A visual prototype helps you judge shape and appearance; a functional prototype lets you examine a defined function. The right choice therefore depends on the decision you need to make. An attractive object does not prove that its assembly is suitable, and a lid that closes once does not demonstrate a service life.
This guide uses the example of a small storage box resting on a table, with a removable lid, no electronics and no safety function. It is an educational example: no actual test or customer result is presented.
Choose what the prototype needs to represent
The word “prototype” alone does not tell you what can be verified. Before asking for one to be made, specify which features need to represent the intended object accurately.
| Your question | What the prototype must allow you to examine | What this does not demonstrate |
|---|---|---|
| Are the shape and proportions suitable? | Volume, silhouette and overall size at a useful scale | Assembly quality or strength |
| Does the lid fit? | Intended supporting surfaces, assembly dimensions and opening action | Wear after repeated handling |
| Are the accessories still accessible? | Internal volume and access with the objects concerned | Ease of use for every person or in every situation |
If colour or texture is part of the decision, agree a reference appearance and a sufficiently representative finish. An unfinished model cannot validate a finish it does not have. Similarly, an enlarged or lightweight version may show a shape without representing how the final object feels to hold.
A single sample can answer several questions, provided you know which ones. The distinction between a model that shows appearance and one that demonstrates a function also appears in the MIT design projects, in English.
If you are still at the idea stage, start by preparing your project from sketch to first prototype to gather the intended use, references and dimensions.
Set the criteria before the test
An acceptance criterion describes what will make a point satisfactory. It is defined before observing the result, together with the checking conditions. This avoids changing your mind about what “large enough”, “properly closed” or “easy to open” means once the part arrives.
Here are three example questions for our box. They are suggestions to adapt with the designer, not universal specifications or tests that have been carried out.
| Question | Check to prepare | Criterion to agree |
|---|---|---|
| Does the box fit in the intended space? | Compare the marked dimensions of the prototype with the drawing and the actual location | Dimensions stay within the ranges accepted on the drawing, without obstructing the identified neighbouring items |
| Does the lid reach its closed position? | Position the lid the right way round on the matching version, using the defined action | The agreed closed-position reference is reached without tools, jamming or visible deformation |
| Can the intended accessories be grasped? | Place the relevant objects in the chosen arrangement and reproduce the intended action | The specified accessories can be removed and put back without being blocked by the rim or lid |
A criterion such as “without forcing” can act as an initial warning sign, but it does not define a measurable force. If the opening force is decisive, agree a method, a suitable tool and an acceptable range. Permitted dimensions, the number of samples and repetitions also need to be defined for the project.
Observe the right version in the right conditions
Before testing, identify the prototype and its associated parts. A lid from an earlier version, a different accessory or an uneven supporting surface may make comparison difficult.
To prepare an observation you can use:
- Record the context. Note the version, date, objects used, person handling them and relevant conditions. For a measurement, record the tool and the points between which it is taken.
- Follow the agreed action. Observe the assembly and handling without adding a load, heating the part or improvising a drop test. Stop if anything jams, cracks or deforms.
- Keep a record of what you find. Note the dimension, contact area or movement that raises a question. Add a photograph if it helps explain the discrepancy. Do not sand the part to make it fit before reporting the problem.
For a use test, let the person perform the action before suggesting a way to succeed. Ask what caused difficulty and observe where they hesitate. This feedback informs the design; a few people do not automatically represent every future user.
What a successful test still leaves open
The conclusion must stay proportionate to what was observed. An assembly check answers a question about fit. On its own, it does not establish ageing behaviour, heat resistance, impact resistance or performance under repeated handling.
The choice of prototype also limits the conclusions you can draw:
- Different material and manufacture: the future object may behave differently. In filament printing, layer direction can affect mechanical properties in particular.
- Different thickness or finish: a change may affect mating surfaces or the expected flexibility; the points concerned need checking again.
- Incomplete conditions: handling on a table does not reproduce exposure to heat, moisture or cleaning products.
- A single test: this is not enough to claim a service life or consistent results in a future production run.
To decide which properties to examine, also see the guide to choosing a material for a 3D printed part according to its use. A material data sheet describes properties under given conditions; it does not, on its own, prove the strength of your manufactured geometry.
The checks suggested here concern a non-critical object. They constitute neither certification nor safety validation. If failure could injure someone or compromise a protective function, the validation plan must be established with the appropriate expertise.
Turn observations into the next step
Classify each question separately: point verified under the planned conditions, discrepancy to examine or no conclusion possible with the available information. An inconclusive test may reveal a missing measurement without justifying an immediate remake of the whole part.
When a change is needed, specify the area and objective. Where possible, limit simultaneous changes so that their effects can be understood. Keep the previous version and ask which checks need repeating: moving a wall may improve internal volume while also changing the lid’s fit.
Before proceeding, clarify the work, cost and timescale for this new stage. Making a prototype does not automatically guarantee that a small batch will be possible; its feasibility and scope need to be reassessed.
Prepare the tests with POWER PRINT
For the 3D prototyping and design service, describe the decision you are unable to make and the information already available. Add the relevant sketch or file, important dimensions and constraints, followed by the questions and criteria you propose to check.
Download the brief for preparing a first prototype — printable PDF, 2 pages
This resource is optional: the tables and method in this article are enough to prepare your initial questions. The tests to carry out and their limits still need to be agreed for your project.
Email the brief, photographs and files to contact@power-print.eu, including your name and project. If you also complete the quote request form, use the same details so that the two submissions can be matched.
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From sketch to first prototype: 7 steps to prepare your project
From sketch to first prototype: 7 steps to prepare your project