Wood-based frames: are there processes that can make wood (composites) suitable for 3D printer frames?

Hi, I just want to gather some facts about these wood-based frames we've seen or still see around. From what I've learned it's either laser-cut plywood (1st gen Makerbot, Ultimaker, etc) of sorts or plain MDF boards (smartrapcore, etc).

I know that wood's main downside is its dimensional instability (influenced by humidity, temperature,etc?) so the transition has been towards more dimensionally stable materials like aluminum, steel or plastic-aluminum laminates (the dibond latest Ultimaker uses).

But going back to wood... such a plentiful and easy to work with material, are there processes that make it just as efficient - for the purpose of 3d printers frames- ? Can it be sealed against the elements? Can the warping or "moving" be somehow accounted for/measured or designed around? Are there competitive wood composites that could offer it the properties a 3d printer frame needs to have?

It's easy to go acrylic, metal or even UHPC that is designed for heavy machinery but is there anything wood still has to offer?

---

RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff

The Rostock Max uses melamine as its primary structural material. The bulk of the wood is blocked from moisture intrusion by the laminate coatings and many builders choose to paint the edges for cosmetic purposes as well as to attempt to block that remaining point of entry. Unless you're having wild humidity swings it seems reasonably stable.

Multiple laminated sheets with impregnation should serve you well.
No idea how it is called in english, but this stuff here
[www.epspoland.de]
[www.epspoland.de]
is pretty much immune to anything but a saw.

---

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Quote
Srek
Multiple laminated sheets with impregnation should serve you well.
No idea how it is called in english, but this stuff here
[www.epspoland.de]
[www.epspoland.de]
is pretty much immune to anything but a saw.

Looks interesting. Is it safe to use indoors? At least with aluminum you have no worries health-wise so it's always good advice to check VOCs and other possible hazardous pollutants.

---

RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff

Quote
Srek
Multiple laminated sheets with impregnation should serve you well.
No idea how it is called in english, but this stuff here
[www.epspoland.de]
[www.epspoland.de]
is pretty much immune to anything but a saw.

That's laminated plywood (sometimes called Phenolic Plywood) - stuff is pretty common in Europe, but I hear its hard to find (and expensive) in USA. Anyway, it's just plywood that uses moisture resistant glue + top coating. It's still a plywood, and so is not guaranteed to be flat (or flat enough), unlike MDF which is usually flat if stored properly. BUT MDF is a lot weaker structurally, and so it can sag over time which may not be desirable, plus it would need some expensive coating (like epoxy?) to seal it properly. As much as I like wood, I could not recommend it for a frame that you expect to use for a long time - unless you happen to live in a suitable country, where moisture content in the air is same throughout the year

P.S. you would still need to seal the plywood edges from moisture - just additional hassle...

Quote
realthor
Looks interesting. Is it safe to use indoors? At least with aluminum you have no worries health-wise so it's always good advice to check VOCs and other possible hazardous pollutants.

It's definitely not safe to breathe in dust made from machining it (or MDF in that case), but I can't say it has any smell when just "left alone". I know that's not a scientific way to test it - just a thought.

Edited 2 time(s). Last edit at 02/25/2016 02:38AM by Dalius98.

I was always wondering about metal. Metal is not immune to dimensional shift with temperature, so it's not dimensionally stable from that pov. It is only immune to humidity. Isn't metal expansion and contraction detrimental to a machine's precision if not compensated for in software just like wood based products are with humidity?

The only difference I can think of is that metal has a predictable variation with temperature whereas wood and humidity can't be predictable for calculation of warping and dimensional shift. But then again, with metal how do you account for expansion/contraction when different elements are at different temperatures and there are all sorts of connections and bolts etc. Isn't it kind of the same?

---

RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff

Usually temperature changes are within five degrees. According to this [www.engineeringtoolbox.com] metals are something like 10 to 30 µm/m*K And it expands every direction evenly and nullifies some of the errors.

As wood is sensitive moiture and it varies a lot. Also wood expands by curving and the movement is huge according to this: [workshopcompanion.com]
Is that something like three or four decades more? At least I can't open my back door during winter and during summer it shrinks so much that lock barely works. So something like 1 cm.

Plywood can be more stable but still it curves somehow. Not predictable way.

Yes that was my understanding too about the process. The Phenolic Plywood that I was made aware of is a good alternative to MDF or exposed plywood.

I am recently researching other engineered woods and while WPC (wood plastic composite) are Phenolic Plywood upped to a new level, they are still sawdust and PP/PE/PVC in a matrix that completely seals the wood from humidity. The downside of WPC is its strength as it inherits it from the plastic used. This is where some fiber-reinforced WPC would come in handy just as with fiber-reinforced concrete. I am mostly stumbling on research papers as this is a new thing apparently, to use whole fibers from the paper industry pulp slurry that is considered a waste (for example).

I don't know of any widely available fiber reinforced WPC, lest something high tech like nano-cellulose reinforced plastics (which will be huge in the coming years/decades). So if it's not widely available it means that if I ever find something like that it's going to be way to expensive, more expensive than aluminum at that point.

---

RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff

The large number of layers make the Siebdruckplatte as good as MD, but a lot mor stableF. You need to treat freshly sawn edges with polyurethane or similar.

---

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Wood and heat are a bad combo, best avoided.

---

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Quote
the_digital_dentist
Wood and heat are a bad combo, best avoided.

Depending on the exact glues and resins used wood can be even more fireproof than metal. The surface might scorch, but it builds up a non flamable chared buffer the will prevent real burnup. A firend of mine is a carpenter and told me that often carpentry workshops are using wooden beams over metal because of this.

---

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Quote
Srek

Quote
the_digital_dentist
Wood and heat are a bad combo, best avoided.

Depending on the exact glues and resins used wood can be even more fireproof than metal. The surface might scorch, but it builds up a non flamable chared buffer the will prevent real burnup. A firend of mine is a carpenter and told me that often carpentry workshops are using wooden beams over metal because of this.

This fireproof craze is overrated. We have put so much fire retardants in everything that latest studies show that people die because of the chemicals released by the heat before any flame touches them. But chemicals have to be sold right ? .

@the_digital_dentist: I am not concerned about wood and the heat of the heated chamber because there should be a good layer of insulation on the walls of a heated chamber so not much heat should creep to the frame. If you have a metal frame and all that heat creeps into it, it would expand and even if it expands symmetrically in theory, all the joints and bolts and holes break that symmetry so it will expand asymetrically ultimately leading to a non-square frame (albeit insignificant maybe). So the frame should be decoupled as much as possible from the heated chamber whichever the material. I was more concerned about any frame and the environmental aspects that make it dimensionally unpredictable.

---

RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff

The potential for a fire is far down on the list of problems with wood and wood products.

---

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

What do you think of FibreCement boards? They are made of cement and wood and are still somehow prone to humidity because both the cement and the wood are somewhat vulnerable (afaik) but specs sheets from different manufacturers brag about dimensional stability. They can be worked with pretty much wood cutting tools (though they will quickly blunt blades).

I also wonder at which point the care for the best frame is rendered useless because other parts in the printer aren't of enough quality. For example an aluminum frame and plastic brackets is a bad combo, but at which point? When does the plastic bracket give in and stop being rigid enough? Is it because plastics expand way much more than the metals with the raise in temperature?

---

RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff

Quote
Srek
Multiple laminated sheets with impregnation should serve you well.
No idea how it is called in english, but this stuff here
[www.epspoland.de]
[www.epspoland.de]
is pretty much immune to anything but a saw.

This is a US supplier of these panels. I use the rounds to make beautiful deer and duck calls. >>> [www.cwp-usa.com]

---

Folger Tech 2020 i3 and FT-5 as well as modified JGAurora A5 with direct drive E3D/Titan. All running the BLTOUCH.
Great kits. Having fun and running the heck out of them.
Running Marlin 1.1.0 RC8 on the i3 and FT5. Custom firmware on A5.
Folger Tech Wiki board >[folgertech.wikia.com]

Quote
realthor
is there anything wood still has to offer?

The coefficient of thermal expansion of wood is less than half that of steel.
The coefficient of thermal expansion of steel is about half that of aluminum.
See Inspectapedia ( [inspectapedia.com] ) for the exact values.

Quote
realthor
the transition has been towards more dimensionally stable materials...

That could explain why P3Steel ( [reprap.org] ) argues that switching from aluminum to steel is an improvement.

That could explain why I see that hardly anyone now uses a steel-framed Darwin RepRap, and many of them now use some wood-framed RepRap.

If you're interested, the Wood category ( [reprap.org] ) links to many RepRaps that use wood.

Thanks @DavidCary for chiming in. I was aware of most of what you said (didn't know about the inspectapedia.com thanks for that) but wood is stigmatized for not having an uniform thermal expansion but mostly for its humidity issues that get its bad name (and warped shape).

So far @Srek's Siebdruckplatte and the WPCs (haven't seen yet any Fiber Reinforced WPCs easily available) look very promising. I don't like steel for its energy footprint but well, it's the cheapest we have. I see Prusa Steel on top of 3DHubs charts so it might say something.

The only problem with wood, of any kind, that will be difficult to overcome is making sure that all bolts and inserts are somehow treated to protect moisture going in. Coating a piece of wood is not difficult but maintaining coating is a challenge once you start bolting the piece to other boards or to a metal frame. Maybe a sprayed clear coat after all is assembled should be a best practices?!

Edited 1 time(s). Last edit at 02/26/2016 08:38PM by realthor.

---

RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff

I wouldn't bother to much, if you get stuff that is as tighlty laminated as this there will not be a problem with moisture. Just treat the long cuts and be done with it.

---

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Just came to mind: is a wood panel bolted to the side of a alu/steel frame as a skin capable of influencing the metal frame's dimensional stability as it warps/shrinks/expands due to the elements? Then is this combo a bad thing considering that the metal contracts/expands itself. Do they work together or fight each other during these movements?

---

RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff

They will always fight each other, there are very few lucky combinations where the thermal expension rates of two materials match so well that this works (steel and concrete i.e.).
There are two solutions, either create a flexible connection, or make the panel of elastic material and so thin that it does't exert enough force to warp the frame.

---

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Quote
Srek
They will always fight each other, there are very few lucky combinations where the thermal expension rates of two materials match so well that this works (steel and concrete i.e.).
There are two solutions, either create a flexible connection, or make the panel of elastic material and so thin that it does't exert enough force to warp the frame.

I don't know if I've been completely clear, what I meant to ask was: is the combined movement during the combo's struggle together resulting in a better stability or they fight so bad against each other than the resulted shape is worse than if they would have been each on its own the frame?

---

RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff

I don't know of any case where the countering forces would be an advantage. They are way to uncontrollable to be helpfull.

---

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

I tend to think that we are overengineering some problems. The printers are not going to be more precise than 0.1mm or maybe if you are really lucky 0.05mm anyway.
So, if I ever get to build my second printer, I would choose plywood.
What one can do to minimize warping or dimensional changes due to humidity is to infuse the wood with some kind of filler (stabilizing it). In the knifemaking community, there are some interesting products that one should in theory be able to replicate at home. It mainly involves vacuum as far as I know. Since we are dealing with thin sheets here, I guess some slight under-pressure from a home rigged system might provide enough penetration.
Alternatively, there are oil based products like tung or boiled linseed oil that do just that.
Afterwards, a coating of PU or acrylic lacquer should seal things up.
Especially for printers that are more or less enclosing the build space, wood makes more sense than metal as an insulator. The insides, though, should reflect as much IR as possible, so a thin layer of polished aluminium on top of treated wood would be my ideal choice.

I did some research into this before building my printer and found the following that talks about plywood's thermal expansion: [www.performancepanels.com]

Quote
PerformancePanels.com
Plywood and wood expand upon heating, as do practically all known solids. The thermal expansion of wood, however, is quite small and requires exacting techniques for its measurement. The effect of temperature on plywood dimensions is related to the percentage of panel thickness in plies having grain perpendicular to the direction of expansion or contraction. The average coefficient of linear thermal expansion is about 3.4 x 10-6 inch/inch per degree F for a plywood panel with 60 percent of the plies or less running perpendicular to the face. The coefficient of thermal expansion for panel thickness is approximately 16 x 10-6 inch/inch per degree F.

Thermal expansion for Aluminum is 13X10-6, a bit more than for plywood in the linear direction.

I calculated that the cast aluminum tooling plate for my delta printer would expand about .3mm more than the plywood (from the center out based on 8" radius mounting points). So I simply installed it with thin stainless all-thread and over-sized holes.

I also installed the rails so they were only firmly fixed at the center, but could still expand length wise. This is a common technique for woodworkers. You would not want to combine wood and any metal in a fixed frame without having a similar accommodation for expansion if it is going to be heated.

Just in case, I did use high temp paint on the internal of the printer, and it has a 1/2" layer of "R-matte Plus 3" (polyiso) foil faced foam insulation inside.

BTW, the plywood I used is called MDO Plywood here in the states. MDO stands for Medium Density Overlay. This overlay makes the surface of the panels very smooth, adds some moisture protection, and takes paint very nicely. This material has been used for architectural concrete forms where a very fine finish is desired.

I run the chamber at about 55C with no issues.

Hope that helps.

---

My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

Nice setup. How would you account for plastic (3D printed) parts screwed into the wood?

---

RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff

Quote
realthor
How would you account for plastic (3D printed) parts screwed into the wood?

I've seen a lot of CoreXY printers that use plastic brackets of various kinds. I don't think there is much expansion/contraction happening with those under normal working temperatures, if that's what you're referring to.

BTW, the MDO plywood I used was 3/4", joined with biscuits and urethane glue (handles the temperatures fine).

---

My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!