Katana Nerf-Blaster

I have always been obsessed with swords and Nerf blasters as a kid. To the little elementary school me, swords were the most badass thing ever, and I also loved having backyard Nerf battles with my friends.

But I asked myself, what if we combine the best of both worlds? This question sparked an idea inside me, one where you can rock both a sword and a Nerf blaster, two in one.

So, I present before you, my invention: a Katana Nerf blaster that combines the aesthetic appeal of a sword, paired with the functional prowess of a Nerf blaster.

With this Instructable, I'll lead you on your journey to make your personal Katana Nerf blaster at home!

Special thanks to Ms. Berbawy's POE class and Berbawy Makers for providing me the resources and opportunity to turn this idea into reality.

This project was designed entirely in the Autodesk Fusion 360 CAD Software.

Materials/Tools

• 3D Printing Filament (I used Prusa's Prusament PLA, any generic PLA filament works too)
• Wooden Dowel Rods (1/4" diameter)
• Compression Spring (18.26 mm x 88.90 mm x 1.05 mm)
• Stainless Steel Socket Head Screw (M4 x 0.7 mm Thread, 20 mm Long)
• Steel Nylon-Insert Locknut (M4 x 0.7 mm Thread, 5 mm High)
• iFixit Moray Driver Kit
• Caliper measuring tool
• Nerf N-Strike Mega Dart

Software

• Autodesk Fusion
• Prusa Slicer

Machinery

• Original Prusa i3 MK3S+ 3D Printer

I started by sketching the dimensions of the sword handle. The sword handle should be in an ergonomic shape that fits your hand. The sword handle also needs holes to fit the wooden dowels that connect it to the rest of the katana. I added tolerances to the holes (0.2 mm to the diameters of the holes in which the dowels will fit and 1.90 mm to the hole in which the Nerf dart will be chambered).

The handle needs to be tall enough to fit both the Nerf Mega dart AND the compression spring! I added a second segment to add to the length of the handle so that I could hold onto the katana with both hands.

From the side of the handle, I made a slot for the bolt-action Nerf launcher mechanism, and also made a two-piece bolt which when pulled back would cock the spring into a ready-to-fire position. The bolt also acts as a platform for the Nerf dart to sit on and is what shoots the Nerf dart out from the handle.

All holes need to be made with tolerances in mind. Add 0.2 mm in diameter to the original diameter of the object going into the holes. CAD is just a simulation under perfect circumstances, but prints will never be perfect in practice!

A cap at the end of the handle is required to hold the Nerf dart without it falling out. In my design, I added a little connector for the handle cap to snap and hold in place. For ease of use, I made a brim that sticks out of the bottom of the handle cap. This allows me to flick open the handle cap easily with my thumb.

Changes are needed for the handle to connect the two pieces. I made a joint to connect the handle cap and the handle, and extruded a hole, cutting through both bodies at the same point.

The diameter of the hole needs to be made according to the size of the M4 screw, with tolerances in mind. I added 0.2 mm to the diameter of the M4 screw when making the hole, as it is what fits best when assembling the printed product. I made another cut into the handle cap in place of where the screw head would be. You can download and insert CAD files of the M4 screw and lock nut from McMaster Carr's digital catalog.

The fillet tool will be your best friend when rounding the edges of the handle cap. If certain edges are not filleted, the handle cap will block itself from opening.

The handguard is the most versatile part of the entire sword, as it can take the shape of anything you can imagine. I made a classically shaped katana handguard. The holes in the handguard should match the size and location of the holes in the handle exactly, since every component of the Katana Nerf Blaster is joined together by the wooden dowels.

The blade is made by joining together three types of blocks. The first, and most used one, is the curved blade segment. The second is the tip of the sword. The third type is the straight blade segment.

1. The curved blade: I first sketched the shape and dimensions of the blade, and added holes for where I want the dowels to be held as connectors. Then, using a second sketch, I drew a path that I wanted the blade to follow. To finish up, I used the sweep tool to make a body following the path that I drew in the previous step.
2. The tip of the blade: I followed the same steps to make the curved blade, but instead of a full length blade, I made it stop halfway on the path. After this, I used the sketch tool to draw a path for which the blade tip would be shaped. Finally, I use the loft tool to form the katana's tip. The sketch lines are used as rails in the loft function to extrude a tapered blade tip.
3. The straight blade: I used the straight blade as a starting segment on the handguard that leads into the curved shape of the katana blade. Simply use the extrude tool to extrude the sketch of the blade into a body.

I used Prusa Slicer with the Prusa i3 MK3S+ 3D printer to print out my Katana Nerf Blaster invention. First I exported my project on Fusion 360 as a .3mf file. Next, I imported the project into Prusa Slicer.

In Prusa Slicer, I separated the bodies, placed each component on the appropriate face, and then auto-organized the build plate. Since some parts of the katana have overhang (the slit for the bolt-action mechanism on the handle and the face from the underside of the handle cap), I enabled supports for support enforcers only and used the paint-on supports option to mark areas that require supports.

I used the gyroid infill pattern for my print. The rest of the print settings should be kept untouched since Prusa Slicer has built-in presets specific to each of their 3D printers.

One specific piece, the katana blade tip, requires separate printing. The katana blade has a very thin tapered tip, and to compensate for this during printing, I set the XY Size Compensation setting in the Advanced settings to 0.25mm (to see this setting you need to turn on Expert mode in Prusa Slicer print settings).

Now that the build plate is ready to be exported, I exported the G-code onto the SD card of the Prusa i3 MK3S+ printer, and started the print.

Now with all of your parts printed, you are ready to put together your very own Katana Nerf Blaster!

Due to the XY Size Compensation, the katana blade tip's holes for the wooden dowel were not be true to size, which meant I needed to use a drill to make the hole bigger. Otherwise, every other part was able to fit perfectly. I used the wooden dowel to join all of the pieces together (the blade segments, the handguard, and the handle).

Finally, I assembled the part that completes the Katana Nerf Blaster: the bolt-action Nerf launcher mechanism. First, I put the compression spring into the hollowed inside of the handle. Next, I stuck the bolt through the slit in the handle and clicked in the cap at the end to secure it in the slit so it does not fall off. Next, I used a scissor at home to cut the Nerf Mega N-Strike dart into half the original size, making it able to fit in the handle. With this, you have completed the journey of building your very own Katana Nerf Blaster!