Manufacturing Guidelines
for ExOne's 420 Stainless Steel/Bronze Material


420 Stainless Steel/Bronze

Manufacturing Guidelines for the ExOne® Infiltration Process.

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ExOne’s 3D Printed 420 Stainless Steel infltrated with Bronze is a matrix material composed of 60% stainless steel and 40% bronze infltrant. This material offers good mechanical properties, is available in annealed condition, and is able to be machined, welded and polished, and offers excellent wear resistance.

Please note that all parts will be subject to engineering review. 


Stainless Steel: Alloy 420
Bronze: 90% Cu / 10% Sn

Wall Thickness


The minimum thickness your model should have at main supportive walls:

Build Dimensions Minimum Wall Thickness
3.175-76.2 1.01 Minimum
76.3-152.3 1.52 Minimum
152.4-203.2 2.03 Minimum
203.3-305 3.17 Minimum
Unit of Measure in Millimeters 

Build Dimensions Minimum Wall Thickness
0.125-3 0.04 Mimimum
3-6 0.06 Minimum
6-8 0.08 Minimum
8-12 0.12 Minimum
Unit of Measure in Inches 




The part minimum wall thickness increases as the part size increases.

  • Basic guidelines do not work with all geometry.
  • Larger parts require thicker walls.
  • Part minimum dimensions must be met for the part to be printable.

Font & Detail



Geometry that is not a main supportive structure will need to hold a minimum wall dimension of 0.76 mm. or 0.03 in.

  • Structures could include: text, numbers and details.
  • Text needs to have a minimum wall thickness of 0.76 mm. or 0.03 in. (reference “x” below) for the depth, width, and height of the text to appear.
  • Extruded text that does not meet the minimum wall thickness will be blown away by the depowdering process.
  • Cutout text features that do not meet the minimum wall thickness will fill with bronze during the infiltration process or may deviate from the original design intent.




Overhangs must be designed to support their own weight.

  • Unsupported features over 25.40 mm. (1.00 in.) will not be accepted.
  • Fillets help support overhang structures during furnace processing.

Interior Cavities


Most interior cavities must have a depowdering hole with enough area to allow the powder to be removed during the depowdering process.

  • The minimum size of interior cavity for an interior hole needs to measure 1.27 mm. (0.05 in.).
  • When cavities are larger and more complex, the depowdering holes need to increase in size and quantity.
  • ExOne cannot guarantee that loose powder is completely removed from interior cavities due to obstructed line of sight.
Please note: these parts cannot be plated.

Inside Edges



Inside edges and sharp intersections need to have a filleted edge that meets the required wall thickness minimum.

  • Wall terminations on inside cavities also need to meet the wall thickness minimums.
  • Filleted edges help ensure successful part tolerances.

Interior Holes


All through holes must have a minimum diameter of 1.01 mm. (0.04 in.). Interior holes that do not meet the minimum tolerances will be filled with bronze during infiltration.

  • ExOne cannot guarantee that interior holes that change direction are clearly depowdered due to obstructed line of sight.
  • Loose powder cannot be successfully removed from a hole that is below requirements.
  • Due to the requirement for a thermal process, mating parts are not guaranteed. Post machining may be required.
  • The greater the depth of the hole, the larger the required diameter to ensure successful depowdering.
Please note: these parts cannot be plated.

Surface Connections


Points between features must have significant surface area connections. Parts that do not have well designed connections could experience breakage.

  • Surface connections can have an effect on infiltration. Poor surface connections do not allow bronze to flow through the part during infiltration fluently and increase the risk of an unbalanced infiltration.
  • Poor connections cause green parts to break easier.

Knife/Pointed Edges



Knife edges/pointed edges will fail during the depowdering process.

  • Fillet all knife edges with a 1.00 mm (0.03 in.) radius to avoid breakage during depowdering.
  • Edges that come to a point lower than the recommended tolerance are subject to rejection.
Parts will be rounded in polishing.

Dumbbell Design/Geometry



Designs or geometries that contain a connection between thin and thick walls, or “dumbbell style geometries”, can be affected by variance in the heating and cooling cycles during the ExOne® process.

  • To avoid part distortion, maintain consistent wall thickness.
  • Part designs with excessive dumbbell style geometry may be rejected.

Moving Parts



ExOne does not typically print moving parts. However, this can be reviewed on a situational basis.

  • Multiple parts can result in improper infiltration.
  • If you are interested in printing a moving part, please contact

Connected or Sprued Parts



ExOne only accepts one single part per file. Avoid connecting multiple parts because connected parts can disrupt build box layouts.

Powder Removal



When designing a part, please take into consideration the powder removal or depowdering process. You will need to make considerations for inside edges, interior holes, interior cavities, and part handling.

  • Cannot guarantee that powder is completely removed from interiors.
  • ExOne polishing process cannot polish interior features.




ExOne design engineers will typically add a stilt to your part. Stilts are necessary to allow bronze to infiltrate the part in post-processing. Stilt placement can be difficult because of part design. Texture and surface areas should be considered in designs.

  • Texture: Stilts need a smooth surface to be placed on
  • Surface area: Stilts require a surface area of 0.05in x 0.03in/ 1.27mm x 0.762mm
  • Part will have slight blemish from stilt removal
  • ExOne will attempt to keep the blemish miminal

Stilt will appear more prominent depending on the selected finish.



ExOne uses a high-energy process which tumbles parts in several different medias. This is a line of sight operation.

  • Part size maximum is 6 x 6 x 6 in. (152.4 x 152.4 x 152.4 mm). 
  • ExOne will determine if polishing is capable once physical part is printed 
  • Some parts cannot be polished 
  • Part geometry can directly affect polishing success or degree
  • Below geometries are unable to be polished or polished well:
    • Wire framed parts
    • Fragile parts
    • Thin-walled parts
    • Large flat parts



ExOne uses a small plating line that requires manual setup and unload.

  • Part size maximum is 7 x 7 x 7 in. (177.8 x 177.8 x 177.8mm).
  • If part contains fluid holding type cavities, parts will be unable to be plated
  • ExOne will determine if plating is capable once physical part is printed
  • Some parts cannot be plated
  • Plating is purely decorative
  • Colors may vary

Please note: plating can wear off over time or as a result of excessive use.

Additional Considerations


Shrinkage occurs during the ExOne® process. Parts should be designed with following shrinkage considerations:

  • Parts from 1-3 inches: up to 2% shrinkage (On Average)
  • Parts of 3+ inches: up to 3% shrinkage (On Average)

Print layer is 0.004in/0.1mm.


  • 0.004in for parts below 15in
  • 0.006in for parts above 15in

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