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

Expand Messages
• After looking at your method of calculation I d recommend that you just use a faster photopolymer with your standard lamp and projector. Something like this:
Message 1 of 47 , Mar 3, 2013
After looking at your method of calculation I'd recommend that you just use a faster photopolymer with your standard lamp and projector.

Something like this: http://www.aboutprojectors.com/Acer-X1261P-projector.html and projected over ~102 x 77mm will get you under 1 second layers 0.1mm thick.

--- In diy_3d_printing_and_fabrication@yahoogroups.com, "torben.mogensen@..." <torben.f.mogensen@...> wrote:
>
> Easy now Arthur, I'm not trying to mock you - all right?
> Your statement "cure with 0.5W in > 1. sec", I wish it was true, would
> be a major thing, but I suspect it needs a bit more work.
>
> However the questions still stands, but should properly be more like:
>
> How much wattage should a 400 Nm LED have, to be suitable for a DLP printer assuming that:
>
> 1. You are modifying a LED based projector by replacing one (or two) the existing LED with a 400 Nm LED
>
> 2. Print area around 150*200mm, distance from projector to object about 250 mm.
>
> As I'm nowhere clever enough to do the "forward" calculation, I'm using a "house-hold budget" approach.
>
> Comparing a bulb to a LED projector you could assume as follows:
>
> A bulb projector use 200W to cure a layer in 7 seconds.
> 1. 15% of bulb light is in useful wave-length.
> 2. 100% UV-LED light is in useful wave-length
> 3. A bulb converts 40% of energy into light
> 4. A LED converts 80% into light
>
> So, if the above is true, a 15W UV-LED would roughly be equal to a 200W projector bulb, and cure a layer in 7 secs.
>
> Does this make sense?
>
> Now look aside from all technical issues - I think it could be useful to establish a kindof rough rule-of-thumb.
>
>
>
> --- In diy_3d_printing_and_fabrication@yahoogroups.com, "arthur2shedsj" <arthur2shedsj@> wrote:
> >
> >
> >
> > I predict that the next problems for most will be:
> >
> > How to get 500mW/cm^2 or more 405nm into the DMD from an LED?
> >
> > Which projector to use?
> >
> > How do you modify or focus the LED on the lightpipe?
> >
> > Why does my lightpipe not work as well as others?
> >
> > How did you do that without a lightpipe in front of the DMD?
> >
> > How come their projector works and mine doesn't?
> >
> > Will this work with a LED pico-projector if I change the LEDs to UV?
> >
> > Will this work with a LCD projector?
> >
> > How do you get the lens to focus so close?
> >
> > How did you build the reflector and lens for the LED?
> >
> > I removed the lamp from my projector and color wheel but it doesn't work now. How do you bypass the color wheel motion and lamp on detect circuits so that my project will think all is ok?
> >
> > How come the open source control software is so broken?
> >
> > How do I generate supports for my 3D models?
> >
> > How come my prints stick better to the vat than to my build stage?
> >
> > Why did my sylgard coating melt after a long exposure?
> >
> > What thickness PTFE film should I use for my vat?
> >
> > Why did my PTFE film melt or tear after a few prints or a long exposure with fast resin?
> >
> > ............
> >
> >
> > --- In diy_3d_printing_and_fabrication@yahoogroups.com, Graham Stabler <grezmos@> wrote:
> > >
> > > On Sun, Mar 3, 2013 at 6:27 PM, arthur2shedsj <arthur2shedsj@>wrote:
> > >
> > > > **
> > > >
> > > > Reduce this to 90% for path losses and you end up with 14.67mw/cm^2
> > > >
> > >
> > > I would suspect it would be much more like reduce by 90% than to 90%
> > >
> > > If your numbers are right then what are we all wasting our time with lamps
> > > for?
> > >
> > > Graham
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > >
> > > > --- In diy_3d_printing_and_fabrication@yahoogroups.com, Graham Stabler
> > > > wrote:
> > > > >
> > > > > > - energy lost due to distance to printed object
> > > > > >
> > > > > Energy is spread not lost, the absorption in the air would be negligible.
> > > > >
> > > > > but I have not seen any 3D printers using small UV LEDs of any sort,
> > > > there
> > > > > is that little SLA system using the laser diode but that's a different
> > > > > kettle of fish.
> > > >
> > > >
> > > >
> > >
> >
>
• 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
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.
Your message has been successfully submitted and would be delivered to recipients shortly.