Sunday, March 30, 2008



The MDF base of my Darwin is getting a little worn where I keep building experiments on it then ripping them off. I decided to bolt something sacrificial onto it to build upon. I had no more MDF, but I did have some balsa wood so I tried that.

It works really well. Above is the X-axis PCB holder. Even with PCL this has a slight tendency to curl up at the ends because it's so long and thin. But with balsa wood, no such problem - it builds perfectly. It works especially well if you run the first layer a little low. This causes the extruder to force the polymer into the grain a bit, giving good adhesion. But the balsa is so weak that it's still easy to separate the built part (though some bits of balsa come away with the part, they are simple to clean off with your fingernail).

Here are two of the general PCB brackets built in one build:

I made a little aluminium template to cut the balsa round with a scalpel and to act as a jig for the holes through which I bolt it to the base. And, as it gets a bit tatty, you can double its life by turning it over, of course.

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That is weird looking balsa wood. Looks like linoleum. :-s
Trick of the light, I think Forrest. It looks like ordinary model-making stuff most of the time.
PS Christine is really Adrian logged into his wife's computer...
Well I guess it makes pretty good sense. Balsa has been used in the aeronautical industry for, I guess ever, because of its lightweight properties and because of its ability to be bent into nearly any shape. The reason for this ability is I think that the wood is very porous, which allows for a lot of wiggle room-- and for the acception of plastic.
It seems to be difficult to buy balsa wider than 4", are the trees very small?

Are there any Darwin bits wider than 100mm?
How thick was it? I see you can get it 1/8 and 1/16"
The stuff I have is 5mm thick and 100 mm wide. It was just what I had lying around in my lab. I was thinking of tiling it for big bits...
nophead: Balsa is definitely available in much larger chunks than you see in hobby stores - people make surfboards out of the stuff - often using either one solid piece or two or three glued side-to-side as the starting point for carving a board.

My father used to run a model airplane store in the UK and he told me that (at least in Europe, ~30 years ago) nobody specifically imported balsa and all of the wood that you ever saw in hobby stores was recycled balsa that had been used to pack delicate items that had to be shipped by sea. He started importing the stuff directly from suppliers in (I think) South America and claimed that because the balsa he sold was hand selected for model making, that it was superior to recycled packaging material!

But now that we have foamed plastics, I can't imagine they're still using this costly hardwood (yes, balsa is technically a 'hardwood') as packaging - so presume that all balsa is shipped directly as a product in it's own right.

So there shouldn't be any good reason why you can't buy it in bigger sizes.
I don't imagine that foamed plastic is cheaper than balsa in all parts of South America.

One requires capital; the other, only land.
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