LCD Based 3D Printer - Introduction

This is the place to discuss DLP projectors, UV Lasers, Galvanometers, LCD screens and similar display devices. Also discussed are optics in general.
Phife
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LCD Based 3D Printer - Introduction

Postby Phife » Mon Jan 20, 2014 3:55 pm


Leinad78
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Re: New Builder - LCD Based 3D Printer - Introduction

Postby Leinad78 » Tue Jan 21, 2014 2:03 am

you´re right, yesterday evening if stumbled over some cheap 3w leds. for my screen size, i guess i should use around 24 to have some good distribution.

johnrpm
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Re: New Builder - LCD Based 3D Printer - Introduction

Postby johnrpm » Tue Jan 21, 2014 4:13 am

Came across this, http://www.youtube.com/watch?v=z_lo-oPlhak

this one is done by hand, http://www.youtube.com/watch?v=APpCrp5W-_g

may be interesting.
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Leinad78
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Re: New Builder - LCD Based 3D Printer - Introduction

Postby Leinad78 » Tue Jan 21, 2014 6:04 am

well, why do tft screens have to polarizing filter foils? the first one with the uv filter behind the screen, followed by two glued glas plates within the color pattern and finally a second polarizing filter foil :shock: i don´t get it, i was thinking the lcd switches the polarized light dark/light, but why do they need a second one?

got it, the lcd unit just switches the light direction at 90°

Leinad78
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Re: New Builder - LCD Based 3D Printer - Introduction

Postby Leinad78 » Tue Jan 21, 2014 6:32 am

Success! :D Curing time is around 3-4s with 35W LED at ~410nm. now lets move to 90W :twisted:

johnrpm
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Re: New Builder - LCD Based 3D Printer - Introduction

Postby johnrpm » Tue Jan 21, 2014 8:47 am

Good news what did you do different?.

Reading the info, it seems that the polarizers, or at least the second one, allow us to see the image, as
without it we see nothing, I have not yet got my head around wether it would cure resin without the second polarizer,
ie, is an image formed but not visable, or no image is formed????. (I think maybe no image)


this site gives a bit of information. http://www.lcd-parts.com/polarizer.aspx

and this one, http://www.gizmag.com/stealth-computer- ... ses/29700/

lcd-panel-structure.jpg
lcd structure
lcd-panel-structure.jpg (27.79 KiB) Viewed 39955 times
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Leinad78
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Re: New Builder - LCD Based 3D Printer - Introduction

Postby Leinad78 » Tue Jan 21, 2014 12:03 pm

it seems that the first polarizing filter is used to set the direction of the light where as the second filter is twisted at 90°, so the light doesn´t travel through the screen. the lcd unit just switches the light at 90°, something like a direction-mirror, so that it can pass the first and second. in this kind of way, the whole screen can be black and partially be enlighted by the backlight.

polarizing filter seem to block light at frequencies lower 400nm, thats why i didn´t had success with 365nm energiesaver bulbs. so the clue seems to be to rip off the uv filter at the first polarizing filter, use somewhat high power lighting (keeping in mind my screen is a tad larger then Din A4 paper) i´m going with 30x3W led (405-410nm) and get some good polarizing filter followed by resin able to cure at frequencies slightly above 400nm.

i have just to discover tomorrow if the width of the polarizing film has any influence on the light power, e.g. the smaller the width the less waste of light power.

Phife
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Re: New Builder - LCD Based 3D Printer - Introduction

Postby Phife » Tue Jan 21, 2014 12:46 pm

Im not sure why you all are so keen on tearing off your polarizers? The system works with the factory polarizers with no little issue so I dont see an advantage to taking them off and replacing them since there isnt ones without UV filters and also the UV filter probably helps the LCD last longer as UV might damage it in some way. I dont think the LCD has a UV filter seperate from the polarizers, I think the polarizers are the UV filters, its part of their function, but its just a guess.

johnrpm
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Re: New Builder - LCD Based 3D Printer - Introduction

Postby johnrpm » Tue Jan 21, 2014 2:40 pm

I think the polarizers are the UV filters, its part of their function
Yes, I think you are right, but also not all polarizers are equal, maybe some allow
more UV than others, depending on the base material perhaps.
I have recently stripped down an ancient astrobeam lcd projector, and the
lcd panel is almost clear, almost glass clear, so maybe projector lcd are different
to monitor lcd, will try to find out.

Im not sure why you all are so keen on tearing off your polarizers
All we can lloose is time, but maybe learn something new,
some years ago I was playing around with polarizers, and found that clear
sla parts display stress just like other polymer parts, this means that force applied to
complicated structures built on an sla visually indicate stress, got to be usefull for
all sorts of things.
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Leinad78
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Re: New Builder - LCD Based 3D Printer - Introduction

Postby Leinad78 » Tue Jan 21, 2014 3:21 pm



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