Injection Moulding Machinery is all about reliability. If you assess well and decide now to stick with one (maybe two) machinery suppliers, then this time spent is a very good investment by itself, says Dr. Hans-Joachim Graf, Rubber Industry Consultant at H-JG Consulting, Germany in an exclusive interview with Rubber Machinery World.
Esteemed readers, as you know, I started “Know A Rubber Leader” series with Jacob Peled, the renowned Executive Chairman at Pelmar Engineering. The interview was widely read for some rare nuggets that Jacob chose to share on this site.
In this post, I present you an intensely thoughtful chat with Dr. Graf.
Dr. Graf was awarded with the Erich-Konrad Medal for commendable achievements in rubber-technology instituted by DKG (German Rubber Society) during DKT’12 edition. With over thirty years experience in the rubber industry, he has authored over 60 publications and paper presentations. He has over 15 patents in his name. A member of the American Chemical Society, Deutsche Chemische Gesellchaft and Deutsche Kautschuk Gesellschaft (DKG), Dr.Graf received his diploma degree from University of Mainz and his doctorate in polymer chemistry from University of Freiburg, Germany.
Here is Dr. Hans-Joachim Graf’s full interview reproduced for you.
- 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?
After finishing my PhD in macro-molecular 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.
- 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?
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 come 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.
- 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?
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 World 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.
- What role has machinery played in this change?
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.
- 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?
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.
- How does rubber compound development benefit with software? Do you see a trend of increased use of software in this field?
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.
- 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?
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.
- 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?
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.
- What are the key changes and trends happening in injection moulding?
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 cross-link density, but injection molding machines should be faster. Hopefully we see more development as seen in the machine industry for thermoplastic processing.
- Great! And one last question. What advice on “machinery selection” would you give to buyers in rubber industry?
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.
Download the full interview in PDF here.
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