BACK GROUND OF INVENTION

Initially the Jaguar Aircraft Front canopy bubble and Rear canopy bubble part nos 121E-26-301-000 AND 121E-26-401-000 respectively were imported from BAe , Then this was taken up for Indigenisation at HAL ,Aircraft Division Bangalore.

The indigenisation of Jaguar Aircraft Front and Rear bubble was started with Grease Forming tool and forming was carried out but the results were not satisfactory because vision defects occuring due to contact of hot sheet with tool surface. The forming was changed from Grease forming to Vacuum forming wherein the contact of hot sheet with tool surface was avoided. The bubble formed by this method has a good vision and contour.

OBJECT OF INVENTION

The main objective of the invention is to find the alternate process to the existing process (grease forming) to increase the production rate and eliminating the rejection and improving the quality of the component.

DETAILED DESCRIPTION OF THE INVENTION

HAL designed and developed a Vacuum forming tool for forming of canopy by Vacuum method to produce Jaguar Front and Rear canopy Bubble.

Brief desciption forming tool.

The forming tool is made of 2 halves , top and bottom. The bottom half is a box like structure with facility to place the heated sheet and clamping with top tool. The tool has got facility to apply vacuum from the bottom of tool. It also has a contour plane which represents the required contour of the bubble. A glass window is provided to monitor the forming of sheet Refer figure 1 for vacuum forming tool

Material details: 8.3MM CLEAR ACRYLIC SHEET

SPEC :MIL P 8184E TYP 2 CLS 2 POLY 84 (OR)WL5.1415.2

Procedure in detail as follows:
protective covering of Perspex sheet is removed and cleaned with soap water followed by running water , wiped dry using grit free cloth, marked to size , cut and deburred and sheet inspected for any defects. (From the trim line of canopy bubble material is left 150mm extra alround 50mm for clamping , 50mm for aligning, and 50mm as safe zone as shown in Figure-2. o The sheet is loaded to oven and heated to 165 deg c, soaked for 35 min vacuum forming tool is prepared for forming by checking the vacuum working The top tool is hung over bottom tool

• Transfered the quickly heated sheet on to bottom tool, bring down top tool on the sheet, clamped all round, apply vacuum and vacuum form to shape slowly to facilitate forming to exact depth, control the vacuum to form the heated sheet to required shape. The template at the bottom tool is used as reference for forming the sheet, allow to cool

• sheet is removed , moved to trim on annealing tool , trimmed , deburred , cleaned and offered for inspection.

• Bubble inspected for vision clearance , thickness and contour. ref Figure 3 and 4 for front view and side view with vacuum point at centre

CLAIMS
1. The defect free bubble in terms of vision . .
2. Rejections due to grease forming is eliminated.