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If
your business includes production line painting processes with manual or
automatic color changes, North American Paint Applications encourages
you to perform an economic impact study using the guidelines below. We can not only assist you at any level in this, but
can provide an expert perspective of all opportunities in your paint
shop, and speedily implement any improvements. |
COLOR
CHANGE
A
color change is the purging of one color from the paint applicator and
the loading of a second color. Sometimes, it includes a paint push
out. Color changes affect quality, throughput, waste, and
maintenance and can have a severe impact on the overall productivity of paint
processes. Whether you have a manual color change or an automatic
color change, you may find the discussion below useful to both operator
and maintenance personnel and as an aid to management in making the
right decisions .
North
American Paint Applications is the world leader in implementation of
efficient color changes for every type of application.
Duration
When
changing colors, the equipment is not painting. It follows then
that the longer the duration to complete the color change process, the
lower the part throughput of the system. Long color changes often
have a negative impact on productivity.
As
an estimate in automated systems, typical color change times are one
second per foot of paint hose from the color valve stack to the
applicator. Manual systems vary widely. With efficient
design, faster color change times can be easily achieved.
Repeatability
Automated
color changes ought to be designed to purge and load the lines
efficiently, repeatably, and with sufficient flexibility to make
allowances for all purging and loading variations among the different
materials. For example, it is common that white may be more
difficult to purge than black and may take longer to load. The
system ought to be flexible enough to support this.
Problems
such as color carryover, insufficient paint load, sputtering, and
overspray contamination should never occur when equipment is functioning
as designed. The system should be repeatable for any
combination.
Waste
Unless
a paint push out is incorporated, all material used during a color
change is waste and must be disposed of. In automatic color
changes, it is normally collected via piping direct to waste
storage. Only a minimal amount of waste material required to clean
the bell or gun is normally sprayed into the booth.
The
amount of material used for color change depends on many factors,
including paint line length and size, paint and solvent chemistry,
equipment, and method of implementation. Paint is the most
expensive material of the waste and the amount used should never be
greater than 120% of the internal volume of the piping system from the
color valve stack to the applicator, and less if a paint push out is
used. For solvent, a good benchmark would be less than one cup per
5 feet of paint line.
Paint
Push Out
Paint
push out refers to the process of 'pushing' paint out of the lines and
onto the part prior to a color change. This is usually done with
solvent. In this way, less paint is wasted during a color change
and color change times are shortened.
Manual
vs. Automatic Color Changes
Many
facilities depend upon labor to implement a color change. While
this may seem most economical at first glance, there is a real cost
associated with manual color changes that must be accounted for.
First,
manual color changes usually take significantly longer than automated
color changes. If the conveyor must be stopped or gaps inserted to
facilitate the change, throughput suffers.
Second,
the operating cost of manual color changes is much higher than automatic
color changes. This results from increased labor costs, increased
material costs, and increased waste handling and disposal.
Third,
the quality of the color change is not certain to be repeated.
NA
Paint is ready not only to automate your color change, but to optimize
it. A cost/benefit analysis must be performed, but it is our
experience that in most applications automating will save large amounts
of paint and solvent, emissions, reduce booth contamination and filter
loading/sludge creation, improve quality and consistency, and increase
paint shop throughput significantly. We look forward to helping
you analyze your existing process.
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