scope:

Description of Driving Event:

1. During the machining and removal of tooling tabs located in a small closed pocket on a bulkhead, one of the loose tabs became entrapped in an adjacent corner. The end mill subsequently struck this loose tab, causing ti eject, resulting in damage to the product. The damage was found to include a bent rib and an approximately 2-inch crack The operator was trained but inexperienced in this particular machining operation.Cutter path verifications using software simulations are useful for detecting most types of part / tooling collision programming errors, but they cannot anticipate how detached tabs (or other waste material or debris) may fall into the a pocket, tooling, etc., and be struck by the mill. On any automated (or manual) machining process, detached parts or debris must be accounted for so they do not hamper the process.

2. Cost of rework estimated at $10K.

Lesson Submitted from the Boeing International Space Station (ISS) Lessons Learned Database:

a. from Boeing ISS dated 4/14/97, was entitled "NC Programming: Tooling Tab Removal"

b. from Boeing ISS dated 4/15/97, was entitled "Bulkhead Damaged During Final N/C Milling"