<wolfspraul>
I wanted to keep in touch over the cases...
<wolfspraul>
we talked about L/ON/R already, that's clear
<wolfspraul>
my next worry was the button tolerances on the inside of the case, maybe you saw it
<roh>
nope
<wolfspraul>
I don't have enough cases to look at though, you know better how you feel about it
<wolfspraul>
ah OK, then I repeat
<wolfspraul>
so here is my concern:
<wolfspraul>
the button is made out of 3 pieces now, the big one on the inside preventing the button to fall out, and pushing it against the electrical switch
<roh>
i am quite busy these days with the move.. my status is: i ordered the metal, and contacted the laser contractor
<wolfspraul>
but I've had quite some problems with cases where after screwing them together, the pressure on the switch was so high that the buttons were stuck
<wolfspraul>
sure great, I totally trust the things is moving on your side
<wolfspraul>
I'm not worried about that
<wolfspraul>
I just want to give some more feedback
<wolfspraul>
this one is about 'stuck buttons'
<roh>
havent heard back from the laser guy, but he said on the phone already he will be on the road the next too weeks (about a week ago).
<wolfspraul>
the thing is that we are talking about 0.1/0.2 mm issues, so I'm not sure whether we should change anything, or maybe that would make things even worse
<roh>
i think the 'stuck button' thing will go away or be 'different' with the better machine (laser optics is more precise)
<wolfspraul>
ok. do you understand my concern first of all?
<wolfspraul>
I am also wondering about tolerances on the PCB side
<wolfspraul>
maybe if we make 80 sets, we will have 5-10 or so where some buttons will just be stuck
<wolfspraul>
we could try to find a thinner inner plastic piece
<wolfspraul>
or we could move the electrical switch on the pcb into the board a few mil
<wolfspraul>
but then what we have now is not bad, so we can easily make something worse than it is now...
<roh>
so if my test runs will show some 'tolerance issues' i will widen the button holes some fractions of a mm
<wolfspraul>
I'm talking about the thickness of the larger plastic piece
<wolfspraul>
the one that sits between the acrylic (on the inside) and the electrical switch
<roh>
that one is 1.0mm.
<roh>
i use 'precision acrylic' there to get real 1.0mm, since regular one has so much tolerance
<wolfspraul>
should we move the switch into the pcb a few mil?
<roh>
it also depends on the fitting of the sides.
<roh>
not neccessary, i can move out the side panel a bit if neccessary
<wolfspraul>
ok, that's a good point
<wolfspraul>
I'd rather not make mechanical changes on the pcb, otherwise it will get messy over time
<roh>
so i guess its easier to keep the button where it is, which would also make the cases 'more universal'
<wolfspraul>
definitely
<roh>
i will redo all the mechanical tests anyhow when i do the testrun on the other machine. no worries
<wolfspraul>
so then just remember this issue, and let's keep an eye onit
<wolfspraul>
it's a pretty nasty problem once it hits the user
<wolfspraul>
they will reassemble the case, tighten the screws: suddenly the box won't boot anymore
<wolfspraul>
and then it's hard to fix too
<wolfspraul>
I am also wondering whether the electrical switches loosen over time
<wolfspraul>
i.e. the pressure to make them connect will go down?
<wolfspraul>
there is probably a tolerance in that pressure too, so some of them may click/connect with less pressure than others
<roh>
hm. dunno.
<wolfspraul>
oh well :-)
<roh>
i think the mechanical 'distance from not pushed to pushed' should be spec-ed anywhere
<wolfspraul>
ideally in a 'unpressed state' (with button from outside), the force applied to the electrical switch should be exactly 0
<roh>
and i would wonder if it would change much
<wolfspraul>
but the distance between 1.0mm plastic and electrical switch should also be 0
<wolfspraul>
of course that's very hard to achieve
<roh>
i could just 'make it a bit wobblier
<wolfspraul>
if there is a small gap, yes I guess it would be wobblier
<wolfspraul>
I think in many cases we do in fact exert some pressure on the electrical switch, even if the user does not press the buttons
<roh>
i did quite some tries to get it 'right' maybe tolerances in reality are just a bit bigger than the 2 pcbs i have
<wolfspraul>
I may also be looking at old cases
<wolfspraul>
mine are from December
<roh>
i tried this stuff with the rc1 mechanical prototype and the rc2 i have
<roh>
will just give it some more slack and see what happens
<wolfspraul>
also we have to make sure that there is no glue residue coming out from between the 2 smaller button pieces and the larger one
<roh>
i will try another glueing method
<wolfspraul>
because if there is, it is exactly at the point that it will move the 1.0mm one further into the case
<roh>
there is some chemical which softens the surface of acryllic and it is intended to be used for glueing
<roh>
will do some tests with it and see if i can pre-glue the stuff properly.. maybe by using some fixture (thinking of an metal with a hole, which would be unaffected by the chemical)
<roh>
Tetrahydrofuran or Dichlormethan
<roh>
i think i have seen some of the latter when packing the 'special glue box' earlier