Introduction: CNC Scissor Chair (Plywood)

Picture of CNC Scissor Chair (Plywood)

CNC + plywood = furniture. Search instructables and you'll come up with over 47,000 results for "CNC furniture." But for the great majority of CNC machines -- the 2-1/2 axis CNC routers that can move only in X, Y, and Z (no tilting or rotating controllers) -- a very specific condition has come to be part of almost all projects that result: the orthogonal joint. The orthogonal joint, essentially a product of the needs for tightly-fitting "notches" to fit together with friction, is a defining characteristic of furniture made this way.

This project, the "Scissor Chair," takes its design inspiration from the non-orthogonal joint cut on a machine capable of cutting only orthogonal (non-beveled) profiles. The finished chair is as purely a CNC project as I could manage: it requires exactly one sheet of standard 1/2" plywood, no extra parts, no hardware, no glue, and no other tools (except maybe a mallet to show it who's boss).

The Scissor Chair will be one of the first chairs available for purchase through Fabsie, a new website aimed at letting people buy highly designed small-run furniture anywhere in the world by connecting buyers with local fabbers and digital designers from all over. James McBennett, Fabsie's founder, made the world's second scissor chair. He is working to smooth out the fabrication process to open up the design everywhere!

More and larger photos are available on my website, http://www.phil-seaton.com (click "Scissor Chair" once you get there). I will share the DXF files with anyone emailing from an academic email (".edu"); in exchange I ask that you send back photos of your process and finished chair, and tell me about any snags you hit while making it. The goal is to iron out problems people encounter during the making process: if you get the file, that's not license to distribute or sell the file or the finished chair.

Step 1: Scissor Plan

Picture of Scissor Plan

From the top (plan) view, the final chair's design rests on the complex joinery required to allow planar sheets to intersect in this way.

Step 2: Joint Studies

Picture of Joint Studies

For this orthogonal-but-not orthogonal design, a series of oblique joints with straight cuts served as generative components for the chair. Tight friction-fit joints are maintained oblique parts. The joint on the right side was abandoned later as the design evolved more purely towards the "scissor" plan.

Step 3: Design Considerations

Picture of Design Considerations

The design assumes a perfect "scissor" plan / top view. Variations of the "tightness" of the scissor joint and the chair's profile serve to produce several design iterations on the same principle.

Step 4: Scale Models

Picture of Scale Models

1:4 tests were lasercut to test the structure and design of the chair. The 1/8" thick masonite makes it possible to exactly test the joint's tightness of fit: The files are scaled down to 25%, and the material is exactly 25% the thickness of the final 1/2" ply.

Step 5: Assembly Diagram

Picture of Assembly Diagram


Step 6: Cut Sheets

Picture of Cut Sheets

The entire chair is cut from exactly one full 4x8' sheet of 1/2" ply. Details in the final file cut corners wide to allow space for a 1/8" router bit to profile cut without destroying the geometry.

Step 7: On the CNC, and Then, Glue-free Assembly!

Picture of On the CNC, and Then, Glue-free Assembly!
Photo and this assembly video courtesy James McBennett of Fabsie (see first page for description). This is chair 2.0, which will become a part of a series of scissor chairs after the same design. Stay posted for more!





Comments

amandaghassaei (author)2017-04-05

whoa, I never saw this before, so cool phil!

HarrisonFilleul (author)2016-06-21

Do you have these shapes in AutoCad?

I want to make one of these as I have access to a CNC that runs on AutoCad/Microvellum.

Cheers!

pseaton (author)HarrisonFilleul2016-06-24

I've been hoping that by limiting this to students (.edu addresses), I'd have more luck getting photos of the finished products people make with the cad files. So far no luck so here's my request: if you use the files for anything, please upload an I Made It !

Here are links to the CAD file, and some notes that I've gotten from feedback along the way:

DXF: https://drive.google.com/file/d/0B6nIu9U60DlGeWZlV...

Fab Notes: https://docs.google.com/document/d/1p6Q_mxhN5HZCWy...

Note that the license for the CAD files is Creative Commons "Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0)", not the same as the license for the Instructable. You can't modify, sell, or distribute the files without permission. You must cite the author in any use.

https://creativecommons.org/licenses/by-nc-nd/2.0/

HarrisonFilleul (author)pseaton2016-06-24

Thank you,

Looking forward to making it!

buck2217 (author)2015-06-25

Awesome , does it come in extra wide for the Mrs?

(just kidding Darling, now put down that knife!!!)

Dai HyekH (author)2015-05-20

oh very nice design but we are need the cut sheet dxf and pdf file. pls share the details on reo0823@naver.com

sbrown9578 (author)2014-03-20

great a chair that expands when your butt does. lol

Samw (author)2013-03-06

Hey this is great. I love the mechanics you use here. Is this an original design?

pseaton (author)Samw2013-03-07

It is, thank you! It's possible I'll have the chance to develop it a little further to make a "form family" of related furniture in connection with Fabsie (www.fabsie.com). This depends somewhat on the success of Fabsie's first venture, on kickstarter now -- https://www.instructables.com/id/This-Stool-Rocks/

Thanks again!

mganpate (author)2012-07-31

very nice design but we are need the pdf pls share the details on mahesh.gan.143@gmail.com

scoochmaroo (author)2012-05-26

Holy guacamole! You should come work for us!

angelabchua (author)scoochmaroo2012-05-29

hahaha!

pseaton (author)scoochmaroo2012-05-26

hey now, that's a great idea!

cephean (author)2012-05-29

Wow looks very close to my chair design for graphics when i was in grade 10:

cephean (author)cephean2012-05-29

Val-S (author)2012-05-27

May I ask, how much does it weigh?

pseaton (author)Val-S2012-05-28

It's not so bad actually... maybe 25-30 pounds? It takes up a whole sheet of ply, but I'm afraid much of it goes up the dust chute.

dagob (author)2012-05-27

Amazing! I looks great! I luv it!

poofrabbit (author)2012-05-27

This is just plain wicked cool!!! Nice work!

biggsfamily2012 (author)2012-05-25

How long did it take you to make...tire actual hours
working on it

pseaton (author)biggsfamily20122012-05-26

hmmm well quite a few if you count all the testing, design time, failed and rejected options, etc. But the actual construction of the chair isn't so bad. It's probably 2-3 hours of CNC time once you get started, and another 2-3 hours of assembly if all goes well.

rimar2000 (author)2012-05-25

Interesting design.

pseaton (author)rimar20002012-05-26

Thanks!

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Bio: Architect by training, Phil is a designer who codes. He abuses CNCs and industrial robots while building fine furniture, mixing digital fabrication and craftsmanship. He ... More »
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