Heißkanaldüsen Typ SLT/-DLT Customer information

Customer information
Preventing flow marks on injection molded parts
The requirements set on molded parts in the visible area
are high, a clean injection point is indispensable. This is of
particular importance for components which are backlit,
as it is the case with light covering panels. Flow marks
caused by flow separation of the melt in the nozzle can
lead to quality problems. To ensure process reliability,
nozzles with multi-purpose pluggable tips are used by
Werner Langer Metall- und Kunststoffverarbeitung, a
metal and plastics processing company.
A PMMA-type material, optimized for transparency and lack of
streaks, is used for light covering panels (between the mold
halves).
Plastics processing company Werner Langer produces
three different kinds of light covering panels for Simon &
Schelle, a lighting manufacturer. The production started
in early 2007. “Our customer's quality standards as well
as the requirements on the light covering panels were
clearly defined,” says Werner Puppe, technical manager
at the plastics processing company from Meschede-
Berge, “a clean injection point, no flow marks or weld
lines, little warpage, absolutely no sink marks on the side
flanges of the covering panels, and a high-quality surface
finish. After all, the light covering panels shall be used as
mirror lightings in the bathroom.”
Use of conventional nozzles is problematic
Standard nozzles with screwed-in tips, sufficient for most
of the injection molding applications, could not be used for
production of light covering panels because their use
goes together with flow separation of the melt. This would
have caused flow marks on the opaque covering panels
which would be visible when backlit. In search of a
solution, the company contacted hot runner supplier
GÜNTHER Heisskanaltechnik.
For any questions, please contact our Application Engineering department at +49 (0) 6451 5008-31 or -63.
The information is given in accordance with our present-day knowledge and is meant to provide technical background.
www.guenther-hotrunner.com
7/12 Subject to technical changes
iA
“Since we have been in contact with this supplier since
1988, and have always appreciated is good consulting
services and technical support, we were looking for
collaboration on this application as well. For this
purpose, we made the 3D design data of the part
available for the hot runner specialist. As a result,
GÜNTHER came up with a proposal to use a nozzle type
with a multi-purpose pluggable tip.” This relatively new
type of the tip enables the melt to be mixed in such a way
that there are no longer flow marks seen on the molded
part. This is a unique selling point of the multi-purpose
pluggable tip on the market.
“The design of the nozzle tip yields a very low shear
potential,” says Walter Ehlert, in charge of consulting and
sales at the hot runner specialist. “Competitive products
do feature some design principles which should result in
flow marks being avoided; however, these techniques
often increase the level of shear stress in the melt, which
may lead to degradation of the plastics. This can often be
seen in the form of streaks on molded parts.” This
problem arises particularly in the case of light covering
panels: The molded part is very long, so it must be filled
quickly. The multi-purpose pluggable tip, designed with
its maximum depth of clearance, produces minimal
pressure drop together with a very low level of shear
stress.
The new multi-purpose pluggable tip, here in a nozzle of the
SET60S type, enables the melt to be mixed in such a way that
no flow marks appear on injection molded parts.
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