Site: EOS GmbH
(Electro Optical Systems)
Zeiss Gruppe
Pasinger Str. 282152 Planegg
Munich, Germany

Date Visited: 25 October 1995

JTEC/WTEC Attendees: L. Weiss (report author), A. Lightman, F. Prinz

Hosts:

Dr.-Ing. Mike Shellabear
Dr. Hans Langer

BACKGROUND

EOS (Electro Optical Systems) was started by Dr. Hans Langer in 1989, and he received financing to initiate production in 1990. He had worked previously for General Scanning (as European manager), where he became acquainted with 3D Systems' stereolithography (SLA) machine as well as the other material scanning systems. Langer secured bank and venture capital funding to start EOS contingent upon an order from BMW for the STEREOS machine. BMW ordered the first machine with conditional acceptance: the performance had to at least match 3D Systems' SLA, and the build speed had to be considerably faster. Langer stated that the delivered machine exceeded BMW's specification, and since then, BMW has ordered four more machines. EOS achieved profitability in its second year of business.

EOS currently employs over 80 employees. Its headquarters and R&D facility are both in Planegg. Production is at the Zeiss facility in Jena, and there is another subsidiary in Lyon, France. Total sales as of June 1996 amounted to more than 100 units, with more than 50% occurring in the preceding 12 months. Recent sales had been split approximately equally between stereolithography and sintering systems. EOS currently holds a substantial share of the European RP market and seeks to expand its share. Several sites now have multiple EOS machines, including BMW (5), Grunewald (4), Bertrandt (3), Hoffman (2), Electrolux (2), and Bubeck (3). Carl Zeiss recently purchased the majority stock position. Its executives saw a strong tie to the company's 3D CMM business, in pattern making and quality verification, and they are attempting to create jobs in East Germany. They foresee a potential customer base within the current ~4,000 CMM sites. Prior to beginning production, Dr. Langer conducted an extensive patent search and found a French PhD thesis with extensive work in layered manufacturing in photopolymers. He also mentioned the work from Japan. The company is strongly driven by its customer base -- BMW, Daimler-Benz, and Fiat -- which companies asked EOS to join them in an EC project. EOS has patented new technologies for recoating and exposure in both photopolymers and powders. EOS executives have made a conscious decision to focus EOS market offerings in the high-end products. They are not currently developing desktop convenience modelers; they are developing machine tools with production capability.

CURRENT SYSTEMS

STEREOS Machines

The EOS STEREOS line includes three models: 250, 400, and 600. The model number indicates the critical vat dimension, in mm. The smaller machine uses the HeCd laser, and the larger machines use argon and solid-state lasers. The STEREOS MAX 600 was redesigned in 1995 for better mechanical rigidity and process reliability, incorporating a cast C-frame that holds the optics and recoating system. Several innovations had been incorporated, including a detachable wiper arm and a roll-out vat that permit rapid material changeover. EOS implemented as an option a diode-pumped frequency-tripled pulsed solid-state laser, which is specified as providing 250 mW UV at the laser head, 10-30,000 pps, with an anticipated lifetime of 10,000 hours and a wall-plug efficiency of approximately 0.1% (as compared with 0.001% for an argon laser). Current systems build with layers as thin as 0.1 mm, and some customers build at 0.05 mm. EOS cooperates with a number of material manufacturers and offers resins from DuPont and Allied Signal for STEREOS machines. DuPont's recent introduction of its epoxy resin SOMOS( 6100 has provided EOS with an alternative to Ciba-Geigy epoxy resin. Published accuracy figures for the SLA User Group test part, using Allied Signal Exactomer resin, yielded (90 = 0.056 mm (0.0022 in.).

The STEREOS MAX 600 uses a non-dipping recoat system: the recoater uses a metered pump to draw up resin and then disperses the resin through a slit nozzle. This provides single-pass smooth coating over any geometry layer built. Exposure of the new layer starts immediately after the recoater finishes its pass.

Sintering Machines

EOS produces three categories of sintering machines: EOSINT P for laser-sintering of plastics, EOSINT M for laser-sintering of metal, and EOSINT S for laser-sintering of foundry sand. The sintering systems use CO2 lasers with 50-250 W power. The systems are optimized for the material. Radiation heaters are used to heat the powder bed when preheating is needed. The powders are joined by a variety of mechanisms: material melting, surface bonding, sintering aids, and polymer coatings. Materials include polyamides (nylon), polystyrene, a proprietary metal from Electrolux, and a polymer-coated sand. EOSINT P works with thermoplastic materials and is focused on investment casting patterns (polystyrene) and model making (polyamides). EOSINT M performs direct sintering of metal (without polymer binder), suitable for tools for plastic molding. EOSINT S was officially introduced in September 1995 but has been in use at pilot customer sites since June 1995. Eight machines were already in use at customer sites as of June 1996. EOSINT S uses a coated sand that solidifies under laser exposure to build molds and cores for direct use in the conventional sand-casting process, including for production manufacturing of limited-quantity specialty items. This method has been patented by EOS.

Polystyrene material overcomes the considerable difficulty European casters encountered trying to use epoxy models. Processing polystyrene closely resembles processing investment casting wax: the polystyrene model can be infiltrated with liquid wax and then surface-finished the same way as traditional wax models. Typical layer thickness is 0.1-0.2 mm.

The Electrolux material has no net volume change during the laser sintering process. Therefore, sintering can be performed in a room-temperature environment under standard atmosphere. Laser sintering yields approximately 70% density. It is a multicomponent material that during the process forms an alloy that has a lower density, so it expands at the same time as the material shrinks due to the melting. The net result is dimensional stability, effectively eliminating the curl issue. Post infiltration has an impact on final accuracy, which is typically limited to system accuracy -- about 0.1 mm. The University of Texas has published results of experiments using a similar material, but Electrolux patented this material in 1989, and EOS has the exclusive worldwide license. Some customers have used the porous part in low-pressure injection molding where the porosity does not prohibit molding. Infiltration materials include hardenable epoxy resins and low-melting-temperature metals such as Sn and PbSn.

In its plastic sintering process, EOS builds a box surrounding the part. Later, when this is removed from the build chamber, the box holds the part in an insulating layer of powder, and thermal cooling can proceed in a room environment. Using its own technology, EOS speeds up the turnaround time for use of the machine. Parts can be removed in a "hot" system, greatly reducing the cool-down, heat-up cycle time. Powder spreading is performed through a slot nozzle the leading and trailing edges of which are contoured to supply the desired force vector as the head is vibrated from side to side. This allows researchers to use a wide variety of powders. The combination of EOS technologies enhances their dimensional capability, the walled volume allowing higher builds and the material processing permitting greater surface area (340 mm x 340 mm x 590 mm for the P350 model, and 720 mm x 380 mm x 380 mm for the EOSINT S 700).

EOS differentiates between model-making and mold-making applications, respectively, for plastic or metal end-parts, and it offers machines specially developed and optimized for these applications, as shown in Table EOS.1.
EOS participates in BRITE EuRAM and EARP programs.
EOS got a third-party software company to create a direct interface from CATIA, which evolved into the common layer interface (CLI) output. Using this direct layer interface can be considerably faster than using the STL interface. It is also used by companies such as Materialise that are writing medical interfaces.

Table EOS.1
EOS Model Making and Mold Making Applications

     ++     Main application
      +     Also recommended
      o     Either not direct (via process chains) or not suitable

The JTEC/WTEC team's hosts noted that medical applications appear interesting and a growth area but are not considered to be a machine sales driver. EOS management will watch carefully but does not think this area will expand until insurance companies cover the costs of building the models.


Published: September 1996; WTEC Hyper-Librarian