Prototypes and Small Series
Sample parts that already know where they are heading: we produce prototypes and small series in injection moulding — with in-house toolmaking that keeps the later series in mind from the first part.
Between an idea and a stable series lies the prototype phase. It decides how many corrections a part still needs later – and how expensive those corrections become. The earlier tooling expertise enters the process, the fewer surprises arise once the production mould exists.
This article explains what prototyping achieves in plastics, how the methods differ and why the choice of route should be made together with the tooling decision.
The key points at a glance
- Prototyping reduces project risk. Design, function, assembly and manufacturability are verified before major investment in a production mould.
- Rapid prototyping settles form and fit. 3D printing is well suited to first geometry checks, but does not reproduce the material behaviour of a moulded part.
- Prototype moulds deliver realistic parts. Samples from the production material allow shrinkage, warpage, surface and strength to be assessed.
- Early tooling expertise saves correction loops. Wall thicknesses, draft angles and gate position are easier to change in the design phase than in hardened steel.
- Cost and time depend on the objective. What the prototype has to prove determines which route is economical.
What prototyping means in plastics
A prototype is a physical sample created before series production. It serves to verify assumptions: does the geometry fit into the installation space, does assembly work, does the part withstand the intended load? In plastics processing, prototyping ranges from a printed geometry model through to moulded parts from a simplified mould.
Which questions should a prototype answer?
Before choosing a method, it is worth defining what exactly is to be verified. The answer determines the route:
- Installation space and geometry: does the part fit, are the interfaces correct?
- Assembly: can the part be joined, do snap connections and clearances work?
- Function under load: does the part hold at the required temperature and force?
- Surface and appearance: do texture, gloss level and colour meet expectations?
- Manufacturability: can the part be produced in the intended process at all?
The first two questions can usually be answered with a printed model. The last three require parts from the actual production material.
Methods compared
- 3D printing (rapid prototyping): fast and inexpensive, ideal for geometry and fit. Material properties, shrinkage and surface differ from the later moulded part.
- Prototype mould: a simplified mould, often in aluminium, that produces parts in the production material. More effort and cost, but realistic results.
- Machined sample: parts milled from solid material. Suitable for geometry and some functional checks, but shows neither shrinkage nor the effects of the moulding process.
In practice the routes are often combined: first a printed model to settle the geometry, then a prototype mould for the series-relevant properties.
Why early tooling expertise is decisive
Many part properties are not determined by the material but by the mould. Wall thickness distribution, gate position, draft angles and cooling influence warpage, weld lines, sink marks and dimensional accuracy. Anyone who involves tooling expertise only once the design is finished has already ruled out options.
A manufacturer with in-house mould making can point out these effects during the design phase – at a point where a change costs a CAD revision rather than steel work. That is where the greatest economic leverage of the prototype phase lies.
Cost and time viewed realistically
A printed sample is available within days and costs little. A prototype mould requires design, manufacture and sampling – but delivers parts whose behaviour matches the later series. Which route is cheaper therefore cannot be answered by price alone, only in relation to what the sample has to prove.
Expensive is not the prototype mould, but the correction loop on the production mould that could have been avoided.
A typical project path
The following describes a typical, anonymised project sequence. It serves as orientation and does not replace a project-specific feasibility assessment.
A customer plans a housing component for an electrical engineering application. Tight tolerances, a defined surface, sufficient stability and a later series with recurring demand are required. First, 3D printing is used to check installation space, form and mounting position. After initial adjustments, a series-realistic validation follows – depending on requirements, a prototype mould can be sensible so that sample parts are produced in the moulding process from a suitable material.
During sampling, dimensions, surface, function and critical areas are examined. If an unfavourable weld line or critical warpage appears, the mould concept can be adjusted before the production mould is finalised. This is exactly where the economic benefit arises: errors become visible at a stage where changes are still manageable.
Prototyping at Schröder + Heidler
Mould making, injection moulding and sampling are located at one site. Findings from the prototype phase therefore feed directly into the design of the production mould, without shipping or cross-company coordination. Where several components are combined, our subassembly assembly takes over the subsequent steps.
Our processes are certified to ISO 9001 and IATF 16949. Existing moulds from other manufacturers can be taken over via tool transfer and transferred into series production after assessment and sampling.
Frequently asked questions
What is the difference between rapid prototyping and a prototype mould?
Rapid prototyping usually means 3D printing: fast, inexpensive, suitable for geometry and fit. A prototype mould is a simplified injection mould that produces parts in the actual production material – more effort, but realistic material behaviour.
When is a prototype mould worthwhile?
Whenever properties are to be verified that only arise in the moulding process: shrinkage, warpage, surface quality, strength or behaviour under temperature. For pure geometry checks, a printed model is sufficient.
What does a prototype mould cost?
That depends on part size, geometry, number of cavities and the required tool life. A single-cavity aluminium mould for a small part lies far below a multi-cavity steel mould. A reliable figure requires the drawing.
How long does the path from prototype to series take?
This depends on part complexity, mould scope and the release documents required. In addition to manufacturing time, feasibility assessment, design release, sampling and production start-up all take time. You receive a concrete schedule with the quotation.
Why is early tooling expertise so important?
Because wall thicknesses, gate position and draft angles determine part quality – and these are far easier to change during design than in a finished mould. Involving a manufacturer with in-house mould making early avoids correction loops on the production mould.
What role do ISO 9001 and IATF 16949 play?
They document that processes are defined, monitored and traceable. In automotive, IATF 16949 is generally a prerequisite for supply; ISO 9001 is the broader quality management standard.
Conclusion: define the objective, then the method
Prototyping is not a fixed procedure but a choice of route that follows from the question to be answered. Whoever defines that question precisely – and involves tooling expertise early – reaches a stable series faster and with fewer corrections.
Are you at the start of a plastics project? Talk to us about feasibility.