Automotive glass

Date: 14 April 2023

Author: Luc Moeyersons

This information corresponds to our current knowledge on this subject. It is offered solely to provide possible suggestions for your own experimentations. It is not intended, however, to substitute for any testing you may need to conduct to determine for yourself the suitability of our advice for your particular purposes.

This information may be subject to revision as new knowledge and experience become available. Since we cannot anticipate all variations in actual end-use conditions, LAMI-Solutions makes no warranties and assumes no liability in connection with any use of this information.

Nothing in this publication is to be considered as a license to operate under or a recommendation to infringe any patent right.

TABLE OF CONTENTS

1. Introduction1.1. Stages of production1.2. Comments

2. Preparation of glass2.1. Stages of production2.2. The glass2.3. Unloading the glass2.4. Cutting the glass2.5. Breaking out of the glass2.6. Seaming2.7. Washing2.8. Separating Agent2.9. Ceramic band2.10. Coated glass

3. Bending the glass3.1. Sag bending3.2. Press bending3.3. Press assisted bending

4. PVB Preparation4.1. Stages of preparation4.2. Interleaved – Refrigerated4.3. Packaging4.4. Unwinding the roll4.5. Adhesion & Moisture control4.6. Stretching

5. Assembly5.1. Preparation of glass5.2. Assembly room

6. Prepressing6.1. A look at different processes6.2. vacuum ring process6.3. vacuum bag process6.4. Roller process6.5. Ovens in use6.6. Edge sealants6.7. Use of clips6.8. Windscreen stacking

7. Autoclaving7.1. A look at different autoclaves7.2. The purpose of autoclaving7.3. Operational parameters7.4. Risk of volatiles evaporation & autoclave fires7.5. The ideal “practical” autoclave cycle7.6. Possible autoclave cycle improvements7.7. Recommended precautions

8. Windscreen finishing8.1. Encapsulation8.2. Trimming of excess PVB

9. Inspection9.1. Defects in the glass9.2. Defects in the PVB9.3. Defects in the laminated glass9.4. the shape of the windscreen9.5. Laboratory testing

10. Lamination Defects10.1. Bubbles10.2. Bubbles: Rule of thumb on root cause10.3 Delamination

5.1.Preparation of glass

5.1.1. Without washing:

5.1.2. Washing:

5.2. Assembly room

5.2.1. Standards of cleanliness:

5.2.2. Windscreen assembly:

6.1. A look at different processes

6.1.1. Overall table:

6.1.2. The basic differences:

Vacuum:

- automated- high investment.

Rolls:

6.2. Vacuum ring process

◦ The ambient temperature vacuum is applied for 20 to 30 minutes.◦ The rings must be cool to avoid edge pinching.◦ The de-airing of rough pattern PVB is easier.

◦ Up to 100 deg. C (Air temp. = Glass temp.)◦ The vacuum is maintained throughout the cycle.

◦ An “oven-tunnel”

- Air temperature:115 - 125 deg. C- Glass Temperature at exit: app. 95 deg. C- Cold de-airing: 20 minutes- Oven Passage: 15 - 20 minutes

The vacuum is maintained throughout the cycle.Ending of vacuum and ring removal at cooler temperatures ( < 40° C) helps to avoid “blow-ins” (edge defects).

6.3. Vacuum bag process

◦ Temperatures of the bags.◦ Temperatures of the glass.◦ Life of the bags. (1-2 years)◦ Specific vacuum of each bag.◦ The heating cycle and temperature of the bags (especially at loading of the W/S sandwich).

◦ Highly curved windscreens.◦ High production volumes◦ Flexibility to deal with various W/S models within the same production run.◦ Energy Consumption remains an issue.

6.4. Roller process

6.4.1. Vertical rolls:

6.4.2. Horizontal rolls:

6.4.3. Single roll process:

6.4.4. Double roll process:

De-airing rolls:

 Faster rolling when risk of bubbles is low◦ Applied on the flat part of the windscreen. Slower rolling when the risk of bubbles is great. Applied on the curved parts of the windscreen, in particular on the trailing edge.

◦ Some adhesion is needed, not only deformation of the surface roughness:- If the PVB is too hot or the speed too great, the rolls may jump over the air bubbles.- If the PVB is too cold, the windscreen may open up after the rolling, allowing air to re-enter.◦ The appearance gives an indication of the quality of calendering:◦ Less transparent than vacuum prepress.◦ Typical appearance.

“Tacking” rolls:

 Edge sealing.

- To prevent compressed air penetration in between PVB and glass during autoclave cycle.

 The air:

-is not removed-is only moved to the trailing edge.

 Glass temperature: 85-105 deg.C

6.5. Ovens in use

6.5.1. Convection (circulating air):

6.5.2. Long wave IR:

6.5.3. Short wave IR:

6.5.4. Micro-waves:

6.6. Edge sealants

6.6.1. Use:

6.6.2. Types:

6.6.3. Risks:

6.6.4. Method of application:

6.7. Use of clips

 Frequently used in areas of poor sealing:

6.8. Windscreen stacking

 6.8.1. Leaf separators:

6.8.2. Rod separators:

6.8.3. Block separators: