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Roughing ("grit" 80)…
predictably, some areas have begun to abradersi before other, as you can see from the following sequence:
But as the roughing proceeds not abraded zones are always reduced more. I think that in a few dried I should be able to scrape the entire surface, after which even a few sessions with the grain 80 to standardize the surface and then I can go to the grain 220.
Not until I have cleaned all to well though ....
Hello and see you soon…
Well, after the surface was abraded uniformly throughout, I practiced more and another couple of sessions with the grain 80 to regularize the form.
After that, I cleaned everything thoroughly, mirror, tool, machine etc., and I moved on to do some session with the grain 220, so start to smooth out the bumps produced from grain 80 and be able to perform the test again with the spherometer to assess the curvature of the upper surface.
From the following video it is quite intuitive as the undulations early, It has completely disappeared, leaving room for a much smoother surface and with uniform curvature:
I see that the machine works well,
and the operator knows just as well adjusted.
Mirco're starting to make me want to revisit
my thoughts aside.hello Giulio, thank you…
Well, I am very glad that this stimulus tread the beginning of your new project and I think if you have time, desire and energy you should definitely undertake it…
But now that you've thrown the, you must tell me what it is…You've obviously intrigued….
Ah!…. It was just the old idea of the rotating plane, at most drive version “Fixed post”. But I would have problems of time and virtually non-resolvable space. So I love your work and still continue to think.
Then Giulio, I hope that somehow you manage to solve these troubles and you can build yourself a rotating top…
Once done, however,, remember that this will be the means, not the end…so then you will need to also think about the optics project that you will need to scrape up…
Grinding end:
At this point, It is seen that the surface is much smoother than the top, I increased the scale rotary speed, bringing about 30 giri / min, more suitable for the "sping grinding" method I am using.
In the following video, It shows an excerpt of a work session with grain 220, 30 g / min of the rotating floor, ooze of about 46mm and 25mm around the eccentric race:I will continue with this technique to the grits 400, 600 e 800, always varying slightly, occasionally, the machine settings.
Updates soon arrive at the end of the sequence of abrasives ...
See you soon ... hello to all .... Noooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo, It broke the balnk!!!
I was virtually reached the end of the sequence of abrasives, and I was ready to start polishing, already bought pitch and everything you need.
To polish I needed a new tool plaster on which then glue the squares of pitch. As I also did the other time, I realized the cylindrical cardboard container, spread a sheet of aluminum foil over the mirror and then poured gypsum mixture by dentists and water inside the mold.
The plaster that has given me this time the dentist, But, it is seen that it was of a type slightly different from the one I used to create the tool for roughing, and when he started the chemical reaction between gypsum and water, its temperature began to rise and rise, much that was hot to the touch. Probably you will come to 70-80 °C. The result of this sudden and localized increase in temperature did split in 2 the bank ... I did not expect just, and when I heard the sharp sound,” TIC”, It froze the blood ...
GAME OVER…
It will be for the next ...
Mamma mia has class!!
As far as I know, I think it is difficult if not experimentally, to know a priori the temperature of the reaction that solidifies the gypsum, also because this varies a little as well based on the quantity of water drawn up.
It reads the data sheets of the extra hard plaster which on average have a beginning made after 15′ by casting, and the end outlet 30′; But after 20′ certain technical sheets recommend removing the menufatto from the mold, and let him finish drying on a metal plane that dissipate the heat generated strong right from the moment that the artifact is removed from the mold to be in contact with the air.These extra-hard plaster, saw their strong overheating do not require further drying in the oven, as required chalk that I used was type A (that is firm but not super hard).
(The gypsum from the dentist in their catalogs are only 3 types: type B (qualcunio calls plaster beta) that is coarse-grained and tender; type A (some call it Alpha) which it is fine-grained and hard, and there is the extra-hard Pioi).
Maybe it would help you to have the data sheet of the used plaster.
What a nasty surprise!!!
I followed with great interest your job because I too had thought of working a lightened glass but thanks to the ribs proves still very hard.
I'm so sorry and I understand well what will be your state of mind.
But I am almost certain that we passed the discomfort riproverai!
Hail
GiuseppeI'm really sorry…But do not beat you've thrown away all the hours of work
Just riproverai you'll treasure this experience
A greetingMirco, I'm very sorry , but this does not detract from the validity of all the work done so far indeed, for many others it was a game over, but for you I am convinced that it will be an additional source of study and experience gained, and I do not be surprised if soon we will have your own publication on deformation breaking glass for thermal nature efforts !
Hi guys, thank you all…
But unfortunately I do not think that soon I will start a new project, because to get to the point of now I'd really put many months and almost all my free time that I had ...
Furthermore, The main reason that pushed me in this new creation was to be able to get a mirror having superior performance to what I have already finished:which is, It is now used, but as in all things they do on the first try, you're never quite sure you did very well.
Fortunately, Friday night, I managed to make an exit in step Brocon with friends, and I got to test the mirror just aluminized eeee……..It proved to be a good mirror (not great, but good), then at the end, pulling a little 'conclusions, I do not think I will invest in short loooong of my time just to make a mirror similar to what I already own.
At best, I think I might consider the opportunity to build one much larger (sempre lightweight) once I have fully exploited, or I will be more demanding in the optical quality than this, but spend the time I know ...
So for now all ..................... stationary or not ......... ..magari a more piccolino ...... ..ah ha ha… See you soon…Hello to all…
Mirco now I try to shoot a bullshit (…”lost lost”):
If the fracture of the broken mirror was NOT too open for this local tension that leaves no edges closer, I ask: Do you think it might be possible to wipe the mirror upside down on old-fashioned oven, with a “riga” of low melting glass powder aligned to cover the back of the fracture, to see if, with the persistence of a temperature not too thrust (in the sense suitable to melt the powder but the glass mass not more often) fusing the powder is unable to seep inside the slit and to weld it also summarily only to the rest.
Eventually you run the risk of recovering the mirror (because if the furnace everything went just well enough, with the subsequent abrasion may certainly find the spherical surface and then the parabolic satisfactory).
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