3D printing vs. injection moulding: When do you choose what?

Table of contents

• What's the difference between 3D printing and injection molding?
• When do you choose 3D printing over injection molding?
• When do you choose injection molding?
• Direct comparison: price, time and quality
• Combining both methods
• What do the two methods cost in practice?
• FAQ

3D printing vs. injection molding is one of the questions we hear most often at Maker Factory. Customers reach out with a CAD file and ask: should I 3D print this, or should I have a mold made? The answer is driven primarily by three factors: series size, geometry and timeframe. If you're producing under 500–1,000 pieces, 3D printing is almost always the right choice. Above 5,000 pieces, injection molding starts winning on price. In between, you need to calculate the specific breakeven point for your product.

Both technologies use plastic — but in fundamentally different ways. 3D printing builds a part up layer by layer (additive manufacturing), while injection molding forces molten plastic into a steel mold under high pressure. That gives them very different strengths and weaknesses, and they complement each other better than they compete.

What's the difference between 3D printing and injection molding?

With FDM 3D printing, plastic filament is melted and laid down layer by layer directly from a digital file. With SLA 3D printing, liquid resin is cured with UV light, layer by layer. What both 3D printing methods have in common is that no mold is required — you go from CAD file to physical part with no startup cost and full freedom to change the design between prints.

Injection molding works the other way around. First, a steel mold — typically hardened steel or aluminum — is CNC-machined, then molten plastic is forced into the mold under 500–2,000 bar of pressure. The mold costs DKK 20,000–150,000 depending on complexity and number of cavities. In return, it can produce thousands of identical parts in 15–45 seconds per cycle.

The fundamental difference is: 3D printing has zero startup cost and a high unit price. Injection molding has a high startup cost and a very low unit price. The breakeven point — where the curves cross — is the number that decides your choice.

When do you choose 3D printing over injection molding?

3D printing isn't only a choice for those who can't afford a mold. It's the technically and economically better solution in a wide range of scenarios, regardless of company size. Here are the situations where additive manufacturing consistently delivers better results:

• Series under 500 pieces where the mold cost can never be recovered through the unit price — applies to prototypes, pilot series and custom parts
• Complex geometry with internal channels, lattice structures or organic shapes that would require expensive slide tooling with injection molding
• Iterative design with 3–6 design versions along the way — changes are free with 3D printing, and can cost DKK 5,000–30,000 with a mold change
• Fast lead time — a functional part in hand in 2–7 days versus 8–12 weeks of mold production
• Customer-specific parts where each unit is unique, e.g. assembly jigs with specific dimensions, custom covers or branding elements
• Spare parts for machines and equipment where the original mold has been scrapped or no longer exists
• Material testing and function validation before you invest in a mold — print in the actual material, test it, adjust

Prototypes and fast iteration

The most obvious use of 3D printing is prototypes — but "prototype" covers more than a visual model. We regularly print functional parts in PETG and PA6-CF that customers test directly in their machines and products. At Maker Factory we see customers run 4–6 design iterations in a week — something that would take months and cost tens of thousands with injection molding.

The typical process: the first prototype reveals a tolerance issue. Version two fixes it. Version three optimizes the weight. All three versions are in hand before a traditional mold maker has even responded to your inquiry.

Custom parts and spare parts with no minimum order

Injection molding needs volume to make sense. If you need 15 pieces of a specific cable routing or 8 pieces of a sensor housing, it makes no sense to invest DKK 40,000 in a mold. 3D printing delivers exactly the quantity you need — no minimum order, no inventory risk.

This applies especially to spare parts. Many machines are 10–20 years old and their original molds have long since been scrapped. With 3D printing, we can reconstruct a part from a measurement or a scanned object and produce exactly the quantity you need.

Complex geometry with no mold cost

3D printing doesn't know the concept of an "undercut" the way injection molding does. A part with internal cooling channels, lattice structures for weight reduction, or organic shapes that follow an ergonomic curve — it costs the same to print as a simple box. With injection molding, the same features would require a multi-cavity mold with slides and cores, which can easily double the mold cost.

When do you choose injection molding?

Injection molding is unbeatable for one scenario: large series of a locked design. Once the mold is paid off and the design is locked, the unit price with injection molding is a fraction of what 3D printing can deliver. It's an industrial technology optimized for volume and reproducibility — not for flexibility.

• Series over 5,000 pieces of the same design — unit price drops to DKK 2–15/pc. depending on complexity
• Surface quality is critical — injection-molded parts have a perfect finish and reproducible gloss straight from the mold
• The design is completely locked and won't change for at least 2–3 years
• Cycle time is critical — an injection molding machine produces a part in 15–45 seconds
• Materials not available as print material: PEEK, POM, PEI and other high-performance engineering polymers

Batch Production above 1,000 pieces

The breakeven point between 3D printing and injection molding typically sits at 500–2,000 pieces depending on the part's size, complexity and chosen material. Above this point, injection molding's low unit price starts to outweigh the mold cost. For large series — 10,000 pieces and up — injection molding is the only realistic option economically.

Perfect surface and reproducibility

Injection molding delivers a surface that's identical part for part — without the layer lines FDM leaves behind and without the slightly matte finish SLA parts can have after post-processing. For consumer products with high aesthetic requirements, or parts that appear in visible assemblies, injection molding's finish is hard to match with 3D printing alone.

Materials that can't be 3D printed

Certain high-performance polymers — PEEK, POM (Delrin), PEI (Ultem) — can technically be 3D printed, but require special equipment and are expensive. For most standard applications, they're available as injection molding materials at a fraction of the cost. Always consider whether your material need actually requires 3D printing, or whether a well-known injection molding material solves the task better.

Direct comparison: price, time and quality

The two methods are designed for fundamentally different needs. The table below summarizes the key parameters:

Combining both methods — the smart approach

Most products with commercial ambition end up using both methods. 3D printing is perfect for the development phase, and injection molding takes over once the design is locked and volume increases. At Maker Factory we help customers with exactly this transition — from first prototype to production-ready part.

The typical process looks like this:

1. Prototype in 3D printing — test form, fit and function in PETG or PA6-CF. Allow yourself to iterate 3–5 times.
2. Pilot series (50–200 pcs.) in 3D printing — market testing and customer feedback before the mold cost. This is where most mistakes are caught cheapest.
3. Transition to injection molding — once the design is locked and you know there's demand. The mold cost is now an investment, not a risk.

This approach typically saves 2–4 months in time-to-market and significantly reduces the risk of expensive mold changes. A mold change costs an average of DKK 8,000–25,000 — an iteration in 3D printing costs DKK 300–2,000. The math is simple.

What do 3D printing vs. injection molding cost in practice?

Let's take a concrete example: a housing for a sensor, roughly 80×50×30 mm in PETG.

• 3D printing (FDM, PETG): approx. DKK 95/pc. regardless of quantity. 100 pcs. = DKK 9,500. Delivered in 5 business days.
• Injection molding: Mold DKK 35,000 + approx. DKK 8/pc. 100 pcs. = DKK 35,800. Lead time: 10 weeks. 5,000 pcs. = DKK 75,000 (DKK 15/pc. incl. mold). Lead time: still 10 weeks for the first batch.

Breakeven in this example is around 400 units. Under 400: 3D printing. Over 400: injection molding — but remember that mold production takes 8–12 weeks. That time cost is real and should be factored into the total project economics. Many product launches have missed their market window because of mold production time.

According to TCT Magazine — which covers additive manufacturing professionally — the breakeven point for many industrial components today sits at 300–800 pieces, as 3D printing unit prices fall with better printers and materials.

FAQ — 3D printing vs. injection molding

When is 3D printing cheaper than injection molding?

3D printing is typically cheapest for series under 500–1,000 pieces. The exact breakeven point depends on the part's size, complexity and chosen material. For a simple housing, breakeven might sit at 400 pieces — for a complicated part with many features, it can be lower, because the mold cost rises faster than the 3D printing price.

Can 3D-printed parts replace injection-molded parts in production?

Yes, in many cases. With materials like PA6-CF and PETG we produce parts used as end products in industry — not as prototypes. PA6-CF has a tensile strength above 100 MPa, comparable to injection-molded nylon. The surface quality is different, and for very large series injection molding is still the right choice — but functionally, 3D printing can meet the spec in many cases.

How long does it take to go from CAD file to finished part?

With 3D printing: 2–7 business days from CAD file to delivered part. With injection molding: 8–12 weeks for mold production, then 15–45 seconds per part. The time difference is dramatic and is often underestimated in project planning. If you have a deadline within 2 weeks, 3D printing is the only realistic option.

What are the key material differences?

PETG, ABS, PA and TPU are available as both 3D printing filament and injection molding material. 3D printing also gives access to specialty materials like carbon-reinforced nylon and technical resins not found in standard injection molding. Conversely, injection molding can process PEEK and POM at very low unit prices in large series. Material choice therefore shouldn't stand alone — it needs to be considered alongside volume and production requirements.

Can you switch from 3D printing to injection molding during a project?

Yes, and it's actually our recommendation for most products headed to market. Use 3D printing for prototype and pilot series, and switch to injection molding once the design is locked and you've confirmed demand. This reduces the risk of expensive mold changes and gives you time to optimize the design in a cheap technology before investing in an expensive mold.

What are typical mold costs for injection molding?

A standard simple mold in aluminum costs DKK 20,000–50,000. A mold in hardened steel for long series costs DKK 50,000–150,000. Molds with slides, cores or multi-cavity design can cost more. The mold cost is a one-time expense — but must be recovered through the unit price, and that requires volume.

Is 3D printing more sustainable than injection molding?

For small series, 3D printing is generally more sustainable — only the needed quantity is produced, and there's no surplus production. For large series, injection molding is more energy-efficient per part, because cycle time is very short and material utilization is high. The most sustainable approach is to match the production method to the actual volume — rather than choosing one method on principle.