DESCRIPTION
TECHNICAL FIELD
The Invention describes a manufacturing process of Windscreen bubble forming for Light Combat Aircraft-Tejas Fighter Aircraft.
The Windscreen configuration is a single bubble type. It is made up of 16mm thick stretched acrylic sheet. However to meet the bird strike requirement at later date, the wind screen frame is so designed that it can accommodate a thicker transparency made of multi layered polycarbonate piles protected on outside and inside with cast acrylic layers.
The windscreen is designed to withstand the temperature variation of limits -54'C to +71'C.The structural elements are optimum in size, in order to minimize obstructions to clear visions. The bubble is also given a generous radius in order to avoid distortion. The materials are non-magnetic so that EMI interferences are less. Design of structure is such that sharp corners are avoided and multiple bolting redundancies are achieved. The Windscreen as a whole does not affect pilot ejection. The quality of the Windscreen is such that it meets the optical requirements of weapon aiming and also minimizes reflection. The design is such that the interchangeability is achieved.
BACKGROUND OF INVENTION
Earlier to achieve the quality of the windscreen bubble there was no proper standard procedure. In manufacturing process there was no standard temperature range, Tolerance Temperature, tools detail & Safety Precaution details. This was leading to confusion for manufacturing Bubble, time consuming and was affecting the quality in each component.
SUMMARY OF INVENTION
For forming of LCA-Tejas Fighter Windscreen Bubble, Procedure has been made which includes standard temperature range with tolerance, tools detail & Safety Precaution, so that final Windscreen Bubble will be achieved. Tolerance of Temperature also may be controlled to the lower band to achieve better results.

DRAWINGS
(1) Windscreen Bubble- (01F-1F-1000-001-O0A),
. (2) Windscreen Assy- (01F-1F-1000-000-00D).
PROCESS DETAIL DESCRIPTION
1. Remove paper covering from acrylic sheet, clean in soap water followed by cold running water, wipe and dry using lint free cloth.
2. Inspect
3. Prepare test specimen Qty 2 nos of dimension 3"x3" for the Reversion test. Prepare test specimen Qty 2 nos of dimension 45mm x 45mm for the Haze test. Reversion test temperature ranges from 98 °C to 106 °C +/- 3 °C .
4. Inspect.
5. Protect sheet, mark and rough trim to suit Pre-forming tool and smoothen cut edges.
6. Transfer Batch No. on to sheet corner and offer to inspection and assist.
7. Inspect the sheet for vision, keeping at an inclined plane in front of a screen with Black background, White horizontal & vertical lines of 25mm square. (Grid check area).
8. Pre-Forming Tool No. 01K-1F-0000-001-000/ 131T1.
Clamp sheet with metal clamp plates and hang sheet inside oven using chain, Load Pre-forming tool over the sheet and tie loosely using soft wire so that the tool can slide down when the forming action takes place.
9. Switch on oven and raise temperature as per Reversion test temperature ranges from 98 °C to 106 °C and allow the pre-form bubble to form, after checking that forming has taken place, Switch off oven, open oven doors and bring the chain closer using rod and pin so that the sheet comes closer to tool contour. Allow to cool slowly to room temperature in oven itself.
10. Inspect pre-forming stage.
11. Forming Tool no. 01K-1F-0000-001-000/ 131T2.
Load on Jig, mark and cut off extra material to tool contour alaround, remove sheet from Jig cut on do all machine and finish file / grind to marking and deburr.
Note: Care to be taken to avoid scratches and tool marks on Bubble.

12. Forming Tool no. 01K-1F-0000-001-000/ 131T2.
Clean tool, Load Pre-form Bubble on tool, lightly tighten with C-clamps alaround, load into oven and raise the temperature at Reversion test temperature ranges from 98 °C to 106 °C. Start the forming cycle by heating the pre-formed bubble.
13. Inspect.
14. Check after oven reaching the required temperature for softening of material. Then fix side plates and clamp lightly with C-clamps alaround . Allow the heating cycle to continue. Check again for forming , after ensuring the forming , tighten fully all the C-clamps and allow the bubble to soak for 2 hrs.
15. Inspect.
16. Remove tool from the oven, check for complete forming in co-ordination with inspection, remove formed bubble carefully from tool and offer for inspection.
17. Inspect
18. Forming Tool No. 01K-1F-0000-001-000 / 13T2,
W/S Bubble Annealing & Trimming Tool No. 01F-1F-1000-000-000/60T1.
Load in tool, adjust to seat snugly mark contour with 10 mm extra remove from tool and cut to marking on do all m/c and finish file / grind to marking with 10 mm extra material alaround .
Note: Use soft packing (or felt) on M/c bed to avoid Scratches.
19. Inspect
20. Note : (1) Test specimens to be carried out on every 5th component as per MIL-P-25690B standard.
(2) This operation is valid only with concurrence of shop inspection. Ref: Snag : A/QMP/LCA/029/14. Dtd.: 05.05.2014 for compliance.
Prepare Test specimen Qty 3 nos of dimension 3"x3" for the Thermal Relaxation Test.
Prepare Test specimen Qty 5 nos of dimension 6"x2" and drill 4.8mm (0.187") dia holes for resistance to Crack Propagation as per MIL-P-25690B standard.
21. Carry out polish for the above test specimens.
22. Inspect Test specimen.
23. Check the Weight of the Windscreen Bubble.

24. Clean the Bubble and Polish the surface using Altupol.
25. Inspect.
26. Protect with Velbex sheet and Protex paper on both sides and cover with Brown paper.
Note: Verify Transparency surfaces are clean and free of Contaminants, Abrasive particles, etc. prior to final wrapping.
27. Inspect and issue a tag.