How to 3D Print Something Bigger Than the Build Plate: Split, Pin and Glue

To 3D print something bigger than the printer, cut the model into parts that each fit the build volume, add alignment pins at every cut, print the parts and glue them together. At Mandarin 3D each part can be up to 250 x 250 x 250 mm; a 500 mm prop is usually four to eight parts.

Done well, the seams are hard to find. Done badly, you get a step at every joint and a part that snaps where it was glued. The difference is where you cut and how the parts line up.

Step 1: Decide where to cut

Good places to cut:

• Along existing edges. Panel lines on armor, the line between a helmet's dome and face plate, the edge of a sign's frame. The seam hides in a line that was already there.
• Across flat faces. A flat cut gives a big glue area and a clean join.
• Where each part can lie flat. Cut so every part has a flat face for the print bed. That removes most supports and gives the best surface on show.

Bad places to cut:

• Through thin features (fingers, horns, fins under 3 mm thick).
• Through text or fine detail.
• Where the joint will carry load. Put the cut where the part is thickest, or reinforce it (step 3).

Aim for as few parts as possible, but don't fight the 250 mm limit with a part that only fits at an awkward angle. A slightly smaller part that prints flat beats a bigger one covered in supports.

Step 2: Cut it in software

You don't need full CAD for this.

The slicer cut tools are the fastest: place the plane, pick "dowel" or "plug", and export each part as its own STL or 3MF. For free CAD options, see the best free CAD software for 3D printing.

Step 3: Add alignment pins or keys

Glue alone lets parts slide while it sets. Pins fix the position.

Separate pins (dowels). Holes in both faces, a printed or bought pin in between.

• Pin: 5-6 mm diameter, 15-20 mm long (half in each part).
• Holes: pin diameter plus 0.4 mm (0.2 mm per side), plus about 0.2 mm because printed holes come out small. For a 6 mm pin, model 6.6 mm holes.
• Use two pins per joint so the parts can't rotate.

Printed plugs. A peg on one part, a socket on the other. Same clearance: 0.2 mm per side, plus the hole allowance. A 0.5 mm chamfer on the peg tip makes assembly easier.

Dovetails or keys. Best for long flat joints like a sign or a panel. Leave 0.2-0.3 mm per face.

Bolts. For parts you want to take apart (a prop that travels, a large enclosure), use M3 or M4 bolts with heat-set inserts or captive nuts. See adding threads to 3D printed parts.

Our tolerance guide has the full clearance table.

Step 4: Print with matching settings

Print every part with the same layer height, wall count and infill, in the same orientation relative to the cut where you can. Mixed settings show up as different surface textures on either side of the seam.

For parts that get handled (cosplay armor, handles), use at least 3 walls, about 1.2 mm with a 0.4 mm nozzle; our wall thickness guide explains why.

Step 5: Glue and finish

1. Dry fit first. Push the pins in and check every joint before any glue.
2. Sand both faces lightly with 120-220 grit. Glue holds better on a rough surface.
3. Pick the glue:
   • Thin CA (super glue): small parts, sets in seconds. Add accelerator for faster setting.
   • Medium or gel CA: a bit of gap filling, a few seconds to adjust.
   • Two-part epoxy (5-30 minute): big parts and joints that carry weight. Fills gaps and gives you time to align.
4. Clamp or tape while it sets. Painter's tape across the seam works for most parts.
5. Fill the seam with filler primer or a thin layer of body filler, sand smooth, then prime and paint.

Common mistakes

• No pins. The parts slide while the glue sets and you get a 1 mm step at the seam.
• Pins with no clearance. They won't go in, or the part cracks when you force them.
• Cutting through the thinnest part. The joint becomes the weakest point exactly where the part is already weak.
• Every part printed differently. Layer lines run in different directions and the seams show through paint.

What we print, and what we don't

We print your parts in PLA, each up to 250 mm per side, in black, white, gray, red, blue or green. PLA sands and paints well, which suits props and display pieces.

A few limits from our prohibited items list: no realistic firearm replicas, no protective helmets or safety gear (a display or cosplay helmet is fine), and no brand logos or licensed characters unless you own or license them. For cosplay specifics, see 3D printing for cosplay.

Get the parts printed

Export each part and drop it in the box below for an instant price. Small parts that fit together on one 250 x 250 mm plate can go in one file. Price is set by grams and print hours (pricing). Need pins or a connector block? Describe it and the AI designer will model it. First order? Read how to get something 3D printed.