Nine Common Causes of CNC Machine Collisions
In CNC machining, machine crashes (collisions) typically result from the following nine causes:
1) Programming Errors
Mistakes in process planning, improper sequencing between operations, or incorrect parameter settings can all lead to crashes.
- A. The coordinate system is set with the bottom as zero, while the actual setup uses the top as zero.
- B. Safety height is set too low, preventing the tool from fully retracting from the workpiece.
- C. The second roughing pass leaves less stock than the previous tool, causing unexpected contact.
- D. After programming, toolpaths must be carefully reviewed and verified.
2) Incorrect Notes in the Setup Sheet
- A. A single-edge positioning is mistakenly noted as four-side centering.
- B. Incorrect annotation of the vise clamping distance or workpiece overhang.
- C. Tool stick-out length is either unclear or incorrect, potentially causing a tool crash.
- D. Setup sheets should be as detailed and clear as possible.
- E. When changes are made, old versions should be replaced and destroyed to avoid confusion.
3) Tool Measurement Errors
- A. Tool offset values are entered without considering the tool holder length.
- B. Tool is clamped too short in the holder.
- C. Tool measurement should use proper, scientific methods—ideally with high-precision instruments.
- D. The tool length should exceed the actual machining depth by 2–5 mm to ensure safety.
4) Program Transmission Errors
- A. Calling the wrong program number, or running an outdated version even after changes were made.
- B. The operator must check all program details before machining—such as creation time and date—and run a simulation if possible.
5) Wrong Tool Selection
Using an incorrect tool type, size, or length for the intended operation.
6) Oversized Raw Material
The workpiece blank exceeds the expected size and does not match the programmed dimensions, leading to interference.
7) Material Defects or Excessive Hardness
Internal defects or unexpectedly high hardness in the material may cause tool failure or unexpected crashes during cutting.
8) Workholding and Clamping Issues
Interference from fixtures or support blocks not considered in the program can lead to tool collisions.
9) Machine Malfunctions or External Factors
Sudden power outages, electrical surges, or lightning strikes can result in unexpected machine movement or crashes.
As a high-precision machine, a CNC machining center must be operated with utmost caution. Preventing crashes is essential. Operators must develop the habits of careful planning, thorough checking, and proper machine handling to avoid costly mistakes and damage.
As the saying goes:
“There was once a great job in front of me… until I crashed the machine.”
Ever crashed one yourself? Come share—what did that moment feel like?
