printed Nipkow Jigsaw

A "new fashioned" televisor, using an Arduino to drive the motor and display.

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printed Nipkow Jigsaw

Postby Andrew Davie » Tue Jun 27, 2017 5:23 pm

I'm experimenting with 3D-printing a Nipkow disk. I've created a 'jig' which is 1/8 of a slice of a disc. It should snap together with similar pieces, using a kind of dovetail/jigsaw connection - hopefully snap-fit. I've also added a gazillion holes - these are a "single" spiral of 32 holes, but all holes on the 1/8 slice at the same time. The concept is that you print 8 of these, snap them together, and then cover the holes you don't want. They should all be in the correct places for a "complete" spiral with appropriate holes covered.

nipjig.jpg
nipjig.jpg (128.82 KiB) Viewed 4491 times


Anyway, thought it was worthwhile seeing how it goes, so it's printing now. I expect the snap-fit to be tricky because of the printing inaccuracies, but I can pare down the edges with a scraping blade and it might work. I'll try and update once the print is done - I'm doing two slices as you see here - but printed separately of course.
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Re: printed Nipkow Jigsaw

Postby Andrew Davie » Wed Jun 28, 2017 1:40 pm

OK, here's the result of printing two units and joining them together. I see that I'm going to have to put a small 'tolerance' in the design to account for a couple of issues with printing inaccuracy. In particular the first layer "smooshes" a bit, so it widens, and thus there's a bit of a sizing issue. I scraped the edges with a blade to try and improve the fit. I ended up, after doing that, giving it a bit of a tap with a hammer because it was so tight. That worked OK, but at the extreme ends you can see the plastic is pushed away a bit, causing a gap. This can all be fixed with, as I wrote, a bit of playing with the dimensions of stuff. Overall I think this is very promising; the two units as they are now are super-rigid and in my view would make a workable disk.

nipjig3.jpg
nipjig3.jpg (269.49 KiB) Viewed 4482 times



It's see-through at the moment because a) I printed quickly so the middle bit was mostly hollow, b) I didn't use a black material. The final version would be opaque.



Edit: for the curious, the head is actually Abraham Lincoln - the Smithsonian digitised a cast made when Lincoln was president, and I took the digitised model and shrunk it a bit so it would fit onto the printer in one pass. So it's basically exactly as Abe looked around 1863 - well, except for the colour :)
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Re: printed Nipkow Jigsaw

Postby Andrew Davie » Thu Jun 29, 2017 4:46 pm

Here's the next iteration. I found an elegant way to place "tolerance" around the snap-fit, and here's the first result. It now fits together snugly without a hammer required, and yet doesn't offer any "give". The plan would be to use some glue as you're putting 8 of these together which should further fine-tune the accuracy. The holes you see aren't really "holes" - they don't go right through, but are only a small indent intended to guide a drill bit. They are arranged so that you can do a correct spiral once all the pieces are fit together (i.e, all the bottom row in one pie-slice, and then the next row up in the next slice, etc).

nipjig5.jpg
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nipjig4.jpg
nipjig4.jpg (214.44 KiB) Viewed 4468 times
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Re: printed Nipkow Jigsaw

Postby Andrew Davie » Thu Jun 29, 2017 5:42 pm

A study in textures and fit...

texture.jpg
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Re: printed Nipkow Jigsaw

Postby Andrew Davie » Thu Jun 29, 2017 5:46 pm

Here's the SCAD source-code for creating one of the segment slices...
Code: Select all

$fn=128;

RADIUS = 150;
HOLESIZE = .75;
SPACING = HOLESIZE*0.75;
POSITION = RADIUS - 32*SPACING - 5;
SYNC = POSITION - 10;
SYNCHOLE = 1;
THICK=3;
SCREWHOLE = 1;
SCREWR = 25;


module holes(){
    for (i=[0:31]) {

            rotate([0,0,(i%4)*360/32+360/64])
                translate([POSITION+(i*SPACING),0,THICK-1])
                    cylinder(r=HOLESIZE,h=THICK+4);
    }

    for (i=[0:3]){
            rotate([0,0,i*360/32-360/64])
                translate([SYNC,0,THICK-1])
                    cylinder(r=SYNCHOLE,h=THICK+4);
    }

    // The screw hole(s)
    for (i=[0:0]) {
        rotate([0,0,i*90+22.5])
            translate([SCREWR,0,THICK-1])
                cylinder(r=SCREWHOLE,h=THICK+4);           
    }
   
}

module pie_slice(r, start_angle, end_angle) {
    R = r * sqrt(2) + 1;
    a0 = (4 * start_angle + 0 * end_angle) / 4;
    a1 = (3 * start_angle + 1 * end_angle) / 4;
    a2 = (2 * start_angle + 2 * end_angle) / 4;
    a3 = (1 * start_angle + 3 * end_angle) / 4;
    a4 = (0 * start_angle + 4 * end_angle) / 4;
    if(end_angle > start_angle)
        intersection() {
        circle(r);
        polygon([
            [0,0],
            [R * cos(a0), R * sin(a0)],
            [R * cos(a1), R * sin(a1)],
            [R * cos(a2), R * sin(a2)],
            [R * cos(a3), R * sin(a3)],
            [R * cos(a4), R * sin(a4)],
            [0,0]
       ]);
    }
}

module jigslice(){
    pie_slice(RADIUS, 0, 45);

    for (i=[1:3])
        translate([RADIUS*(i-0)/4,-15,0]) {
            translate([-5,5])
                square([10,10]);
            circle(10);
        }
}

module finalslide(){
    linear_extrude(3)
        difference(){
            jigslice();
            rotate([0,0,45])
                offset(0.5)
                    jigslice();
        }
}


difference(){
    finalslide();
    holes();   
}
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Re: printed Nipkow Jigsaw

Postby Harry Dalek » Thu Jun 29, 2017 5:52 pm

Looks good Andrew i have to reread but are you gluing them together ? may be an idea to print out a thick ring strip and over lap the pie shapes under the light holes area to stop any wobble as we all know best flat the disks may be glue that or bolt together interested to see how it go's .
You could also do a mirror drum on the flat and laminate then together in the 3d shape of the thing add the mirrors ,i can see how to do this but i would be .hopeless to transfer that idea to a PC to print not my thing ...i will watch and learn /
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: printed Nipkow Jigsaw

Postby Andrew Davie » Fri Jun 30, 2017 3:55 pm

Two more parts printed. It takes about 3 hours/pair to print. Next step is (yes) to glue them together. After that I'll test the rigidity perhaps by drlling holes and mounting - for now I'm really just testing the ability of the disk to be flat and have the hole positions marked accurately.

nipjig6.jpg
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Re: printed Nipkow Jigsaw

Postby Harry Dalek » Fri Jun 30, 2017 4:54 pm

Andrew Davie wrote:Two more parts printed. It takes about 3 hours/pair to print. Next step is (yes) to glue them together. After that I'll test the rigidity perhaps by drlling holes and mounting - for now I'm really just testing the ability of the disk to be flat and have the hole positions marked accurately.

nipjig6.jpg



OH i didn't see the mounting holes for your motor mount that might be enough to keep it all rigid .
i also just saw the gaps do need filling hot glue gun is good for that paint matte black ?
Last edited by Harry Dalek on Fri Jun 30, 2017 5:02 pm, edited 1 time in total.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: printed Nipkow Jigsaw

Postby Andrew Davie » Fri Jun 30, 2017 5:01 pm

Harry Dalek wrote:OH i didn't see the mounting holes for your motor mount that might be enough to keep it all rigid .
Are you going to paint it matte Black ?



No, this is just a test-print to see if it's rigid. I believe it will be just fine, but I can always glue a plate to the back as you suggest.
The final version will be printed in a black material. I won't paint this, as it's just a prototype. I'll finish printing this one and drill the holes and mount it to see just what sort of picture it produces - I will then know if it's accurate enough to trust the hole positions. I think it will be OK, not great. But we shall see!
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Re: printed Nipkow Jigsaw

Postby Harry Dalek » Fri Jun 30, 2017 5:14 pm

Andrew Davie wrote:
Harry Dalek wrote:OH i didn't see the mounting holes for your motor mount that might be enough to keep it all rigid .
Are you going to paint it matte Black ?



No, this is just a test-print to see if it's rigid. I believe it will be just fine, but I can always glue a plate to the back as you suggest.
The final version will be printed in a black material. I won't paint this, as it's just a prototype. I'll finish printing this one and drill the holes and mount it to see just what sort of picture it produces - I will then know if it's accurate enough to trust the hole positions. I think it will be OK, not great. But we shall see!



I suppose the bigger you can print it more accurate it is .
i do see theres light gaps between the pie shapes you will have to fill those make light proof...can you over lap the pie shape edges connections so this doesn't need filling ?
Tongue and groove would be good but hard to make so small ..
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: printed Nipkow Jigsaw

Postby Andrew Davie » Fri Jun 30, 2017 5:18 pm

Harry Dalek wrote:i do see theres light gaps between the pie shapes you will have to fill those make light proof...can you over lap the pie shape edges connections so this doesn't need filling ?
Tongue and groove would be good but hard to make so small ..


It's haning "loose" in the pictures. With glue it's a pretty tight fit, however I might put a splash of paint in there to make it more lightproof. But your idea of a tongue/groove is interesting and quite easy to do - I might try that next! Good thinking.
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Re: printed Nipkow Jigsaw

Postby Steve Anderson » Fri Jun 30, 2017 5:41 pm

Even just a lap-joint would do it, i.e. half a tongue and groove. Perhaps even just a beveled edge at an angle.

Also I suggest using black as the colour of the disc, it may not seem like much, but the residual light leakage through other coloured plastics could easily be more than what comes through the tiny hole you wish. If using this for a camera you may need an IR filter as the plastic, even black, may let IR through. Though it depends on what the camera light-sensor is.

Steve A.
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Re: printed Nipkow Jigsaw

Postby Klaas Robers » Sat Jul 01, 2017 9:40 pm

Realise that the holes, you look at each moment through only ONE hole, have a over all transparency of only 0.1%. So the disc itself should have a light damping (darkness) of 99.9% and then you get a contrast of only a factor of 2. You wat to have a contrast of at least a factor of 50, so the disc should have an untransparency of at least 99.999%. This is also the reason that photographic discs are far too transparent.

So I don't believe in the blackness of black PMA. On top of that 3D-printing routines print only thin walls and fill up the empty space with a thin structure.
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Re: printed Nipkow Jigsaw

Postby Andrew Davie » Sat Jul 01, 2017 10:09 pm

Klaas Robers wrote:Realise that the holes, you look at each moment through only ONE hole, have a over all transparency of only 0.1%. So the disc itself should have a light damping (darkness) of 99.9% and then you get a contrast of only a factor of 2. You wat to have a contrast of at least a factor of 50, so the disc should have an untransparency of at least 99.999%. This is also the reason that photographic discs are far too transparent.

So I don't believe in the blackness of black PMA. On top of that 3D-printing routines print only thin walls and fill up the empty space with a thin structure.



I'm planning to glue a reflective-coated (mirrored) cardboard back on the black disc. It won't have any transparency problems - not an issue IMHO. Remember this blue disk is a test prototype just to see how accurate holes are and a jigsaw-disc works. As to the "printing empty space with thin structure" and "thin walls" yes in general this is true, but it is is configurable in your 'slicer' - and in my print I set it to solid all the way through. My walls, so to speak, are 3mm thick (i.e., the disc is solid filament with no gaps internally). The blue material is rather transparent yes, but the black material is pretty opaque. And in any case, I am putting a backing on the disc to reflect the light back into the box.
Should be OK :)
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Re: printed Nipkow Jigsaw

Postby Andrew Davie » Sun Jul 02, 2017 2:52 am

My first attempt to glue the pieces together has been pretty messy - the glue didn't set right and it was hard to apply to the tight seams without having it squeeze out on both sides and thus stick to the table on which I'm trying to ensure the join is flat. I gave up half-way through. Also, the pieces themselves have a tendency to warp/lift on the edges. I need to improve my skills at printing things really flat - perhaps by playing with the temperature profile of the print bed as it's printing. But the real gotcha is I used PLA for the material. There's not much that dissolves PLA that isn't also deadly. However, ABS which is somewhat tricker to print with and tends to warp a lot... well that dissolves with acetone. So I'm going to re-do the print, but instead use ABS for the material. Then the joining will be a simple matter of assembling the unit and putting just a few drops of acetone in the joints. It's powerful stuff - completely welds bits together by dissolving them into each other and forming a new whole. It's not a glue at all - it's very much a welding process. So, next experiment - ABS print, acetone weld!
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