Shape Control
for Finished Aerosol
Cans
Three dimensional cameras are an important step
toward enhanced can inspection...
Murphy’s Law—“Anything that can go wrong will go
wrong”—does prove true from time to time in the complex
production process of aerosol cans. This presents
a challenge to automated inspection—all quality aspects must be
considered, otherwise automated quality control concepts miss
their fundamental objectives. As long as quality is not monitored
continuously, the concept of a zero defect policy cannot really be
put into practice.
New designs, new problems
Today, aerosol cans are more than just
simple containers. Based on new findings
resulting from materials research, modern
aerosol cans have become more resourceconserving,
efficient and highly designable
objects. Thinner walls, combined with
newer materials, helps reduce production
costs and impact on the environment.
However, these developments also
increase the risk of defects. More complex
can-shape geometries require a variety of
forming processes which, along with embossing,
may further weaken the material
of the can. Even the smallest defects prove
critical, which presents a challenge, especially
for automated visual quality control.
Advanced technologies
from image processing
While print inspection has been extensively
discussed in recent times, other
factors—surface and shape—need further
consideration. Beyond their improved
aesthetic, aerosol cans are merely pressurized
containers. Surface defects can make
them leak or even explode, which is not a
pleasant thought considering we all deal with aerosols every day.
Several standards have been defined for the pressure stability of
an aerosol can, including buckle/distortion and blow. Although
the wall thickness of cans is constantly reduced, these standards
have never been altered, which is one more good reason for precise
and reliable quality inspection. The most vulnerable parts of
the can are curl, shoulder and shape since they undergo multiple
forming processes with high material strain. Consequently, these
areas are in the focus of visual inspection where new or advanced
image processing technologies have lately been introduced.
Two-dimensional inspection
When considering geometric bodies such as aerosol cans, a threedimensional
measurement process seems obvious. However, the
choice of the right inspection method is linked to location and
criteria. These may need further evaluation, as not every flaw
appears as three-dimensional; stains or printing defects would not
be spotted by a three-dimensional inspection. Only a two-dimensional
inspection method is able to include all quality aspects.
The essential requirement in this approach is that there should be
no blind areas.
32 Spray January 2018
Dr. Ralf Freiberger
& Christiane Blasius
The Mühlbauer Group
Can top inspection inside the necking machine
This paper was originally presented at the New York Aerosol & Dispensing Forum.