How do operators today determine good injection moulding conditions?
Is there software available which allows the user to determine good
injection moulding conditions (melt temperature, mould temperature,
back pressure, etc.) based on empirical models?
Would it not make sense to correlate product characteristics with
injection moulding conditions? I don't find journal papers mentioning
anything of this sort. I understand that this would be mould-dependent
and machine-dependent, but if the dependency is significant, the
operators too would have to deal with that and find good conditions
for each mould, each machine.
With kind regards,
Go to http://www.moldflow.com . Injection molding software; there are a
few others but moldflow is the most popular.
-- Billy Hiebert
HIEBERT SCULPTURE WORKS
Small part plastic injection molding
Web site: http://www.hieberts.com
I looked through and it looks like their software is not based on
empirical models. The focus is more on the mould and fluid dynamics
than on finding suitable moulding conditions. Please correct me if
you know that they also have solutions based on empirical models.
>> How do operators today determine good injection moulding conditions?
>> Is there software available which allows the user to determine good
>> injection moulding conditions (melt temperature, mould temperature,
>> back pressure, etc.) based on empirical models?
>> Would it not make sense to correlate product characteristics with
>> injection moulding conditions? I don't find journal papers mentioning
>> anything of this sort. I understand that this would be mould-dependent
>> and machine-dependent, but if the dependency is significant, the
>> operators too would have to deal with that and find good conditions
>> for each mould, each machine.
>> With kind regards,
>> A. Bulsari
Sorry, I am not aware of how these systems actually work, I assumed some
variation of FEA principles. I probably don't understand what you are
looking for. You refered to finding suitable molding conditions; it
seems to me that those conditions are determined, at least in part, on
the mould and the fluid dynamics of the materials involved. Moldflow is
probably used more by mould builders than by moulders. --Billy
In the medical device field, the FDA consider plastics processing as a
"special process", where the final parts are not 100% verifiable.
In this industry, there is a huge amount of up front work done in both
molding and extrusion in process characterization just for what you are
describing. The process needs to be pushed to failure during
characterization, where that failure is either in the process's ability to
make the part, or until the part itself fails some specific predefined test
or tests. It is best to do this work with multiple lots of the resin.
After completion of the characterization, a validation protocol is drafted
with IQ for the equipment (installation qualification) if it is new, OQ
(operational qualification) for the specific part on that specific equipment
where an operational "range" is established as outlined in the protocol, and
a PQ (performance qualification) where the nominal conditions are tested,
most likely numerous times. All of the data is then looked at statistically
and matched up with the predefined criteria established in the validation
protocol. All associated tools such as molds, dies, tips, etc. are given
drawings and part numbers.
Once the protocol is completed, from the validation, a process specification
is authored. Once completed, the parts have to be manufactured within the
constraints of the process specification, or else they cannot be used unless
they are determined by cross functional team of QAE, Manufacturing
Engineering, Regulatory, and other functions as usable (usually called a
Material Review Board, or MRB). For the most part, it would include a lot
of testing of the component and the product.
In the past, in extrusion, I have seen many engineers institute validation
protocols that lead to many problems in manufacturing. Such things as
specifying a screw RPM range and a FPM range. A slight shift in the SG or
bulk density, and you cannot produce parts within the specified range, and
you need to convince a panel of other individuals that know very little, if
anything, that a change needs to be made (DCO), which may push the part back
into the validation cycle.
In a well run organization, this detailed approach can work wonders. With
the proper controls in place, the decisions that can be made by the
operators are (theoretically) proven to make functional products.
Look up articles on scientific injection molding by John Bozzelli (SP?). He
has dedicated much of his work to scientifically determining the proper
molding parameters for parts. He has written many articles about this as
well as the concept of a universal set-up sheet. Please let me know if this
is what you are looking for.
Bozzelli's ideas are also interesting, a bit different from what I am
thinking of. Articles/documents I found describe procedures without
much theory, or an explanation of why his way. Calling it scientific
did not sound convincing. I agree that injection moulding work is
going more to cheaper countries in Asia, because the developed
countries are still not offering anything which is of much superior
I think we have a good solution to determining suitable injection
moulding variables (and looks like there are no competitors
either). (1) The user can decide the product characteristics he wants
to take into account. (2) The software system plans out a set of
experiments. (3) The user carries out the experiments and feeds the
data to the system. (4) The system tunes models (not plain linear
regression like SPC) based on that data for each product
characteristic. (5) The user can specify his requirements, and the
system calculates suitable variables (injection moulding conditions).
Now we should slowly start looking for representatives willing to
distribute this software system. Our (Nonlinear Solutions Oy) modest
Internet site does not tell very much, and there is still no
description of the software system there, but I will be glad to
communicate with interested people first. (My e-mail address is
firstname.lastname@example.org, or write from the contact page of the company's www
With kind regards,
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