For bottled or canned milk powder, usually, there are the following four reasons for sealing.
- The quality problem of bottle/cans and lid.
In many cases, it may be the quality of the bottle and cap. If the bottle and the lid are not well-matched, there may be air leakage when screwing the cap, and the screw cap is not tight.
If the quality of the cap is not good, the hardness is too soft, or the painting process on the outside of the cap is not good, the cap may be scratched when the cap is screwed.
- The debugging of the machine.
The capping machine of milk powder is generally needed to be installed and debugged. If you do not adjust it properly or adjust some parameters at will, it may cause the equipment to comply with the original capping rules. In this case, it is generally recommended to contact the manufacturer, see if it is a matter of adjustment.
For example, the equipment mold is not suitable or the program is not suitable, etc. These are all things that need to be solved by contacting the manufacturer.
Each packaging machine has the best applicable scope. So please consult the manufacturer first when choosing bottles and caps.
For vffs packaging machine for milk powder, usually, there are following three reasons for sealing.
- The melt fluidity of the stretched film heat seal layer.
Usually, the sachet of milk powder is back sealing, The horizontal seal of the packing bag has two layers of stretch film in some places, but four layers of stretch film in some places. The thickness of the film is different, but the same sealing effect must be achieved in one sealing during the horizontal sealing, this requires the heat-sealing PE of the packaging material have a certain melt fluidity under the action of temperature and pressure, in the heat sealing process, fill the sealing area, better seal the junction of two-layer material and four-layer material.
- The thermal adhesive strength of the heat-sealing layer of the stretch film is insufficient.
Thermal adhesive strength refers to the heat-seal strength of the packaging film after being sealed under heat and pressure without cooling. This index is very important for the automatic vertical form to fill seal machine because the working principle of the automatic sachet filling machine is that the stretch film is back-sealed during operation firstly, secondly horizontal sealing at the bottom, thirdly the filling head starts filling, at last, cutting sachets. When the heat sealing knife loses at that moment, the milk powder drops to the bottom of the sachet from top to bottom. If the thermal adhesive strength of the film is not large enough, some parts of the horizontal seal will be blown away at the moment of filling, causing air leakage.
- The powder sticks to the inside of the sealing.
This problem occurs in the horizontal sealing of VFFS machine, which is also the most difficult problem to solve. There are many reasons for this kind of problem, it may be the poor cooperation between the VFFS packaging machine and the metering auger, or the unreasonable design of the unloading valve leads to inconsistent pace during operation, or the floating dust from the blanking material is adsorbed on the sealing area.
If it is the first case and the second case, you need to adjust the accessories of the VFFS packaging machine. If it is the third case, it is necessary to choose the stretch packing film with a certain amount of anti-static agent and slip agent added to the inner layer of PE. At the same time, the anti-pollution and heat-sealing properties of PE materials must be considered.