MJ Engineering Knows 3D Printing! - MJ Engineering

In addition to their fused deposition modeling (FDM) desktop 3D printer (see 3D Printer Series—Part 1), MJ Engineering also owns a stereolithography apparatus (SLA) desktop 3D printer. The SLA printer from formlabs is used to make parts for test fits and dry runs.  

3D printing materials-SLA

The SLA printer uses photosensitive thermoset polymers in liquid form. An ultraviolet (UV) laser beam selectively hardens (cures) the polymer resin, layer-by-layer, through a process called photopolymerization, which creates strong unbreakable bonds. As the part is being built, the build platform rises, lifting the part upward, out of the resin bath.

Is an SLA printer worth it?

 Although the FDM printer can make parts that are stronger and more durable, the SLA printer is ideal when high accuracy or a smooth surface finish is desired. The SLA printer excels at tight tolerances, to the tune of plus or minus one thousandth of an inch—10 times more precise than the FDM printer.

3D printing materials-FDM

MJ Engineering’s Markforged FDM desktop 3D printer builds parts using a black thermoplastic filament called “Onyx,” which is primarily used when parts are needed to check form, fit, and function. The Onyx plastic can be reinforced with different continuous fibers, depending on the intention for the part being printed. Some examples of fill materials used with Onyx are:

  • Fiberglass—basic, cost-effective reinforcement material
  • High strength, high temperature (HSHT) fiberglass—to maintain strength in high-temperature settings
  • Carbon fiber—to withstand fatigue and improves stiffness and strength
  • Kevlar—to endure high impact and high deflection applications

To add the reinforcement material, the 3D printer uses two different nozzles. One nozzle dispenses plastic (Onyx), while a second nozzle dispenses the reinforcement material in the locations specified by the software. Typically, the reinforcement material is internal to the part and is enclosed in plastic.

Putting parts together

If a part fits within the parameters of the printer’s build plate and height restrictions, it can be printed as one piece. Otherwise, it can be bolted or glued. For example, as a test for a machine MJ Engineering is working on, a part like the one pictured here can be printed out of Onyx on the FDM printer in two pieces and then superglued. Once the finalized design is determined, the printed part can be bolted to the actual machine. “We can make sure it works the way we want it to and there are no flukes,” says mechanical engineer JC Kraml, “before we send it to our machine shop and spend 100 times more.”

To discover more methods by which MJ Engineering is using 3D printing to improve its projects, parts, and processes, check out Part 3 of our 3D Printer Series.