Bumps on PET Bottles: Why & How?

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SUMMARY

The discussion centers on the design of PET bottles, specifically the presence of 'bumps' or feet at the bottom. These features enhance stability during production, filling, and usage by preventing tipping and maintaining structural integrity under internal pressure. The feet provide a rigid support that minimizes deformation, unlike a flat surface which could create instability and suction due to condensation. Overall, the design is crucial for ensuring the bottles remain upright and functional throughout their lifecycle.

PREREQUISITES
  • Understanding of PET (Polyethylene Terephthalate) material properties
  • Knowledge of pressure vessel design principles
  • Familiarity with basic physics concepts related to stability and balance
  • Awareness of manufacturing processes for plastic bottles
NEXT STEPS
  • Research the mechanical properties of PET and its behavior under pressure
  • Explore design principles for stability in pressure vessels
  • Learn about the impact of surface area on stability and tipping points
  • Investigate alternative bottle designs and their performance characteristics
USEFUL FOR

Product designers, packaging engineers, and anyone involved in the manufacturing and design of plastic bottles will benefit from this discussion, particularly those focused on stability and structural integrity in product design.

abhiroop_k
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why does the bottom of any average PET bottle have those 'bumps' instead of being flat?
does it have something to do with improving the balance, if so how?
 
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abhiroop_k said:
why does the bottom of any average PET bottle have those 'bumps' instead of being flat?
does it have something to do with improving the balance, if so how?

What's a PET bottle?
 
i meant any plastic (other than glass) bottle generally used for storing cold-drinks, water etc.

:)
 
For stability during production, filling, and end-user use. The factory uses the feet to position the bottles in the factory for various purposes, the end-user relies on them so the bottle doesn't tip over easily. You'll see them in bottles which have internal pressure as the legs are much more rigid than a large flat surface and will remain fairly constant in their shape, making the bottle more stable when unopened, even after a long, bumpy transport.
 
thanks.
:)

how are multiple curved surfaces more suitable for balance as compared to a single flat one?
is it because they account for a larger contact surface area?
 
Also, condensation along with a single flat surface would create a suction to the table which is not desirable.
 
ahh nice hadn't thought of that! :)
 
abhiroop_k said:
how are multiple curved surfaces more suitable for balance as compared to a single flat one?
is it because they account for a larger contact surface area?

Well,
1) The bottles are plastic and so a flat bottom surface would, if unsupported, deflect under pressure creating a bubble on the bottom which would be horrible for stability. Not to mention it would be a pretty poor design as far as pressure vessels are concerned.

2) The legs have less overall surface area touching the table, but they are consistent in shape.

3) There are bottles which do not have the legs, but instead have a round rim along the bottom with the center recessed (so only the rim touches the table or other surface). This is for the same reason. A rigid area to stand the bottle on which will not deform under pressure.
 
  • #10
the pressure argument makes sense!
:)
i meant more contact area when a bottle tips over!
 

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