[Arm-netbook] video of laptop casework demo available

Tue May 5 06:47:38 BST 2015

Luke,

1) We print 3d parts with one professional company doing it on good
equipment. I can give you contacts if you like and you can ask for quote.
Usually best scenario is to print several parts on your printer and when
you think you are done, pay for better prints (for example if you need to
shoot video or present it to investors you need the best you can get, don't
spare on this).

2) I had several bad attempts with the mold makers but I think I found
qualified one in China (this is specialized shop only in molds, the guy has
been working on parts of HTC, Apple etc.). if you like I can give you
contact and you can send him parts for quote to see if you can lower cost
for mass production. He can also produce. As a rule of thumb, if you are
going to China for mold go in Shenzen area, the best molder makers are
there and opposite and if you go to i.e. Ningbo area good chances are that
you are going to finish with bad quality parts, looking cheap. If you are
not sure what you are looking in term of finishes, go to some mobile phone
store, find some telephone (that you have exact model that you can point to
molder so you have same reference) and ask molder if he can do that and
that type of finish. I am not a mold specialist, but making several
thousands pcs of one mold is way too low. Mold should last at least 100k
pcs, depend on the quality of material can last 200, 300k pcs. Again, speak
to qualified molder, ask for quotation and ask for number of produced
units, ask for advice and second opinion. if they still reply you this low
number ask why.

Hrvoje

On Mon, May 4, 2015 at 7:00 PM, Luke Kenneth Casson Leighton <lkcl at lkcl.net>
wrote:

> On Mon, May 4, 2015 at 5:29 PM, Paul Boddie <paul at boddie.org.uk> wrote:
> > On Monday 4. May 2015 12.32.47 Luke Kenneth Casson Leighton wrote:
> >> http://rhombus-tech.net/community_ideas/laptop_15in/news/
> >
> > It looks rather promising, and I can see how the limitations of the
> printer
> > might make prototyping difficult: I've also had people print me things,
> and it
> > has required a lot of "post-processing" on their part to get
> mechanically-
> > acceptable results.
>
>  yeah tell me about it.  i learned only recently that you have to
> switch on "antiooze retract".
>
>  one of the problems i'm encountering is that the inner walls are
> really quite thin.  repsnapper isn't too smart, so it goes "i'll draw
> that inner part - 1mm thick - as a square, and right next to it i'll
> draw *another* inner part buuuut, because they're separate, i have to
> go zip-zip-zip (from 1st square to 2nd and back) to get the bit of
> oozing plastic off of the nozzle".
>
> uuunfortunately, that "bit of oozing plastic on the nozzle" can be as
> much as 3-4mm long.  it accumulates *per layer* on the exterior of a
> wall 1mm thick that's being built up 0.2mm at a time.
>
> you can tell what's going to happen, can't you... :)  yep you guessed
> it: that "bit of oozing plastic" makes the corner of the inner wall
> eeever so slightly higher by 0.2mm than the surrounding sides being
> built up... by the time you get 10mm high the corner is a whopping *4*
> millimetres higher than the height where the printer head is
> travelling!!
>
> that ends up with a corner pushing the bed down, causing no end of
> problems including the entire part breaking free of the heated bed.
>
> by switching on antiooze retract, the zip-zip-zip which causes 3-4mm
> of plastic to be dumped in a corner is replaced with "bzzz-zip-bzzz"
> which is:
>
> * z-axis going backwards a couple of millimetres
> * x-y positioning to the new location
> * z-axis going forwards a couple of millimetres
>
> and it carries on from there.  it seems to work and produces much
> better quality work.
>
> *if* however the walls on the parts i was printing were, say, the
> quotes normal quotes thickness - most people print 3D parts with walls
> *at least* 5mm thick, and *especially* if they were being printed as
> solid parts (which i am not), then there would *not* be the problems
> that i'm encountering.
>
> looking at the parts that make up the mendel90, almost all of them are
> completely solid.  holes are at least 8mm in diameter.  any "interior
> walls", the smallest thickness i can see on any of the 100 parts is
> about... 4mm.
>
> by contrast, i'm printing *hollow* parts where the walls are in some
> places only 0.7mm thick.  certainly, the interior support struts are
> only 2 runs of the print head back-and-forth.
>
> so it really really does depend on what you're doing, paul.  i can say
> that now, after working with this mendel90 for... five months? :)
>
>
> > I imagine that this would be adapted to more scalable processes once
> > prototyped, however, which would infuriatingly eliminate some of the
> precision
> > issues experienced during prototyping. Or would you first go through an
> > iteration or two of higher-specification 3D printing first?
>
>  right.  ok, the plan is as follows:
>
>  * phase 1: get 3d printed parts working (as +ves)
>  * phase 2: split all parts into two -ves
>  * each 1/2 part will be subtracted from a "block"
>  * this "block" will fit inside a metal container
>  * the two 1/2 -ve parts will be fitted inside the metal container
>  * low-viscosity injection mold plastic will be used to create a prototype
> part
>
>  phase 3:
>
>  * the two 1/2 -ve parts will be printed out on flash-thermal resin (on a
> DLP)
>  * the two 1/2 -ve  parts will then be flash-cast to metal.
>  * the resultant 1/2 *METAL* parts will then be used for *production*
> injection molding.
>
> the reason for using high-accuracy thermal resin to cast the molds in
> metal is that - i hope - they will be much more accurate, so will not
> require polishing.
>
>  if they *do* require polishing (i.e. not look good enough) then what
> i will do instead is investigate some casting methods that give the
> cast parts a "sandy surface" look, meaning that any blemishes simply
> won't show up as significant.
>
>  $USD 20k on polished injection molds when they're only going to last
> 2 to 3 thousand units before they wear out due to abrasion - it's
> silly.  there has to be a better way.
>
> l.
>
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