How to Add Dowels, Pins & Connectors to 3D Printed Parts

Author: Arndt von Koenigsmarck · Last reviewed August 2026 

When you print an object in several pieces, the parts have to fit back together reliably. Dowels, pins, rods, screws and magnets all do this job, and each one needs a matching recess modeled into both halves. This guide shows how to add connectors to 3D printed parts in Cinema 4D, from cutting clean recesses with a Boolean Generator to building a reusable, fully parametric connector you can drop into every project. It is part of our larger guide on Cinema 4D for 3D printing, and it follows on naturally from splitting large models.

For large objects made of several printed components, or whenever real structural strength is required, connectors make the difference between a fragile assembly and a solid one. Decorative items, cosplay props and device prototypes all benefit from being able to insert wooden dowels, metal rods, or nuts and bolts into the parts. To do that, you need to build matching openings or recesses into the model, and the Boolean Generator is ideally suited to the task, because it lets you subtract or add separate objects to your printed parts as needed. You will find it under Create > Generator > Boolean.

Cylindrical shapes are ideal for connecting separately printed parts, and matching openings are easy to create by subtracting a parametric cylinder. Place the sub-model to be printed first under the Boolean Generator, then place the shape you want to subtract as the second object beneath it. In the Boolean Generator's settings, the Operation option controls the calculation mode. By default it is set to Union, which adds all objects together. To cut a recess, set Operation to Subtract instead.

As long as the sub-model is a closed, watertight shape and the two volumes overlap, the Boolean works immediately. Everything remains fully editable, so you can still move the shape to be subtracted or adjust its size at any time. If you need several cutouts, just place the additional objects beneath the Boolean object in the third, fourth and further slots.

A plain cylinder works, but you gain far more flexibility by building a connector from a Cone Node Generator, which you can then extend and reshape with grouped Node Modifiers. This is a genuine strength of Cinema 4D, because the result stays fully parametric and reusable across all your projects.

Open the Asset Browser from the Window menu (or via its icon) and search its Search field for the "Cone" generator. Drag it into the Object Manager. Next, search for the "Select Facing" node and place it under the Cone. Configure Select Facing with Type set to Polygons and Axis to Y+, so the faces on the top surface of the cone are selected automatically. Then add an "Extrude" node with Type Polygons and Use Islands enabled, and drag it in as a second object below the Cone, so it acts on that top-cap selection.

With this setup, you control the shape entirely through numeric values. The cylinder radius is set by the Cone's Top Radius, the fineness of the divisions by its Rotation Segments, the cylinder length by the Extrude node's Offset, and the funnel shape at the base by the Cone's Height and Bottom Radius.

With the node system there is no limit to the parametric connectors you can build, and to save you the setup, we have prepared a parametric dowel and connector object for you. After unzipping it, load it straight into your project with File > Merge…

When you select the object, it offers various settings in the Attribute Manager. You can switch between cylindrical and rectangular connector shapes and specify the dimensions numerically with exact precision. It also includes a dedicated Create Dowel mode that generates a slightly scaled-down version of the shape, ready to print as the physical dowel itself.

The parametric dowel has its axis system exactly at its center, which you can use for precise placement on the surface of a part. Switch to Model Mode and select the dowel you want to position. Choose the Place Tool from the left toolbar (also in the Tools menu), then move the pointer over the surface of the sub-model while holding the left mouse button, and watch the dowel glide across the surface.

To place the dowel's center axis on the surface rather than one of its ends, set the Place Tool's Reference Point to Axis. If the dowel points into the model with the wrong end, check the Up Direction setting and switch between Y and -Y depending on which end should sit inside the part.

For the connectors to fit precisely into the neighboring part, the same dowel objects must be subtracted from it too. Simply use copies of the final, placed dowel objects and subtract them from the second part with a new Boolean Generator. To reuse a configured dowel multiple times, Ctrl-drag it in the Object Manager to create copies (or use standard copy and paste).

If you chose a rectangular recess, you can adjust its rotation directly by dragging the curved element of the Place Tool. When the shape of a part requires a dowel or threaded rod to sit at an angle to the cut surface, use Cinema 4D's standard Rotation tool. The one rule to remember is that if you need several recesses, they must all share the same angle, otherwise the printed parts will not fit together.

3D printers do not necessarily print at 100% accuracy, so you are often safer making any shape intended for removal, where an element will later be inserted, slightly larger than strictly necessary. An extra tenth of a millimeter is usually enough. This is exactly why the parametric dowel object includes a mode to specify a percentage reduction, so a dowel you print yourself comes out slightly smaller than its recess and fits cleanly.

Dowels are only one option. Metal sleeves with internal threads, available in screw-in or press-fit versions, let you screw parts together for a connection you can undo later, which is ideal for transport or replacing a component. Magnets and standard screws work similarly. Hinges, whether modeled directly or added as piano or rod hinges, allow flexible, moving connections. In every case, the recesses for these elements are created the same way, by subtracting the appropriate shape with the Boolean Generator. The physical joining methods themselves are covered in modeling for 3D printing.

Next in the workflow: design for strength and printability from the start in modeling for 3D printing.