Plastic products in the commissioning and
production processes are all types of injection defect occurs, cause of the
defects are many, processing of raw materials, injection molding machines,
injection molding process, the production environment and other factors, the
most important factor is - mold.
Here we focus on the reasons of all kinds
of plastic molds product defects and some improved methods for mold.
1. Size does not match the size
requirements of drawings, product development, processing, basic use, the
product size is wrong, simply can not assemble and use. Therefore, to ensure
the product size is the most fundamental, but also the greatest difficulty and
workload. Molds mainly from the following aspects to ensure product dimensional
accuracy:
2. Choose a reasonably accurate shrinkage,
in addition to material suppliers parameters, but also must consider the flow
direction of the product shape and plastic; • The design of the mold, according
to the requirements of accuracy class product, the product is converted into
the mold parts tolerance tolerance, while leaving the safety margin repair
mode;
3. part design, it will be an important
product dimension is reflected in the size of the parts diagram, labeling
tolerances, and detection and control;
4. improve the machining accuracy and
surface quality, and controlled;
5. rational design of cooling system (mold
temperature control). First, a variety of techniques trial, select one closest
to the product size requirements of the process, and the stability of this
process down. Then according to product size, to repair the die size. For
non-critical dimensions or does not affect product assembly and function of
size, can be communication and consultation with the client, whether
concessions release.
2. The product is unstable in the case of
molds and raw materials, and injection molding process remain unchanged, after
injection molding products out, not only is the appearance or size, or that
other aspects vary greatly, resulting in product sometimes qualified sometimes
scrapped. In this case, the mold can not make any amendments, in particular
dimensions, because no one can refer to the reference, so to ensure the
stability of the product formed, it is the basic condition subsequent
modification mode.
2.1 Cause: mold parts deformation; mold
parts guide and positioning allowed; mold temperature control system is
uneven or unstable; moving parts of the gap is too large, resulting in
per-action deviates;
2.2 improve Opinions: increase mold
guiding and positioning mechanism, such as a fine positioning. reduce mold
part gap.
3. burrs (burrs) flash, at the sub-surface
and juxtaposition line position, the extra plastic, foil or hairy. In the
injection molding production, the most frequent problem, the position appears
greater. Any set of molds, more or less will have some flash, a little bit
higher product requirements, will require repairs. In this regard, we will
increase the workload after the process; the same time, will increase the risk
of product quality. Therefore, no flash each injection enterprises injection
will be lowering the efficiency of an important issue.
3.1 Cause: mold steel hardness is not
enough, easy to wear; insufficient strength, easily deformed; lack of
precision mold parts processing, assembly clearance; die not wearing good,
especially sub-surface location, closure is not tight or way that is force;
mold plane falls within the foreign substance or metal inserts
3.2 improve Opinions: at the design
stage, preferred high hardness steel, such as hardened steel; at the design
stage to ensure that the size of the part of sufficient strength enough;
improving mold machining accuracy; reconfiguration mode, reducing typing
surface gap; Die regular cleaning maintenance; clean up the parting foreign
body, keeping the mold closed well.
4. sink marks (indented) products
relatively thick wall thickness or wall thickness mutation region, because the
material accumulation, shrink larger, resulting in surface pitting. Generation
of sink marks, mainly in product design is not very reasonable, so we have to
communicate with customers at the time of the pre-analysis of proposed
amendments. While in the mold structure optimization aspects to do.
more information http://www.cnmoulding.com/plastic_injection_molding_china.htm
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