Know How & Trouble Shooting
Introduction
High quality of EVA laminated glass is obtained due to followings,
- Proper design, carefully selected materials, parts and components and well constructed vacuum heating and laminating machine.
- Adequate production technology know-how
- Regular machine maintenance
- Qualified EVA interlayer film.
Items 1 and 4 are what we always call ‘hardware”. Item 2 is so called “software” that, sometimes, plays important role when excellent quality of EVA laminated glass is required. Adequate process would also result in high production yield.
Since EVA interlayer is not delicate, handling is easy. The process is simple and easy. A general operator could manipulate the process skillfully after few days of training and practicing.
Process know-how is slightly varied when manufacturing different types of EVA laminated glass.
Parameters Vary In EVA Thickness
When EVA melted in between two pieces of glass during heating, thick EVA interlayer, for instance, 0.76mm flows faster than 0.38mm EVA. Temperature and timing should be slightly adjusted for adequate processing parameters.
EVA Thickness Vary In Design Film Thickness
Suitable thickness of EVA interlayer shall be selected according to different decorative design films. EVA with thickness 0.25mm is generally used for thin design film. Thicker EVA, say, 0.38mm would be better for encapsulation of thicker design film. If necessary, multi-layers of EVA interlayer could be piled up providing sufficient enough EVA materials for proper encapsulation.
Free Air Evacuation
Temperature resistant thin wire net spacer should be placed in between glass and silicon pad edges. The nets prevent top and bottom silicon pads from physically contact to each other. One of the nets should also be overlap with vacuum exits which leads to vacuum pipe outside the silicon pad and all the way to vacuum pump. It allows free room of air evacuation.
Assembled glass should not be placed too closed to silicon pad edges. Enough space should be left for air evacuation.
When there are two or more glass placing within the same silicon pad, spacing between glass should not be less than 10mm.
Proper Vacuum
The vacuum should be -0.1 MPa at steady status. Make sure all vacuum pipes and tubes are well connected with no air leaking.
Enough Glass Cooling
In case cooling fan inside the oven is not powerful enough, Extra fan blowers may be required to boost cooling if necessary, especially when room temperature is high.
Adequate Interlayer Cutting
EVA and decorative design films should be cut in sizes a little bit larger than glass.
Glass Edging & Polishing
If laminated glass is required to further edging and polishing, It is recommended to process at least 24 hours after glass is removed from oven.
Well-Preserved Silicon Pads
Make sure vacuum silicon pads, vacuum bags or vacuum rings are in good shape and well preserved. No holes are allowed. If there is crack, it should be mended before it grows larger.
Selected Glass
Glass Flatness
Glass should be flat enough. If glass is not flat enough, thicker EVA or multi-layers of EVA interlayer are recommended. More attention should be pay with when it is tempered glass which could be wavy.
Glass Thickness
If it is unnecessary, glass with different thickness should not be loaded within same batch, especially when the thickness different is great.
Glass Edge
If possible, glass edges should be polished. Non-polish glass edge would lead to easy wear and tear of silicon pad.
Glass Cleanliness
Glass should be cleaned. If cutting lubricant or oil is used for glass cutting, make sure lubricate or oil are removed thoroughly. If glass is cleaned with agents such as alcohol or acetone, allows agents to evaporate thoroughly before cover the glass with interlayer films.
General Heating Profiles
1.When well-assembled glass with EVA is loaded inside oven, vacuum is started for about 15 minutes at room temperature.
2.It is increased from room temperature to 60 ℃ and keep it for 20 ~ 30minutes.
3.It is then further increased to 130℃ and is kept for duration according to below table.
| Glass & EVA films Thicknesses (mm) | Heating Time at 130℃ (minutes) |
| 4 + 0.38 + 4 | 40 |
| 4 + 0.76 + 4 | 45 |
| 4 + 1.14 + 4 | 50 |
| 4 + 1.52 + 4 | 55 |
| 5 + 0.38 + 5 | 45 |
| 5 + 0.76 + 5 | 50 |
| 5 + 1.14 + 5 | 55 |
| 5 + 1.52 + 5 | 60 |
| 6 + 0.38 + 6 | 50 |
| 6 + 0.76 + 6 | 55 |
| 6 + 1.14 + 6 | 60 |
| 6 + 1.52 + 6 | 65 |
| 8 + 0.38 + 8 | 60 |
| 8 + 0.76 + 8 | 65 |
| 8 + 1.14 + 8 | 70 |
| 8 + 1.52 + 8 | 75 |
| 10 + 0.38 + 10 | 70 |
| 10 + 0.76 + 10 | 75 |
| 10 + 1.14 + 10 | 80 |
| 10 + 1.52 + 10 | 85 |
| 4 + 0.38 + 4 + 0.38 + 4 | 55 |
| 4 + 0.76 + 4 + 0.76 + 4 | 60 |
| 4 + 1.14 + 4 + 1.14 + 4 | 65 |
| 4 + 1.52 + 4 + 1.52 + 4 | 70 |
| 6 + 0.38 + 6 + 0.38 + 6 | 65 |
| 6 + 0.76 + 6 + 0.76 + 6 | 70 |
| 6 + 1.14 + 6 + 1.14 + 6 | 75 |
| 6 + 1.52 + 6 + 1.52 + 6 | 80 |
| 10 + 0.38 + 10 + 0.38 + 10 | 75 |
| 10 + 0.76 + 10 + 0.76 + 10 | 80 |
| 10 + 1.14 + 10 + 1.14 + 10 | 85 |
| 10 + 1.52 + 10 + 1.52 + 10 | 90 |
| Remarks: This table is just for reference. Parameters may vary according to actual situation. Trial and test may be required to obtain the most optimum heating profiles | |
4.Cooling is then started until it is cooled down to 50 ~ 60℃. Vacuum should be remained on throughout the entire cooling period.
Ultra Thin Glass Heating Profiles
| Glass Layers & Compositions | Layers of Stacking Laminated Glass① |
Heating Process |
| 0.5mm Glass + CT② + 0.5mm Glass | 1 ~ 2 Layers |
|
| 3 ~ 5 Layers |
|
|
| 0.7mm Glass + CT② + 0.7mm Glass | 1 ~ 2 Layers |
|
| 3 ~ 5 Layers |
|
|
| 0.7mm Glass + CT② + 0.7mm Glass | 1 ~ 2 Layers |
|
| 3 ~ 5 Layers |
|
|
|
① Stacking of multi-layers of laminated glass results in higher productivity. ② CT refers to the series of ultra clear EVA film. |
||
| Remarks: This table is just for reference. Parameters may vary according to actual situation. Trial and test may be required to obtain the most optimum heating profiles | ||
Low Temperature Heating Profiles
Ordinary EVA films are usually cured at more than 120℃. However, laminated glass with EVA film is sometimes required to cure at temperature not more than 100℃. This is because the glass is usually laminated with functional interlayer such as PDLC film and interlayers for electronic. These functional films may be damaged when temperature is higher than 100℃. Therefore, low temperature cured EVA film is designed for this particular application. Processing parameters of low temperature cured EVA film is.
- Increased from room temperature to 60 ℃ and kept for 20 ~ 30minutes.
- Further increased to 80℃ ~ 90℃ and maintained for 70 ~ 80 minutes.
Trouble Shootings
| Symptoms | Possible Reasons | Recommendations |
| EVA interlayer of finish product is not fully melted | Uneven heating Weak hot air convection |
Extend steady heating time Adjust hot air flow quantity control plate |
| Improper blower wire connection | Reverse blower wiring | |
| Bubbles in centre of finish product | Silicon pads are not well seal | Well seal edges and corners |
| Silicon pads surfaces are perforated or tear | Mended with adequate sealant or replace if necessary | |
| Vacuum pipe and tubes are not well connected | Make sure connected well | |
| Vacuum pipe and tubes are perforated | Replace | |
| Vacuum tubes are nip when oven door closed | Turn off oven, remove tubes when door is open | |
| Vacuum is not powerful enough | Change vacuum pump oil | |
| Glass is not flat and/or EVA interlayer is not thick enough | Employ glass and/or EVA interlayer with enough thickness | |
| Bubbles at edges of finish product | Not enough cooling time and/or glass not cool enough when vacuum is turn off | Extend cooling time and/or turn off vacuum only when glass is cool enough, for instance 40℃ |
| Foggy at glass edges | Glass edges are not clean enough. It could be contaminated with cutting oil. | Remove cutting oil thoroughly. If silicon blanket is found contaminated, try heating the oven to get rid of contamination with empty glass loading. |
| Vacuum pump motor oil is, by very little chance, sucked via hose back to silicon blanket when pump motor is shut down. | Disconnect vacuum hose when pump motor is shut down. If vacuum hose is found contaminated with oil, get rid of it. If silicon blanket is found contaminated, try heating the oven to get rid of contamination with empty glass loading. | |
| Water vapour created on silicon blanket due to high moisture environment. This is usually happened if the oven is not used for certain time which is long enough for water vapor migrated into silicon blankets from environment. | Try heating the oven to get of rid of contamination with empty glass loading. | |
| Too short pre-heating time | Extend preheating time up to 40 minutes at approx. 60 ℃ | |
| Foggy in glass other than edges | Glass is contaminated probably by cleaning agents. | Allow cleaning agent to evaporate thoroughly prior to cover glass with interlayer films. |
| Glass edges’ colour is lighter than glass center | This symptom is usually happened on white or colour EVA films. It is due to too high temperature and/or too long heating time. Melted EVA becomes highly flow liquid when temperature is too high. At that time, vacuum applied pressure on glass. It squeezes melted EVA from edges. Edges has less or even no EVA. Edges becomes lighter than center. | Try lower temperature and short heating time. |
Remarks
All data, information and images contained in this document is just for reference and may vary without prior notice. Xinology is not responsible for any costs or expenses arised in any circumstances due to execution according to this document by any parties.
