EOS P 396

The EOS P 396 is a medium-sized plastic SLS 3D printer from EOS. (Image courtesy of EOS.)

The EOS P 396 is an upgrade to the company’s previous EOSINT P 395 range, improving on its predecessor in terms of speed and efficiency. According to the manufacturer, the newer machine consumes 38 percent less energy and 3D prints up to 32 percent more quickly. This is in part due to the use of a new 70W CO₂ laser, a low-wearing, high-speed recoater for dispersing powder and a new point pyrometer, which measures the temperature of the powder to improve the precision of the recoating process. Featuring a build volume of 340 x 340 x 600 mm (13.4 x 13.4 x 23.6 in), the EOS P 396 can print objects at speeds of approximately 48 mm/h (1.9 in/h) and with layer thicknesses as fine as 60 microns (0.00236 in). This all depends on the material used, however, of which this system can handle quite a few. 

The most popular material used in all SLS machines is polyamide (PA), typically known in its synthetic form as nylon. The EOS P 396 can process a wide variety of PA materials, including the aluminium-PA blend alumide, flame-retardant PA, glass bead–filled PA, carbon fiber–reinforced PA and other specialty PA powders. Given the versatility of PA, as well as its relative strength, this system is capable of producing a variety of functional components and prototypes for industrial, aerospace, automotive, medical, jewelry and other applications. Additionally, this system can 3D print with polystyrene, which, due to its low melting point and dimensional accuracy, makes it useful for creating patterns for investment casting.

How the EOS P 396 Works

As a powder bed fusion technology, SLS uses a heat source, specifically a powerful laser, to fuse material powder together into a three-dimensional object. In the case of the EOS P 396, a thin layer of plastic powder is spread across the build platform within an inert nitrogen gas chamber before a 70W CO₂ laser melts the powders together. The platform is subsequently lowered and another layer of powder is spread onto the bed, at which point the laser does its magic once more. This process is continued until the object is completed.

The use of a laser to precisely sinter the plastic powder allows for a high level of detail at faster speeds than fused deposition modeling. The powder surrounding the printed object acts as a support material, allowing for the possibility of particularly complex prints, including moving parts. Once the print is removed from the print bed, airbrushed and put into a tumbler, the object is ready to go. In terms of post-processing, SLS is somewhat less time intensive than many other 3D-printing methods.

Despite their precision, SLS plastic prints are often characterized by a somewhat rough finish. Additionally, because the unsintered powder in the build area is also heated to just below melting point, the material cannot be reused repeatedly. Instead, the powder is mixed with new material to produce the necessary results. Other issues that occur with SLS plastic parts are their overall porosity and the limited colors available, though EOS is working to change that through an investment in a company called DyeMansion, which is developing new dying processes for SLS.

The EOS P 396 in Action

Once a year, the Institution of Mechanical Engineers in the United Kingdom hosts the Formula Student race series, which sees students teams from across the globe build and race their own formula-style race cars. In response to the effects of climate change associated with fossil fuel use, the program opened up a vehicle class dedicated to the use of electric engines. To meet the challenge, the students from DHBW Engineering Stuttgart built the eSleek14, which featured two electric motors capable of delivering 60 horsepower each, powered by 24 lithium-polymer battery cell modules with a 6.7-KWh capacity total. EOS acted as the additive manufacturing expert for the team, supporting them in the construction of a 3D-printed cooling system for the vehicle’s motors.

Due to the composition of the batteries, the possibility of overheating and even fire within the battery system needed to be mitigated by the student team. Therefore, a method for cooling the battery was required. At the same time, the weight of the vehicle had to be kept to a minimum. As this was a custom race car and not your average four-door sedan, a cooling duct that would suit their needs could not be purchased off the shelf and injection molding was not suitable for the design the team had in mind. With all of these variables in mind, DHBW Engineering turned to 3D printing.