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LCD Based Printer; Photopolymer Samples

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  • apu_16
    Hi everyone, I m new to this group so I ll introduce myself: I m a graduate student in Canada. I m an avid DIY hobbyist, so far I ve mostly worked on CNC
    Message 1 of 45 , Feb 21, 2013
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      Hi everyone,

      I'm new to this group so I'll introduce myself:
      I'm a graduate student in Canada. I'm an avid DIY hobbyist, so far I've mostly worked on CNC router/mills, and I'm very interested in 3D printing, especially resin based printing. Like many other people, when I first read about DIY stereolithography I had the idea of using an inexpensive LCD panel rather than a DLP projector, with an appropriately bright light source.
      After a couple days of intense reading and searching, I've figured that the major things to consider with this type of project are:
      - transmission spectrum of LCD panels. Inexpensive LCDs are manufactured with color filters built in, and use polarizers to create contrast. Both have limited wavelength rages where they are transparent.
      - absorption spectrum of resin. UV resins are cheaper but UV doesn't pass much through LCD panels. Near-UV (420nm) and visible (470nm) resins are also available, and may work.
      - emmittance spectrum of light source. Commonly used lamps in DLP projectors (known to work) are Metal Halide lamps and Mercury Vapor lamps. These have spectra with peaks corresponding largely to mercury - 405nm, 436nm, etc.
      - diffusion caused by LCD panel. LCD panels diffuse light from the backlight, so that their images are viewable from more angles. This is not good for photo polymerization precision.
      - layer detachment from vat. Upside down printers all have this issue, but most resins are known to work with PDMS or Teflon. Some printers use sliding to relieve vacuum.
      - useless pixels blocking light. Since most resins work in the blue/near-uv range, all the red and green sub pixels in a LCD panel will just block light. This will mean that only 1/3 of incident light gets through to cure the resin (at most) and it also means that there will be gaps between the blue sub pixels, where red and green are. This may be a problem, but diffusion of light might help to cure the resin in the gaps.

      Is there anything else I should consider? I'm fairly comfortable with the mechanical aspects of this kind of project, as well as the electronics and software.
      I know there has been at lease one attempt by someone in this group (Phife54, Nick?) to build an LCD based system, using a monochrome LCD. But I think that thread has been quiet for a while? Does anyone know what kinds of results were achieved?

      At present, I'm fairly confident in the LCD based approach, but to address those major points above I need to do some testing. I have everything on hand except resin. Spotamaterials seems to be out of stock in everything, and bucktownpolymers seems to only be selling Gallons (unless I just can't figure out the website) for a price a little too steep for me to afford for just the proof-on-concept stage. So my request to the group is, would anyone be willing to sell me a small quantity (100mL) of near-uv (420nm) curable resin? Preferably Spot-GP from spotamaterials, or any color of PS100-V420 from bucktownpolymers? I've tried email both to ask about the possibility of purchasing a sample, but I haven't received replies yet.

      Thanks!
      Ali
    • chenw1115@yahoo.cn
      holle,do your lcd printer work now?
      Message 45 of 45 , Apr 23, 2014
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        holle,do  your lcd printer work  now?
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