3D Printed Omnissian Axe

Making cosplay props can feel like a time-consuming, difficult, and daunting process---but it doesn't have to be. With the help of a 3D printer and CAD software (like Autodesk Fusion 360), you can easily design and fabricate your own epic cosplay prop! The Omnissian Axe is an iconic weapon from the Warhammer 40,000 franchise. I'll go through the steps I took to bring it to life through CAD and 3D printing. I hope these instructions can help you make something awesome!

This project was made as part of Ms. Berbawy's Principles of Engineering class.

Tools/Software used:

• 3D printer (I used the Bambu A1)
• Autodesk Fusion 360
• Bambu Studio
• Hand saw

Materials:

• ~1300g PLA filament (I used Matterhackers' basic gray PLA. Color doesn't really matter since we'll be painting over it anyway)
• 2 7/8" x 48" wooden dowels
• Epoxy
• Superglue
• Spray paint (I used Rust-oleum metallic paints)
• Masking tape

First, I looked for some reference art to model my axe after. This helps with determining the size of our prop and gives us some inspiration on the details. The official artbook for the Warhammer 40,000: Mechanicus video game has just what we're looking for. I've imported the part we want into Fusion as a canvas as shown.

I decided I want my axe to be around ~190cm (6'3") long, so I scaled the image to size. We'll print the axe section by section, glue the parts together, and paint it with spray paint. For structural integrity, we'll have a wooden dowel running down the length of the axe.

Let's start from the top. First, I created the main blade as well as the circular hub that connects the blade to the handle. I made a sketch of the outline and extruded it, then used chamfers to give it the shape I wanted. I made my blade 2.4cm thick. It's a fair bit smaller than the one in the reference drawing, since I thought the game proportions looked a bit silly in real life.

After that, I made the other pokey bits sticking out from the hub. I constructed some tangent planes to the hub, extruded circular profiles from them, and worked from there. I lofted a circle to a rhombus for one of the blades and integrated a sphere into the spear tip. There's a lot that can be customized here. Chamfers and fillets make it look extra fancy! I made sure that each of the pokey things is a separate body from the hub, since they're going to be printed separately.

Next, I did the part where the hub connects to the shaft of the axe. I made a profile below the hub, then extruded it to the hub as shown, making sure that this was also a separate body. Then I added some details.

Finishing with a few more decorations, I extruded a skull and cogwheel emblem from the hub and added rivets to the axe blade.

Next, I designed the long pole that the axe is mounted on. First is deciding its diameter. I found 35mm to be a good size. Because the previous part was around 56cm long, I extruded the pole to a length of 134cm to meet the desired total length.

I used extra extrusions to make some parts of the pole thicker, then added details around those sections. For most of the features, I designed a single instance, then used the circular pattern tool to replicate it around the pole. I followed the reference art pretty closely, but you can always go further and really show off your CAD skills!

For the crisscross patterned grips, Fusion's coil tool is extremely helpful. I used it to make helical grooves on the pole as shown. Make one groove, mirror it, and circular pattern both copies. Chamfer the edges as shown, and we have a nice, crisp pattern!

Now that we have an awesome CAD model, it's time to prepare it for 3D printing. First, I extruded the hole for inserting our dowel into. Getting the size right was a little tricky. Ideally, the dowel should fit snugly with a little bit of friction. For my 7/8" dowels, I found 23mm to be a good diameter after making a few test prints. The dowel should run through the pole and into the hub.

Then, I split up the model into printable parts. Some of this was done already, since our pokey things from earlier are already separate objects. For the remaining splits, I kept in mind my printer's build volume (250mm x 250mm x 300mm) and looked for places where seams wouldn't be too noticeable. Above, you can see the end result.

The hub and blade warrant some special attention. I made a 47.5mm x 15.5mm rectangular extrusion from the blade section that fits nicely into a matching 48mm x 16mm slot in the hub. Then, I split the hub into two halves down the center. This lets us print the two halves on a flat face, glue them together, and stick in the blade.

We're almost ready to start printing! Before that, though, we have to make sure that the parts can be aligned properly for assembly. I did this by adding small protrusions on a face and corresponding slots on the opposing face. When the two faces are put together, this would prevent them from sliding around.

For the pole sections, my protrusions were triangular profiles with dimensions shown, which were partially revolved around the pole's axis. The slots were made the same way, with slightly larger dimensions for tolerance.

As for the blade sections, I made a sketch on one face and extruded out at -45 degrees, then made a slightly larger slot (0.3mm longer and wider) in the opposing face. Using angled faces instead of flat overhangs allow both parts to be printed easily.

Finally, for the hub, I made circular holes to help with put the two halves together. We'll print circular pegs to insert into these holes separately.

Finally, we can transfer our 3D model into real life! I exported the design and put it into Bambu Studio. I printed my parts over 5 print sessions not counting test prints. I set the layer resolution to 0.16mm, a good balance between print time and quality.

Each component has a flat face it can be set on. Some of them required supports, so I turned on automatic supports and let the software do its thing.

Most of the parts were printed in Matterhackers Build Gray PLA filament. I underestimated the amount of filament required, which was why some components had to be printed in a different gray PLA from Hatchbox. At 15% infill, printing everything took a bit more than 1kg of filament and around three days. Patience is key!

After printing all the parts, we can put it all together. Cyanoacrylate glue, aka superglue, works great for this. I started by gluing the two halves of the hub together, then added the pokey parts to the hub.

Next, I inserted the main blade and the dowel. For this part, there turned out to be small gaps where the parts are supposed to fit together, so I used some epoxy to fill in the gaps. Then, I slid on the pole section below the hub and again used epoxy to secure it.

Because one dowel wasn't long enough, I assembled half of the axe on each dowel. Each section was placed onto the dowel as shown and secured with superglue. You may have noticed that I left one section in the middle alone; this is very important for the next part.

At this point, I had a fair bit of extra dowel left over at each end. I sawed off most of it, leaving only a length slightly less than half that of the section set aside earlier. I glued that section onto the top half. Then, I slid in the bottom half without using glue. This allows the two halves to be separated again for transport and storage.

Now we can witness our axe in its full glory---or almost. We haven't installed the blade edge yet; that comes after painting.

At last, we can start making the axe look like shiny metal instead of boring plastic. First, I went over everything with a metallic paint and primer. This is a great base coat for our creation and looks good enough by itself in some places.

To add other colors, we'll carefully cover the parts we don't want to paint with masking tape, then apply our other paints. We can go back to our reference art for guidance.

Going back to the blade edge pieces that we put aside earlier, I painted them as shown and glued on the cog teeth, then used some more glue to attach them to the axe itself.

There we go! Now we have our very own Omnissian Axe. Time to go forth and use this blessed weapon to enforce the will of the Machine God! Above, you can see me showing it off at CarrierCon (ft. a friendly R2-D2).