver, it is very possible that the DC input is not the same as the common ground used for the driver inputs. Connecting the driver power supply negative to the ground bar could blow your driver.

Gantry Ground

Connect the last of the three ground bar wires to the gantry bolts holding the X motor mount in place.

Other Grounds

There will be other grounds that you will be connecting to your grounding bar.

Plasma Cutter Work Lead

If you add plasma cutting operations to your CNCCS, you will connect your work clamp to the ground bar, as shown here.

Here I made my own work cable that will connect directly to the ground bar.

You can purchase the cable here:

6 Gauge Welding Cable

The Dinse 25 connector can be purchased here:

Dinse 24 Connectors

The Dinse 25 end of the cable connects to the plasma cutter.

The other end of the cable connects to the ground bar.

Plasma Cutter Chassis Ground

If your plasma cutter has a chassis lug, connect it to the grounding bar.

Ground Rod

For plasma systems, a grounding rod is a must. Use 6 gauge wire to connect from the grounding bar to your grounding rod.

Even if you don’t plan on adding plasma operations to your machine, a grounding rod could help with other EMI, or RFI issues. In any case it wont hurt.

Layout Board Cover

I plan on making a cover for the electronics layout board. When complete, the cover will be tied to the grounding bar.