Why Is My CNC Machine Vibrating? Let's Sort It Out
Your machine's shaking. Something doesn't feel right. Before you start Googling parts or calling in favours — read this first.
Vibrating or Chattering? Get This Right First
These feel similar but they're not the same, and the fix is different.
Vibration is a low-frequency shake through the frame — you'll feel it underfoot. Chatter is faster and leaves wave patterns on your finished surface.
Both are fixable. But you need to know which one you're dealing with.
The Usual Suspects
We see these every week across the UK:
• Worn spindle bearings — gets worse at higher RPM, often with a low rumble. Classic sign the bearings are on their way out.
• Tooling out of balance — a tool not running true wobbles at speed. Your surface finish knows before your ears do.
• Loose workholding — aluminium or PVC not properly clamped will flex against the cutter. Check the clamps before you blame the machine.
• Ball screw wear — tiny play in the axis drive shows up as vibration during cutting moves. Easy to miss, gets worse fast.
• Machine not level — seriously, check the feet. A rocking machine sends vibration everywhere.
• Feeds and speeds too aggressive — pushing aluminium too hard drives it into resonance. Back the feed rate off and see if it stops.
Quick 2-Minute Check
Run the spindle at different speeds with no tool loaded and just listen.
Noise peaks at a certain RPM? That's resonance or bearing wear. Consistent at all speeds? More likely mechanical looseness.
Then do a quick walk-around — loose guards, swarf in the wrong place, anything visually off. Nine times out of ten, the answer's staring you in the face.
Still Shaking? Time to Call It In
Workholding fine. Tooling fine. Machine level. Still vibrating?
Stop guessing. Spindle bearings and ball screws aren't things to get wrong twice. We deal with exactly this every week — machining centres, autosaws, bandsaws — all across the UK.
Give us a ring. Our engineers can usually point you in the right direction in five minutes, even over the phone.
0121 272 5242 | service@cncguru.co.uk | www.cncguru.co.uk
CNC Spindle Not Working? Check These First.
Spindle's stopped. Machine's stopped. Production's stopped. Before you reach for the phone — give this two minutes first.
Check These First
• Alarm code on screen? Write it down. Don't just click past it.
• Door fully shut? All interlocks happy? Check before anything else.
• Open the cabinet — is the spindle drive showing fault lights?
• Check air pressure. No air = no tool change = spindle won't play.
• Look at the toolholder. Swarf on the taper or a damaged holder causes grief every time.
Drive Fault or Mechanical Fault?
Drive faults usually show as a clean alarm code. Mechanical faults — worn bearings, dodgy drawbar — show up as noise, heat, or a surface finish that makes you wince.
If it's grinding or running hot: stop it now. Every minute you keep running costs more in repairs.
The Golden Rule
Stop resetting and hoping. If the same fault comes back, it's not having a bad day — it's telling you something's wrong.
Third reset and you're gambling with an expensive part.
Spindle fault stopping production? We diagnose and repair spindles across the UK — usually same working day response.
0121 272 5242 | service@cncguru.co.uk | www.cncguru.co.uk
CNC Alarm Codes — What They Mean in Plain English
Your CNC just threw an alarm. Before you start pressing Reset and hoping for the best, here's what the different codes actually mean.
What the Main Alarm Categories Mean
• Axis/servo alarms — something's wrong with a movement axis. Could be electrical, mechanical, or a feedback signal issue.
• Spindle alarms — the spindle motor or drive has detected overload, overheating, or an encoder fault.
• PLC alarms — a safety circuit has flagged something. Door not closed, pressure switch unhappy, limit switch triggered.
• Program alarms — something in the NC code doesn't make sense to the controller.
• Communication alarms — the controller has lost contact with a drive, encoder, or peripheral.
• Battery low alarm — this one needs acting on fast. See below.
The Battery Alarm — Act on It Now
That small lithium battery keeps all your stored data alive when the machine is off — parameters, tool offsets, programs. When it dies, that data goes with it. Battery swap is cheap and simple, but must be done while the machine is powered on to avoid data loss. You've got a few weeks — don't sit on it.
When the Same Alarm Keeps Coming Back
One-off alarm that clears? Possibly a glitch. Same alarm repeating? Something is failing. Every reset just masks a deteriorating component. Get it diagnosed before a small fault turns into a big repair bill.
Got an alarm you can't figure out? Give us the machine make, the code, and what it was doing — we can often diagnose remotely. Give us a ring.
0121 272 5242 | service@cncguru.co.uk | www.cncguru.co.uk
CNC Machine Won’t Home — Causes and Fixes
Your CNC machine won’t home and nothing will run until it does. Here’s what to check.
Why Homing Matters
Homing is your machine finding its reference point. Without it, the controller has no idea where any axis is.
Most controls won’t let you run a single program until all axes have homed correctly. No home, no go.
Most Likely Causes
• Home limit switch failure — swarf and coolant wear these out over time.
• Switch cam bent or knocked — the physical trigger for the switch has shifted.
• Wiring fault — broken or loose connection. These can be maddeningly intermittent.
• Servo drive fault — if the drive has an alarm, the axis won’t move at all. Check for drive alarms first.
• Mechanical obstruction — something physically blocking the axis from reaching its home position.
How to Diagnose It
First question: does the axis actually move during the homing attempt?
No movement at all = drive or electrical fault. Moves but stops in the wrong place = switch or cam issue.
Most controllers have a diagnostics screen where you can watch switch inputs in real time.
If the input doesn’t change state when the switch triggers, the switch or its wiring is your problem.
Homing fault stopping you dead? Give CNC G a ring — we deal with these regularly and can get you sorted fast.
0121 272 5242 | service@cncguru.co.uk | www.cncguru.co.uk
Why Is Your CNC Machine Losing Position?
Holes landing in the wrong place. Profiles drifting out of tolerance as the shift goes on. That's not bad luck — that's axis drift.
What 'Losing Position' Actually Means
A machine that's always been a bit sloppy is one problem. A machine that USED to be spot-on and isn't anymore — that's drift, and it only gets worse from here.
Three Causes, In Order of Likelihood
• Mechanical wear — worn ball screws and linear guides create play. The machine commands a position; the slide doesn't quite get there.
• Feedback faults — encoders clogged with swarf, degrading, or wired wrong feed the controller bad position data.
• Thermal expansion — cold machine, no warm-up cycle, and the whole frame grows as it heats. Drift that settles down by lunchtime is thermal, not mechanical.
Nine times out of ten it's more than one of these stacking up at once.
A Five-Minute Test You Can Run Today
Clamp a DTI on the axis carriage, zero it, jog back and forth. Doesn't return to zero? That gap is your backlash.
Compare it against the tolerance in your manual. Over spec? The ball screw needs attention.
Patch It or Fix It?
Backlash compensation in software buys you accuracy short-term. It doesn't fix worn steel underneath it.
Sooner or later that's a ball screw service or replacement job — and we can carry out both.
Parts drifting out of tolerance is an expensive habit. Get a positional accuracy check booked in before it costs you a batch.
0121 272 5242 | service@cncguru.co.uk | www.cncguru.co.uk
What's That Noise? CNC Machine Sounds and What They Mean
Your machine's been trying to tell you something for weeks — you just haven't been listening.
A new rattle, a grinding note, a rhythmic knock. None of it's random. Here's what each sound actually means.
Grinding or Rumbling from the Spindle
Low grinding or rumbling that changes pitch with spindle speed? That's spindle bearing wear, almost always.
Stop the machine now. Keep running it and a straightforward bearing swap turns into a full spindle rebuild — and a much bigger bill.
Rhythmic Knocking During Axis Movement
• Knock at regular intervals during travel — usually a damaged section of ball screw
• Clunk when the axis changes direction — backlash or looseness in the drive train
Neither needs an instant stop, but don't ignore them. They only get worse.
Squealing or High-Pitched Noise
• From the spindle — dry or poorly lubricated bearing. Check your lube schedule
• During aluminium cutting — tool's rubbing, not cutting. Check tool condition and parameters
• From the cabinet — could be a cooling fan bearing on its way out
Rattling
Usually the least urgent — loose covers, swarf in the chip conveyor, loose fixturing. If it's coming from inside the cabinet though, get it checked.
Heard something you can't place? Describe it to us — we're good at diagnosing machines over the phone.
Call CNC G on 0121 272 5242 or email service@cncguru.co.uk.