A broken plastic clip, a missing knob, a cracked bracket holding a household appliance together — these failures usually mean buying a $40 replacement part for a $60 appliance, or throwing the whole thing out. With an FDM printer and basic measuring skills, most of these broken components are reprintable for the cost of a few grams of filament. This guide covers the systematic process for measuring a broken part and modeling a functional replacement.
Measuring a Broken Part
If you have both pieces of a cracked part: Tape them together in their original position and measure the whole. This gives you the true original dimensions even if a fragment is missing.
If a piece is missing entirely: Measure the surrounding context. A broken knob’s missing shaft socket can be measured from the device’s shaft diameter directly. A broken bracket’s mounting points can be measured from the screw hole spacing on the device itself.
Caliper technique for small features: Digital calipers measure internal and external dimensions to 0.01mm precision. For a broken clip, measure: overall length, width at the widest point, thickness, the engagement hook depth and angle, and the screw or snap mounting point spacing.
For complex curved parts: Photograph the part next to a ruler or known-size reference object from multiple angles. Import the photo into Blender as a background reference image and model by tracing the silhouette at the correct scale.
Modeling the Replacement
Start simple. Most household replacement parts are combinations of basic shapes: a box with rounded corners, a cylinder with a hole through it, a flat plate with mounting holes. TinkerCAD handles the vast majority of household replacement part designs without needing Blender’s complexity.
Build the part as a series of primitive shapes combined with Boolean operations, exactly as covered in earlier guides on deck box design. Add 0.2-0.3mm clearance to any dimension that needs to slide into an existing slot or over an existing shaft (see the FDM tolerance guide for the full clearance reference).
For parts under continuous mechanical stress (gear teeth, load-bearing brackets, anything that flexes repeatedly): print in PETG rather than PLA. PETG’s improved impact resistance and ductility make it the better choice for replacement parts that need to survive real use rather than just look correct.
Common Replaceable Parts
- Appliance knobs and dial caps (measure the D-shaft or splined shaft profile carefully)
- Cabinet and furniture hinges, brackets, and corner braces
- Vacuum cleaner wheels, latches, and attachment clips
- Remote control battery door latches
- Blind and curtain rod mounting brackets
- Toy parts: wheels, axles, connector pegs
- Garden hose nozzle adapters and connector fittings
- Car interior trim clips and cup holder inserts
The time investment for a simple replacement part (measure, model in TinkerCAD, print) is typically 30-60 minutes total. The cost savings vs buying a manufacturer replacement part, when one is even available, is almost always significant.