Common Faults and Troubleshooting Methods for Tool Magazine and Tool Changing Manipulator

During tool changing in a machining center, the robotic arm’s tool arm frequently gets stuck in the tool magazine. The main causes are: unexpected power outages (kinetic energy cutoff), insufficient air pressure, frequent tool changes, machining abnormalities, and mechanical wear of the tool-changing components. Below, we analyze the main causes of tool jamming and their solutions.

1. The tool magazine cannot rotate

Loose coupling between the motor shaft and the tool magazine’s rotary shaft

Tighten the coupling screws.

No PMC output

I/O interface board relay failure

Check the corresponding PMC contact signals.

2. The Tool magazine does not rotate fully

Error in the transmission mechanism

Adjust the transmission mechanism.

3. The tool falls off the robotic arm

Damaged or inelastic robotic arm clamping ring

Replace the clamping ring or readjust it.

Tool overload.

Select the appropriate cutting tool.

4. Tool drop during tool change:

The robotic arm starts pulling the tool before it has reached the correct position.

Adjust the robotic arm so that the gripper firmly holds the tool holder before pulling the tool.

5. Robotic arm tool change speed too fast or too slow:

The tool change cylinder pressure is too high or too low, or…

The tool change throttle valve opening is too large or too small.

Adjust the pressure or flow rate of the tool change pneumatic circuit.

6. The tool holder cannot clamp the tool:

The adjusting screw on the tool holder is loose, or the spring is too loose, resulting in insufficient clamping force.

Turn the adjusting nuts on both sides of the tool holder clockwise to tighten the spring.

The spindle box does not return to the tool change point during a tool change.

7. Key points for protecting the tool magazine and tool changer:

1) It is strictly forbidden to load overweight or overlength tools into the tool magazine to avoid tool drop or collision between the tool and the workpiece or fixture during tool change.

2) When using the sequential tool selection method, ensure the tools are placed in the correct order within the tool magazine. For other tool selection methods, also ensure the selected tool matches the required tool to avoid errors.

3) When manually loading tools into the tool magazine, ensure they are properly seated and securely fastened, and that the locking mechanism on the tool holder is reliable.

4) Regularly check the tool magazine’s zeroing position and the machine tool spindle’s return-to-tool-changing point. Adjust immediately if any problems are found; otherwise, tool changing will not be possible.

5) Keep the tool holders and tool sleeves clean.

6) Upon startup, allow the tool magazine and robot arm to idle to check for malfunctions, especially the limit switches and solenoid valves. Check the robot arm’s hydraulic system pressure and ensure the tools are securely locked in place. Address any abnormalities immediately.

8. Tool Magazine Malfunctions

Major tool magazine malfunctions include: the tool magazine failing to rotate or rotating incompletely; the tool holder failing to clamp the tool; and the tool holder not reaching the correct height.

(1) Tool Magazine Failing to Rotate or Rotating Incompletely: Reasons for the tool magazine failing to rotate may include:

① Loose coupling between the motor shaft and the worm gear shaft;

② Inverter malfunction; check the inverter’s output and voltage for abnormalities;

③ Uncontrolled PLC output, which may cause the relays on the interface board to malfunction;

④ Overly tight machine connections;

⑤ Low mains voltage.

Reasons for the tool magazine not rotating fully may include motor rotation malfunction or transmission mechanism misalignment.

(2) Tool Holder Failing to Clamp the Tool: Reasons may include a loose adjusting screw on the tool holder, a loose spring resulting in insufficient clamping force, or the tool being overweight. (3) Tool holder not in the correct height: This could be due to improper assembly or excessive machining deviation, resulting in inaccurate shift fork position; or an inaccurate or improperly adjusted limit switch, causing incorrect indicator light signal.

9. Tool Changer Malfunctions

(1) Tool not clamped tightly and falls out: This could be due to insufficient clamping jaw spring pressure, loose nut behind the spring, excessive tool weight, or the robot’s clamping lock not functioning.

(2) The tool cannot be released after clamping: This could be due to excessively tight spring pressure, preventing the clamp from retracting. The nut should be loosened to ensure the maximum load does not exceed the rated value.

(3) Tool falls out during tool change: If the spindle box does not return to the tool change point or the tool change point drifts during tool change, or the robot does not reach the correct position before pulling out the tool, it can easily lead to the tool falling out during the change. In this case, the spindle box should be moved back to the tool change point position, and the tool change point should be reset.