just a few notes below

On 27 July 2017 at 10:45, Ricardo Wurmus rekado@elephly.net wrote:

Heya,

this idea is too late for the current batches of laptops, but I was wondering if it wouldn’t be easier and faster to mill the laptop plastic parts out of recycled blocks of plastic (“plastic lumber”) with a CNC mill.

The advantages are as follows:

• suitable plastic lumber can be made from a wider range of plastics than 3d printer filament

• plastic lumber can be made from readily available plastic waste. HDPE from plastic bags make for cheap sturdy blocks of material.

• a CNC mill cares much less about the melting point of the work piece during operation than a 3d printer

actually during milling you also develop heat, potentially much higher then during 3d printing. You will need to test speeds, bits etc...

• there are fewer concerns about material shrinkage at construction time, because the work piece isn’t partially liquid at any time of the CNC operations.

• processing the work piece is faster because it doesn’t require as much motion as printing sturdy zig zag patterns.

• even rather unsophisticated CNC mills can be used as the work piece is rather soft compared to the usual CNC mill work pieces such as aluminium.

Actually, first of all not all parts can be milled. It totally depend on specific parts, so each part is separate problem.Also, if plastics are soft it does not mean that you need unsophisticated milling machine. You still need some range of precision and depend on parts 4 or 5 axes. So, it may turn to be very expensive. Also you are talking quite small parts that you need to hold&process somehow. I would say it is a project within a project.

Then, if all these is doable in theory. Then you need a person who is very knowledgeable about processing materials (specifically plastics), one need to know a lot about processing speeds, depth cuts, tooling types etc and must be able to create tool paths on some kind of CAM software and this include trial & error process for each part.

Then, lets imagine you found person that have that kind of machines, knowledge to do it, I guess it would be cheaper to create mold tooling from aluminum for each part and easily produce each part in thousands.

The most obvious disadvantages are:

• there seem to be much fewer vendors of plastic lumber than there are vendors of high quality 3d printer filament

• this approach isn’t quite as common, so it may be harder to find good advice from experienced people.

What do you think?

(I’m currently in the process of setting up a plastic recycling work space for my plastic lumber needs.)

-- Ricardo

GPG: BCA6 89B6 3655 3801 C3C6 2150 197A 5888 235F ACAC https://elephly.net

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On Thu, Jul 27, 2017 at 9:45 AM, Ricardo Wurmus rekado@elephly.net wrote:

Heya,

this idea is too late for the current batches of laptops,

it isn't

but I was wondering if it wouldn’t be easier and faster to mill the laptop plastic parts out of recycled blocks of plastic (“plastic lumber”) with a CNC mill.

ok, so some of the parts are only 0.7mm thick in places: i'd be concerned about fibre chunks / variations.

also it would mean a lot of software work writing a library (backend) for pyopenscad that outputted formats suitable for CNC machining.

also it would be quite likely that the actual machining time would be far, far longer than 3D filament printing.

i very much appreciate the idea though.

l.