1. Workpiece Overcut

Causes:

1. Tool deflection due to insufficient strength, excessive length, or small size.
2. Improper operation by the operator.
3. Uneven cutting allowance (e.g., 0.5mm on curved sides and 0.15mm on the bottom).
4. Inappropriate cutting parameters (e.g., too large tolerance, excessive SF setting).

Solutions:

1. Tool selection principle: Use the largest possible tool with the shortest feasible length.
2. Add corner clearing programs and maintain uniform allowances (keep side and bottom allowances consistent).
3. Adjust cutting parameters reasonably, and round off corners with large allowances.
4. Use the machine’s SF function for operators to fine-tune speeds for optimal cutting performance.

2. Centering Issues

Causes:

1. Inaccurate manual operation by the operator.
2. Burrs on the mold perimeter.
3. Magnetism on the centering rod.
4. Non-perpendicular mold edges.

Solutions:

1. Double-check manual operations; center at the same point and height repeatedly.
2. Remove burrs with an oilstone or file, wipe clean with a rag, and confirm by hand.
3. Demagnetize the centering rod before use (consider ceramic centering rods).
4. Check mold perpendicularity with a dial indicator; consult fitters for solutions if errors are significant.

3. Tool Setting Issues

Causes:

1. Inaccurate manual operation by the operator.
2. Improper tool clamping.
3. Errors in fly cutter blade installation (fly cutters inherently have minor errors).
4. Tolerances between R-end mills, flat-end mills, and fly cutters.

Solutions:

1. Double-check manual operations; set tools at the same point repeatedly.
2. Clean the tool shank with an air gun or rag before clamping.
3. Measure the fly cutter arbor when installing blades; use a single blade for surface finishing.
4. Create a separate tool setting program to avoid errors between R-end, flat-end, and fly cutters.

4. Collision – Programming

Causes:

1. Inadequate safety height or no safety height set (G00 rapid feed causes tool/chuck to hit the workpiece).
2. Mismatch between the tool listed on the program sheet and the actual program.
3. Errors in tool length (cutting edge length) or machining depth on the program sheet.
4. Mistakes in Z-axis zeroing values on the program sheet vs. actual settings.
5. Incorrect coordinate system setup during programming.

Solutions:

1. Measure workpiece height accurately to ensure the safety height is above the workpiece.
2. Ensure tool information on the program sheet matches the actual program (use automated program sheets or images for clarity).
3. Measure the actual machining depth on the workpiece; specify tool length and cutting edge length clearly (typically, the clamping length should exceed the workpiece by 2–3 mm, and the cutting edge should clear by 0.5–1.0 mm).
4. Perform actual Z-axis zeroing on the workpiece and document values carefully (double-check manual entries).

5. Collision – Operator

Causes:

1. Incorrect Z-axis depth setting.
2. Errors in centering, touching off, or data input (e.g., single-side zeroing without accounting for tool radius).
3. Using the wrong tool (e.g., using a D10 tool instead of D4).
4. Running the wrong program (e.g., executing A9.NC instead of A7.NC).
5. Mismatched handwheel direction during manual operation.
6. Incorrect direction when using manual rapid feed (e.g., pressing +X instead of –X).

Solutions:

1. Confirm the zeroing position (bottom, top, or analysis surface) when setting Z-axis depth.
2. Double-check centering, touching off, and data input results.
3. Cross-verify the tool with the program sheet and code before clamping.
4. Run programs sequentially in order.
5. Improve the operator’s proficiency in manual machine operations.
6. Raise the Z-axis above the workpiece before moving rapidly in manual mode.

6. Surface Finish Accuracy

Causes:

1. Unreasonable cutting parameters leading to rough surfaces.
2. Dull tool edges.
3. Excessive tool overhang or cutting edge extension.
4. Poor chip evacuation, air blowing, or coolant flushing.
5. Inappropriate tool path (consider climb milling where possible).
6. Workpiece burrs.

Solutions:

1. Optimize cutting parameters, tolerance, allowance, spindle speed, and feed rate.
2. Regularly inspect and replace tools as needed.
3. Minimize tool overhang during clamping; keep cutting edge extension to a minimum.
4. Adjust spindle speed and feed rate appropriately for flat-end, R-end, and round-nose tools.
5. Burrs are related to machine performance, tool condition, and tool paths. Understand the machine’s capabilities and perform touch-up passes on burr-prone edges.

For more information, contact Debaolong Seiko.