- This topic has 21 replies, 4 voices, and was last updated 6 years, 8 months ago by
.
-
Posts
-
Is there a specific reason why all machines are made in much the same way? O rotate a lower tool diameter above the mirror or stepping forward displacements back. For other operations, as the machines are deliberately inaccurate, always repeat the same operations and according to me in the long run the defects of this repetitiveness come out.
Why not take a car that reflects the movements that are done manually as the chordal, the 1/3, W, etc. with a variable randomization preprogrammed? That, I do not understand why there are limits to sti two movements on the cross when you could do anything you want, even at the amateur level.The professional machines today (..I'm talking about the ones you see also work in movies youtube execution of degrees telescopes) They are the numerical control type, but the basic principle is not very different from that of the veteran.
The scope of work of such a machine is always to ensure the realization of a reflective surface generated by a perfect shape of revolution (therefore serves a rotating plate) with absolutely random tool movements, to exploit the well-known principle of automatic elimination of peak and valley defects, and in the process of performing the parabolizzazione “countersink” of the spheroid generated from them, in the form of parable.
Certainly one of today's software programming could ensure a random level of the mechanical arm movement (also already in manual labor similarity) probably better than just mechanical random derived from the combination of various eccentrics; at the bottom of what is the real problem of realization of an optimal machine, accompanied by the costs and knowledge and experiments manufacturer.
It goes without saying that the simplest things are usually less expensive and more feasible for many, while innovation requires experimentation not so easy to achieve a positive end result.
Well anyway I think in the future as I could evaluate it as in software, electronics and mechanics would not have major problems to do some experiments
Maybe combining it all with your knowledge might come out something interesting no?
Now I will concentrate on my blank and its manual processing and preparatory, but it is something we'll talk…
I'm perfectly agree.
In fact I argue that always sharing the problems is how to work in a group; and by working together the various experiences are collateral source, and allow considerable advantages which are always reciprocal. In other words: All of us always learn something.Ciao
I take this topic because I have well equipped workshop and resale of mechanical transmission components,Electronic software level but know very little building everyday machines on customer request….I have no problem to build an automatic grattavetri
perhaps with the help regarding your electronics and design.hello Fabrizio.
The union and sharing are the force.
Here among us there are people like Mirco Bartolomei “Bart”; Franco “Frenkq_it”; Enzo “Enzo55”; Giuseppe Mura “GiM”, who already have some proven experience, also described in this forum. But even the idea of Stefano StefanoSky is good.
Indeed, exploiting the issue of random coefficients within a certain range of limited values as you want; putting ourselves in the midst of perhaps the usual Arduino, It could lead to some work to correct parameter to simulate the manual action. But I think we also need to study well what part mechanical, and how those changes are implemented. And maybe they will complicate things a little.
I did a few things with Arduino, in its infancy; for which very little valgus. But we are many and each one has the right to expression. So the way in the company is easier, although somewhat uphill.I saw on youtube that many use this type of very simple machine to be built,this clearly if I only knew for roughing. But do you think is effective?
That the two movies that you posted is the most simple machine.
But with that Gordon Waite it makes us all (roughing, polishing and parabolizzazione).
It has only one engine, which drags in rotation the tool induced differential, which must have a diameter in a precise relationship with the mirror in processing; and that is decentralized with the policy to do more work at the center, or in the suburbs, or in the neutral position, to create a good ball.
The machine is called FIXED POST, that is, “fixed pole”, due to its operating principle that I have had occasion to describe structural details, in another post that you can read by clicking on the following link, with other equally interesting projects:
https://www.grattavetro.it/forums/topic/costruiamo-forse-il-piano-rotante/#post-8436In other various films of Gordon Waite you find its always detailed description of all the stages of its processing, including parabolizzazione that makes hand on the same turntable.
The effectiveness of simple machine is given by the many design technical devices, of which speaks in his films.
As in the two movies you posted says (from the first movie that you've posted) the centering method with repetitive precision of the mirror on the turntable; or always different position of the start of polishing steps (the second video you posted) after it has removed the tool for the usual recovery operation of the pitch of the grooves, etc. His movies are a mine of information, and most of the tutorials.A few years ago still it worked the instructive little program POLSIM.EXE, downloadable today from here:
http://martin-cibulski.de/atm/polishing_simulator/But my antivirus will not let me download only a precaution because “old and used by few”…(me too, without problems on older PCs), then only for this fact, would be “average potentially dangerous” (codice WS.reputation.1), and I cancel downloading Norton (but I hope I put it in quarantine for liberarmelo sooner or later).
The small program visually simulating the progress of the processing, (as seen in the following Youtube movie), showing in plan and profile of the material removal zone which stemmed by the insertion of the mirror diameter values and tool; speed, decentring (…that zeroed simulated the fixed post).
Good morning,
then my idea era to make an electro machine.
Build a guided sliding table (on bushings,skates,castors or what one has or finds)
where the thrust of the arms would be replaced by a pneumatic actuator controlled by a solenoid valve,then builds a fifth wheel to rotate the work plane (even with an old buffer) and every few passed back and forth you turn ¼ or 1/6 or 1/8 This plan based on what you need. The rotation will always be done with a pneumatic actuator ,with the forward thrust spins the turntable and the return rearms ready for the next shift.
With a simple plc you can enter the working data,for example, every 10 past the table makes a shift
This replaces the operator's work verbatim. Sorry if I was unclear, but I think it makes the idea of the thing.Surely it is a viable, and it would be a machine closely imitates human labor.
But I see it hard because I fear that its operation would be rather jerky. Also keep in mind that doing a certain number of forward runs back and then rotated by a certain angle, is a complication, however, that the concept pardossalmente Charice to the movements of the neophyte.As in manual labor, rotating step by step and slowly but continuously around the table, while continuously do the forward back with glass which holds, continuously rotating slowly in the opposite direction, It is an equally valid system, it's more “smooth”.
I think that since the turntable is the common part of all the machines, perhaps it would agree from what, already doing in order to experience other improved functions.
In this regard, today the electronics of an inverter with single-phase and three-phase output entry, It could break free from initial mechanical complications which then may affect the future work, because a mono-tri phase inverter + moto-reducer worm phase 220 this was 400 watt,with output 30 rpm, can be rotated with from zero speed 60 revolutions per minute with perhaps a total expenditure motor-inverter around 200 euro.
Of a pneumatic drive I would be afraid of shock and mechanical vibration of a reciprocating motion, that when there are deleterious to glass, having to be treated glass as smoothly as possible, having regard to the working tolerances of 68 millionths of a millimeter.
But these are just my ideas, and I do not intend to influence your thinking, but only to do “devil's advocate” highlighting the problems already encountered along that road with manual work.
I always find it interesting detailed descriptions of Gordon Waite, that being intended for a very simple machine, They are basically valid for all machines that use a rotating floor more or less sophisticated. So put these descriptions “the flea in the ear” what are the difficulties to be overcome in automating more or less manual work.
In the first video you posted (that of the roughing of 20″ F3,3), says some things instructive, works , to people like me who like numbers, suggest some technical account.
The first movie of Gordon Waite, It is fairly recent. In it he explains a few things:
First says that the blank showing the mirror in processing, he has already arrived with the face of the curve “hot forged” (with the procedure that I have found and seen in the last images of this very short movie of what he appoints as a supplier):
The baked blank with the curvature imprinted by the mold punch is apparently that of one of many of today's commercial catadioptric telescopes (see also the image of the first blank on the left to this lik):
https://www.unitedlens.com/industries-astronomical/Let's see’ of numbers:
Diameter of raw glass disc 20 "= 508mm; focal length (500*3,3)=1650mm, radius of the origin ball (2 *]1650)=3300mm = a circa 130”.The reflective surface will have a diameter of about 500mm, however, because there are deducted the approximately 6mm always indispensable to the realization of the chamfer 3mm, which it is the first thing to do, against the danger of chipping of the reflective edge. What he does using a diamond-hard fresetta, while the flat turn 3 or 4 rpm, that is, the minimum speed of the machine (when in other movies he also specified the maximum expected in its operations which is about 60 rpm).
Gordon says that the blank concave surface formed at the press, It is convenient to the trenching savings, and measures the beam with the spherometer, writing wont glass 117 inch (while the final should be 130), but he writes other values in the surrounding area,. This means that the surface produced by the press is more profound, and it is not homogeneous, and it will be scraped with a tool that makes it uniform even bringing it to the radius 3300 wanted, using an abrasive that he chooses very "rough" with a grain 24 (Average grain diameter 0,72mm alias 724 microns).
The arrow of curvature of the excavation will have a depth in the center of the mirror
3300- root (3300^2 / radius ^ 2 mirror)=
3300-root (10890000/62500) = 9,48mm, so very deep.While the depth of the blank arrow, corresponding to the radius 117 ", It is 10,53mm, then (10,53-9,48) = 1,05mm already deeper than they should.
So Gordon prepares the tool (usually of diameter for the machine fixed post equal to 75% mirror, then he uses a diameter 16 "). Draw a circle with a diameter of the tool and puts a sticker polyethylene sheet on the mirror with the adhesive facing upwards, and it supports us with a set of dice comparable to the M12,. Closes a ribbon around the rim 16 "and puts it around the dice, and placing it on the adhesive sheet there is pasted against, and acts as the dentist's chalk container with which the tool will leak plaster "vel-mix-die-stone-gypsum." of KERR (vel-mix-die-stone-gypsum) in Italy:
https://www.kerrdental.com/it-ch/kerr-laboratory/gypsumMine, bought in Asti, is of the same color but different brand and chose precisely not the hardest because it was cheaper, without knowing that it was even better.
The texture of plaster for casting said to make eye, so that it is equal to a cream a little thick, with the aim of facilitating the entry of the gypsum into the hole of the metal nuts; poured slowly to prevent the nuts from moving. Following will retouches filling with teaspoons liquid plaster, the dice remained partially in the hole without chalk.
He says the truth when he says that the plaster is very hot (even beyond the 100 °) during hardening (that lasts 45′), and I comment that it may be critical for the species of little thickness glazing. So it is good thing, buy a plaster dental choosing not type very hard (heating seems to depend on the hardness of the quality of purchased chalk), I should then do as I did, casting a thermometer to check the hand in which temperature rises during hardening, because among the thousand data accompanying those chalks, I never have seen indicates the solidification temperature (that in fact the dentist is inidifferente, while the amateur may be required to preheat.
So Gordon prepares the machine, saying that for each diameter to be machined has a mechanical centering circle that allows to put it perfectly concentric mirror in the same position of any previous disassembling. And once the mirror is inserted into the inner space of the circle, He has no other fixture, and the small movement that the mirror can freely do inside centering ring, It helps avoid astigmatism (and I add, imitating the approximation of manual labor).
The work begins with decentring zero tool, ie only tangent to the edge mirror, because at the beginning of species work with abrasive grits so big, no danger of chipping to the edge, and therefore charging a single weight by 4kg and turn 30 rpm; then increase to 8kg and gradually 40 and then 60 revolutions per minute which is also the maximum speed provided by the machine Ola.
Interesting information on the machines for parabolic mirrors already translated into Italian.
On the site click “Machines”….then choose “Main types of machines”, and see the different animations.Warning that automatic translators overturn the meaning of certain phrases.
For example: when that site is translated “This system does not work on mirrors”, TRANSLATOR erroneously translates the phrase “This system does not work above mirror”, THAT CORRECTLY TRANSLATED AND ': “this system can not work with mirror above and below the tool”, (and the thing is also trivially obvious).Ciao
From modest experience that I was able to acquire in the design and construction of machines for processing of mirrors as well as in their use I can only confirm what has already been said in the past, namely that it is useful machines in the roughing stage, where greatly relieve the work and shorten the processing time. At this stage, I have used various configurations but the best it seemed that with the mirror above the tool of equal diameter below with past similar to the "chordal", which is carried out in manual. You dig very quickly, but with a poor ball. Reached a fair degree of depth usually alternating aggiustavo the ball past 1/3 CoC mirror under tool above and vice versa using the biggest abrasive and checking the result with the spherometer. So always with the past 1/3 I arrived fairly quickly (1 hour or so for grain with the mirror 200mm) until the grain 1000 or even to 1200 where they usually came scratches the problems that forced me many times to return to the larger grains. Then I have understood that with finer grains must absolutely avoid letting too dry the two surfaces. So I passed to polishing with pitch patina and aluminum oxide or cerium until reaching the ball. In this phase it has been very useful program POLSIM. In this regard I would suggest to Julius temporarily disable the antivirus program and download the possibly saving on memory stick. The parabolizzazione is the only stage where using the single rotation (very slow) of the plan are manually intervened.
As you can see the settings I used in my work are very different from those suggested by Gordon Waite. By this I mean that I think these change depending on what you have available. I have tried to create a machine that could at least roughly reproduce the handwork, with the possibility to vary the amplitude and the type of passed. Time ago, I was also reminded of the idea to change these parameters with stepper motors controlled Arduino just as suggested by one of you. Then I decided to let it go. With my type machines systematic errors are very limited by the backlash that inevitably are created with buildings like this DIY. So unless the machine is not allowed to work for hours and hours without any setup changes I see difficult they occur.
As I have already said some time ago when I described the construction of that car, I love DIY, I love challenges and I love to learn from my mistakes. It's taken me a few month or so of time but in the end I managed well and now I am happy to have it available. Having said that I want to tell you that the building is not trivial, and for those who begins processing a mirror would advise him to devote himself to that and forget the car. Indeed for those before construction even a miss Pharaonic projects and to start with a 200mm, or at most a 300mm Newton configuration.
Projects Cassegrain type or similar or machining diameters greater than 300mm are difficult and often those doing them without any prior experience leaves half the battle because of the difficulties that sooner or later you have.
My advice is: started with small projects and bring them to term if he stays there the desire you can always indulge in something bigger and challenging.
As for the machines are not indispensable, you can work quietly the hand mirrors, but if you really costruitene there one that is within your reach and then you learn to use it in the best way.
The user guide in these cases is not supplied and easier than you have to write it.
Julius the site you indicated is very attractive and in fact I read about it a lot when I decided to make my car as you noticed that it looks a lot like the Elgin Waineo represented them. The only substantial difference lies in the fact that the point at which it is hinged the rod that connects the swinging arm with the eccentric I have connected with the pin that moves the tool or the mirror depending on the circumstances, so as to limit stress of the motor. As you probably guessed by observing the last of the represented machines, placing a second motor with an eccentric at the point where it is hinged to the rocker arm could transform the machine into a Zeiss considered by many the best in this field at least at amateur level. In fact, if the two eccentrics and the rotary table are driven by three different engines is practically impossible that they remain perfectly synchronous providing that randomness which prevents the generation of periodic motions dreaded, but frankly so far I have not felt the need.
Hello everybody
- You must be logged in to reply to this topic.