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Re: To those using UV Dlp mod. Have you guys seen any damage..

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  • torben.mogensen@ymail.com
    To anyone interested in using UV LED projectors Converting an LED projector for DLP printing in more tricky that bulb projectors, mainly because its not been
    Message 1 of 47 , Mar 4, 2013
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      To anyone interested in using UV LED projectors

      Converting an LED projector for DLP printing in more tricky that bulb projectors, mainly because its not been done before - or I haven't come across anyone who wants to share the knowledge.

      How many lumens a UV-LED emits does NOT matter - really - and on most UV-leds you will find is not measured in lumens, but in milliwatt mW.
      What is all important is the spectrum of emitted light (googling it will give a give understanding) which must be 380 - 420 Nm, which is basically violet light. Light over about 420 Nm is useful for ligthing up you desk only, it will not cure anything. Light under 380 (UVB/UVC)
      you want to avoid, it will for sure ruin your projector and is really nasty stuff for your health.
      The resins we are interested in will cure in the area 380 - 420 Nm.

      Replacing the UV-LED is a tricky and difficult job. You will need to look into circuitry of the projector and handle a GPIO on the controller . Most likely your UV-LED will need a different power supply, and can not be powered by the projector's supply and control of the LED must be taken away and given to an arduino or in my case I use a raspberry pi.

      Bulb projectors will split each frame image into a red, green and blue (or more colours) by use of a colour-wheel - that's why it has to be removed in bulb projectors. Now in LED projector this is done by turning on and off LED very fast. This has to go, because it would give us only 1/3 of the energy from UV-LED, and a software switch has to made in the microcontroller (raspberry pi), I have opted to make my own image generator on the raspberry pi, that then controls on/off of the UV-LED.

      Removing and LED and replacing with it with a UV-LED is also not straight forward, as there is no info out-there on specific projectors that I have come across. But in essence the detector wire has to be located and in most cases has to be shorted to ground - BUT doing this wrong will most likely ruin your projector!

      The MAIN reason for using UV-LED in the first place, is to have ample UV power to do experiments where the available UV is not a limitation, and consequently being able to speed up the process significantly.

      But another problem soon arises, vaccum between the printed area and the build-palte. This has been done tilting/sliding the VAT to release the vaccum. This however is quite time consuming and kindof de-valuates the whole idea using UV-LED. So to have full value of a UV-LED this must be solved also. There is likely many ways to do this, but I am convinced it can be solved.

      My strategy to tackle this I call: Big area = big vaccum, small area = small vaccum.....its a bit diffcult to explain in text and dont have helping images at hand now, but here goes:

      The layer-image is overlayed with black stripes - maybe 0.1 mm wide.
      so now half the image is exposed and cured. The next layerimage is inverted and now cures into the previous layer that was left uncured AND half of the next layer. The layers now connect in a "zig-zag" patten. This is maybe as bad explanation, but if anyone is interested I will be happy to discuss.

      Okey, if you have gotten this far you must be really interested, and you should know that I do this from purely egoistic motivation, because the promise of 3D DLP brings huge potiantial for me, BUT only if the speed can be improved significantly.

      My goal is a print-cycle of 2-3 secs.

      Honestly if not I would just get myself a Makerbot to play around with :-).

      I'm all PRO open-source - community development, and ANTI "marketing-by-patent-lawyer" - "greddy bankers" with a passion.
      I would be happy receive comments, ideas contributions and discuss.
      But of cause comments to the effect "I'm clever - you are stupid" isn't really helpful or wanted.














      --- In diy_3d_printing_and_fabrication@yahoogroups.com, "luis h" <luisguillermo98@...> wrote:
      >
      > Hi Torben,
      > I have heard good thing about the Chinese led, I have seen them in youtube and they are very bright. According lo some articles LED produce wavelength in the visible light better than UVB-UVC. I am also looking for speed as you, I want to built printers for production and not DIY so speed is an issue for me. Have you tried the cheap resin for Solarez or similar? IF your led module is 90w that means you are putting 8000 lumens or more in the resin so that is more than double than the 200watt HIP bulb can deliver..
      >
      > What resin are you using that cure over 400nm?
      > What projector are you using and how are you bypassing the bulb check?. Is it easy to find the line that goes from ballast to the board?
      >
      > Luis..
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      > --- In diy_3d_printing_and_fabrication@yahoogroups.com, "torben.mogensen@" <torben.f.mogensen@> wrote:
      > >
      > > Hi Luis,
      > >
      > > I went for ledengin.com in US, but they are quite expensive.
      > > I would have gotten a Chinese one, but could not find one at the time.
      > >
      > > As far as I understand: higher frequency = higher energy, meaning the
      > > shorter wavelength will carry more energy, but I'm no expert either, so I cant really say why :-D
      > >
      > > I did do some trials on curing with the LED and it is very fast.
      > > My guess is that cure time will be between 1-2 secs per layer, once I get everything tuned in just right. Cure depth 0.2mm
      > >
      > > To get absolute control over the process I using a raspberry pi as controller for steppers and image generator, meaning all the coding is more or less from scratch. This is taken much more time than my worst fears.
      > >
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      > > --- In diy_3d_printing_and_fabrication@yahoogroups.com, "luis h" <luisguillermo98@> wrote:
      > > >
      > > > Torber,
      > > > I am also looking to convert the projector to LEd using a 100watt. This bulb emit much much less energy than HP and almost 80000 lumens. I am not sure but I believe the lower the wavelength the cooler is the light?. IR is the highest in temp.. What brand of Led did you buy, any thought about those Chinese led module?. What projector are you using?
      > > >
      > > >
      > > >
      > > > --- In diy_3d_printing_and_fabrication@yahoogroups.com, "torben.mogensen@" <torben.f.mogensen@> wrote:
      > > > >
      > > > > Hi Arthur,
      > > > >
      > > > > I am working down that route and will soon be testing using a 90w UV led at 400 Nm. So you will soon know :) My aim is to speed up the print cycle significantly.
      > > > >
      > > > > I looked as deep as possible into the TI documentation of the "normal" DMD. The documentation says that 400 Nm is OK, BUT max temperature and
      > > > > low spectrum light (400 Nm) should not occur at the same time.
      > > > >
      > > > > Else where in a TI forum I found (someone who seems to knowing what he was talking about) saying failure would be seen as stuck pixels (micro mirrors) over time.
      > > > >
      > > > > My guess is the trick will be to keep the cool < 50 degrees C, since
      > > > > 400Nm contains more energy that a normal mixed spectrum of visible light.
      > > > >
      > > > > Considering that 400Mn is within the spectrum a projector will normally produce, my guess is that I will not see stuck pixels as long as the DMD is kept cool.
      > > > >
      > > > > The DMD UV version will go much lower spectrum, 300Nm as far as I remember. Also it seems that going lower than 400Nm the issues are the optics more than the DMD.
      > > > >
      > > > > TI does NOT make this to figure out - I suspect because an industrial projector is 50 x more expensive ... but that's just my guess :-|
      > > > >
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      > > > > --- In diy_3d_printing_and_fabrication@yahoogroups.com, "arthur2shedsj" <arthur2shedsj@> wrote:
      > > > > >
      > > > > > I haven't heard of any Digital Micro Mirror Devices (DMD) dying from the removal. But I have seen some optics that have melted after the removal of the color wheels. The color wheels also block some IR.
      > > > > >
      > > > > >
      > > > > > --- In diy_3d_printing_and_fabrication@yahoogroups.com, "luis h" <luisguillermo98@> wrote:
      > > > > > >
      > > > > > > Is this is mito or fact?.
      > > > > > > has any one experience any damage of the dlp chip after removing filters, wheel?. According to some expert and articles I have read, dlp micro mirror has aluminum coating or made entirely of aluminum and this metal is one of the best material to reflect UV, it is even better than silver and If more reflection of UV is needed they re-coated the aluminum surface with dielectric material and this is what mirror manufacturers market this type of mirrors as "enhance aluminum mirrors" so I need to know if these micro-mirror really get damage or this is a hoax by TI to charge more for UV chip? If problem is on the board where chip is mounted then there should be a way to protect this area. Creating a micro mesh that surround the mirrors should not be that hard. We can even use a dlp projector to create an tiny mesh made of polymer to protect those exposed area.. Any suggestions from the expert in this forum?
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    • arthur2shedsj
      The other issue we have run into is the waste heat converted by a lamp. Compact designs require lots of airflow to keep the electronics cool. The heat may also
      Message 47 of 47 , Mar 7, 2013
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        The other issue we have run into is the waste heat converted by a lamp. Compact designs require lots of airflow to keep the electronics cool.

        The heat may also be conveyed to the photopolymer in the vat to reduce the viscosity via a heatpipe. If you use LED's then you can just add a cartridge heater to the vat.

        --- In diy_3d_printing_and_fabrication@yahoogroups.com, "doyle_arthur@..." <doyle_arthur@...> wrote:
        >
        > Lamp life, to my view, is the only benefit that can be gained by using leds.
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