Indirect Additive Manufacturing: Pros & Cons
Indirect Additive Manufacturing: Pros & Cons
Investment casting (lost wax casting)
The gold ring below shows a clean cast finish with no visible imperfections. Here, traditional wax was replaced with our castable 3D resin: 3Dresyn Perfect Cast HPP Yellow , printed on a low-cost monochrome LCD printer.
Direct vs. indirect additive manufacturing
Modern 3D printing technology enables on-demand manufacturing across medical, transportation, industrial, and consumer applications. Depending on your goals, production can be approached via direct or indirect additive manufacturing. This page focuses on indirect AM: how it works, when it wins, and key trade-offs.
Indirect additive manufacturing processes
Unlike direct AM (printing the final part in one step), indirect AM is a multi-step workflow: first you print the mold, then you inject or cast waxes, resins, plastics, or ceramics and metals into it.
Resin & injection casting
- 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 & 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 in. Today, 3D-printed castable resins can replace wax for fast, high-detail sacrificial models.
Pros & cons of indirect additive manufacturing
Pros
- Faster & 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 & metals by combining 3D printing with CIM/MIM.
- Only the durable or sacrificial mold resin needs tuning—usually once per printer.
- Ceramics & 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’s 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 summary tables
The following tables summarize common direct and indirect manufacturing routes where SLA, DLP, LCD, and Inkjet are used.
Direct additive manufacturing (AM)
| 3D resin | Process | Product | Properties | Benefits | Limitations |
|---|---|---|---|---|---|
| 3D resins | Direct AM | 3D printed resin objects, optionally filled with functional additives; can be formulated with ceramics, metals, polymers, and exotic materials | Polymer properties + performance tuning from additives; specialty formulations with ceramics, metals, polymers, and exotic materials | Cost-effective direct production for short runs | Typically cost-effective only for short runs |
| Direct printing of sinterable ceramics, metals, polymers & exotic materials | Resin printing + debinding + sintering | Sintered ceramics, metals, polymers & exotic materials | Properties of sintered technical materials | Direct production of short runs of pure sintered objects | Expensive printers; difficult tuning; slower debinding; limited feature sizes (often ~1–3 mm); higher micro-cracking risk vs indirect routes |
Indirect additive manufacturing (AM)
| 3D resin | Process | Product | Properties | Benefits | Limitations |
|---|---|---|---|---|---|
| Castable 3D resins | Direct investment casting (DC) | Metal cast objects | Typical properties of cast metals | Cost-effective casting of metal objects | Many competitor castables show fine-detail defects or imperfections |
| Non-castable 3D resins | Indirect investment casting (IC) | Metal cast objects | Typical properties of cast metals | Very high resolution master models | More steps → slower process |
| Durable injection molding 3D resins | Direct plastic, and sintering ceramic/metal, polymer (e.g., polyimide), and exotic feedstock injection in durable molds | Plastics, ceramics, metals, polymers, exotic materials | Properties of the injected/sintered materials | Cost-effective production for simple shapes and repeatability | Not suitable for complex intertwined geometries |
| Easy breakable sacrificial 3D resins | Direct plastic injection in easy-break sacrificial molds | Soft plastics, rubbers, silicones | Properties of soft plastics, rubbers & silicones | Great for complex shapes where demolding is difficult | Mold is sacrificed (lost) during production; unnecessary for simple shapes |
| Sacrificial 3D resins (water/solvent soluble) | Direct plastic, and sintering ceramic/metal, polymer (e.g., polyimide), and exotic feedstock injection in sacrificial molds | Plastics, ceramics, metals, polymers, exotic materials | Properties of the injected/sintered materials | Cost-effective molds for complex internal channels and intertwined parts | 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—also described as Cold Metal Fusion (CMF), Cold Ceramic Fusion (CCF), and Cold Exotic Powders Fusion (CEPF): Powder binders for Cold SLS printing . 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 & metal , polymers (e.g., PTFE, PEEK), and exotic materials .
The lost wax / investment casting process
Castable 3D printed resins are becoming increasingly important because they combine fine detail, repeatability, and fast iteration—helping manufacturers move from prototype to production with fewer compromises.