Everything You Need to Know About METAL 3D PRINTING
Design Guidelines for Metal 3D Printing
Design guidelines for metal 3D printing determine whether a part can be manufactured reliably and cost-effectively. Learn more here about, among other things:
- Wall thicknesses, holes, and channels
- Overhangs,
- Tolerances,
- Thread,
- the correct orientation
- and much more
- In-House SLM Manufacturing
- Personalized consultation
- Everything from a single source
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Design Values at a Glance
The same minimum wall thickness of 1.0 mm, the same minimum diameter of 2.0 mm for holes and channels, and the same general tolerance of ±0.3 mm for component sizes up to 100 mm or ±0.3 percent for sizes larger than that apply to all metal materials. What is possible beyond these specifications in individual cases depends on the geometry, part size, part orientation, and post-processing.
| Design Feature | Guideline | Note |
|---|---|---|
| Minimum wall thickness | 1.0 mm | 0.5–1.0 mm at the customer's risk; cannot be reliably displayed below 0.5 mm |
| Free-standing pins | 2.0 mm Ø and larger | Freestanding struts and slats require greater material thickness |
| Holes and Channels | 2.0 mm Ø and larger | Smaller diameters achieved through mechanical finishing |
| Opening for powder removal | 3.0 mm and up | For branched or long channels, the size should be correspondingly larger |
| Minimum Distance Between Walls and Crossbars | 1.0 mm | Merge or split smaller gaps |
| Overhangs without a supporting structure | at a 45-degree angle to the building panel | Flatter surfaces require support structures |
| Engravings and Lettering | 1 mm stroke width, 1 mm depth, 5 mm character height | Applies to standard fonts |
| General tolerance as-built | up to 100 mm ±0.3 mm; above that, ±0.3% | Tighter tolerances through CNC finishing; technical drawing required |
| Additional Material for Rework | approx. 1.0 mm | On fits, threaded sections, bearing seats, and seal seats |
| Thread | not printed | Design core holes and clearance holes in accordance with DIN 13-1 and DIN 76-1 |
These values are design guidelines for components that meet process reliability requirements. For specific information regarding your component, please contact the Rapidobject metal 3D printing team.
Key Design Specifications in Detail
The following guidelines apply uniformly to all metal materials that Rapidobject processes using the SLM method. They are design values for components that ensure process reliability; they are not machine limit values.
1.0 mm
Minimum wall thickness
0.5–1.0 mm at the customer's risk; thicknesses below this cannot be reliably reproduced. Freestanding ribs, slats, and pins require greater material thickness.
2.0 mm
Holes and Channels
Smaller diameters are achieved through mechanical finishing. Smaller diameters result from subsequent mechanical finishing.
3.0 mm
Opening for powder removal
To ensure reliable removal of the unfused powder, the openings should be at least 3.0 mm in size; for long or branched channels, they should be correspondingly larger.
1.0 mm
Addition of Material
Surfaces that will be machined after printing must already have an allowance of approximately 1.0 mm in the CAD model. This applies in particular to fit holes, threaded areas, bearing seats, and seal seats.
45°
Limit on Overhangs
Flat surfaces require support structures. These stabilize the component during the manufacturing process and dissipate process heat. Support structures must be removed after manufacturing.
±0.3 mm
General tolerance
For component sizes up to 100 mm, ±0.3 percent; for larger sizes, ±0.3 percent. Tighter tolerances, defined fits, and sealing and bearing seats are achieved through targeted mechanical finishing, such as CNC milling, reaming, or turning.
You can download more detailed information on all policies here:
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From Model to Finished Metal Component
Upload 3D Data
Upload your model as a STEP, STL, or 3MF file. Rapidobject is ISO/IEC 27001 certified, and the transfer is encrypted.
Select Material and Process
Price list for available materials and surface finishes.
Have the design reviewed
The metal 3D printing team checks component orientation, critical geometries, and post-processing requirements prior to manufacturing.
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For complex or custom projects, please use the inquiry form.
Additional Design Guidelines for Metal 3D Printing
Uniform Wall Thicknesses and Cross-Sectional Transitions
Wall thicknesses should be as uniform as possible across the component. Step-like changes in volume create local residual stresses during layer-by-layer melting and lead to warping, striations, or surface defects. Transitions with generous radii rather than sharp edges further reduce the notch effect and increase the component’s fatigue strength.
Voids and Powder Removal
Enclosed cavities that cannot be cleaned are not permitted in metal components produced using the SLM process. After printing, these cavities contain unfused metal powder that cannot be safely removed and pose a risk of explosion or implosion when temperatures change. If a cavity cannot be avoided due to design constraints, accessible openings and drainage channels that are as large as possible must be provided.
Thread
Threads are not printed as part of the SLM process but are cut, milled, or turned afterward. To accommodate this, the component must be designed with the appropriate core hole and the necessary clearance per standard—for example, in accordance with DIN 13-1 for the core diameter of metric ISO threads and DIN 76-1 for the clearance. Additionally, the component requires a secure clamping mechanism and sufficient clearance for tool movement. The threading process is ordered separately.
Orientation and Anisotropy
In the SLM process, the build direction is primarily chosen to ensure printability and detail accuracy. Since the layers fuse completely with one another, there are no layer-related weaknesses in strength, as is the case with plastic-based processes. However, the orientation affects surface roughness, the need for support structures, detail reproduction, and the amount of post-processing required. For complex or delicate parts, a test print helps determine the optimal orientation.
Structural Optimization, Ribs, and Topology Optimization
Thin wall sections and large surfaces can be reinforced with ribs or diagonal struts without adding volume to the component as a whole. Internal lattice structures increase stiffness but must not create inaccessible cavities. Topology optimization—a FEM-based process that distributes material according to load cases and design objectives—is ideal for maximizing material efficiency and can significantly reduce both weight and costs compared to the initial design.
Data Quality and STL Export
For manufacturing, 3D data in STEP, STL, or 3MF format is required; if tolerances and functional specifications are provided, a technical drawing in PDF format is also needed. When exporting STL files, the recommended settings are the “Binary” output format, a chordal deviation tolerance of 0.05 mm, and an angular deviation of 2 degrees. For most parts, a file size under 5 MB is sufficient; for very complex geometries, meshes, or 3D scans, a file size under 50 MB is sufficient. As a rule of thumb: If facets are visible in a 1:1 view on the screen, they will also be visible on the printed part later.
Lettering, engravings, and fine details
Text, logos, and fine details can be incorporated directly into the part using the SLM process. For clear results, a minimum line width of 1 mm, a minimum depth or height of 1 mm, and—for standard fonts—a minimum letter height of 5 mm are required.
Consider Heat Treatment and Warpage
The layered construction process generates residual stresses in the part. Long, thin, or large-surface-area geometries are therefore prone to warping. Heat treatment relieves these stresses and is best performed after debinding and before cutting the part free from the build plate and support structures.
The Complete Design Guide for SLM Metal 3D Printing
All the rules on this page are explained in detail, with dimensioned sketches, design examples, and the recommended export parameters for STL data. Available for free as a PDF.
Documents on Tolerances, Data, and Installation Spaces
Lightweight construction with good thermal conductivity
Aluminum AlSi10Mg
A cost-effective material for prototypes, small-batch production, and components subject to moderate stress.
Extremely strong, lightweight
Titanium Ti6Al4V
A lightweight, high-performance material for strong, corrosion-resistant, and thermally resilient components.
Durable and corrosion-resistant
Stainless steel 1.4404
A corrosion-resistant material for robust functional components that offers good machinability.
Curable for tool and mold making
Tool steel 1.2709
High-strength material for wear-resistant components,
For high operating temperatures
Inconel 718
Nickel-based alloy for high-temperature applications.
Wear-resistant and polishable
Bronze CuSn10
Good sliding properties for bearings, fittings, and design components.
Conducting Heat and Electricity
Copper
For heat transfer, inductors, and complex cooling structures.
Your contact person
Still in the design phase?
Send us your 3D model and the key requirements for the part. Rapidobject will review the part’s orientation, critical geometries, necessary post-processing, and potential cost optimizations prior to manufacturing.
- Design Review Prior to Manufacturing
- Recommendations Regarding Materials and Component Orientation
- Notes on Tolerances and Post-Processing
- Quote for a prototype, small-batch production, or replacement part
Markus Prokscha
, SLM Expert in Metal 3D Printing at Rapidobject
+49 341 231 837 32
metall@rapidobject.com
FAQ
Frequently Asked Questions About Design Guidelines for Metal 3D Printing
Answers to questions about wall thicknesses, tolerances, threads, overhangs, and data formats—concise and drawn from real-world manufacturing experience.
What is the minimum wall thickness possible in SLM metal 3D printing?
Rapidobject specifies a minimum wall thickness of 1.0 mm for SLM metal printing across all materials. Wall thicknesses between 0.5 mm and 1.0 mm are possible at the customer’s risk; geometries thinner than 0.5 mm cannot be reliably produced. This value applies equally to aluminum AlSi10Mg, titanium Ti6Al4V, stainless steel 1.4404, tool steel 1.2709, Inconel 718, bronze CuSn10, and copper.
Do the design guidelines apply equally to all metallic materials?
Yes. At Rapidobject, the design guidelines for SLM metal printing apply uniformly to all metal materials. Depending on the material, the post-printing process chain varies: For titanium Ti6Al4V, heat treatment is an integral part of the manufacturing process; for the other materials, it depends on the part and its application.
What is the minimum size for holes and channels in metal 3D printing?
In the SLM process, holes and channels with diameters of 2.0 mm or greater can be reliably produced. Smaller diameters may require post-processing. Openings for powder removal should be at least 3.0 mm in size; for branched channels, they should be correspondingly larger.
At what angle do overhangs require support structures?
In SLM metal 3D printing, surfaces that are flatter than approximately 45 degrees relative to the build plate require support structures. These structures dissipate process heat and stabilize the part, but must be removed after printing, and the resulting burrs must be sanded down.
What tolerances are realistic in metal 3D printing?
Rapidobject's general tolerance for the SLM process is ±0.3 mm for nominal dimensions up to 100 mm and ±0.3 percent for dimensions greater than that. Rapidobject achieves tighter tolerances through targeted CNC post-processing of the relevant functional surfaces. This requires a technical drawing with the specified dimensions.
Does DIN ISO 2768 apply to 3D-printed metal components?
DIN ISO 2768 specifies general tolerances for machined and formed workpieces and does not automatically reflect the process capability of additive manufacturing processes.
For nominal dimensions up to 100 mm, Rapidobject’s manufacturing tolerances are ±0.3 mm, and for nominal dimensions of 100 mm or more, they are ±0.3 percent. Therefore, DIN ISO 2768 mK is not fully complied with. If necessary, compliance can be achieved through mechanical rework. For this, we require a technical drawing.
Can threads be printed directly in metal 3D printing?
No. Threads are not printed as part of the SLM process; instead, they are cut, milled, or turned afterward. The component must be designed with the appropriate core hole and clearances in accordance with applicable standards, such as DIN 13-1 and DIN 76-1. The creation of the threads is a separate service.
Does the build direction affect the strength of an SLM component?
In the SLM process, the layers fuse completely; therefore, layer-related weaknesses in strength are unlikely to occur. However, the build direction affects surface roughness, the need for support structures, detail accuracy, and the amount of post-processing required.
How can I prevent warping in 3D-printed metal parts?
Distortion is caused by internal stresses that arise during layer-by-layer melting. Uniform wall thicknesses, generous radii instead of sharp edges, the avoidance of sudden changes in volume, and appropriate part orientation help reduce distortion through design. In addition, heat treatment prior to separating the build plate from the support structures relieves these stresses.
Why are closed cavities not allowed in metal 3D printing?
Enclosed cavities contain unfused metal powder after pressurization, which cannot be safely removed. Metal powder is harmful to health and, in the case of reactive materials such as aluminum and titanium, is also highly flammable. In addition, there is a risk of explosion or implosion due to temperature changes. Cavities that cannot be avoided must have accessible openings and drainage channels.
How much allowance should be factored in for CNC post-processing?
For surfaces that will undergo machining after printing, an allowance of approximately 1.0 mm should be included in the CAD model. This applies in particular to clearance holes, threaded areas, bearing and seal seats, as well as flat surfaces, and should be indicated in the technical drawing.
What file formats does Rapidobject require for 3D metal printing?
Rapidobject processes 3D models in STEP, STL, or 3MF formats. For fits, threads, sealing surfaces, and geometric and dimensional tolerances, a technical drawing in PDF format is also required. For STL export, “Binary,” a chord length of 0.05 mm, and an angular deviation of 2 degrees are suitable settings.
When is metal 3D printing a better option than casting or CNC machining?
Metal 3D printing is cost-effective when no tooling or minimum order quantity is required; when geometries include internal channels, lattice structures, or topology-optimized shapes; when prototypes and small production runs must be available quickly; or when replacement parts need to be reproduced without existing drawings. For simple geometries produced in large quantities, casting and machining remain the preferred methods.