This patent application filed by Stratasys claims to invent the concept of printing seamless 3D objects by hiding layer path endpoints inside the object’s visible outer surface. Letting this patent issue in its current form could allow Stratasys to prevent anyone else from printing 3D objects with the claimed features.


  • Title: “Seam concealment for three-dimensional models” Application
  • Number: 13/707,884
  • Publication Number: US 2013-0095303 A1
  • Assignee: Stratasys, Inc.
  • Priority Date: September 23, 2009 (prior art must predate this)
  • Availability for Challenge: Open until at least October 18, 2013.

APPLICATION OVERVIEW: This patent application from Stratasys seeks to patent 3D-printed objects with hidden seams. Specifically, the application claims to invent the concept of printing 3D objects in such a way that layers endpoints (or at least one endpoint on at least one layer) terminate inside each layer’s outer perimeter, as opposed to having the endpoints meet at a point visible from the exterior of the object.

WHY IT MATTERS: This is a very broad patent application with the potential to exclude many people from doing what they are already doing. We believe this technique has been in use for a long time. But belief is not enough. We need PROOF that this type of technique was used in 3D printing before September 23, 2009. That’s where you come in!

QUESTION: Have you seen anything that was published before September 23, 2009 that discusses:

  • Printing 3D objects (with a 3D printer) in a way that hides at least one layer path endpoint inside the outer surface of that layer so that seams will be minimized or eliminated from view?

If so, please submit evidence of prior art as an answer to this question. Please submit only one piece of prior art per answer below. We welcome multiple answers from the same individual.


  • A reference to anything that meets all of the criteria above AND ALSO describes how far the endpoint or endpoints terminate inside the inner region of the layer, specifically whether that distance is between 50% and 200% of the road width (the width of the layer path).
  • A reference to anything that meets all of the criteria above AND ALSO describes different patterns for how the endpoints terminate inside the layer’s inner region such as in the following images: enter image description here enter image description here enter image description here enter image description here enter image description here enter image description here

Claim 1 requires each and every element below:

A three-dimensional object:

  1. built with an extrusion-based digital manufacturing system (i.e., 3D printer),

  2. the three-dimension object comprising a plurality of layers of an extruded material,

  3. wherein at least one of the layers comprises:

    • a perimeter of the extruded material,

    • the perimeter comprising a start point and a stop point; and

    • an interior region of the layer defined by the perimeter, wherein at least one of the start point and the stop point is located within the interior region of the layer.

  • New open source slicers come into existence regularly. All have many tricks for minimizing "phenomenon" LOL. I see no reason in the universe to patent a simplistic calculation of an extruded path. Was there some sort of patent for the simple retract option? How about a patent for making layer heights smaller than nozzle diameter. Very LOL that one. I am doing some simple shapes via manually typing the gcode. I guess I am going to go to prison for moving the tool inward first before starting a path. So to will decades of countless cnc gcode producing software that have been doing this oh so spe
    – user8077
    Mar 8, 2014 at 21:13

3 Answers 3


I contributed to a project on github github: https://github.com/reprappro/host which is about an implementation of a slicer in java.

And it contains code that allows to do what this patent claims: The file PolygonList.java contains this at line 1204: https://github.com/reprappro/host/blob/master/src/org/reprap/geometry/polygons/PolygonList.java#L1204

 * This assumes that the RrPolygonList for which it is called is all the closed outline
 * polygons, and that hatching is their infill hatch. It goes through the outlines
 * and the hatch modifying both so that that outlines actually start and end half-way
 * along a hatch line (that half of the hatch line being deleted). When the outlines
 * are then printed, they start and end in the middle of a solid area, thus minimising dribble.
 * The outline polygons are re-ordered before the start so that their first point is
 * the most extreme one in the current hatch direction.
 * Only hatches and outlines whose physical extruders match are altered.
 * @param hatching
 * @param lc
 public void middleStarts(PolygonList hatching, LayerRules lc, BooleanGridList slice)

The implementation changes the outline (what is to be printed on the perimeter) so that it starts and ends within the interior region of the layer.

The github repository has its first commit dated at Sep 03, 2010. But within the git repository there is a svn repository checked in, so I was able to extract from that .svn repository these log messages:

r3199 | adrian-bowyer | 2009-07-24 23:35:26 +0200 (Fr, 24 Jul 2009) | 1 line
More work on code to start and end outline polygons in the middle of solid areas to minimise dribble.
r3196 | adrian-bowyer | 2009-07-24 00:58:27 +0200 (Fr, 24 Jul 2009) | 1 line
Started adding code to start and end outline polygons in the middle of solid areas to minimise dribble.

So this would predate the date of the patent claim.

Edit: The svn repository (http://sourceforge.net/projects/reprap/) is publicly available at sourceforge since 2006-02-09. And here is the link to the commit r3196 from the above log: http://sourceforge.net/p/reprap/code/3196/ So this implementation has clearly been published before the patent claim.


The concept of terminating seams in the inside has been used when manufacturing clothing for centuries. Applying this to 3D printing is not an inventive step and is an obvious application to anyone trained in the art.

Compare the drawings in the patent with cross-sections of sewing seams of various forms, in particular the "French Seam."


Also see prior patents EP 0855148 A2 and US 6497934 B1

http://www.google.com/patents/EP0855148A2?cl=en http://www.google.com/patents/US6497934

Vik :v) http://diamondage.co.nz

  • The sewing "art" and the additive manufacturing "art" might be a little too distant from one another for this to apply.
    – George White
    Aug 8, 2013 at 17:19

Adrian Bowyer also blogged the technique here: http://blog.reprap.org/2009/07/build-quality.html

  • Welcome to Ask Patents! Could you add some more details here? A representative quote from the blog post would help other readers understand the relevance to this prior art request. Sep 22, 2016 at 5:15

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