Forum Replies Created
-
Posts
-
Uh, wow Joseph lavorone…
bravo, beautiful creation…
is in fact only in the last video with pitch and cerium oxide and tool full diameter is seen that the motor eccentric fatigue lot…It would no doubt a scooter with a few watts more…for very good rest… See you soon…ciao
Ciao Uraniborg,
to love anything is possible if you have the right tools and knowledge, But I see mooooooolto really hard to build a bell for aluminizing homemade, that it works.
The first problem is being able to reach the vacuum pressure necessary, each pump has its pressure limit (empty) He manages to reach. If I remember correctly for this type of application you must get at least on the millibar (10-5 torr). So every minimum infiltration of air between the seals, welds, in fittings etc., not to mention the outgassing of materials, They would never allow to achieve those values.
Other real headache to solve is the construction of the steel case. Going high vacuum, The case is to be considered in all respects a pressure tank (Depression here) in which there is almost an atmosphere that tends to crush inwards. That's if the tank is not designed properly, apart from being able to break, could also only slightly deformed, that adversely affects the seals (then air infiltration). It must therefore be very rigid and well-studied.
When building components for the high vacuum is very important the quality of the welds, you should make you do by specialized firms, They do well to pay.
Finally, you know you'll build or otherwise handle an electrical apparatus, which must reach voltages of the order of 50-70000 Volt to be able to adequately vaporize the aluminum filament. With all the security issues etc. which you will of course keep account.
in conclusion, I see it as a very challenging project, only very expensive, and there would be penalties only if you plan to use it often or for work. The commercial cost, all things considered modest, does not justify the un'alluminatura, in my opinion, an investment of time and resources into a project like this.
Not that this is meant to stop, is just to expose the ones I think are the problems to be solved in order to succeed, Then if you still want to partake in the project, I will be happy to read the posts of your progress and maybe exchange ideas and opinions on the difficulties you'll encounter. hello Giulio,
Yes sure, lost lost, I could do a test, although I have serious doubts are able to do…But it can not hurt… 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…
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 ...
hello Henry, really very happy to hear from you ...
I hope so, that you are able to better organize your work commitments, even if I know, it doesn't have to be easy, especially if they also affect family life ...
Anyway, you know we are always with open arms waiting for you, and we can't wait to read all your posts on the progress you will make in "glass scratching"…
See you soon… 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 .... 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… 
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….
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: 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…
Thanks Massimo…
I am really very happy that you like the project…
But how do you know, I'm doing this is now the easy part…we will see later when the time of generating the ball first and then as a parable I will manage… Roughing ("grit" 80):
He eventually began roughing, I'm doing with the grain 80.
At the moment, since there are ripples on the surface of the glass to be processed, I set a relatively low number of the number of revolutions of the rotary plate of the machine, or around 12 giri / min.
Note that this is not a classic work Fixed pure post, but I admit a small right-left shift, the order of 2-3 cm, tool to avoid excessive repetition of abrasion in some typical areas of the right fixed post.
The swiveling out of the tool with respect to the blank below hovers around 15% the tool diameter, then roughly 47mm, and periodically, is the extension of the left-right tool racing, both the amount of the ooze do vary slightly, so as to avoid as much as possible the formation of zonal errors.Support:
The entire mirror machining the mean accomplish with the blank already mounted on its cell, even because, as for the back is made, It would not be very easy to be fixed on the work surface, not being able to bind with the usual 3 wedges lengo.
In fact, as I have thought from the beginning, inside the holes (8mm) drilled in the center of each glass diskette present in the blank back, I'm going to paste of threaded plastic inserts M6, so as to be able to fix directly the various of the blank cell holder triangles same. This allows me to keep it firmly in position above the mirror cell, preventing the vertical movements, that side (good thing if I have to work it in the car) which will then allow me to not have to predict, nor the mirror support strap, generally necessary with the inclination of the telescope vary, any of the side latches to keep it centered with the axis otic.The cell is a classic cell 18 support points, whose positions have been calculated already before realizing the blank, with the special software GuiPlop, and the triangles of supports have been realized in PLA by means of a 3D printer.
The cell I finally screwed on the back of the blank with the M6 screws, and I is interposed between the supporting triangles and the glass of a thickness of 1.5mm rubber diskettes. Despite this rubber is rigid enough, It will always be the most compliant element in the chain and will he eventually to deform, to the glass leaving the freedom to expand or contract the little that serves as the temperature varies.The support elements were finally mounted on an aluminum plate of thickness 10mm, which will in turn be bound on the rotating surface of the machine. Whenever I want to wash, to clean, make test, on the mirror, I'll just disengage the latches that hold in position the aluminum plate on the rotating floor, and I can xport in blocking all the assembly blank cell +.
And here all positioned on the rotating surface of the machine, during the phase of centering:Well, It has finally arrived to get started with the grinding grain 80…
soon and hello to all… Tool:
In order to work the blank, already precurved, I could use a glass disc plane, as it is usual to do when we start with the machining of two plane-parallel discs, but I had to build a tool, convex, having the same curvature as the blank.
For the type of processing that I intend to bring forward, or roughing and polishing machine, It is necessary revving, having a diameter equal to 75% the diameter of the mirror, or about 310mm.
To realize I mixed water and gypsum by dentists (kindly offered me the head of the laboratory of my trusted dentist) in proportions 35/100 (or 25% of water and 75% gypsum) I then poured into a circular shape cardboard, I had previously realized and supported above the concave surface of the blank, until obtaining a thickness of about 3cm.
Once the plaster has hardened and dried out for good, I lined the posterior and the lateral surface, with a pair of polyurethane paint from boats, to make the waterproof tool and protect it from dirt.
With regard to the part that will rub against the mirror with the interposition of the abrasive, There are several schools of thought or methods that you can follow, there are those who drowns directly into the plaster casting a whole series of stoneware tiles or hexagonal steel nuts:or as I decided to do myself, pasting of glass squares with the epoxy bicomponent glue.
As mentioned, in primis, I cut a series of squares of about 1,5 cm side by a sheet of glass from 6 mm thick, and then I placed them on top of a sticky paper (in my case scotch) in such a way that they can lift and arrange all together over the glue once spread on the tool.At this point I mixed with about 60g of epoxy sealing film, and I coated with a metal rod (P.S: the glue is very viscous and it is hard to pull) on the curved surface of the tool, taking care not to exceed the 5 min of time that you have available before the beginning of the crystallization process of the glue, I applied and above all glass squares, pressing them well to get a good bonding.
On the back of the tool, I finally drilled a hole, into which I glued a plastic insert, printed with the 3D printer, in whose interior will engage the spherical head of the machine oscillating arm.
To be continued…
