Giant 3D Printed LEGO Style Pumpkin

I love LEGO-style builds, and apparently making one giant seasonal decoration was never going to be enough.

For Halloween, I wanted to decorate the front of my Invention Shed at Gulliver’s Valley with an enormous LEGO-inspired pumpkin. The finished pumpkin is approximately 70 cm wide and made from more than 100 individual 3D printed pieces.

Printing it was only part of the challenge. Because the pumpkin would be installed outside at a public attraction, it needed to be assembled securely, mounted on a wooden plinth and reinforced with fibreglass and resin.

I also made oversized branches and wreaths, then covered them with 3D printed LEGO-inspired Halloween decorations to create a complete display.

The pumpkin files are available to download free from Printables.

You can also watch the complete build in my Giant LEGO Style Pumpkin video.

This is an independent fan-made project and is not affiliated with or endorsed by the LEGO Group.

3D printing

1. Access to one or more 3D printers
2. Orange PETG filament
3. Green PETG filament for the stalk
4. Additional filament colours for the Halloween decorations
5. The Giant LEGO Style Pumpkin files
6. Slicing software suitable for your printer

I used Polymaker PETG filament. You can use the code RUTHAMOS for 15% off through my Polymaker link.

Assembly

1. 3D Gloop or another adhesive suitable for PETG
2. Clamps or weights
3. Masking tape
4. Marker pen
5. Flat working surface
6. Scraper or deburring tool
7. Sandpaper or files
8. Disposable gloves

Thank you to 3D Gloop for supplying the adhesive used in this build.

Plinth and reinforcement

1. Exterior-grade plywood or another suitable sheet material
2. Timber for the plinth frame
3. Wood screws
4. Wood glue
5. Drill and driver
6. Saw
7. Fibreglass mat
8. Compatible resin and hardener
9. Mixing containers and disposable brushes
10. Appropriate protective gloves
11. Safety glasses
12. Suitable respiratory protection
13. Protective clothing

Always follow the manufacturers’ safety instructions and Safety Data Sheets when using adhesives, fibreglass and resin. Work in a properly ventilated space and use protective equipment appropriate to the products you choose.

Before printing anything, decide where the finished pumpkin will be displayed.

The pumpkin is approximately 70 cm wide, so check:

1. The width of your workshop doors
2. The available assembly space
3. How you will move the finished pumpkin
4. Whether the display will be indoors or outside
5. How it will be prevented from moving or tipping
6. Whether members of the public will be able to touch it

I nearly assembled the entire pumpkin inside before realising it might not fit through the workshop door. I therefore assembled it in sections and combined the larger sections outside.

If you are building the pumpkin for a domestic display, your mounting requirements may be simpler. For a public installation, make sure the structure and installation are assessed by a suitably competent person.

Download the model from Printables.

Import the parts into your slicing software and check:

1. The orientation of each piece
2. Whether supports are required
3. The quantity of each component
4. The estimated printing time
5. The amount of filament required
6. Which pieces form each layer
7. Whether the pieces fit your printer’s build volume

This is a very large print made from more than 100 pieces. Organising the files before printing will save considerable confusion later.

Create a simple labelling system for the parts. You could label them by layer, position or filename. Keep each completed layer or section together as it comes off the printers.

I printed the pumpkin in PETG because the finished build was intended for an outdoor display.

PETG is a practical choice for this project because it is more suitable for outdoor use than standard PLA. However, no printed material is indestructible, and long-term exposure to sunlight and weather can still affect it.

Use the recommended settings from the model listing as your starting point, then adjust them for your printer, nozzle and chosen filament.

For a build of this size:

1. Check the first layer carefully
2. Make sure the filament is dry
3. Inspect every completed print
4. Remove strings, blobs and support material
5. Check that joining edges are clean
6. Label each piece immediately
7. Keep spare filament from the same colour batch

A huge thank you to Paul from Pimoroni, who helped print this monstrosity. Sharing the workload between several printers made the project much more achievable.

Before using adhesive, lay out the pieces for one complete layer.

Check that:

1. The pieces are in the correct order
2. The curves line up
3. The stud pattern remains consistent
4. The joining faces meet cleanly
5. No piece has been printed at the wrong scale or orientation

Do not force parts together. If something does not fit, check the part number and orientation before removing material.

Small print variations can accumulate across a structure this large. Dry fitting each layer makes it much easier to identify a problem before it becomes permanently glued into the pumpkin.

Once you are satisfied with the dry fit, glue the pieces together.

I used 3D Gloop formulated for the printed material. Use only an adhesive that is compatible with your filament, and follow the manufacturer’s instructions.

Work on one manageable section at a time:

1. Place the pieces on a flat, protected surface.
2. Apply adhesive to the joining faces.
3. Bring the pieces together carefully.
4. Check the outside alignment and stud spacing.
5. Hold the joint using clamps, tape or weights as appropriate.
6. Allow the joint to cure fully.
7. Add the next piece.

Avoid trying to assemble the entire pumpkin in one go. Building it in layers makes alignment easier and prevents the finished object becoming trapped inside your workspace.

It also helps with the inevitable stage where every orange component begins to look identical.

he pumpkin needed a stable base because it was going into an outdoor public display.

I made a wooden plinth using a timber frame and sheet material. The exact dimensions will depend on your pumpkin, display location and installation requirements.

The plinth should:

1. Support the full footprint of the pumpkin
2. Resist bending under the completed weight
3. Provide secure fixing points
4. Remain stable on the display surface
5. Be suitable for the intended environment
6. Allow the pumpkin to be fastened from inside

Assemble the frame with exterior-grade wood glue and screws. Attach the top panel securely and seal or paint the wood if it will be exposed to moisture.

Test the empty plinth in its final location before attaching the pumpkin.

Position the lower section of the pumpkin on the plinth and mark its location.

Secure the pumpkin to the plinth using a fixing method appropriate to the printed shell and wooden base. I bonded the pumpkin in place before adding internal reinforcement.

Make sure that:

1. The pumpkin is centred
2. The front is facing the intended direction
3. The base sits flat
4. The fixings do not pull through the printed material
5. Any mechanical fixings are backed or reinforced
6. The completed object cannot slide or rotate

For a public display, do not rely on adhesive alone without assessing whether additional mechanical fixing is required.

Once the pumpkin was assembled and fixed to the plinth, I reinforced the inside using fibreglass and resin.

This connected the individual printed sections and created a much stronger internal shell.

Before starting:

1. Confirm that the resin is compatible with the printed material
2. Test the process on a spare piece
3. Protect the surrounding area
4. Wear suitable protective equipment
5. Work with adequate ventilation
6. Follow the product’s mixing and curing instructions exactly

Apply the fibreglass and resin to the inside of the pumpkin, concentrating on:

1. Seams between printed sections
2. The connection between the pumpkin and plinth
3. Large areas that flex when pressed
4. Points that will carry installation loads

Work in manageable sections and allow the resin to cure fully.

Do not guess resin-to-hardener ratios. Use the manufacturer’s specified ratio and working conditions.

Once cured, check the structure for sharp fibres, uncured resin or unsupported sections.

Once you have made the giant pumpkin, you do not have to stop there.

I decorated the surrounding branches and wreaths with oversized, brick-inspired Halloween pieces, including ghosts, bats, spiders, skulls and smaller pumpkins. You could use them to decorate a doorway, garden, workshop or Halloween tree, or build an entire spooky display around your pumpkin.

1. Download the Giant LEGO-Style Pumpkin files
2. Explore my other giant 3D-printed Halloween decorations

Try different colours, scale the models to ridiculous sizes and add battery-powered lights to any hollow decorations. Use the files as a starting point, then make the display completely your own.

One giant pumpkin is good. An entire oversized Halloween world is better.