DESCRIPTION

TECHNICAL FIELD

The invention describes the process for avoiding warpage during manufacturing of lengthier rib part (Material: Aluminium alloy bar of specification BSL 168 T6511) used for Light Combat Aircraft (LCA). Length of the part is 4800 mm

BACKGROUND OF INVENTION

Rib part is 4.8m (4800 mm) in length having varying section with variable contour; it is having 14 tooling holes with size 8H7 out of which 8 holes are used to locate on the nose box assembly
jig- With the use of conventional process of fabrication it was noticed that warpage of about 8 to 12 mm is occurring in Z direction of the part at the nose box assembly stage on jig, due to this warpage part was to be pushed with light force at one of the end to align to the corresponding pins on the jig.

SUMMARY OF INVENTION

Following aspects were considered while developing new process.

• Slenderness nature of the component

• Machine parameters like Speed, Feed and Depth of cut

• Internal stresses induced during machining

• Number of setups used for machining

• Special fixture requirements while machining

• Storage and handling mechanism of the part Intermediate stress relieving, use of special fixture during rough machining and final machining were adopted while developing new process.

PROCESS DETAIL DESCRIPTION

To produce distortion free parts new process was developed as below

a) A fixture (Fig 1) is designed for holding while machining the part on CNC machine for rough machining as well as finish machining to minimize distortion.

b) Holding fixture was manufactured to accommodate the existing assembly tooling holes, which enabled to avoid additional tooling requirements. ■

c) The Machining parameters for CNC were optimized to use high speed machining.

d) Stress relieving of part was introduced after rough machining and again stress relieving was carried out after final machining in fixture as per below cycle Stress relieving at 140-160 deg c for 3 hrs, Air cool.

e) The same fixture was re designed for transportation and storage of the part to avoid distortion

DRAWINGS

Fig.l: Holding fixture showing locators for loading part Fig.2: Parts mounted on holding fixture

CLAIMS

We claim,

1. Introduction of new fixture enabled to avoid distortion for lengthier complex profiled metal part during fabrication, handling and storage

2. Intermediate stress relieving after rough machining improves the final dimension on the part.