In the following several days, we will introduce the common PPGI defect which the PPGI end users often come across. Today, we will introduction the two PPGI defects of PPGI: Paint Stick and Paint Drop. Besides, we will also provide some method for how to resolve the two defects.
1.PPGI Defect-Paint Stick
What is the Paint Stick of PPGI?
Paint stick means: when the PPGI is delivered as Coils or Sheets Status, the paint between coating premier was removed or broken due to the adhesive between top side surface and back side surface.
Why does the Paint Stick happen?
The main reasons are as under:
- The time for Curing coating premier is not enough.
- Some parts of painting premier are extruded
- The paint material type of coating premier for top side and back side is not matched.
- The characteristics of paint
What is the specific performance of Paint Stick?
1.Due to some parts of eye to wall coils are pressed, the back side’s paint is adhesive to the top sides’ paint. The most of time for this defect is happened for the 2+1 paint PPGI (such as when the shipment of PPGI, the layer of PPGI coils is over 1 layer.
2. Sometimes the paint of top side and back side is broken at the same time. The contusion injuries could be found on the paint along the reverse direction of top and back side.
paint stick
2.PPGI Defect-Paint Drop
What is the Paint Drop?
Paint Drop means: When the PPGI is processed by end-users, some parts of paint happens dropping or removing.
What is the reason of Paint drop happened?
Paint Drop is usually related with the following:
- The adhesion strength between painting and sheet or between the coatings.
- The anti scratch property of paint.
- The end-user’s processing machine and processing condition.
The different performance of paint drop is very different due to the different reasons.
-
When the coil is opened, the contusion injuries will lead to paint drop. The paint drop shape is similar as “chicken claw”.
| Item | Description |
|---|---|
| Defect Feature | Spot or a line paint drop along Longitudinal |
| Defect Happened Part | Any parts of PPGI |
| Defect Happened Reason | The processing machine is not synchronized with decoiling machine |
| Inspection | Inspect the corrugated machine is synchronized with decoiling machine or not. When the corrugated machine stops, the decoiling machine must be stopped. Please do not let the coils relax on the decoiling machine |
| Problem Resolve | The paint drop part could be refinished. |
-
The PPGI is scratched when they are corrugated, thus the paint drop is happened.
| Item | Description |
|---|---|
| Defect Feature | Continuous or make-and-break Paint drop along longitudinal with the fixed period |
| Defect Happened Part | Any parts of PPGI |
| Defect Happened Reason | There are burrs on the pinch roller |
| Inspection | 1. To remove the burrs by oilstone or sand paper on the pinch roller. |
| Problem Resolve | 2. To adjust the gap of pinch roller and make the gap of roller is adapted as the thickness of PPGI sheet. |
| -The first three pairs of rollers ‘gap should be the same or smaller a little than the actual thickness of PPGI. The last of four pairs of rollers’ gap should be according to the actual thickness of PPGI and the corrugated type. The gap is about 0.5-0.8mm bigger than the thickness of PPGI. | |
| 3. The other pairs of rollers could be about 1.0-1.5mm bigger than the thickness of PPGI. | |
| The paint drop part could be refinished. |
How to resolve the part of paint drop on the PPGI surface?
- Lamination and oiling so as to increase the lubrication
- Repair and refinish
How to confirm the appearance of paint drop?
-
The bending angle is the biggest part of the PPGI sheet?
The main reasons are: PPGI production technology (Based Sheet rusty, Prepainting or baking temperature is abnormal.)
-
The corrugated part is the biggest part of PPGI sheet?
The main reasons are: a) the abnormal of corrugated machine such as the part of pinch rollers are defected or the gaps of them are too small. b) The performance of anti-scratch is bad.
-
The paint drop on the PPGI is happened during the decoiling:
The main reason is tension wave during the opening coils.
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Are the PPGI coils at the warehouse over 1 year?
The main reason is: Time effectiveness of painting.
Hot to resolve the problem of paint drop(PPGI defect):
- Adjust the gap of pinch rollers or bending agle.
- Remove the burrs of rollers
- Increase the lubrication (use oiling or wax)
- Avoid of coil tension change during the opening the coils
- Lamination during corrugation
- Repair by professional refinishing paint.
- To use those defect PPGI as other usage
- Make further test and analysis of PPGI. (bending and anti-scratch)
