azonenberg changed the topic of #scopehal to: libscopehal, libscopeprotocols, and glscopeclient development and testing |,, | Logs:
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<azonenberg> DuncanHaldane: so, the big reveal:
<d1b2> <DuncanHaldane> Looks like the mold loved the part too much and didn't want to let go
<d1b2> <DuncanHaldane> Good filling though, don't see many bubbles at all
<azonenberg> (18:25:59) azonenberg: So far, my postmortem takeaways are...
<azonenberg> (18:26:05) azonenberg: 1) I forgot to actually use the mold release spray
<azonenberg> (18:26:10) azonenberg: 2) thickness on the edges was too thin
<azonenberg> (18:26:35) azonenberg: 3) the silicone has next to no adhesion to the PCB material itself. Meaning the board is gonna jsut be sitting there held in place by essentially friction
<azonenberg> (18:26:44) azonenberg: and i need to rely exclusively on the edges to hold the halves together
<azonenberg> (18:28:39) azonenberg: 4) The tip cavity around the solder terminals and resistors filled with silicone. So i need to probably fill it with sulfur-free clay (I have some on order already) to provide a seal
<azonenberg> (18:29:01) azonenberg: 5 Cure time of 4 hours on the jar is insufficient, in fact 5 is insufficinent
<azonenberg> (18:29:14) azonenberg: maybe my lab is cold, idk
<azonenberg> (18:29:08) azonenberg: the puck i made last night and cured overnight was a lot less gooey than this
<azonenberg> (18:29:39) azonenberg: 6) the SMA connector does not fit in the mold, i mismeasured somehow
<azonenberg> (was just talking to somebody in another chan about this screwup)
<azonenberg> DuncanHaldane: The actual PCBs are still on order anyway
<azonenberg> So my current plan is to respin the mold with fatter sidewalls, correct the dimensions of the SMA cutout
<azonenberg> actually use mold release spray next time
<azonenberg> There was also a lot of flash due to flexure of the 3d printed plastic mold
<d1b2> <DuncanHaldane> For this, a softer mold would help as well. Something like a 25-30 durometer rubber, either silicone or polyurethane depending on what you are casting into it.
<azonenberg> the final mold will be cnc'd aluminum
<azonenberg> I'm treating this as an injection molding setup
<azonenberg> since that's effectively how i'm doing it
<d1b2> <DuncanHaldane> Ah this is going to production then.
<azonenberg> Well, i hope to be making these in some level of volume eventually yes
<d1b2> <DuncanHaldane> Seems like the injection worked well!
<azonenberg> I did have some aeration in the syringe, i think the luer lock fitting leaked
<azonenberg> i ordered some larger needles to see if that helps
<azonenberg> (drawing up the silicone faster)
<azonenberg> But yes i think the method has promise
<d1b2> <DuncanHaldane> Re: cure time. The platinum cure silicone s can be touchy about mix ratios, and the curing is highly temperature dependant.
<d1b2> <DuncanHaldane> You can accelerate with higher temps, but beware the thermal expansion coefficient is huge, so too high and you get deformation
<azonenberg> I measured with a milligram scale and tried to get within 1% of the 1:1 ratio it calls for
<azonenberg> My lab is a controlled 70F +/- 2
<azonenberg> I applied gentle heating to the red prototype, hot plate set to something like 40C
<azonenberg> Just mixed up a second batch for another experiment. This time I am using mold release spray and curing overnight
<azonenberg> I still need to respin the mold in order to get a better fit on the SMA, just need to identify the exact location it's hitting
<azonenberg> so far it's not obvious where the clearance violation is
<azonenberg> it's small, the mold is maybe 100-200 μm short of closing fully
<azonenberg> (with the SMA in place)
<azonenberg> it might even be a simple as me mistaking a nominal dimension for a max material dimension or something
<azonenberg> or the 3d printed mold being at the extreme of some tolerance
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<_whitenotifier> [scopehal-apps] azonenberg opened issue #297: Allow preferences to be reset to default values -
<_whitenotifier> [scopehal-apps] azonenberg labeled issue #297: Allow preferences to be reset to default values -
<_whitenotifier> [scopehal-apps] azonenberg assigned issue #297: Allow preferences to be reset to default values -
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<_whitenotifier> [scopehal-docs] azonenberg pushed 1 commit to master [+5/-0/±4]
<_whitenotifier> [scopehal-docs] azonenberg d67e742 - Added new section for filter graph editor. Documented 64/66b decoder, major improvements to documentation of 8b10b and TMDS decodes.
<_whitenotifier> [scopehal-apps] nshcat commented on issue #297: Allow preferences to be reset to default values -
<_whitenotifier> [scopehal-apps] azonenberg commented on issue #297: Allow preferences to be reset to default values -
<azonenberg> anybody have feedback on the first 3 filters in section 14?
<azonenberg> i'm doing a big revamp of the documentation, trying to finish documenting all of the stuff i never wrote anything for
<azonenberg> as well as just making the filter documentation look better
<azonenberg> I did those 3 as a test but wanted to get some comments before doing all 90 of them :p
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<azonenberg> Demolded second prototype
<azonenberg> Came out closer to intact than the last one but was still sticky, as was the silicone in the pot, despite a 12+ hour cure cycle
<azonenberg> wondering if something is inhibiting the cure
<azonenberg> I think later today i am going to do another experiment: no PCB
<azonenberg> mix the silicone in one little cup
<azonenberg> pour into a second one, draw it up from that one with a syringe and inject into the empty mold
<azonenberg> leave some in the first cup
<azonenberg> So now we have three different casts of the same silicone under three different conditions
<azonenberg> control (cured in the original mix up, no contaminants)
<azonenberg> exposed to syringe and needle (in second cup)
<azonenberg> and cured in mold (in third cup)
<azonenberg> this will also allow me to test de-molding of a solid silicone cast without any peeling risk because there won't be any PCB inside it
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<miek> hmm, is it common for scopes to let you measure trigger rate? i don't see any option on mine
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<azonenberg> miek: what do you mean "trigger rate"
<azonenberg> WFM/s?
<azonenberg> no, i dont think i've ever seen a scope with that capability
<miek> yeah, i guess so
<azonenberg> i added it to glscopeclient primarily for benchmarking/profiling purposes
<miek> for now i'm just feeding the trigger out signal to my DMM :p
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<azonenberg> DuncanHaldane: turns out, upon some reading, that platinum cure silicone is incompatible with acrylic photopolymers
<azonenberg> welp
<azonenberg> Guess i need to make a new mold :p
<azonenberg> I'll try fixing the SMA clearance issues, then reprinting it in SLS nylon. The surface finish won't be as good, but will hopefully be decent enough for a prototype
<azonenberg> then i can move to cnc aluminum
<azonenberg> Actually it looks like there is a surface treatment that might help
<azonenberg> i might do that first
<azonenberg> Since the photopolymer does have much better surface finish than SLS
<azonenberg> also, next AKL-PT2 prototype received from fab
<azonenberg> so i should have it by the weekend
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<d1b2> <DuncanHaldane> Oh, interesting. I had hit the non-sulfur free clay issue before. Acrylic polymers is a new one.
<d1b2> <DuncanHaldane> I was a bit stumped as to the issue because your method sounded quite well done.
<azonenberg> Yeah i tried to do my research and was aware of the sulfur issue
<azonenberg> I only discovered the photopolymer incompatibility after the fact
<azonenberg> I ordered some Inhibit-X which is apparently some kind of petroleum based surface treatment that helps mitigate this problem
<azonenberg> will see if it helps
<d1b2> <DuncanHaldane> Machine wax makes for a great molding material if you've got a CNC around. Even something like the Othermill can do well.
<azonenberg> I do not have a CNC. I have a 3-axis Sherline but it's full manual
<azonenberg> geometry this complex would take forever to do by hand
<d1b2> <DuncanHaldane> Yeah that would take some patience.