Small batch plastic injection moulding is a segment many industrial buyers think they understand. Few truly master the tooling cost / part cost / industrial risk ratio. Here is what you need to know to launch a small injection moulding séries in Belgium without unpleasant surprises.
Small batch: how many parts are we talking about?
The term 'small batch' covers very différent realities across sectors. In médical, 500 parts per year may already justify a steel mould. In automotive, small batch is anything below 50,000 parts per year. At Moulding Injection, we define small batch as between 500 and 50,000 annual parts, with a key economic tipping point around 5,000 parts.
Below 500 parts, a soft silicone or resin mould may suffice - provided tolerances and final material properties allow it. Above 5,000 parts, a steel injection mould (P20, H13 or stainless steel depending on the injected material) is almost always the most cost-effective choice over three years.
Steel mould vs soft silicone mould
A soft silicone mould is fast to build for low volumes, typically 20 to 200 parts per cavity before mould dégradation. It is suited to casting polyurethane or époxy resins.
Watch for the classic trap: the mechanical properties of a cast polyurethane part and an injected PA66 part may look similar visually, but their behaviour under fatigue, température and moisture absorption are radically différent. Validating a design on a silicone mould and then finding that the final steel-tooled part behaves differently is a fréquent mistake in lighting and electronics sectors.
A steel injection mould offers a service life of 200,000 to 1,000,000 cycles depending on the steel grade and injected material. Amortised over several production years, it is the optimal choice once annual volume justifies it. Our tip: for séries between 2,000 and 8,000 parts per year, a single-cavity P20 steel mould offers the best cost/durability ratio. This avoids over-engineering a multi-cavity mould whose tooling cost never amortises at low volumes.
Concrete case: enclosure for a Belgian médical device
A médical equipment manufacturer based in Brabant wallon contacted us for a diagnostic device enclosure in médical-grade ABS (UL94-V0). Required volume: 3,000 parts per year. Geometry: 2 side actions, integrated assembly clips, leather-grain texture finish on 3 faces.
First step: DFM (Design for Manufacturing) analysis. Result: 4 risk areas identified, including an insufficient draft angle on a textured wall. Correction made in the design office before any mould manufacturing. Tooling selected: single-cavity P20 steel mould. The customer was able to start séries production on schedule and without any tooling rework.
Why producing in Belgium remains a real advantage
We do not subcontract our mould manufacturing. Tooling is designed by our partner LGR Design Studio and machined in our workshop in Ath. Design and production are fewer than 60 km apart. This proximity enables 24-hour turnaround for iterations, real-time tooling adjustments and full material and process traceability.
In automotive and médical sectors, traceability is not an option. A part subject to IATF 16949 or ISO 13485 requirements needs documentation of every material batch, every injection parameter, every dimensional check. Producing in Belgium with a single point of contact from mould to assembly radically simplifies supplier audits.
Beware of turnkey offers with offshored production and a Belgian commercial office: in case of non-conformance, who bears responsibility? Who modifies the mould? Within what lead time? These questions carry real cost that the initial quote never reveals.
The 4 most fréquent mistakes in small batch injection moulding
1. Ordering tooling before validating the design. Commissioning a mould from a 3D file that has not been through DFM means risking paying twice. At least 30% of the parts we receive for first analysis require corrections before tooling.
2. Underestimating the importance of material sélection. PP and PA66 have very différent moulding shrinkage behaviour. A mould designed for one will not give correct dimensions with the other. Material must be chosen before mould design.
3. Overlooking the hidden costs of low-cost tooling. An imported mould at a low price may look attractive. But if tooling rework is needed, the lead time can reach 8 to 14 weeks and modification costs are often not contractually guaranteed.
4. Failing to anticipate volume growth. A customer starts at 1,000 parts per year and reaches 15,000 two years later. If the initial mould was a soft tool or entry-level steel mould, the question of second tooling arises. Anticipating growth potential from the start allows correct tooling dimensioning.
Overmoulding: an often overlooked option in small batch
Overmoulding (injecting a second material onto an already-moulded part) is often seen as reserved for high volumes because of the second mould cost. This is not accurate. For parts requiring a rigid section (PP or ABS) and a soft section (TPE), small-batch overmoulding is feasible from 2,000 parts per year with appropriate two-shot tooling.
Our tip: in some cases, insert overmoulding (pre-manufactured rigid part placed in the mould, then overmoulded with TPE) allows using two simple moulds rather than one complex two-shot mould. Total tooling cost can be significantly reduced for suitable géométries.
Moulding Injection: ISO 9001:2015 certified plastic injection moulder in Belgium
We are ISO 9001:2015 certified. Every material batch, injection parameter and dimensional check is documented. Our partner LGR Design Studio handles DFM design and CNC mould machining. We process standard and engineering thermoplastics: PP, ABS, PA, PC, POM, TPE, TPU.
Our small-batch customers include manufacturers in médical, electronics, lighting and industrial equipment sectors, based in Belgium and northern France.
Start with a free DFM analysis
Send us your 3D file (STEP or IGES), your target annual volume and intended material. Our engineering team analyses your part's small-batch injection feasibility within 48 working hours. You receive structured feedback: risk areas, material recommendations, tooling estimate.
FAQ
From how many parts is small batch plastic injection moulding cost-effective in Belgium?
At Moulding Injection, the economic tipping point is around 5,000 parts per year. Below that, a soft silicone mould may suffice to validate a design. Above that, a single-cavity P20 steel mould is almost always the optimal choice over three years. Tooling amortisation is the key factor to assess from the study phase, before any order.
What is the différence between P20 and H13 steel moulds in small batch?
P20 steel (pre-hardened) suits small to medium séries, up to 300,000 to 500,000 cycles depending on the injected material. It costs less to manufacture. H13 steel (hardened) is reserved for high volumes and abrasive materials (PA GF, POM). In small batch, P20 is the standard choice if the injected material is not abrasive.
What is DFM analysis and why is it essential before ordering a mould?
DFM (Design for Manufacturability) analysis reviews a plastic part to identify design issues before the mould is built. In small batch, where every tooling investment counts, DFM detects sink mark zones, insufficient draft angles, non-uniform wall thicknesses and warpage risks. Correcting these issues after the mould is machined is systematically longer and more expensive than before.
Does Moulding Injection manufacture its own moulds in Belgium?
Yes. Our partner LGR Design Studio, based in Wavre, designs the moulds and operates an in-house CNC machining workshop. Injection is carried out in our workshop in Ath. The proximity between design and production enables fast iterations, full traceability and shorter tryout lead times compared to offshored production.
Is overmoulding possible in small batch?
Yes. Overmoulding (injecting a second material onto an already-moulded part, for example PP plus TPE) is feasible in small batch from 2,000 parts per year. In some cases, an insert technique allows simplifying the tooling and significantly reducing the total project cost. A DFM analysis determines feasibility for your specific geometry.
