[GTA04] When is the next and more powerful openmoko releasing

Al Johnson openmoko at mazikeen.demon.co.uk
Sat Oct 23 15:40:04 CEST 2010

On Friday 22 October 2010, Dr. H. Nikolaus Schaller wrote:
> Am 22.10.2010 um 02:17 schrieb Al Johnson:
> > On Friday 22 October 2010, EdorFaus wrote:
> >> On 10/21/2010 07:59 PM, Alfa21 wrote:
> >>> you should try 3d print like this:
> >> <snip>
> >> 
> >>> made in ABS which is a good plastic and up to 0.01 inches resolution
> >> 
> >> Unfortunately, that's not quite good enough (different units).
> >> 0.01 inches = 0.254 mm, which is 2.54 times the required size:
> >> 
> >> On 10/21/2010 07:32 PM, Dr. H. Nikolaus Schaller wrote:
> >>> the required precision (0.1 mm, 0.5 mm wall thickness, etc.)
> >> 
> >> 0.1 mm is approximately 0.0039 inches.
> >> 
> >> I have a question, though - is this precision required for making *any*
> >> well-working case design (due to the electronics etc.), or is it just
> >> for making more of the current case design?
> >> 
> >> If it's the latter, it would be possible to create a new case design
> >> that would be easier to get manufactured...
> > 
> > The electronics don't need much precision in the case design. Cases that
> > clip together firmly and securely do need precision though, and that's
> > true of the current design. An alternative design needing less precision
> > is possible, especially if we accept things being screwed together.
> Generally yes. If we sacrifice quality, ergonomics, and size, we can
> find simpler and less expensive case constructions.

I'm sure we can find alternative case construction methods that don't 
sacrifice much in any of those departments. They just won't be methods used in 
the mass market because they don't scale up to those production volumes, just 
as their methods don't scale down to ours. The pcb might need some design 
elements suited to a different method of mounting than the current 'clip it 
into the injection moulding' variety, but this is for future generations not 
the current pcb.

> One aspect to keep in mind for precision are the push-buttons (AUX and
> Power). The buttons [1] are specified for a "Travel 0.3 mm +0.1 –0.2 mm".
> I.e. if we don't want that the buttons get stuck we come to this 0.1mm
> precision. We have experienced the same with the PCB design where the
> position of the buttons must be within these 0.1mm...

That doesn't mean the case needs that tolerance though. It just means the end 
of the actuator needs to stick over the edge of the pcb by the right amount to 
be operable. The external button can be lightly spring to take up the 
tolerance, or rest slightly clear of the button actuator. Alternative switch 
types are an option for future designs, including a change to capacitive 
sensors as provided for by the v2 nav board.

> The same is with mounting the display. If that is not precise enough, touch
> operation will be deteriorated.

Can you elaborate? There may be ways around this one too.

> So if we reduce precision of the case production process, the buttons
> become larger and finally, the phone is more a brick than a handheld phone
> :)
> Personally, I am in favour of high-end high-quality design (like the
> iPhone) even if it costs money. But it should never cost freedom and
> independence...

high quality design doesn't have to be expensive to manufacture. I suspect 
something attractive could be made in low volume at a reasonable price using 
laser cut plastics. I'll try to ask the local cutters about their precision 
and cut thickness in different materials.

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