Closed impeller
A printed internal core forms enclosed passages. The cores are cleaned, inspected, fitted and assembled before casting by Chaophaya Foundry.
closed impeller casting process3D Printed Sand Cores for Complex Castings
Speed3D Mold produces binder jetting sand cores using silica sand and a furan binder on an ExOne S-Max system. The cores can form curved, enclosed and interconnected passages that may be difficult to make with conventional core boxes.
The cores are used in coordinated casting projects with Chaophaya Foundry.
3D printed sand cores · 3D sand printing · patternless casting
What are sand cores?
A sand core forms internal cavities and passages that the mould alone cannot create. In a closed impeller, for example, cores form the enclosed passages between the shrouds. Pump casings and bowls may also need cores to form internal flow paths.
Conventionally, cores are made in core boxes. Complex geometry can require multiple core-box elements and manual assembly.
closed impeller castingWhy use a digitally produced core?
Complex internal passages
Sand core printing can produce complex internal passages directly from approved digital geometry, including curved, enclosed and interconnected passages, undercuts and integrated features.
Fewer separate core elements
Selected geometries may be consolidated, reducing the number of separately made core elements.
Revise the digital design
Engineering changes can be made in the digital model without modifying a physical core box.
Useful when original tooling is unavailable
This route may suit one-off and replacement castings when the original core box is missing or no longer usable.
replacement pump impeller casting · pump replacement casting
How printed sand cores are made
- 01
Prepare the core geometry from CAD, drawings, scan data or a physical component.
- 02
Slice the approved geometry into digital layers.
- 03
Spread a layer of silica sand across the build area.
- 04
Selectively apply furan binder where the layer must be bonded.
- 05
Repeat the cycle layer by layer.
- 06
Remove unbound sand to reveal the printed core.
Unbound sand supports the geometry during the build. After recovery, loose sand is removed and core passages, locating features and interfaces are reviewed before assembly.
Printing capability for cores
| System | ExOne S-Max® industrial sand binder jetting |
|---|---|
| Build volume | 1,260 litres |
| Build dimensions | 1,800 × 1,000 × 700 mm |
| Layer height | 0.2–0.5 mm, depending on material and process settings |
| Dimensional accuracy | ±0.5 mm on printed sand geometry, depending on part size and geometry |
| Sand and binder | Silica sand with furan binder |
| Data commonly received | STEP, STP, STL, DWG, DXF, PDF drawings, scan data or a physical component |
Accuracy refers to the printed sand geometry. Final casting tolerances also depend on alloy shrinkage, mould design, pouring conditions, heat treatment, finishing and machining. full printing capability
Documented projects using printed cores
Four double-suction impellers
Four mould-and-core packages were arranged in one job box. The reported mould-and-core production period was seven days for a package measuring 900 mm in diameter by 700 mm high, using 650 litres of build volume. Casting and machining were reported as separate periods.
Four double-suction impellersObsolete marine cylinder head
A 19-piece mould package measuring 725 × 630 × 572 mm was reported as printed in 10 hours. Printed cores were placed in the mould before closing; the project’s reported delivery period was two weeks.
Obsolete marine cylinder headOther core applications
Printed cores have also been used in a cast iron pump casing, a steel pump bowl and an engine-box cylinder head. Reported project times are specific to those projects and are not general lead-time guarantees.
The photos show cores assembled with 3D sand printed moulds.
Printed cores with conventional moulds
A hybrid route can use reusable pattern equipment for the mould and a printed core for complex internal geometry. This adds a second production route to coordinate, so suitability depends on the component and the available tooling.
When printed cores make sense
Printed cores may be a strong fit for one-off or low-volume castings, complex core packages, missing tooling, frequent design revisions and replacement components with difficult internal geometry.
Conventional core boxes may suit stable, high-volume repeat production or parts that gain little from complex core geometry. Printing cost recurs with each build, so the appropriate route depends on geometry, quantity, material, inspection requirements and schedule.
Materials poured with printed cores
The site lists aluminium bronze and nickel aluminium bronze, tin bronze and other copper-based alloys, gray and ductile iron, carbon and alloy steel, stainless steel, and aluminium among its material families. Material suitability is reviewed for each project.
What to send for a core quotation
Share whatever project information is available:
- A drawing, CAD file, scan data, photographs or a physical sample
- Material or alloy requirement
- Quantity and approximate dimensions and weight
- Required internal passages and core requirements
- Critical dimensions and interfaces
- Machining, inspection or documentation requirements
- Target delivery date
Frequently asked questions
Sand cores form internal cavities and passages that the mould cannot create by itself. They can define enclosed passages in an impeller or flow passages inside a pump casing.
Silica sand is spread in layers, and a furan binder is selectively deposited to bond the required geometry. The cycle repeats layer by layer; unbound sand is then removed to recover the core.
No core box is needed to print the core. Engineering review, cleaning, fitting and assembly are still required before casting.
A printed core may be used as part of a hybrid route with a conventionally made mould. Suitability and fit depend on the mould and core interfaces.
The published capability is ±0.5 mm on printed sand geometry, depending on part size and geometry. Final casting tolerances also depend on alloy shrinkage, mould design, pouring conditions, heat treatment, finishing and machining.
The site lists aluminium bronze and nickel aluminium bronze, tin bronze and other copper-based alloys, gray and ductile iron, carbon and alloy steel, stainless steel, and aluminium. Material acceptance is reviewed per project.
A conventional core box may suit stable, high-volume repeat production or geometry that does not benefit from printed complexity. The best route depends on the project’s geometry, quantity and production requirements.
Reported project examples include seven days for four double-suction impeller mould-and-core packages and 10 hours for a 19-piece cylinder-head mould package. These are project-specific results, not general core lead-time guarantees. Timing depends on the data, complexity, build size and production schedule.
Send your core drawing or CAD
Share a drawing, 3D model, scan data or an existing part. Our engineers review the core geometry, material and quantity before recommending printed cores, conventional tooling or a hybrid route.
