Accuracy,
Simplicity of Gravimetric Metering Technology
Built into Economical New TrueFeed™ Feeder
from Conair
New
TrueFeed™ color and additive feeders from
Conair employ gravimetric (loss-in-weight) metering
technology to improve accuracy, while making the
units simpler to operate. Unlike volumetric feeders,
which have been standard in the plastics industry
for years, the new Conair gravimetric feeders
are self-calibrating, adjusting automatically
for changes in material type, bulk density or
pellet geometry. This, in turn, results in easier
set-up and greater processing up-time for increased
productivity. With prices starting at just $3495,
the new TrueFeed units are economical too…
less than 25% more than the company’s old-style
volumetric BFH feeders.
“Twenty
years ago, gravimetric blenders accounted for
fewer than 10% of all blenders sold in the plastics
industry,” recalls Gary Hovis, Commercial
Mgr., Blenders & Feeders. “In the last
two decades, those percentages have reversed,
with very few volumetric blenders being sold outside
of certain niche market segments. Volumetric feeders,
on the other hand, have held onto their market
share for somewhat longer because gravimetric
units have been quite expensive. Now that we have
been able to get the TrueFeed pricing to volumetric
levels, they have the potential to take over the
feeder market the way gravimetric blenders came
to dominate the blender market in the late 1980s
and through the 1990s.”
The
new TrueFeed gravimetric feeder uses a rotating
tube to meter material more consistently and more
accurately than the flighted auger used in most
volumetric units. The metering tube is driven
by a microprocessor controlled stepper motor,
which starts and stops more precisely than the
conventional DC motors that are common in volumetric
feeders.
However,
the accuracy of the TrueFeed really arises from
the fact that the ingredient hopper is weighed
continuously. As material is dispensed, the weight
loss is registered and the feeder runs until the
exact amount has been delivered to the machine
feedthroat. Then it stops. If material characteristics
(bulk density, particle geometry, etc.) change,
the speed of the metering unit is adjusted automatically
to compensate. The digital weighing unit is accurate
even under high-vibration conditions.
With
volumetric feeders, on the other hand, users are
required to collect and weigh as many as a dozen
material samples to determine how long the auger
must turn to dispense a given weight. If the character
of the material changes, the time-consuming calibration
process must be repeated.
Even
with proper calibration, volumetric units are
notoriously inaccurate and processors have traditionally
compensated by using more additives or colorants
than are really needed. Sometimes these ingredients
can cost up to $50/lb or more, so using even a
small amount more than necessary can be quite
expensive. With the digital precision of the TrueFeed,
processors can be assured they are getting just
the right amount of color or additive. And in
many cases they find they can get by with a lower
setting since it is being dispensed so precisely.
The
basic TrueFeed unit is sized to feed as little
as 0.02g/sec (0.07 kg/hr) or as much as 20g/sec
(72 kg/hr). For higher throughput requirements,
a unit with a larger stepper motor can be supplied
to feed as much as 50g/sec (180 kg/hr). The feeder
can be ordered with a standard hand-fill hopper
or with an integral compressed-air loader. The
loader, when supplied, is controlled through the
standard microprocessor control that comes with
the TrueFeed.
The
control itself is easy to use. The operator sets
the color or additive percentage, enters the part
weight and cycle time, and presses the start button.
After initial calibration, no calibration is required
for accurate, consistent metering. These operating
parameters can be stored in memory for easy recall
the next time the same job/material is run. The
system can store up to 1500 set-ups. A standard
communications package is available to deliver
material usage data to a central host computer
for inventory control or process documentation.
When using two feeders on the same molding machine
or extruder, this communication port can be used
to tie the two units together for improved product
quality.
For
more information, call the New Product Hotline
at 1-888-486-6601
Contact
us directly from our online form.
