4 Common Causes & Easy Fixes (No Technician Needed)

Have you ever faced this frustrating situation on site?

The rebar is already set, you press the start button, but the motor doesn’t respond at all.
The schedule is tight, sweat is pouring down — and the machine lets you down at the worst moment.

Good news:
In most cases, a rebar thread rolling machine motor that won’t start is caused by simple, common issues.
You don’t need to call a technician right away. With basic checks, many problems can be fixed on-site.

Below are 4 high-frequency causes and step-by-step solutions, explained clearly even for beginners.

01. Safety First — Power Off Before Any Inspection ⚠️

Before troubleshooting any issue:

👉 Disconnect the main power supply
(Unplug the machine or switch off the main breaker in the distribution box)

Thread rolling machines use high-voltage three-phase power.
Electrical repairs without cutting power can cause serious electric shock.

Safety always comes first.

02. 4 Common Causes & How to Fix Them (Step by Step)

❌ Problem 1: Phase Loss in the Power Supply (Most Common & Easily Overlooked)

Why it happens

Rebar rolling machines use three-phase power.
If one phase is missing due to:

• Loose wiring

• Broken cable

• Poor contact in the distribution box

…the motor will fail to start and may even burn the coils if forced.

How to check

1. Check the indicator lights in the distribution box

   • Normal: 3 lights ON

   • Phase loss: 1 light OFF

2. Use a multimeter (if available)

   • Normal voltage: approx. 220V per phase

   • Missing phase: 0V

How to fix

1. Make sure the power is fully OFF

2. Inspect the three-phase wires:

   • Loose terminals

   • Broken wires

   • Damaged insulation

3. Tighten loose terminals

4. Replace damaged cables with the same specification copper wire

5. Restore power and test

   • If all three indicator lights are on, the motor should start normally

❌ Problem 2: Faulty Start Switch

Why it happens

Over time, the internal metal contacts of the switch can:

• Wear out

• Burn

• Lose conductivity

Typical signs:

• No “click” sound when pressing

• Button doesn’t return properly

• No response from the motor

How to check

Press the switch:

• No clicking sound?

• Feels loose or stuck?

👉 Very likely the switch is defective.

How to fix

1. Buy a replacement switch with identical specifications
   (Example: 16A / 380V)

2. Take a photo before removing the old switch
   (This helps avoid wiring mistakes)

3. Disconnect the old switch

4. Wire the new switch exactly as shown in the photo

5. Tighten all terminals securely

6. Power on and test

❌ Problem 3: Overload Protection Tripped (Motor Self-Protection)

Why it happens

If the motor:

• Runs under heavy load for too long, or

• Encounters sudden resistance (e.g. oversized rebar)

…the overload protector automatically trips to prevent motor damage.

👉 This is a protection feature, not a fault.

How to check

1. Look at the overload protector in the control box

   • If the red button has popped out, it has tripped

2. Touch the motor housing

   • It may feel warm (normal after overload)

How to fix

1. Let the motor cool down for 5–10 minutes

2. Press the red reset button back in

3. Reduce the load before restarting

4. Power on and test again

❌ Problem 4: Mechanical Overload (Rollers Too Tight or Rebar Too Large)

Why it happens

The motor may be “stuck” due to:

1. Thread rolling rollers adjusted too tight

2. Rebar diameter exceeds machine capacity

Example:
Machine rated for Φ16–Φ25, but Φ28 rebar is used.

How to check

1. Power OFF

2. Try rotating the rollers by hand

   • Very hard or impossible → too tight

3. Check rebar size against the machine nameplate

How to fix

1. Loosen the roller adjustment screw

   • Turn counterclockwise 1–2 turns

2. Rotate rollers by hand until smooth

3. Use rebar within rated capacity

4. Power on and test

03. Important Final Tips (Very Important)

✔ If you smell burnt insulation or the motor housing is extremely hot,
👉 STOP immediately — motor windings may be damaged.
Call a professional technician.

✔ Always use insulated tools when working on electrical parts.

✔ After repair:

1. Test the machine without rebar (no-load test)

2. Confirm smooth rotation

3. Only then resume normal processing

Final Thoughts

Most motor startup failures are simple, fixable issues — not serious breakdowns.
A calm, step-by-step inspection can save:

• Time

• Money

• Project delays

If you maintain your machine well and avoid overload, it will serve reliably for years.