Lemur Enclosure Gate

Project Summary

Redesign and fabrication of removable divider/connector parts for small lemurs' enclosures. 

Project Details

Mouse lemurs and fat-tailed dwarf lemurs are housed in a network of suitcase-sized cages connected by cage "tunnels" (made from the same wire-mesh material). At the end of each tunnel is a part that connects it to the larger cage and has a slot for keepers to insert a divider. Lemur center staff use these dividers to restrict or allow the lemurs' motion throughout the cage network. 

The Lemur Center is planning to construct a new network of enclosures for their mouse lemurs, but their method for manufacturing the connector piece needs improvement. The connecting part that the Lemur Center brought to the DesignHub for redesign was an assembly of two hand-machined hard plastic sheets. Fabricating the assemblies is apparently labor-intensive and somewhat dangerous, and the finished parts need thread-cuttings screws to be inserted at assembly, making them relatively challenging to install. Several dozen are needed to construct a full cage network. Overall, the connector/divider assembly was a very good candidate to be redesigned for manufacturing using either a CNC milling machine or 3D printing. 

The first design proposal from DesignHub had a number of issues but is included because it made clear some of the Lemur Center's requirements for the new part. 

In the interest of saving cost, the first design proposal consisted of a single part (with a divider) designed to be milled out of an engineering plastic using two tools: a 1/4" end mill and a 1" diameter keyseat end mill. An image of this first design proposal with the divider is in the image slideshow. The heads of screws installed in threaded inserts (in the inner four holes) would hold down the edge of the cage tunnel while screws with washers and lock nuts would be used to attach to the larger cage section (as in the original). The keyseat end mill would be used to cut a slot into which a divider could be inserted and removed. Bumps in the divider and corresponding impressions in the connector would enable the divider to be effectively "snapped" into place, preventing it from easily sliding out. 

The first design review meeting revealed a number of design criteria that had not been considered in the first design, inspiring changes for subsequent designs. Although stiffness of the snap-in divider system could be tuned by changing the specific geometry of the divider, the client noted that industry regulations dictate dividers/doors on animal enclosures have a more secure locking mechanism. Additionally, the client noted several places where mouse lemurs might be able to get their fingers wedged between two parts, most notably at the interface between the cage tunnel and the connector. The installer also noted that inserting screws parallel to the cage tunnel (which was planned for securing the cage tunnel to the connector) might be challenging in tight spaces; some of the cage tunnels are rather short. He expressed a preference for inserting screws perpendicular to the tunnel direction into a considerably thicker rim, as in the original assembly from the Lemur Center. Finally, the client expressed their preference for printing parts rather than milling, even if the cost would be increased somewhat. Subsequent designs were then freed from the limitations of being manufactured on a milling machine. 

Clients were impressed by the snap-in divider from the first design even though it needed a more-secure locking mechanism. The first divider was laser cut from clear acrylic because it was readily available. The divider for the finished system needs to be resistant to heat and chemicals so that it can be sanitized regularly. The client also expressed interest in having both clear dividers and opaque dividers. 

In the second prototyping cycle, two competing designs were produced. The first reflects exactly what the client asked for in the first review meeting, locking the divider shut with a barrel bolt mounted to another location on the cage (to be installed by the Lemur Center). The second proposal locks with a pin that is inserted into the connector itself, reducing size and facilitating installation. Both designs surround the aperture through which the lemurs can move completely, preventing the lemurs from reaching around the end of the cage tunnel. These designs are due for review. 

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