[Arm-netbook] first prototype microdesktop casework

[Luke Kenneth Casson Leighton]

On Mon, May 8, 2017 at 2:07 AM,  <doark at mail.com> wrote:
> I apologize for DOS'ing the list, I can only get online about once a week.
>
> On  Sat, 29 Apr 2017 12:42:29 +0100
> Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:
>>
>> On Sat, Apr 29, 2017 at 6:08 AM, Luke Kenneth Casson Leighton
>> <lkcl at lkcl.net> wrote:
>> > http://rhombus-tech.net/community_ideas/micro_desktop/news/
>>
>>  ok, ouch, onto the fourth revision of the corner-pieces already, and
>> some minor changes to the plywood are needed as well.  this really
>> would have been awkward if someone else did it.
>>
>>  the anycubic 3d printer is holding up well.  the higher-quality PLA
>> from the company i found on aliexpress seems reasonable so far (the
>> "standard" quality definitely isn't: it literally crumbles under
>> pressure).
> <snip>
>
> Luke, (I can call you Luke, since you sign your name that way, right?)
> PLA stands for Poly-Lactic-Acid and if they are selling you something
> else you can complain, if not sue for false advertising. That's why we
> label things, so that we know what they are, right? So one PLA aught to
> be the same as any other. Aluminum is aluminum, titanium is titanium, why
> is PLA not PLA?

 it's partly down to where the lactic acid comes from: like any
chemistry you get a different yield and a totally different
composition depending on the process, the purity and the ingredients.

 most companies use corn for the raw materials, and they don't process
(purify) it properly.  the result is that the PLA gives off acrid
fumes, deforms under pressure, does not adhere properly (to itself...
which is kinda important) and is generally completely fucking useless
for well... everything to do with 3D printing.


> I own a Reach3D printer. It's an all aluminum housing and z axis gear
> printer. I'm still in the construction phase, but if me and my caliper
> (it's auto-calibrating but I want it perfect :) work well together then I
> should be printing sometime around the 21st. I could help you with my
> printer at limited expense (unless something big happens in my life :)

 :)

> Also, I bought on Amazon 2 spools of PLA and one of PC. The PLA cost ~$20
> per KG while the PC was ~$30.

 ok, i'd like you to do a test.  take a small piece about 5cm long and
bend it very very fast, as quickly as you can, making the loop as
small as you can (8mm or less if you can).

 good PLA will snap.

 shit-quality PLA will discolour, going light-coloured.

 another test - a really really important one - is to make a long
rectangle (35mm high x 5mm x 10mm would probably do) - the height is
important - then clamp one end to a desk.  on the other end suspend a
weight tied with string as close to the end as possible.  make the
weight... let's say.... 0.5kg or so.  not very much.  now leave it for
a month.

 good quality PLA will be ok, and when you take the weight off the
shape will be retained

 shit quality PLA will snap any time within hours to weeks, and when
you take the weight off you'll find it's bent.

 that amazon PLA you bought i can guarantee will be shit quality.




> It seems to me that you might be better off
> with PC if finding a good PLA supplier and making a case that is not
> flimsy with PLA is such a problem.

 faberdashery's PLA is extremely strong.  it actually has better
rigidity than PETG.  PC requires a higher temperature and has less
available colours as it's not so common for 3D printing.

l.