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Hello everyone
I am going to start writing my thesis and I decided to design a telescope from top to bottom so I'll open several discussions in different sections.
The first course covers the Blank: I build a plaster mold so as to create a blank of about 30mm / 35mm in thickness and 400mm in diameter (f5) with hexagonal cavity in the back to make it as light as possible; also I try to create the mold in such a way that the glass has already reached the desired curvature of the sphere.
someone has already done something and he succeeded to give me advice / information / opinions?Hello Marco, What are you majoring in ?
Regarding the glass melting is a Mirco experimentation with borosilicate, https://www.grattavetro.it/forums/topic/primario-420mm-foca/ he is sure to give you all the necessary information, but I think it's a job that goes a little’ beyond “normal” autocostruzione.in mechanical engineering, that is, I still miss a year, but I think the designs require all the time; I thought of asking for help to mechatronics teacher for the frame, that of geometric modeling for the whole of the CAD, to materials science and finally to that of turbulence as the turbulence in the tube concerns precisely. And of course the help of all of you
Hello Marco, a welcome from my…
mechanical engineering, good, where ?
Then the construction of a glass blank for fusing is not simple, and I'll tell you why I did a lot’ evidence, go all more or less OK, once for one reason after another…Anyway, this allowed me to experience and understand that, obviously, as in all things, serve the right equipment and machinery, otherwise the result will not get there…
Having said that I am very curious to read and understand how you intend to implement your project, that if you want, I can somehow, try to give you some tips for what little experience I gained.in the meantime if you want qua laws:
although I have not given everything I've experienced, there's a little something… A Udine. However, I read your article and you say that you did a complex job! My first problem was to create the back in order to have the supports to the support but after seeing your'm coming to a resolution. As for the merger rather I did not understand, You have created the mold and subsequently the molten glass inside or the two pieces were carved and then “bonded”?
Then, I state that I did not understand what you mean by: “create the reverse side in order to have the supports to the support”, but vabbhè…
As for fusing, I first realized the plaster mold, and then I loaded with glass grit, with which the temperature has merged.
But here I should open a whole chapter on the difficulties that I encountered, from the non-perfect fusion of the flakes due to the temperature not adequately high, to the temperature holding time that is a whole say, the air bubbles that are trapped in the molten, to the mold resistance, to cracks that are generated in cooling etc.…
Precisely because of these and other problems, that still would not be able to avoid with certainty, I was at the end directed towards the softening process rather than in that of pure fusion.Here are a few pictures of the first race I had done (a lot of hours of work, for a negative result. But the game is so and we must accept…
):P.S: but I live in the province of Vicenza, and I also I graduated in mechanical engineering, But in Padua…
I mean, being the rear part of the blank constituted by a me was a difficult moment series of cavities understand how best to position the “feet” for supporting the primary support (I do not know if I have explained). As for fusing I intend shortly to take a stroll in the Murano glassworks. Although they treat the glass to make artistic works I think will help me
Ah, ok, I understand what you mean…
eh, There may be many ways to do this, as you see in the picture above, the plaster mold has a whole series of rectilinear cavity inside which will form the ribs, which then converge in “knots”, where there are those cylinders purposes and long chalk. In this way I got a blank with a similar back to this:
into those cylindrical holes I would then went to innestarmi with some kind of pin outgoing from the primary cell.Or as I did here:
in which I predicted in the back, a whole series of perforated disks, in which the hole had pasted into threaded plastic inserts, on which I then went to anchor with screws that I predicted the triangles of the primary cellbut I assume there are thousands of ways yet, you can really indulge your imagination…
in well, there is no doubt, to speak with someone who handles and fuses glass all day can only be of great help.
Although they are not the astronomical mirrors their industry experience will definitely be able to provide valuable information… it is the first time
however I mirco I initially thought I was doing the hexagonal cavities as I have seen in many of the very light glazing. I would say at this point (as I advised me tiberini) by starting from the design of the support with Guiplop and try to find a way to bring together the vertices of the figures that form the cavity at the points where it should find the pivot of the support.And, this can be a proper way to do, in fact both the gypsum cylinders in the mold, both perforated disks in the second example that I have given you, are all positioned exactly in 18 Suggested support points by Gui plop. Then I draw the ribs starting from these fixed points.
Nobody, however, prohibits to do differently and use a diagram hexagons, square, triangles, then will you have to figure out where to best position the support points…
In short, the viable ways are many, It is up to you to choose the one you deem right and even easier to do (which it is not a thing to be underestimated)… You could make the positive with a 3D printer, then the negative plaster and then fill it with glass powder…
To be honest it was what I wanted to do from the beginning, especially for the creation of “cupola” which would have given to the mold and consequently to the curvature of disk I needed, but I will give up because the 3D printing just costs a lot of the dome.
Anyway I was starting to take their first accounts: it seems appropriate that a 406mm f5 have to dig an arrow of about 10mm? because in that case the thickness of the glass without the part with the “cavity” I would 15mm
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