From prototype to low-volume production in industrial automation

For many industrial engineering projects, there isn’t a dramatic moment when prototyping ends and production begins.

A component may start as a one-off part for a development machine. Then three are needed for trials. Ten are required for the first customer installations. Six months later, the same part is being ordered repeatedly for a family of machines.

At some point, the manufacturing process that made sense for the first component may no longer be the best way to produce the next hundred.

Knowing when to stay with 3D printing, move to CNC low-volume production or invest in injection mould tooling can make a significant difference to cost, lead time and flexibility.

What is low-volume production in industrial automation?

Low-volume production simply means manufacturing repeatable end-use components in quantities below conventional mass production.

There is no universal quantity at which “low volume” begins or ends.

In automation and special-purpose machinery, the volumes can be particularly modest because the equipment itself is often built in low numbers.

A manufacturer may need:

Five sets of components for an initial machine build
Twenty replacement jigs across several sites
Fifty housings for a production run
A few hundred machined parts each year
Regular batches of a component as individual machines are ordered

The right manufacturing process depends not only on quantity but also on material, geometry, future design changes and how often the parts are likely to be reordered.

When should you stop prototyping and start thinking about production?

A useful trigger is repeatability.

If you are repeatedly ordering the same component, it’s worth asking whether the current manufacturing method still makes sense.

Signs that the project is moving towards low-volume production include:

The design has become stable
The part has passed functional testing
Multiple machines need the same component
Customers are receiving the part as part of finished equipment
Replacement parts need to be stocked
Part-to-part consistency has become more important
Orders are becoming regular rather than occasional
Unit cost is beginning to matter more

This does not necessarily mean changing the manufacturing process.

Sometimes the process used for prototyping remains the most appropriate production method.

Can SLS 3D printing be used for end-use industrial parts?

Yes.

SLS doesn’t have to be regarded purely as a prototyping technology.

Functional PA12 components can be used for suitable end-use applications where their mechanical and environmental properties meet the requirements.

This can make SLS particularly attractive for low-volume automation components because there’s no dedicated tooling investment.

Typical examples might include:

Robotic tooling
Sensor housings
Cable management components
Machine covers
Jigs and fixtures
Handling components
Custom brackets
Positioning nests
Low-volume replacement parts

When does staying with SLS make sense?

Continuing with SLS can be attractive when:

Volumes remain relatively low
Geometry is complex
The design may continue to evolve
Several variants are required
PA12 is suitable for the application
Tooling costs would be difficult to justify
Parts need to be produced on demand

SLS also allows multiple unrelated parts to share a build, making it well suited to high-mix, low-volume engineering requirements.

When might you need to move away from SLS?

A different process may become more appropriate if the component needs:

Metal construction
Tighter critical tolerances
Different wear characteristics
Greater stiffness
A production thermoplastic not available through the printing process
Much higher quantities

At that point, CNC machining or injection moulding may offer a better route.

When is CNC low-volume production the right choice?

CNC machining has an unusual advantage in automation: the prototype process can also be the production process.

If a part has already been successfully tested in aluminium, stainless steel or an engineering plastic such as acetal, it may be possible to move directly from a one-off CNC prototype into repeat batches without redesigning it for a completely different manufacturing method.

This makes CNC particularly useful for specialist machinery.

Applications include:

Machine components
Brackets
Mounting plates
Actuator components
Bushes
Spacers
Housings
Fixtures
Tooling
Production machine parts

What quantities suit CNC low-volume production?

There is no fixed answer.

We commonly support projects ranging from a handful of parts to a few hundred, and in some circumstances larger quantities may also be appropriate.

The key consideration is whether machining each component remains commercially sensible compared with investing in tooling.

For a high-value industrial machine produced in modest numbers, CNC machining may remain the right production process indefinitely.

Why is CNC useful when designs continue to change?

Automation products often evolve throughout their commercial life.

A customer’s specification changes. A supplier discontinues a sensor. A new motor requires a slightly different mounting arrangement. A cable route needs adjusting.

With CNC machining, a mould tool doesn’t need to be physically modified. Instead, a new CAD revision can be programmed and manufactured.

That flexibility can be worth more than achieving the absolute lowest possible unit cost, particularly when production quantities are small.

When does injection moulding start to make sense?

Injection moulding requires an upfront investment in tooling but reduces the manufacturing cost per component as quantities rise.

It also provides repeatable parts in production-grade thermoplastics.

For industrial equipment manufacturers, injection moulding becomes worth considering when:

The plastic component design is stable
Repeat orders are expected
Quantities have increased
Consistent production material is important
A moulded finish is required
The expected tool life justifies the investment
Unit cost is becoming increasingly important

We offer UK-made tooling in aluminium, pre-toughened steel and hardened steel, allowing the tool specification to be matched to expected volumes and programme requirements.

What materials can be injection moulded?

Material choice should be driven by the component’s requirements.

We work with materials including:

Polypropylene (PP) for applications needing chemical resistance and flexibility.

ABS for tough, rigid components with good impact resistance.

PA6 for durable mechanical components where wear resistance is useful.

Polycarbonate (PC) for applications where strength or transparency is required.

Glass-filled and flame-retardant variants are also available where additional performance is required.

One of the key advantages of moving to injection moulding is that parts can be produced in the intended production thermoplastic rather than a prototyping substitute.

CNC machining or injection moulding: which is better for low volumes?

For many engineering teams, this is the critical production decision.

CNC machining is often better when:

Quantities are relatively small
The design may change
The part is metal
Very high tooling expenditure is difficult to justify
Several design variants are required
Material must be machined from solid
You need the freedom to make CAD changes between batches

Injection moulding is often better when:

Quantities are increasing
The design is stable
The component is thermoplastic
Consistent repeat production is required
Lower unit cost matters
The moulded surface and material are important
Ongoing demand justifies tooling

There’s no magic crossover quantity.

Part size, complexity, material, machining time and tooling cost all affect the calculation.

A simple component that takes significant CNC machine time may justify moulding sooner than a complex low-volume component that machines efficiently.

The sensible approach is to compare the whole expected requirement rather than the cost of the next ten parts in isolation.

What about vacuum casting?

Vacuum casting sits between one-off prototyping and production tooling.

A silicone mould is produced from a master pattern and used to create polyurethane copies.

This can be useful when you need a small batch of parts but are not ready for injection moulding.

For industrial projects, examples can include:

Housings and covers
Flexible protective parts
Handles
Seals
Components needed for several machine builds
Production-representative parts for testing

Vacuum casting is generally best thought of as a small-batch process rather than a long-term manufacturing route for large repeat orders.

However, for genuinely low-volume equipment, a vacuum cast component may also be suitable as the finished part.

Should you redesign the part when you change manufacturing process?

Often, yes.

A design optimised for SLS is not automatically optimised for CNC machining.

Likewise, a machined plastic part should not simply be sent for injection mould tooling without considering Design for Manufacture.

Each process has different requirements.

Moving from SLS to CNC

A printed part may contain internal geometry, enclosed passages or complex curves that are difficult to reach with cutting tools.

It may therefore need to be simplified or divided into several components for machining.

Moving from CNC to injection moulding

An injection moulded design needs to consider features such as:

Draft angles
Wall thickness
Ribs
Bosses
Undercuts
Gate location
Ejection
Sink and warpage

Changing process is therefore a design decision as well as a purchasing decision.

Discussing the likely future production route early can prevent unnecessary redesign later.

What is bridge production?

Bridge production fills the gap between prototype development and a more established production method.

Imagine an automation product has been launched, and the first machines need to ship, but the final production arrangement is not yet ready.

SLS, CNC machining, vacuum casting or low-volume injection moulding may provide a temporary production route.

This can allow early machines to be built and delivered without delaying the whole project.

In other cases, “bridge” production simply becomes the permanent method because volumes never rise enough to justify mass-production tooling.

What about spare and replacement parts?

Industrial equipment has a much longer life than many consumer products.

That creates another question when choosing a manufacturing process: how will this component be replaced in five or ten years?

For suitable 3D-printed or CNC-machined parts, keeping approved CAD data can make replacement straightforward without holding large quantities of physical stock.

This can be particularly useful for:

Specialist machines
Low-volume equipment
Customer-specific variants
Tooling and fixtures
Components that wear occasionally but unpredictably

A digital inventory is not appropriate for every application, but it can reduce the need to manufacture and store parts “just in case”.

Can different processes be used on the same machine?

Absolutely.

In fact, that is often the best approach.

A special-purpose machine might contain:

CNC-machined aluminium structural parts
Acetal guides and bushes
SLS sensor brackets and cable guides
SLS gripper components
SLA covers or development housings
Injection moulded production components

Manufacturing processes are tools, not competing camps.

The aim is to use the process that makes the most technical and commercial sense for each component.

Planning the route from prototype to production

When discussing a new component with a manufacturing supplier, it’s helpful to provide some indication of future demand even if the numbers are uncertain.

For example:

Prototype requirement: 2 parts now
Pilot requirement: approximately 20 parts in three months
Expected production: 100 to 200 parts per year

That information could lead to a different recommendation from simply asking for a quote for two components.

A process that looks most economical for the first prototype might create unnecessary cost later.

Equally, investing in tooling too early can be expensive if the design then changes.

The best production route balances what you need today with what is reasonably likely to happen next.

Supporting automation projects from prototype to production

We work with automation engineers, machine builders and industrial equipment manufacturers from early development through to repeat low-volume manufacture.

With SLS and other 3D printing technologies, CNC machining, vacuum casting and UK-based injection moulding available through one supplier, the manufacturing route can evolve as the project does.

You don’t have to decide on day one how a component will be made for the rest of its life.

Start with what the part needs to achieve now, then plan for what comes next.

To discuss a prototype, pilot batch or ongoing low-volume requirement, call 01763 249760, email office@prototypeprojects.com, or request a quote.