Noise, EMI, & Grounding


Some customers might find their machine is stopping mid-way through a job or disconnecting from their g-code sender. This behaviour has many causes, the most common being static buildup / electrical noise causing inconsistent CNC behaviour. Most times, you can trace this back to your dust collection system. Dust collection inherently generates static electricity when fine wood dust flows through plastic components such as hoses and cyclones. If your dust collection system is not set up with proper grounding these charges will find and disrupt the LongMill controller.

If you believe this is happening to you, you can bring cutting reliability back to your machine by having an escape path for built-up charges. This ‘ground point’ works because it’ll be a path of least resistance which stray charges will prefer to take instead of sticking around

Before starting, ensure that you only use one ground point for your entire machine setup (including dust collection). For example, if your home has just one electrical panel, you can ground it on that or the attached ground stake outside. This avoids possible ground loops which can create additional interference.


  • Bare solid copper wire between 10 to 18 AWG
  • Fastening hardware such as prong connector, screw, or ground plug
    • Depending on how you wish to fasten the wire, you may need to drill a hole into enclosures, solder and/or crimp wire ends

You can also pick up something like the Grounding Kit that’s offered by Lee Valley. This is a collection of essentially speaker wire, twist-on wire connectors, and some screws:


  1. Wrap the copper wire around the body of the dust shoe and hose securely. Take any steps necessary to avoid getting the wire caught in any moving parts.
  2. Fix the wire in place with your fastening method of choice at the dust shoe end.
  3. Fix the wire in place at the ground end, with some slack so that the wire does not constrain the movement of the machine. Directly attach the wire to the ground stake or through grounded items such as:
  • Outlet box
  • Electrical box
  • Grounded power bar (3 prong)

UPS Backup for power smoothing

Depending on where you live or how your shop is wired up, power flickers and brief outages can make their way through to your shop outlets. This might not be noticeable for regular power tools, but it can effect precision machines like a CNC or even for a desktop computer. You can identify this problem for yourself if, after grounding your machine, you still get unexpected behaviour from your machine such as:

  • unexpected stopping
  • random disconnects
  • random, single movements that shift your cutting job

A backup UPS solves these issues by continuing to provide power to your computer and CNC temporarily when your shops power flickers off. This will allow you to either keep your LongMill running reliably, or if the power outage is severe, return it to a set point before waiting for power to return.

You can find these on Amazon or big box stores, by searching up “UPS backup 1500VA.” Good quality, high power UPS backups are around $200 CAD. Look for UPS devices with 1000-1500VA and at least 4 plugs with battery backup functionality. This should have enough power to sustain your machine and computer. Depending on the UPS, you can connect your router as well however we recommend prioritizing your CNC and computer first. For information on the power consumption of the LongMill, check here.