Deformation problem on surface after cabinet foamed 1

[Mox-TT]

Hi, all.
We have a cabinet that is finished by foaming in mould. We got problem that top surface drumed and sheet metal peeled off from foaming. It looks like there is air between them.
below is product information:
Cabinet material: Sheet metal- EN1.4301 (t=1mm) (length=725mm height=600mm Width=450)
Liner material: ABS(t=6mm)
Diameter of exhausting hole: 1.5mm(2 holes at back side)

Foaming information:
Temperature of mould:45 degree
Time of heating in mould: 30mins

Clues: 1. Sheet metal peeled off from foaming when removing mould(Normally top side)
2. It occurs more frequently in winter than summer
3. In the begining the surface is not flat and very hard, after cooling in air for half an hour it can be better and seems flat

My opinion:
It is caused by deformation of 1mm sheet metal when heated in 45 degree.
Do anyone know the reason of this problem? Thanks!

 

[Compositepro]

Your problem is almost certainly caused by trapped gas during injection and foaming. The flow front of the expanding foam must be controlled in such a way that the flow fronts meet at a vent. Once the vents are covered with foam there is no longer any venting possible and any remaining gases will be trapped.

Clue #3 indicates that there is pressurized gas under the sheet metal and when it cools the pressure is lost.

 

[Mox-TT]

In the first time I also guess it was caused by pressure in cabient during foaming, but last week I went to supplier to check foaming and found one cabient had shrink on side surface.It is a little hard to explain this defect. Yesterday I took one cabient and put it in the chamber to heat in 45 degree. But no deformation appeared. Seems more likely caused by pressure.

 

[chicopee]

Perhaps, one control may be that the foam formulation needs to be deaerated before injection.

 

[Mox-TT]

Thx for your comments!
I will check again in supplier side.