Couplings in a Cage

Last month I shared with you my design to contain lots of replacement short Rapido couplings inside a cage-style container.  You can find the post here.  In this post I wanted to show you how it all came out.

The reasons for making this cage were to firstly keep the hundreds of small parts contained and secondly to reduce the cost of the parts.  These have been printed by Shapeways and their new pricing structure, although reducing the cost of their Black Strong & Flexible material, now takes into account a fee per individual part.  So as you can imagine, printing several hundred loose parts will incur a hefty fee. To counteract this the cage was designed so that it used the least amount of material but did not have any holes large enough for the parts to fall out: therefore Shapeways treat it as one item when pricing it for printing.

Rapido Replacments Cylinder

This particular cage has been designed to hold 240 short Rapido couplings, in the computer model the cage appears densely packed, as shown below, allowing for the spacing between each part.  This is because there has to be a minimum gap between each part, otherwise they could be unintentionally joined together by the 3D printer.

3D Printed Cage Full Render - Short Rapido Couplings 3

When the actual print arrive it appeared to be only half full.  This is because once the support material which provides the spacing had been removed all the couplings fall to the bottom of the cage.

3D Printed Cage - Short Rapido Couplings 1 3D Printed Cage - Short Rapido Couplings 2

The cage structure is, as the name of the material suggests, very flexible and can easily be squeeze in the middle sections where the material is at its thinnest but it retains its strength and springs back into shape.  The end rings forming the 90° corners are strong however that is more to do with the design of the structure.

To remove the couplings I used a pair of side cutters to cut out a section from the top; then they could be emptied out as required.

3D Printed Cage - Short Rapido Couplings 3

This is a very effective method of printing hundreds of these couplings at once without the need to mount them on a sprue thus removing the need to cut them off before they can be used.

This container of 240 couplings is available through my Shapeways here.

I also offer these replacement short Rapido couplings in packs of 20 for £5.  Please contact me through the contact page or you can email me directly at if you would like a set, or more.

This weekend just gone I was at another train show, November is a busy month for shows here in the UK, and in next week’s post I will show you some of the layouts at the show.