Hi, A lot of fascinating steps. It would be real fun if one would do a coarse in which one would actually build a handful of crystals oneself, to learn the basics, and measure them up. It would be a fun summer-coarse to do.
I have no expectance that it would be spectacular performance, just being to build something which would result in an oscillating oscillator would be quite cool. Cheers, Magnus On 2021-02-18 22:07, Bob kb8tq wrote: > Hi > >> On Feb 18, 2021, at 9:17 AM, Lux, Jim <[email protected]> wrote: >> >> On 2/18/21 3:53 AM, Poul-Henning Kamp wrote: >>> -------- >>> Bob kb8tq writes: >>> >>>> Turning an “idea” into a production capable part involves making many >>>> batches of test samples. Think in the thousands of batches and hundreds >>>> of parts in each batch. You have a “search” process at the blank chopping >>>> level. You also have a search at the resonator fabrication level. Getting >>>> the >>>> chopping part right is only a small part of the whole process…. >>> I realize this used to be a manual process, but today I would expect >>> that you could automate a lot, of not most of it, if you wanted to ? >> >> That was my first thought, and then I thought through all the steps. I think >> it would be challenging to automate (and that brings up your question below >> about "is it worth it?") >> >> First, are you starting with natural or grown quartz? ( While grown quartz >> is used for most crystals, isn't there some performance benefit from natural >> crystals?) > Finding natural mono crystalline quartz is a challenge. Finding big pieces of > it is > more of a challenge. (sand is easier to find that big chunks). > > Finding un-twinned crystals ( it comes in left and right hand orientations) > is impossible. You > are left working out a strategy on a per chunk basis to avoid twinning and > inclusions. > Once you are done, it’s slow growth quartz so it may be better in some > respects. > >> I assume there is some sort of process to create "bars" of quartz from the >> raw boules or crystals. > Quartz is grown from a seed. You dump raw quartz bits along with a chemical > soup into a pressure vessel. ( think in terms of a 16” naval gun barrel ….). > You > seal it up, pressurize it and heat it up. At high enough temperatures the > silicon > dioxide feeder material dissolves into solution. You try *not* to dissolve > your seed > blanks at the same time :) > > The temperatures of the vessel ( = there are multiple zones) are varied over > time. > The pressure could also be varied as well. As you drop the temperature the > crystals > grow on the seed bars. The faster they grow, the more likely there are to be > minor > defects in the resulting crystal. > > The seed gets cut out of the bar before it really goes anywhere. > >> I believe you'd need to do some analysis to determine the crystal axes and >> then the bars go into a series of saw steps - those might be automateable, >> in terms of sawing angles - is the sawing with a wire, with a diamond blade, >> or these days, perhaps abrasive water jet? > For volume production, a multi pass wire saw or a blade pack saw are pretty > common. > For one off “lab” stuff a diamond saw might be used. In between the “grow it” > and > “cut it” stages there is an x-ray process and some method of mounting the > material > in a holder. > > >> That would give you a bunch of slabs with the cut with the right angles - >> I'm sure the machine they use today probably dumps them in a hopper, and >> I've watched enough food packaging shows to know that you could get those >> fairly large slabs onto a conveyor. > For an OCXO crystal, the “slab” is going to be < 25mm square, generally much > less. > >> Then you'd have to cut your desired crystal shapes out of the slab (whether >> round, rectangular, or some other shape) - another sawing or grinding step, >> I assume. > The most common shape for a precision part is a round blank. You stack the > angle corrected > squares together and put them on a centerless grinder. … oh, angle correction > … Well you > can’t cut blanks accurately enough with a sawing operation, you have to > correct the angle > after you have lapped them flat … oh, yes, you have to take the parts that > come off of the > saw over to a lapping machine and get the sides parallel, generally to a > fraction of a light > band. > >> And then mount in a holder automatically. > Before you put it in a holder, you need to contour the blank. There might be > another angle > correct stage in there. Once you go through contour, you get to polish and > then to chemical > etch (to remove the debris). After that you baseplate the parts. Without > that, you have no > way to get an electrode on the “bottom” ( think TO-5 / TO-8 / HC-40) of the > blank. > > After baseplate the blank goes into the mount. If it’s a 4 point mount, > that’s a manual > process. Next up is epoxy and baking to cure the epoxy. After that finish > plate and seal. > > For an OCXO part, you do as many of those steps (past baseplate) without > breaking vacuum > as you possibly can. You also do a bit of cleaning and bake before the final > seal. > >> All the individual steps are sort of "mass production" but I think today, >> there's significant (manual) setup time for the machine between steps (kind >> of like making tiny screws on a Swiss Screw Machine - some time for setup, >> then feed in bar stock and tiny screws or spacers come out of the machine) >> >> https://www.youtube.com/watch?v=mhwUHgWzzKs >> >> >> >> >>> It would still be a lot of work, and very expensive, but like >>> biochemist trying out hundred of thousand compounds from their >>> "libraries", robots really lower the cost. >> Lot of work, I think, underestimates the magnitude of the task. It would be >> interesting to compare the processes used for creating high performance >> crystals (e.g. for a USO, where they start 1000 blanks to get a dozen or so >> oscillators) and those used for mass production of crystals for things like >> kitchen timers and microcontrollers. > The real contrast is to watch crystals. You photo fabricate multiple crystals > from > one blank. You also may not do much of a seal on them. Indeed there are > crystals that are not destined for a watch that get processed that way as > well. > > Fun !!!!! > > Bob > >> I have heard that for USOs, there's a couple people who have the "knack" >> for installing the crystal in the holder in a way that minimizes the >> stresses, etc. That is *really hard* to automate. >> >> This is, of course, where SiLabs has a thing - they make hundreds (if not >> thousands) of MEMs oscillators at once with lithography, so the piece parts >> are very inexpensive - but they're performance limited by the material. >> >> >>> The real question must therefore be, if anybody reasonably expects >>> there to be any superior "new" cuts to find in the first place ? >>> >>> What properties would you program a quartz-crystal-prototyping robot to >>> search for ? >>> >>> Which parameter(s) of current crystal-cuts are "their weak point" ? >>> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
