Chriske

10 hours ago, Gasman said:

Nice one Chris. Will you be releasing the plans ? Would be interested to see them having made my own mirrors many moons ago and relied on a razor blade on a stick for the focault test ?. Also would give me more ammo to get myself a 3d printer.

Regards

Steve

If someone wants to copy this Foucault-tester I'll post the STL files here on the forum.
I could also post the source files. So if someone wants to make some changes feel free to do so.

11 hours ago, kbrown said:

Following with great interest. Focault/Ronchi tester has be on my to do list too but having never used one or the other I don't have the knowledge or experience to design one. 

Is it essentially just a platform that moves along the optical axis and carries a light source and a camera plus another platform that moves across the axis and carries the knife blade or the Ronchi grating in front of the camera? What about height? Does that need to be adjustable too? 

It is adjustable in height, it needs to be.
This tester is also equipped with a green laser. Purpose of that laser is to adjust the tester in a matter of seconds.
The very first time the tester is adjusted toward a mirror the old fashion way. It always takes some time for that to do so. Especially for novice ATM it is very difficult to adjust the white lightsource and reflect it onto the knife.
Once the mirror and tester's white light are 'in line', the (adjustable)laser is lit and pointed toward the exact centre of the mirror. The reflection of the laser-beam is visible on a very small screen very near that white light-source.
Now, the next time you need to adjust the Foucault-tester toward a mirror you only need to lit the laser, point that laser beam toward the very centre of your mirror and then adjust the mirror stand so the reflection point to that little screen  located at you're tester and you're done. When the initial setup is performed correct, the reflection of the white light falls exactly on the knife, every time again.
there's only one 'but', I'll explain some more when the new tester is assembled.
Because it's a printed version it is very light, so I added a 2kg steel weight at the bottom of the tester.

Needles to say, when someone do setup a Foucault tester toward his mirror only once, there's no need to use that laser at all.
It's only when the tester needs to be removed from that location and setup again the following day or so, then the laser comes in very handy.
Also in my case when different mirrors needs to be tested (during course) that laser is also a very handy tool. It saves me LOTS of time.
 

My first 3D printed Foucault tester did work very well.
Only thing was that all axis were running in PLA'bearings'. It's motion was rather 'heavy'. For measuring a parabola you need a very smooth motion.
So busy designing V2. This time I will use linear bearings to support all these axis.
The tester in the picture is V1
Busy printing V2 now. I'll post some more pictures later on.

At second 55 the man in the movies says : there's nothing stopping you and I from updating Chinese printers.....
That's were I stopped viewing any further. Maybe quitting was not a good Idea, I know but...
The original question in this tread was : Just casually wondering what 3D printers anyone has / would recommend...
She's not asking how to perform modifs on printers. That is the last thing novice users want to hear about...
 

1 hour ago, pete_l said:

Without wishing to start a war   here's an interesting video:

No worries Pete...

In the past we made(copied) about 25+ different printers.
In the end my pal Marc ended up copying Prusa's because at the time it was the best you could buy or build (I designed my own)
I do visit a large forum, all(and only)about 3D printing. Not all, but most of them, buying cheap rubbish will eventually end up repairing/modifying their printers.
Lots of these cheap printers are not capable of producing perfect perimeters at all. And If I may say so that is the most important item on my wishlist... good/perfect perimeters.

My advice : do not by a cheap printer..!
I myself have 3 printers of own design producing perfect perimeters. My friend has copied a few Prusa i3 Mk3. Well these Prusa's almost do copy my perimeter quality.
I'm not saying Prusa is the only good printer, not at all, but it is a very reliable printer.

If you still go to school(and of course you do...) you can download a Autodesk Inventor version for free. You have to give a name of a school and your done.
Best 3D design software ever(together with SolidWorks).

Software : Autodesk Inventor (I do have a license from my last employer)..Lucky me...!

Printer is of own design.
Together with a few friends we've built about 20+ different models over he last 5 years. All these models/drawings were downloaded from the internet. Non of them were 100% to our satisfactory. So in the end I decided to build my own printer. I call it Ulti-Printer.
Busy building a few(5) Ulti-Printers-Mark3 300x300x500 this very moment. A few friends copied it and are very pleased with it.
Mark 2 was provided with fast interchangeable hotends.
Mark 3 I added interchangeable filament, meaning I can easily switch between 1.75mm and 2.85mm filament in a matter of seconds.
 

Hi,

During open door at our local observatory last weekend there was much interest in my set of focusers. Because of its focusing-smoothness my Helical focusers with ball bearings(far left) got lots of attention.


The only drawback is that this focuser requires a aluminium eyepiece-barrel. Not to many people have aluminium tube that size in their workshop, let alone a lathe to handle that size of tubes.
To solve that problem I redesigned this focuser and replaced that alu-barrel and a printed barrel will be used now.

The perimeter of a printed cylinder does not allow very smooth focusing. As a matter if fact it actually does, but not to my standards. Making a focuser it should have a very smooth action just the same as any expensive commercial focuser.
To deal with these tiny irregularities from the barrel's outer perimeter I need to remove  a very small fraction of that perimeter. It's only 'cleaning up' that has to be done, so just a fraction of a millimetre will be removed. Only drawback is : there's  still a lathe involved, there's no way around that.
Second : to prevent deforming of that barrel(in time) I drew the barrel's wall rather thick. 5mm will do the job nicely.
And I also changed the angle of the ball bearings inside the focuser, V1 has a 6° angle. In this new design, V3 I changed to 4°.

I need to find me a supplier who can sell me 2.85+mm filament, so I can go beyond 2.5mm nozzles Gina...

This scope is printed a few years ago.
All is done on a Prusa i2 - 200x200mm bed.
So all parts fit on that bed and all these parts were bolted together.

Meanwhile these printers are cannibalized to make me better and larger printers.
The printers I use today are of own design, I call them Ulti-printer. This very moment, together with a few friends and pupils, we're  building 5 of these Ulti-printers V3. (Build surface 300x300mm).

Gauge '1'..?

On 31/07/2018 at 10:44, Davey-T said:

Good find, I had to drill 2 x 6mm holes in 10 concrete posts to bolt on brackets for my wifes railway, took for ever using an assortment of masonry, diamond and steel drills 

Dave

Steam powered...???

I might be interested if there's a printed dome included... 

On 30/04/2018 at 23:46, Gina said:

...maybe I should sell some

Knurling the focusing axis will do the job nicely.

2 hours ago, tekkydave said:

 

Clean surface & let it cool - pops right off for me

 

Yep, for me the same.
Just clean the glass and wait to cool completely. You want another print to start as soon as possible, just buy 1 extra sheet of glass.

Nicely done, ver nifty...!

The knobs are really nice...!
If I'm not mistaken these are not knurled. I think it is a milling job, correct..?

I know Gina, nowadays we use them in our telescopes, isn't it funny...?
Point is they really work perfect as dual speed knobs. You only have to add 2 knobs, and that's one reason we have printers for ...

I always use these, rather cheape.

http://www.orenelliottproducts.com/planetary-reduction-drives
Need some tuning, well performed it'll give you the same smooth action as any 300£ focuser.

Nicely done...!

I always use dual speed knobs too to allow smooth action, saves me tonnes of money.

12 hours ago, tekkydave said:

 

I did add a grounding point to the metal part of the bed for safety.

 

 

 

 

 

Did it to, good work..!