Chair Design Series, Part 5 – Precursor

Precursor is the first prototype chair. The final version will have all 3d printed parts (Including a printed cushion) and a higher back. The cushion has already been tested.

K’NEX Chair by Mr. Muggle.

I found a chair design that informs about improving the design of this chair project. An Instructable for the K’NEX chair explains how to make a chair with K’NEX construction toy pieces. Looking at how Mr. Muggles put the chair together helped me see how to solve the problem I had with designing the seat. My thinking was focused on dividing the seat into 4 equal parts. The K”NEX chair helped me realize that there could be a center section transferring weight to four legs. Side panels could expand the seated area.

The Precursor’s chair legs are primarily shaped as a trapezoid with a flared top. There are internal blocks connecting 3 sections. The blocks are filled with plugs. Simple right? It was difficult to execute. I designed the legs in Blender. It was one of the few times I wished I had a CAD program. The connecting blocks fit perfectly in Blender, but not after printing. Adding to my frustration were/ prints at various infill levels requiring different tolerances. I came to the conclusion that printing all parts at 20% infill was necessary if I wanted to finish.

Initially, the entire leg was divided into two sections. Later, the top portion was split into two sections as well due to printing time and printing orientation. I wanted as much of the leg as possible to be printed laterally for improved strength.

Three of the legs were screwed to the plywood seat with the plugs facing outwardly. This was done because I suspect they will pop out as I could not remove several of them for stabilization with hot glue. The back of the chair extends about an inch beyond the seat. The plywood seat was originally cut to serve as a tabletop. The chair back was designed in Blender.

If you are interested in working with the chair legs, let me know and I will email them to you. I feel they are too much of a draft to post on any of the print repositories.

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