3D Printing ProcessesAdditive ManufacturingMetal Additive ManufacturingPost-Processing

Getting to know furnace sintering for AM with Elnik President Stefan Joens

Bound metal AM technologies will increasingly require it but how much do you know about it?

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Founded in 1969, Elnik Instruments, Inc. was established as a wholly owned subsidiary of W.H. Joens & Co. GMBH, in Germany, to market the company’s line of temperature controllers, recorders, and programmers. These instruments were designed for use on industrial furnaces, vacuum furnaces, and a variety of plastic extrusion and injection molding machinery. Today Elnik Systems manufactures the most advanced metal injection molding (MIM) first stage debinding and second stage debinding/sintering furnace equipment. Its MIM 3000 Sintering Furnace is a one-step debind and sinter furnace, enabled by some of the most sophisticated technologies available. This means that it is also the ideal furnace sintering tech for AM processes.

Elnik began to focus its efforts on the manufacture of complete vacuum furnace systems in 1982, serving clients such as Raytheon Corporation. By 1986, demand for custom vacuum furnaces was increasing at a rapid pace. A new company, Elnik Systems, was formed to meet this growing demand. In 1992, a ‘one-step’ debind and sinter partial pressure furnace was developed to meet the needs of the MIM market. The MIM 3000 provided a cost-effective alternative to the two-furnace technology then being used. Now a new era is about to begin, with the adoption of bound metal additive manufacturing systems in many segments of industrial production. These AM technologies need to sinter parts in a furnace as a post- process and few companies can boast extensive experience with these systems as Elnik.

We had the opportunity to interview Elnik System President Stefan Joens, who explained in great detail how his company is going to cater to this new market demand, helping us to understand a lot more about the entire furnace sintering process.

If you are currently looking to safely and effectively integrate metal binder jetting in production workflows you really need to read on.

Davide Sher: Can you explain your offer of furnace sintering products?

Stefan Joens: “Elnik developed 25 years ago its MIM3000 line of furnaces which are used to thermally debind the backbone or secondary binder in a traditional MIM part and continue on to sinter the part in the same furnace. Before this system was developed, MIM required a 3 steps process to remove the first stage wax, second stage binder and presinter, and then sinter, using three different pieces of equipment. Additionally, in the early 2000’s we also developed a catalytic debind oven to remove the first stage polymer from BASF Catamold or other POM based feedstocks. We also offer a solvent debind oven to remove a wax based first stage binder as well.”

DS: Are the products used for additive manufacturing the same as those used for MIM?

SJ: “Most of the AM industry growth we see is coming from binder jetting. These technologies will only need to have our MIM3000 series unit to remove their binder and perform complete sintering in one step process. The process of Binder Jetting creates a part similar to a MIM Brown part. This is the result of performing the first stage of binder removal on a green MIM part. Our MIM3000 series furnace fits this processing demand perfectly. Since the processing requirements are 1 for 1, it makes transitioning our efforts and support to this industry very simple. We make graphite versions of our furnaces as well for any ferrous-based metals that don’t require refractory metal or hydrogen processing environments.

furnace sintering tech for AM
The MIM300 sintering furnace from Elnik Systems

DS: Have you seen a surge in interest since new bound metal (binder jetting, bound metal filament) technologies were introduced to the market?

SJ: “Yes, the interest in our equipment is high. We have been the leader in the furnace industry for debind and sinter processing for 25 years. Our ability to not just make highly functional equipment that lasts but really our motivation to educate our customers and help them every step of the way is driving our success. We have a sister business called DSH Technologies, which is an in-house service business that manages processing experimentation, toll contracts and R+D work with the metal part making industries, using Elnik equipment to carry out the work. These are all full-sized equipment, not small laboratory items. We have helped a lot of companies that are currently in the AM industry get started. DSH offers Elnik’s state of the art equipment without the need for CapEx until the customer is ready.

DS: How does the demand of your products from AM users compare to the demand of your products from MIM users?

SJ: “The systems are functionally identical. We have made a few modifications to the standard MIM3000 unit to offer the AM industry the ability to process larger parts than normal MIM parts. Over the last 2 years, our sales have been about 50/50 MIM and AM. Although the interest in our organizational equipment has heavily been outweighed by AM over the last couple of years.”

DS: What should AM companies that starting now to introduce binder jetting technology in their workflow consider when evaluating a furnace sintering system?

SJ: “One challenge that any new part maker faces is that there are some companies pushing furnaces into the industry with the “Easy Button” recipe builder. These systems often do not have the capabilities to provide processing environments that are ideal to processing all metals being offered into the AM industry, especially Stainless Steel, which is what most AM equipment developers are starting out with. Through DSH, we have learned about a lot of the issues that some customers have faced with this approach. We have a lot of experience in the processing industry and feel that it is important to properly provide all customers with the right information to make the right decisions. There is no “EASY BUTTON” to process metal bound parts via MIM or AM. Our mission at Elnik and DSH is to help keep the information transferred clean, clear and understood.”

DS: Have you had a chance to evaluate metal binder jetting and metal filament extrusion technologies? Which do you think are more effective and functional?

SJ: “Each technology has pluses and minuses. Binder Jetting will lead the way with production capability and more MIM-like part results, but it is difficult to build or fabricate enclosed structures without trapping powder within the cavity. This is where filament based printing wins with true part geometry flexibility. But then you are limited in surface finish quality without some form of pre- or post-processing rework. The winner comes down to what the objective for part development is and where the parts will be used.”

DS: Can your furnace products be used with any of these technologies from any manufacturer? Or do they need to be calibrated and/or need machine parameters from AM hardware producers?

SJ: “Our furnace has the capability to process any known metal with any known binder on the market today. The furnaces we make are highly flexible in their use and offer a lot of processing variability control. A user can operate up to 1650°C temperatures under a variety of gas atmospheres (depending on the partial pressures) or vacuum environments. They also have the capability to mix gases or switch gases during the same furnace run. The systems can operate under Hydrogen, Nitrogen, Argon or Vacuum environments.  All program parameters are developed into an Excel Spreadsheet. The use of Excel makes programming very easy and provides any equipment user or company engineer the ability to work on program development without having to be in front of the furnace. They can do this from the comfort of their own home or office.”

furnace sintering tech for AM
The MIM3001 Lab system

DS: How do your products compare with those offered directly by the AM hardware manufacturers such as Markforged and Desktop Metal?

SJ: “This topic links back to the statements above: our furnaces are industrial-based in design, they offer the full range of processing capability with argon, nitrogen, pure hydrogen, vacuum, and up to 1650°C temperatures, which is higher than most competing systems currently on the market. Our furnaces are made typically in all metal zones, which allows for processing in every environment, at any pressure up to almost atmospheric.

What is particularly interesting is that the material the AM industry is starting with – stainless steel – is best processed in full hydrogen to achieve the results most customers are looking to achieve. Yet many new and competing systems on the market are not offering this capability. The reason why is that dealing with pure H2 gas is a safety risk and a liability for many customers. On the other hand, about 90-95% of our equipment leaves our floor with H2 gas processing capability. Our systems have gone through extensive reviews and evaluations to ensure we are safe to operate with H2 gas within the explosive limit. We have a lot of interlocks and safety devices built into the equipment to ensure the system is safe for use by the operator.

We also believe that to get started in the metal part making industry it takes some real knowledge of processing requirements and guidelines to achieve the end results one is targeting.  While these companies are offering their end users a starting spot, we believe that the abilities we have at DSH to not only begin the experimentation on the best equipment in the industry, we also provide invaluable education of the process along the way. So once the part maker is ready to take off, they can make educated decisions about what systems they need in place and how they can start the projects successfully.  We feel the value of performing R+D or lite toll processing work with the support of DSH for those starting out in the AM industry is a much wiser investment in an AM part makers future than the costs of any furnace equipment in the industry today and the education learned along the way is priceless.

DS: How does this superior performance reflect on the system’s price?

SJ: “We have been asked numerous times to make a $100K furnace that has the capability to do all the same things our current furnace can do. However, our current equipment has almost that much worth of H2 safety features alone, so that is just not possible.   The need for a lower priced piece of equipment is there and it is something that we have been discussing, but we need to ensure it still maintains the Elnik standard of quality and performance. Elnik does not choose components for its equipment based on price but rather quality and longevity.  In the interim, as mentioned earlier, DSH is the greatest offer for any AM part maker that wants to have access to equipment with functionality that Elnik offers.

DS: Is it true that furnace sintering is a more repeatable and predictable process than laser sintering during the AM phase?

SJ: ”  I have not heard this statement before. Each AM process offers its challenges and benefits. In Laser Sintering, you are building a part via a process similar to welding. You have to deal with Splatter effects, tension in the part during the build (which is later removed during an annealing process), structural supports and the build plate that all have to be removed post-build. And your surface finish is less than desirable for most applications. But you can use these processes to fabricate some very intricate parts. With any furnace demanding process, like binder jet or metal filament-based 3D printing, you can get some very interesting parts printed. However, much like in the MIM industry, the engineer designing the part needs to understand the process the part needs to go through. Meaning, they have to understand the part will experience pretty uniform X+Y shrinkage and a greater Z shrinkage (directionally from the printer). So how the part is printed and how the part is later staged in the furnace for processing needs to be taken into account. MIM had demonstrated the repeatability of the process and has really dominated in its applicable markets for years. The AM industry needs to perform enough experimentation and data analysis to reach this same level on consistency. The processing side is certainly challenging, but only without the right support and team in-house to get the work done. If you don’t have the capital or manpower to get the work done in-house, this is where our sister company, DSH Technology really shines. We help part makers from the ground up. Build the foundation of knowledge needed so that one day they can take over the process, bring it in house and excel in their respective industries they are trying to enter.”

DS: How do users of your products deal with part shrinkage, dimensional stability and maintaining tolerances?

SJ: “The real answer to this question is looking at the science of it all. Not only does the printing process have an effect on the part throughout the process, but the binder used, the metal particle sizes and distributions can all impact the results of the parts. Let alone the type of furnace, the accuracy of temperature control, the environment used to remove the binder material. There are a lot of factors. But it is all manageable when you understand what you are trying to manage. The printing companies are doing a pretty good job gathering print analysis data and we are hoping to see some real results in terms of guidelines for printing based on total geometry. As for the furnace side, each individual part technically can demand a specific program. But that is not really practical. The AM industry is looking for flexibility and reduced variability. So in our systems, the functionality of the equipment lets the user develop recipes based on the largest or thickest part in the furnace during the run. This means that, so long as the metal and binder are the same, you can process a variety of parts all in the same run and not worry about part orientation or location to optimize gas flow. A good processing facility will still need to have in-house or have access to a true “Process Metallurgist” and not just a material science expert. Again, another plug for where DSH can be of assistance. We offer Block times of support to any customer throughout the world. They don’t have to be an Elnik or DSH existing customer either. We are looking to educate the world on process metallurgy. We have a dream of developing a DSH University to allow material science students and people that want to learn more about the process side of this industry to spend time with us either via an Internship, temporary employment or even long term if it works out. There is a lack of education being provided to teach our specific technology and our goal is to help future companies have the right candidates in-house to get the work done!”

DS: Will some of this be eventually done at a software level during part design or through the software managing the sintering process?

SJ: “As for software managing the furnace process, there is currently nothing available in the market that is reliable. There are variables that need to be considered in terms of processing parameters that are generally not available during the printing design process. Perhaps, something may eventually be developed. The real challenge is realizing that any solution provided will be a conservative approach to processing. And anyone interested in deep diving process optimization will need to analyze this with a good process metallurgist.”

DS: Do you think that AM will eventually grow in size to compete with MIM and other formative processes?

SJ: “It certainly can. It will require good repeatable results driving by valid scientific data analysis and demonstration of what works and what doesn’t. MIM has limitations as well and groups like MPIF, EPMA, and other private technical organizations have done a really good job providing technical standards to help part makers rely on a benchmark. This is still at the starting phases in the AM industry. The faster this gets up and running, the sooner companies will know where they stand. Like the MIM industry 30 years ago, the AM industry is in its “Wild West” phase. The leading companies or those that really want to have a voice in this process need to get involved with technical boards to help drive this process further. The biggest challenge they face right now is that knowing where to start, a bit like drinking from a firehose. Taking the lead from some MIM part makers and getting some insight from the MIM tech boards might be a good avenue to press on.

The Casting industry should be mindful of the AM industry. AM opens the doors to higher part complexity, wider metals range and can really make a dent on that industry.

The machining industry should also begin to bring this process in house. AM will allow them to develop really challenging pieces that only need minimal machining to be in line with their customer requirements.”

Research 2021
Ceramic AM Market Opportunities and Trends

This market study from 3dpbm Research provides an in-depth analysis and forecast of the ceramic additive ma...

Davide Sher

Since 2002, Davide has built up extensive experience as a technology journalist, market analyst and consultant for the additive manufacturing industry. Born in Milan, Italy, he spent 12 years in the United States, where he completed his studies at SUNY USB. As a journalist covering the tech and videogame industry for over 10 years, he began covering the AM industry in 2013, first as an international journalist and subsequently as a market analyst, focusing on the additive manufacturing industry and relative vertical markets. In 2016 he co-founded London-based 3dpbm. Today the company publishes the leading news and insights websites 3D Printing Media Network and Replicatore, as well as 3D Printing Business Directory, the largest global directory of companies in the additive manufacturing industry.

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