[Arm-netbook] CNC milling of plastic lumber instead of 3D printing?

[Hrvoje Lasic]

just a few notes below

On 27 July 2017 at 10:45, Ricardo Wurmus <rekado at 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
>
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> https://elephly.net
>
>
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