Epson Printer Knocking Noise and "Guitar String" Twang Sound - Causes and Fixes After 4 Years of Use

Question:

My printer suddenly started making a knocking noise that comes and goes. I also hear what sounds like a guitar string "twang," also intermittent. The printer is still printing correctly and alignment seems fine, but the sounds are very strange.

Here's what I've already checked:

1. The printhead guide rail is clean and properly lubricated.

2. There are no obstructions. With the printer powered off, I can manually move the carriage across the rail without collision.

3. The belt does not appear damaged.

I've been using this printer for about four years to make film transparencies for screen printing, and it has been wonderful until now.

Answer:

 

Understanding the Knocking and "Guitar String" Twang Noise

Since:

• The printer still prints properly

• There are no alignment issues

• The rail is clean and lubricated

• The belt shows no visible damage

• The carriage moves freely when powered off

This suggests the issue is likely developing internally rather than being caused by a physical obstruction.

After four years of regular use-especially in screen printing transparency production-wear-related mechanical stress becomes a realistic factor.

Here are the most common causes.

---

1. Carriage Belt Tension and Resonance (Most Likely Cause of "Twang")

The "guitar string" twang sound is highly characteristic of belt vibration or resonance.

Even if the belt looks intact:

• The internal fiberglass strands can begin to stretch.

• The tensioner spring may weaken.

• The belt can momentarily oscillate during rapid carriage direction changes.

When the carriage changes direction quickly, the belt snaps tight, and that tension release can create a twang-like vibration.

Because your prints are still accurate, this suggests the belt is not slipping yet-but it may be slightly stretched or losing optimal tension.

What to check:

• Inspect belt teeth closely under magnification for wear polishing.

• Check for uneven tension along the belt length.

• Gently pluck the belt (like a string) with the printer off-if it vibrates excessively, tension may be reduced.

• Inspect the belt tensioner spring (if accessible).

If belt tension continues degrading, you may eventually see:

• Horizontal banding

• Slight layer shifts

• Carriage hesitation

---

2. Carriage Motor or Stepper Motor Resonance

A knocking that comes and goes may indicate:

• Stepper motor bearing wear

• Motor gear wear

• Internal vibration under certain RPM loads

Motors can develop minor internal bearing wear after years of use. This typically:

• Does not affect print quality at first.

• Produces intermittent knocking during acceleration.

• Gets louder over time.

If the knocking happens primarily during:

• Fast travel moves

• Startup positioning

• Direction reversal

Then motor wear becomes more likely.

---

3. Encoder Strip or Encoder Sensor Vibration

Even though alignment appears correct, sometimes:

• The encoder strip becomes slightly loose.

• The encoder sensor housing vibrates.

• The strip oscillates when the carriage accelerates.

That oscillation can cause:

• Clicking

• Knocking

• High-pitched resonance

Look closely at:

• Whether the encoder strip is taut.

• Whether the strip brackets are secure.

• Whether the encoder sensor housing is firmly mounted.

A loose encoder strip can sometimes create a "string" vibration effect.

---

4. Carriage Frame Micro-Looseness

After years of use, screws securing:

• The carriage frame

• Motor bracket

• Rail supports

May slightly loosen.

When the carriage rapidly changes direction, the mechanical impulse can create a knocking noise, even though movement feels smooth by hand when powered off.

Check:

• Motor mounting screws

• Rail mounting screws

• Carriage frame fasteners

Even a quarter-turn tightening can eliminate intermittent knocking.

---

5. CR Motor Gear Wear (Less Common but Possible)

Inside the carriage motor assembly are small reduction gears. Over time:

• Gear teeth can slightly wear.

• The mesh pattern becomes imperfect.

• Intermittent knocking occurs during specific torque loads.

If this progresses, you might later see:

• Error codes such as 0xEA CR Motor Error

• Carriage stall errors

• Grinding noises

Since you're not seeing error codes yet, this is likely early-stage wear if it's motor-related.

---

6. Paper Feed (PF) Motor or Secondary Belt Resonance

Sometimes the sound source can be deceptive. A feed motor belt or gear can resonate, especially if:

• The printer does automatic platen movement.

• The paper feed motor activates briefly between passes.

Try isolating:

• Does the sound happen only when printing?

• Does it happen during initialization?

• Does it happen during cleaning cycles?

That can help narrow whether it's CR (carriage) or PF (paper feed).

---

Why It Prints Fine (For Now)

The reason your output is still excellent is that:

• Positional accuracy is controlled by encoder feedback.

• The printer compensates for minor mechanical inconsistencies.

• Early-stage mechanical wear doesn't immediately affect print precision.

However, unusual noises are early warning signs. Mechanical issues tend to progress gradually before performance degrades.

---

Practical Next Steps

Here's what I would suggest:

1. Closely inspect belt tension and condition.

2. Check all carriage and motor mounting screws.

3. Verify encoder strip tension.

4. Observe when the noise occurs (acceleration? return stroke? cleaning?).

5. Consider replacing the carriage belt if the printer has heavy usage history.

After four years of production work, belt replacement is often preventative maintenance rather than repair.

---

Should You Continue Using It?

If:

• There are no error codes,

• No carriage stalls,

• No print misalignment,

• No CR motor error messages like 0xEA,

Then it is generally safe to continue operating while monitoring closely.

However, if you notice:

• Increased noise frequency

• Print shifting

• Grinding instead of knocking

• Carriage hesitation

Then stop and inspect immediately.

---

Addressing printer issues can be complicated because they are very hands-on and mechanical in nature. For that reason, we're not able to provide remote troubleshooting, detailed step-by-step repair guidance, or direct repair support. We do offer in-person diagnostic and repair services through our local evaluation facility at BCH Technologies Printer Repair Service (https://bchtechnologies.com/printer-repair-service). Due to high demand, we operate on a first-come, first-served basis, and it may take a few weeks before we're able to schedule a drop-off. Our services are structured to repair either complete printers or specific assemblies, with clear intake instructions. We do recognize that our rates may not be the most economical option, so we strongly recommend exploring self-help solutions first. A great place to begin is YouTube or our BCH Technologies YouTube channel homepage (https://youtube.com/@bchtechnologies). Use the search icon next to "About" on the right-hand side of the menu bar to find specific topics. After creating videos for over nine years, it's difficult for me to remember every single one, so using YouTube's search feature is the fastest way to locate relevant content. YouTube may also recommend helpful videos from other creators that address your issue.

Again, thank you for your continued support and for trusting your printer to us. We truly appreciate you being part of our community, and we're here cheering you on as you keep your screen printing workflow running smoothly.