Elastic/Flexible Wood Species

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Forum topic by MSQUAREDPRODUCTS posted 06-21-2019 01:09 AM 634 views 0 times favorited 11 replies Add to Favorites Watch


1 post in 621 days

06-21-2019 01:09 AM

Topic tags/keywords: cnc phone case carving milling shaping wood types design bending wood bending wood properties wood characteristics manufacturing

I’m an industrial designer and I’m currently developing a line of wood phone cases. I’m investigating different methods of approach to this design and I’d appreciate your advice and opinions on wood species that are relatively resilient/elastic/flexible. I’d also be curious to hear if anyone has heard of ways to chemically treat wood in order to permanently increase its flexibility. I have my own thoughts on this, but I’m curious to see what others have to say.

Some random notes and background on the project.
-When I say flexible/resilient/elastic, I mean the ability to bend the walls of a phone case outwards in order to insert the phone into the case, then the wood snapping back into place around the border of the phone. Similar to what you’d see on an injection molded phone case, but obviously not quite that flexible.
-The main body of the case will be carved using a CNC machine.
-We are developing a wood phone case that is a SINGLE piece and NOT multiple pieces assembled by the end user.
-We’ve designed several methods of creating a “composite” wood phone case, that would involve the limited use of resins/plastics in key areas to create bend points that allow the case to snap onto a device.
-We’ve also investigated kerf bending, which has its own advantages and disadvantages.

I’m not naive, I know that wood is wood and can only be pushed so far. That being said, a good design can enhance the mechanical properties of different woods.

I love hearing new ideas and lessons learned from other peoples experience! Thanks for your help in advance!

11 replies so far

View wuddoc's profile


359 posts in 4728 days

#1 posted 06-21-2019 01:28 AM

I suggest you contact Dr. Gene Wengert (the Wood Doctor) through:

Dr. Gene Wengert (the Wood Doctor) is Professor Emeritus in Wood Processing, Department of Forestry, at the University of Wisconsin (Madison) and writes for Trade publications in a Q & A format.

-- Wuddoc

View 4wood's profile


88 posts in 964 days

#2 posted 06-21-2019 02:00 AM

Have you checked out anything about compressed wood. This company has a process of compressing wood to make it flexible. Some of it can be tied in a knot. As long as it stays wet it is bendable, but once it dries it does not bend.

View bondogaposis's profile


5953 posts in 3362 days

#3 posted 06-21-2019 03:25 AM

I doubt you will be able to find a wood that does what you want, certainly not with out some sort of industrial process that would be lot more costly than using a synthetic product.

-- Bondo Gaposis

View CaptainKlutz's profile


4155 posts in 2505 days

#4 posted 06-21-2019 05:09 AM

Wood is not wood!
Wood is a heterogeneous, hygroscopic, cellular and anisotropic material. It consists of cells, and the cell walls are composed of micro-fibrils of cellulose (40–50%) and hemicellulose (15–25%) impregnated with lignin.
(courtesy wiki)

from engineering stand point, we know this:
- Cellulose fibers are well understood. Are only flexible when fibers are short and oriented in single plane with thickness is limited (paper). Place long fibers in matrix ‘wood’ becomes rigid mass that breaks when enough stress to cause deformation is added (composite panels).
- The deformation before breaking strength of wood can be increased with greater space between fibers, and flexible type lignin holding the fibers together. This is why swollen wet wood cells bend .vs. dry wood cells break; and why low melting point sap rich soft woods are more flexible than high melting point sap balanced hard woods.

IME – The woods that are most flexible are the ones that prefer to grow near water sources to have largest water concentration, lower lignin levels, and contain long skinny cell formations.
Most woods that fit this description, like willow and cottonwood; are also the most foul smelling woods (due mold/fungus) that have marginal non-descriptive wood figure (due long straight fibers).

Since modern phone are becoming water proof; one route to making an all wood case is to:
create a man made design of the cellulose structure using a styled paper thin veneer outer layer and a flexible polymer replacement for lignin;
that could be soaked in water,
then opened/closed/formed around the phone;
then dried to remove the water.
With right polymer replacement for lignin, process could be irreversible just like water based polyurethane coatings and adhesives.

Same concept might work using heat to relax polymer/veneer to help it fit, but requires significantly more polymer development and might add couple years to schedule unless an existing polymer is already hiding in a lab somewhere.

If you put together $5-$10 million USD for research work, and provide access to decent pulp and fiber lab, plus find a couple of active commercial partners for adhesive development; a solution could be engineered in 2-3 years, with a fully commercialized mfg solution in < 5 years. Provided of course the market for wood cases is large enough?
This would be just like glulam and every other man made wood product has been developed in last 20 years. Oh, and the fiberboard packaging companies have been developing similar tech to this for years already.

Yes, in a previous life spent most my waking time developing new technologies involving polymer material sciences and specialized mfg equipment to use them on products. :)
This was fun, thanks for letting me play the game. :-)

Best Luck on your endeavor.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

View SMP's profile


3442 posts in 916 days

#5 posted 06-21-2019 05:21 AM

I remember experimenting with oak and walnut soaking in ammonia for a week or so. But it hardens again when dry even though it does change some of the structure. The only thing i could think is maybe just a rim type(like the apple ones) that the end user could soak for x minutes in water, then microwave for x seconds/minutes, install and let dry. Or something like that.

View torus's profile


525 posts in 1423 days

#6 posted 06-21-2019 01:51 PM

bamboo is not wood, but…. it is good/interesting option

I agree with above: to make plastic looks like wood is much cheaper than make wood behave like plastic.

-- "It's getting better..." - put this on my RIP stone!

View Ocelot's profile


2883 posts in 3648 days

#7 posted 06-21-2019 03:41 PM

Thin layer of dense foam between wood and phone might work.

-- I intended to be a woodworker, but turned into a tool and lumber collector.

View tomsteve's profile


1150 posts in 2229 days

#8 posted 06-21-2019 06:05 PM

the species of wood youre looking for is called printed wood

View Madmark2's profile


2308 posts in 1599 days

#9 posted 06-21-2019 07:06 PM

Get a copy of the USDA’s “Wood handbook: wood as an engineering material” it’s free.

-- The hump with the stump and the pump!

View Snipes's profile


459 posts in 3255 days

#10 posted 06-21-2019 10:50 PM

Pm me, we can work out a consultant fee and go from there. Thanks

-- if it is to be it is up to me

View runswithscissors's profile


3128 posts in 3035 days

#11 posted 06-24-2019 03:57 AM

I’m with Torus. Bamboo. Flexible, tough, hard.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

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