Interview with Dr. Hans-Joachim Graf

Interview With
Dr. HansDr. Hans--Joachim GrafJoachim Graf
Consultant bei H-JG Consulting
Awarded Erich-Konrad Medal in 2012 for
Commendable Achievements in Rubber-Technology
©2015 - Published by Rubber Machinery World. http://rubbermachineryworld.com

Hello Dr. Graf. First of all thank you for accepting an interview with Rubber
Machinery World and sharing your thoughts. Your journey started from
pharmaceuticals and subsequently moved to rubber industry. Was this a
planned move?
11
After finishing my PhD in macromolecular
science I decided I did not want to stay in
university and become a researcher. I am
more of a hands on person. My first job was
with the owner of a small company as I felt
that fit me best. I put my nose in almost
everything from tooling to compound
development. I even established the first
manufacturing quality control system in this
company. There were new challenges every
day and I had fun. I cannot say it was planned.
It happened.
“There were new challenges
every day and I had fun. I
cannot say it was planned.
It happened. ”

Your journey from Design Process (at Kloeckner Desma) to Director of Materials (at
Cooper Standard Automotive) and now as an active educationist has been a long
and varied one. Which is the position that you enjoyed the most?
22
There were two positions I enjoyed most. The most innovative group
I worked with was at Desma. We developed many innovations, which
you can find even today in different publications. I utilized my group’s
expertise from mechanic to engineer, and electrician to chemist. The
group did not depend on anybody else in the company. My boss
protected me from the administration. We achieved the respect of a
lot of customers and that was our motivation.
The second position I enjoyed most was with Cooper Standard in
Canada. I was the elder in a very young dynamic group, but the most
multi-cultural I have ever seen in any company. We had Asians,
Europeans, North Americans and even Canadians in the group.
Whenever I go to Canada, I still get together with many friends. Here,
I utilized my engineering and chemist expertise in this group. This
group created one the most advanced mixing centres in industry. The
bad thing is, upper management never recognized it.
“I utilized my
group’s
expertise from
mechanic to
engineer, and
electrician to
chemist. ”

Would you say that rubber compounding has undergone change in the last 3.5
decades that you have been with rubber industry? What were the drivers for this
change?
33
The 50’s and 70’s saw the big polymer and ingredient
suppliers work out the basics of compounding.
Significant technological advancements were seen and a
large amount of literature was produced at this time. It
was needed because of the tremendous growth of the
rubber industry after Word War II. Following the first
economic crisis, along with early retirement programs
and more crises – for example, the breakdown of the
Comecon (specifically Europe) – technical knowledge to a
large extent was lost and polymers became
commodities. Leadership in the supplier industry
changed from technical to sales. From this time forward,
rubber parts manufacturers had to take the
responsibility of development in their own hands, but
with limited resources.
“……..technical
knowledge to a
large extent was
lost and polymers
became
commodities. ”

What role has machinery played in this change?44
This is a difficult question for me. The machine
industry has followed the same trend as the
polymer industry. We had sophisticated machines in
the 80’s but slowly this position has worsened. This
is very different with the technology for the
machines used in the thermoplastic industry. At one
K-Show, machines were presented that had a cycle
time of less than 3 seconds! It is different with
rubber parts - because of its inherent slow heat
transfer qualities, the major influence on the cycle
time is the rubber. As a result, engineers believe
that machine time does not play a big factor. There
is no real optimization of compounds going on to
accommodate machine and mold necessities.
Engineers and Chemists do not work together. Both
parties see more differences than similarities
between rubber and thermoplastic processing.
“Engineers and
Chemists do not work
together. Both parties
see more differences
than similarities
between rubber and
thermoplastic
processing”

Design of Experiments [DoE], though being a standard tool in optimization of
materials and processes in many industries, has not many takers in rubber
manufacturing industry. Why?
55
In my opinion, it is the fear of failing. If an
experienced compounder is doing a DoE,
he has to design the experiment and leave
it up to a series of mathematical
equations. He cannot interact with the
experiments as he is used to do when
performing trial and error procedures. The
DoE results of the experiments may be a
confirmation of his existing knowledge,
but it may not. It may challenge and force
him to question that longstanding
knowledge.
“In my opinion, it is the fear
of failing.”

How does rubber compound development benefit with software? Do you see a
trend of increased use of software in this field?
66
Around the time the Design of Experiment was invented, some
companies (Cabot, Bayer beside others) performed some superficial
trials on filler / oil designs. After more than four decades this tool has
not penetrated the field of compounding as it should have. Its growth is
much too slow, and I would not call it a trend. Software exists today (like
FEA), for the engineering of rubber parts. This is standard. However,
interaction between part design and compounding is still trial and error.
While properties of a compound are an input for the FEA calculation, it
is rare to design a compound to fit the FEA requirements for the part.
On the other hand, compounding groups have created a lot of recipes,
but most of it is based on trial and error. From my perspective, it is lost
knowledge, because DoE Software cannot make any use of it. I felt that I
had to help to somehow utilize this data not only for my benefit but for
others. This is the basic idea behind the “GrafCompounder” software. I
have the experienced compounder in mind, who would like to use his
company’s historic compound date base instead of filing it away.
“.. it is rare to
design a
compound to
fit the FEA
requirements
for the part.”

What are the various tools and methods of recipe development and its advantages?
Which of these is the most optimized method that has clear economical advantages?
77
Preferably, the strategy for initial recipe development should be the
analysis of the compound in various machines and during its part
life. We call that: data analysis, time series analysis, correlation of
root cause and effect via observations. You have to work with the
compound - process system. This can only be done successfully if the
statistic experimental design approach is taken. The economic
advantage of this is clearly superior when you take into account the
reduced costs for statistical design experimentation versus trial and
error, minus the cost of the final result. A second development area
of similar importance is to ensure secure supply. This needs material
replacement and multiple approval strategies. It depends on raw
material, process and service life knowledge. This knowledge is
attained only again, through experimentation.
Upper management needs to understand that development
sometimes means failure and they have to allow for this. We all
learn from failed experiments. We never learn if everything is
running at a steady state
“You have
to work
with the
compound
- process
system.”

In 2004, you had stated that the extruder has been around for some time and
changed very little. And you viewed the extruder as a black box analyzing the
energy and mass (input and output). Is the extruder different today?
88
I have been out of the extruder industry
for some time and have not followed the
ongoing developments here close
enough to comment. What I can say is:
the combination of an extruder and gear
pump truly has its advantages, because it
is a volumetric pump and it pressure
dependence is zero. This provides
superior straining of a compound
without changing its properties.
Is a gear pump is useful for compounds
with very high viscosity? I do not know
its limits.
“the combination of an
extruder and gear pump truly
has its advantages, because it
is a volumetric pump and it
pressure dependence is zero.”

What are the key changes and trends happening in injection moulding?
99
We have been quite successful in decreasing
energy consumption during moulding. Next
we need to focus on developing a much
faster process to stay competitive with TPE.
The technique to induce heat into the
compound by shear is developed, but
control of the vulcanization process is
urgently needed. We have come a long way
with heating time regulation (Barber
Colman) to inline temperature history and
heating time close loop control (CAS-Jidoka)
and its linkage to crosslink density, but
injection molding machines should be
faster. Hopefully we see more development
as seen in the machine industry for
thermoplastic processing.
“We have been quite
successful in decreasing
energy consumption during
moulding. Next we need to
focus on developing a much
faster process to stay
competitive with TPE.”

Great! And one last question. What advice on “machinery selection” would you
give to buyers in rubber industry??
1010
I can comment on injection molding
machines only. One topic in my
“Injection Moulding” seminar is
about machine assessment. With a
couple of experiments one can
analyze the capability of an injection
molding machine. It is not rocket
science. It needs about two days of
intense experimentation. Another
topic I would like to comment on is
maintenance and spare part
management. This is all about
reliability. If you decide now to stick
with one (maybe two) machine
suppliers, then this time spent is a
very good investment.
“One topic in my Injection
Moulding seminar is about
machine assessment…….. This is all
about reliability. If you decide now
to stick with one (maybe two)
machine suppliers, then this time
spent is a very good investment. ”

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©2015 – Interview Published by Rubber Machinery World in May 2015.

Interview with Dr. Hans-Joachim Graf

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