Indirect Additive Manufacturing: Pros & Cons

Investment casting example

Indirect additive manufacturing (AM) combines 3D-printed molds or patterns with injection or casting to manufacture plastics, ceramics, metals and more. It is often the most cost-effective and scalable route for medium to long runs, while retaining the geometric freedom of 3D printing.

Gold ring cast finish

Example: investment casting (lost wax casting)

The example shown illustrates a clean cast finish with no visible imperfections. Traditional wax can be replaced by a castable 3D resin such as 3Dresyn Perfect Cast HPP (Yellow), printed on a low-cost monochrome LCD printer.

Direct vs. indirect additive manufacturing

Modern 3D printing enables on-demand production across medical, transportation, industrial and consumer applications. Depending on your goals, production can follow:

Direct AM: you print the final part.
Indirect AM: you print an intermediate tool (mold, pattern or sacrificial structure) used to manufacture the final part through a secondary process.

This page focuses on indirect AM: how it works, when it wins, and the key trade-offs.

Indirect additive manufacturing processes

Unlike direct AM (printing the final object in one step), indirect AM is a multi-step workflow: first you print the mold or pattern, then you inject or cast the target material into it.

Resin and injection casting in 3D-printed molds

Resin / plastic injection: thermoplastics (e.g., polyamide) can be injected hot (e.g., ~290ºC) into 3D-printed molds.
CIM (Ceramic Injection Molding): ceramic feedstocks with binders are injected hot into printed molds.
MIM (Metal Injection Molding): metal feedstocks with binders are injected hot into printed molds.

Metal casting by lost wax and 3D resins

Lost wax (investment) casting uses a wax or castable pattern to build a ceramic/gypsum shell. The pattern is burned out, then molten metal is poured into the cavity. Today, 3D-printed castable resins can replace wax for fast, high-detail sacrificial models.

Pros and cons of indirect additive manufacturing

Pros

Faster and more cost-effective for medium and long runs (higher number of units).
Low mold cost with the right SLA/DLP/LCD printer setup.
Ideal for tougher plastics (e.g., polyamide) and durable end-use parts.
Excellent route for ceramics and metals by combining 3D printing with CIM/MIM.
Only the durable or sacrificial mold resin needs tuning, usually once per printer.
Ceramics and metals: faster debinding/sintering, affordable mold printing, and often better final properties (higher density, lower porosity, higher isotropy).
Investment casting supports a wide range of metals and high-detail geometries, with good recyclability of process materials.

Cons

Multi-step workflow (mold + injection/casting), so it is less instant than direct AM.
Can be less cost-effective for short runs (low number of units).
Slower than direct printing for basic plastic prototyping.

Process routes at a glance

Direct additive manufacturing (AM)

Photopolymer direct AM
Product: 3D printed resin objects, optionally filled with functional additives; can be formulated with ceramics, metals, polymers and exotic materials.
Properties: polymer properties plus performance tuning from additives; specialty formulations with ceramics, metals, polymers and exotic materials.
Benefits: cost-effective direct production for short runs.
Limitations: typically cost-effective only for short runs.
Direct printing of sinterable ceramics, metals, polymers and exotic materials
Process: resin printing + debinding + sintering.
Product: sintered ceramics, metals, polymers and exotic materials.
Properties: properties of sintered technical materials.
Benefits: direct production of short runs of pure sintered objects.
Limitations: expensive printers; difficult tuning; slower debinding; limited feature sizes (often ~1–3 mm); higher micro-cracking risk versus indirect routes.

Indirect additive manufacturing (AM)

Castable 3D resins (direct investment casting, DC)
Product: metal cast objects.
Benefits: cost-effective casting of metal objects.
Limitations: many competitor castables show fine-detail defects or imperfections.
Non-castable 3D resins (indirect investment casting, IC)
Product: metal cast objects.
Benefits: very high resolution master models.
Limitations: more steps, slower process.
Durable injection molding 3D resins (repeat-use molds)
Process: direct plastic injection and injection of ceramic/metal/polymer (e.g., polyimide) and exotic feedstocks in durable molds.
Product: plastics, ceramics, metals, polymers and exotic materials (with downstream processing where applicable).
Benefits: cost-effective production for simple shapes and repeatability.
Limitations: not suitable for complex intertwined geometries.
Easy breakable sacrificial 3D resins (breakaway molds)
Process: direct plastic injection in easy-break sacrificial molds.
Product: soft plastics, rubbers, silicones.
Benefits: great for complex shapes where demolding is difficult.
Limitations: mold is sacrificed (lost) during production; unnecessary for simple shapes.
Sacrificial 3D resins (water or solvent soluble molds)
Process: direct plastic injection and injection of ceramic/metal/polymer and exotic feedstocks in sacrificial molds (with downstream processing where applicable).
Product: plastics, ceramics, metals, polymers and exotic materials.
Benefits: cost-effective molds for complex internal channels and intertwined parts.
Limitations: mold is lost during production; unnecessary for simple shapes.

Alternative: direct AM by SLS using binder powders

Selective Laser Sintering (SLS) selectively fuses layers of powders to create 3D objects.
3Dresyns has developed universal bio-based non-photoreactive binder powders for physical mixing with ceramic, metal, polymer/plastic or exotic powders/fibers. These routes are also described as Cold Metal Fusion (CMF), Cold Ceramic Fusion (CCF) and Cold Exotic Powders Fusion (CEPF).
This can be considered direct AM because the printed shape is mold-free, while still requiring debinding/sintering before final use.

Benefits of 3Dresyns SLS bio-based binder powders

Ideal for SLS printing of ceramic and metal, polymers (e.g., PTFE, PEEK), and exotic materials.
Explore: Powder binders for Cold SLS printing and About CMF / CCF / CEPF.

Recommended materials and starting points

Castable 3D printing resins for investment casting patterns.
Sacrificial and mold-making 3D resins for indirect molding and complex cavity creation.
Water soluble sacrificial 3D resins for controlled water-based removal.

IFU and printing parameters

3Dresyns materials are process-dependent systems. Final performance depends on formulation version, printer technology, exposure strategy and post-processing workflow. Use our official guidance as your reference starting point in Instructions for Use (IFU) and Printing Parameters.

Need help selecting the right route?

If you are unsure whether investment casting, injection/casting in printed molds, sacrificial removal, powder feedstock workflows or hybrid routes are best for your project, contact our technical team with your application, target material, geometry constraints and expected volumes at info@3dresyns.com