Terry Wohlers, Wohlers Associates, Inc.
This paper was presented in December 2002 at EuroMold in a conference titled "Worldwide Advances in Rapid and High-Performance Tooling."
This paper discusses developments in rapid and high-performance tooling. Among those under development or commercially available are Direct Metal Deposition (DMD) from The POM Group, Direct Metal Laser Sintering (DMLS) from EOS, Electron Beam Melting (EBM) from Arcam, Laser Engineered Net Shaping (LENS) from Optomec, M3 Linear from Concept Laser GmbH, ProMetal from Extrude Hone, RSP Tooling from RSP Tooling LLC, Sprayform tooling from Ford, SLS tooling from 3D Systems, and Ultrasonic Consolidation from Solidica. New and developing software tools, also discussed in this paper, assist the tool designer in making rapid and high performance tooling a reality.
Industry consultant, author, and speaker Terry Wohlers is president of Wohlers Associates, Inc., an independent consulting firm he founded 16 years ago. He has authored more than 260 books, articles, reports, and technical papers on engineering and manufacturing automation. Terry has presented to thousands of engineers and managers and has been a keynote speaker at major industry events around the world. His appetite for adventure has driven him to climb the Great Wall of China, hike the rain forests of New Zealand, dive among sharks in Belize, bathe in the Dead Sea, and encounter lions and rhinos in Africa.
In 1992, Terry led a group of 14 individuals from industry and academia to form the first association dedicated to rapid prototyping. In 1993, the association joined the Society of Manufacturing Engineers (SME) to become the Rapid Prototyping Association (RPA) of SME. In 1998, Terry co-founded the Global Alliance of Rapid Prototyping Associations (GARPA) involving 14 member nations around the world. Today, GARPA serves as a catalyst for the exchange of information on rapid prototyping and tooling across international borders.
Over the past few years, methods of rapid and high-performance tooling have improved to the point where they now provide vital strategic benefits to various organizations. Some of these methods enable users to embed cooling channels that conform to the shape of mold and die cavities, thus improving production cycle time. Other methods reduce or eliminate the need for EDM (spark erosion), saving significant time and expense.
The following provides news and updates on Arcam, Ford Sprayform, Optomec, ProMetal, and RSP Tooling. It also discusses tool design software including Magics Tooling from Materialise and a development that is underway at TNO Industrial Technology.
Arcam is a Swedish company that began to commercialize a method named Electron Beam Melting (EBM) in 2001. In its early years, the company struggled with direction and technology, but it now seems to be on track. EBM is similar to laser sintering of metal. The process fuses metal powders layer by layer to form strong metal parts. EBM parts are nearly 100% dense, but the surface of the parts is rough and requires finish machining.
The machine is named EBM S12 and sells for $500,000. The machine’s build volume is 250 x 250 x 200 mm (10 x 10 x 8 inches) and uses two materials that are certified for use with the machine. One is H13 tool steel and the other is a metal powder named Arcam Low Alloy Steel. Parts produced in H13 result in properties that are identical to parts machined from H13 stock. Parts in Arcam Low Alloy Steel are intended for prototypes or prototype tooling because they are easier to machine. This metal was not designed to match a particular specification
Arcam’s primary target market is the production of tooling inserts for series production. Arcam expects to also address the market for functional metal prototypes. The company sold two systems through the end of last year, achieving the goal that Lars-Erik Andersson, chief executive at Arcam, had voiced in early 2001. The two customers are RZ-gruppen AB and Formteknik Verktygs Ab.
Ford’s process, called Sprayform, uses twin wire metal arc guns to spray carbon steel onto the surface of a ceramic pattern. In producing the patterns, Sprayform uses a special freeze-casting process that ensures stability and accuracy of the ceramic. Robotically controlled wire spray guns, manufactured by Praxair, deposit the metal onto the pattern to produce a shell.
The deposition rate of Sprayform is about 6.8 kg (15 lbs) of wire material per hour. The work cell can currently accommodate parts up to 760 x 1015 x 250 mm (30 x 40 x 10 inches), though Ford has a preliminary design that will be capable of spraying components 1.83 x 1.83 m (6 x 6 feet). The “height” dimension of the new work cell design will be determined in the future. Smaller sections can be added together to create the final work piece if a part is larger than the work cell. The company is making experimental dies that are 60 Rockwell in hardness. Ford quotes accuracy of ± 0.075 mm (0.003 inch), but is more comfortable with ± 0.15 mm (0.006 inch).
Sprayform is being used to produce production dies for sheet metal stampings of non-visible parts, such as inner hood reinforcements, brackets, and stampings for transmissions. The company is also using Sprayform to produce sand cores and foam seat molds. More recently, the process has been applied to both injection molding and composite lay-up tooling. At some point in the future, the company hopes to use it for Class A surfaces (also referred to as Class 1 surfaces), which are the visible sheet metal body parts, such as hoods, roofs, doors, and quarter panels.
Ford used Sprayform to produce a die for a torque converter rotor blade in four weeks, compared to 16–20 weeks using the conventional approach. The die was used to manufacture 750,000 parts, many of which were installed in cars. On average, Sprayform saves about 30% in time and cost, according to the company. In some cases, it has shown a 50% improvement.
Optomec Inc. offers a method named Laser Engineered Net Shaping (LENS), a manufacturing process that produces metallic parts directly from CAD solid models. The process produces metal parts, including complex prototypes, molds, and components, made out of difficult-to-process materials such as titanium alloys. The process is also used to repair components such as injection mold inserts.
The LENS process injects metal powder into a pool of molten metal created by a focused Nd:YAG laser beam. The fabrication process occurs in an argon chamber for oxygen-free operation. A motion system moves a platform horizontally and laterally as the laser beam traces the cross section of the part being produced. After forming a layer of the part, the machine’s powder delivery nozzle moves upward prior to building the next layer. The LENS method produces near net shape parts that require finish machining or some other finishing process.
Like other RP techniques, LENS is an additive fabrication method, although it produces fully dense metal parts. To date, most parts fabricated with the LENS process are 316 and 304 stainless steel, nickel-based superalloys such as Inconel 625, 690, and 718, H13 tool steel, 2024 Al (aluminum), and Ti-6Al-4V titanium alloy. Tungsten and nickel aluminides have been processed successfully, but the company has limited experience with them.
The ProMetal division of Extrude Hone has been developing MIT’s 3DP (3D Printing) process for metal part fabrication for many years. However, it wasn’t until the 2001 to 2002 time frame that development and commercialization activity came to life. Currently, several ProMetal initiatives are underway, including a $10.8 million Office of Naval Research project. Its purpose is to integrate ProMetal into the development and repair of weapon systems.
The process uses inkjet print heads to jet a binder onto the surface of metal powder. Layer by layer, the machine builds metal parts in 316L or 420 stainless steel. A furnace cycle burns out the binder and brings the parts to full density using a bronze infiltrant. The final part consists of about 60% steel and 40% bronze.
Late in 2001, the company introduced its R4 and R10 machines for $275,000 and $650,000, respectively. The R4 offers print heads with 8, 16, or 32 jets, while the R10 offers 8, 32, and 96 jets. In 2002, ProMetal introduced its R2 machine for an introductory price of $150,000, but now sells for about $200,000. The company sold four of its systems in 2001.
Idaho National Engineering and Environmental Laboratory (INEEL) has developed a rapid tooling method called Rapid Solidification Process (RSP) Tooling. RSP Tooling is a spray deposition technology tailored for the production of molds, dies, and related tooling in nearly any tooling alloy, including popular tool steels such as P20, H13, and D2. The approach combines rapid solidification and net-shape materials processing in a single step.
With RSP Tooling, a pattern of the tool being developed is generated from a CAD solid model. A ceramic reversal is poured and created from this pattern. Then tool steel or another alloy is sprayed onto the ceramic to form the pattern’s shape, surface texture, detail, and required thickness.
From a crucible, molten metal is pressure-fed into a nozzle and atomized by contact with a high velocity gas jet. The resultant metal block is cooled to room temperature and separated from the pattern. Typically, the exterior walls are machined, allowing it to be used as an insert in a mold base. “The overall turnaround time for production tooling in tool steel is about three to five days, starting with an RP master,” said Dr. Kevin McHugh, inventor of the process.
In January 2002, James Knirsch, Belcan Corp., and The Technology House worked together to form RSP Tooling, LLC to commercialize the RSP technology. The three signed a worldwide exclusive license for use of the patents for any tooling application with INEEL. Belcan Corporation, under contract with RSP Tooling, LLC, has designed and is building the first beta machine. The system is on track to go into operation during the fourth quarter of 2002.
For rapid tooling to occur, the tool designer must have access to software tools that speed the preparation of the tool design data. One software option is Magics Tooling from Materialise of Belgium. The software imports CAD designs in STL model format. After importing the STL data into Magics Tooling, the user works through the mold setup process, which involves the selection of the overall size and outer shape of the mold insert. The user then uses the tools in the software to identify and create the parting planes. Much of this occurs automatically, but some manual adjustments and changes are sometimes required. Once the parting planes are complete, it is possible to preview the mold. The view is similar to that shown in the following image.
The next step is to check the design for draft, a process that is automatic. The analysis may show that it is necessary to add or remove material from the part to create sufficient draft. Creating or modifying features of the part using Boolean operations accomplishes this.
Undercuts are processed and slides are created automatically as separate STL files.
The mold inserts are also saved as STL files. The STL data is then imported into a CNC machining center for milling or into an alternate device, such as a laser sintering machine for insert production.
An optional assembly module is available to complete the assembly of the mold. An EDM module is also available to those who wish to automate the design of electrodes. Overall, I found the Magics Tooling software powerful, mature, and relatively easy to use.
TNO Industrial Technology of Holland is also developing software that it hopes will streamline the tool design process. Called FlashTL Mould, the software promises to simplify the process and reduce the number of steps in the mold design process. For very simple molds with no slides, it is possible to push the “Go” button and the software does everything for you. Some designs, however, require manual adjustments.
The software is still in development and will require testing and refinement. Even so, it seems to work reasonably well at this early phase. It currently offers only a fraction of the tools available in Magics Tooling, but for simple, straight-pull tools with no slides, it may become a good option for many companies.
Several interesting developments are underway. Among them are EBM from Arcam, LENS from Optomec, ProMetal from Extrude Hone, RSP Tooling from RSP Tooling LLC, and Sprayform from Ford. Each of these methods produce metal parts for tooling and each come with its own sets of strengths and limitations.
Tool design software, such as Magics Tooling from Materialise, speeds the process of preparing data for tooling component fabrication. New tools are under development such as the FlashTL Mould software from TNO Industrial Technology.
Note: Parts of this paper were taken from Wohlers Report 2002, a 250-page worldwide progress report on the rapid prototyping and tooling state of the industry. Details on the report are available at http://wohlersassociates.com.
Copyright 2002 by Terry T. Wohlers