Custom Ring Mail

Introduction

A parametric file to create ring mail can be tuned using the input variables to produce both good and miserable results.  For example, a small ring diameter (rwidth) with (thick) ring material could create a stuck-together mass when printed.  The ring diameter (rwidth) and the ring thickness (thick) need to be adjusted for a satisfactory result.  The optimum ring diameter and thickness values are related but were included as separate variables in the file to allow individual adjustments. 

Then consider the number of sides in the rings (num).  A large number leads to large STL files plus a resolution beyond printing capability. To reduce file size the number of flat sides in the rings was also chosen to be the number of sides in a ring cross section.   I think the optimum number of sides is around seven or eight.  This provides enough inside area for connecting adjacent rings and when a ring is tilted at a 51.4 degree or 45 degree angle it provides a flat surface on the print bed.

The patch size of the mail section is set by the ring diameter and (nx) and (ny) the number of links in the X and Y direction.  Note: (ny) is twice the size of (nx) so that each link can capture its four nearest neighbors.

Other tuning variables are used to make sure that links aren’t intersecting when printed in place.  The variable (rgap) adjusts the X direction gap between all rings and (ypos) adjust the Y offset of the +ang tilted set of rings.  The ring tilt angle (ang) can be manually set or determined by the number of sides (num) in the rings by commenting out the appropriate line, to determine the ring tilt. 

Design Hints

First, decide how large the ring cross section should be.  As a general rule I found that the ring diameter (rwidth) is about 5X the ring material thickness (thick).  You will be printing the rings standing at an angle so the cross sectional area and printed layer-to-layer adhesion will determine the strength and durability.    I chose thick = 4mm as a starting point. 

Now set nx and ny to some starting value (I chose nx=3 and ny=6 for initial tweaking).  As you initially try low values of rwidth the rings will intersect. If printed, this would be a solid mass. At (rwidth = 20) notice that there are air gaps between rings and some neighboring rings intersect.  If the adjacent ring touching is in the X direction, the (rgap) can eliminate this.  But, too large a value will cause X direction touching where rings loop together.  For rings touching in the Y direction the (ypos) variable slides the set of rings tilted at +ang back and forth in the Y direction. 

The optimum crossing angle (ang) for the rings is 45 degrees.  This determines the optimum number of sides (num) to be 8 because then there is a flat side for each ring to touch the build plate for adhesion when tilted at 45 degrees. This also provides a large inside area for neighboring rings to loop through.   I’ve also found that num=7 and ang=51.4 degrees also works well.

If tuning the (rgap) and (ypos) variables doesn’t eliminate rings touching the ring size (rwidth) has to be increased for the given value of (thick).  Of course, the ring material size (thick) could be reduced at the expense of strength and durability.

When all the parameter tweaking is finished there will be an air gap between all the nearest neighbor rings.  The gap may be small but it must be there.  If rings touch they will be connected after printing. Rotate the view and zoom in to observe and check this.  When this design is sliced the rings will be separate but when printed the rings may be slightly stuck together due to the plastic over extrusion (they can be snapped apart).  The slight touching of the printed rings can also help prevent rings from breaking loose while printing.

Split Rings

A set of rings with a cut on the bottom segment is included for connecting multiple patches of mail.  Note: if they aren’t printed with the same parameters the rings in the patches may not line up.  In stitching together patches of mail each split ring should loop through four other rings.

Printing Hints

Print without support.  Adding support can result in a mess removing it.

If a couple millimeters of brim is added to the sliced file this will surround the contact of each link to the bed and can help prevent individual rings breaking loose during printing.