Form model or functional prototype: which one do you need?
A form model lets you see and handle the part: size, proportions, ergonomics. A functional prototype lets you use it: assemble it, load it, make it work. Choosing the right one avoids paying for a test that does not answer your question. It is the first thing we agree on in every prototyping project.
The form model
It reproduces the look and the envelope of the final part. You use it to judge proportions and grip, show the product to a client or a colleague, and check that it fits the space available. It does not carry loads, so it can be printed in PLA, the simplest and quickest material to print.
The functional prototype
It is built to be tested. It has to mate with other parts, close with a clip, move on a hinge, withstand the heat or humidity of the place it will work in. Material, wall thickness, tolerances and print orientation all matter here: that is why it is designed following the rules of design for manufacturing and printed in PETG, ABS or ASA depending on the use.
The differences at a glance
| Form model | Functional prototype | |
|---|---|---|
| Question it answers | What does it look like? Does it fit? | Does it work? Does it hold? Does it assemble? |
| Typical material | PLA | PETG, ABS, ASA |
| Tolerances | Indicative | Designed for the fit |
| Finish | Often more refined, because it is shown | Whatever the test needs |
| When | Early, to settle the shape | Before tooling or production |
How to choose
Ask yourself three questions before requesting a quote:
- What must the part prove? If the answer is about appearance, a form model is enough. If it is about an assembly or a load, you need a functional prototype.
- Where will it be tested? Sun, heat from a motor or a damp environment change the material. The differences are on our materials page.
- How many versions do you expect? It often pays to start with a quick form model and move to a functional prototype once the shape is settled. How this affects the price is explained in our guide on how much a prototype costs.
Can one prototype do both?
Sometimes: a well-designed PETG part can be shown and assembled. But a functional prototype with a refined finish costs more, and a form model used for a mechanical test can break without telling you anything useful. If you are not sure, describe the use: we will tell you which one fits.
Frequently asked questions
Which material is used for a functional prototype?
It depends on the test. PETG for clips, enclosures and parts that need to flex; ABS for housings and parts near heat sources; ASA for outdoor components.
Does a 3D printed functional prototype behave like the final part?
Not always. An FDM part, built by laying molten filament layer by layer, is weaker between layers and the material may differ from the production one. We tell you in advance what the prototype can and cannot prove.
Can I start without a 3D file?
Yes. A sketch, photos and measurements are enough; we build the model. If you have a file, our guide on which file to send explains which format to use.
Can a functional prototype be used for a small batch?
Often, yes. When the 3D printed part already meets the requirements, we can produce a small batch in the same material; otherwise we tell you which process fits better.
Tell us about the part you need.
Attach the file if you have one, or describe the part with photos and measurements. We reply within 24 working hours with a quote or the technical questions we need answered.
Request a quote