Re: LCD Based Printer; Photopolymer Samples
- Hi Ali,
A fellow Canadian, where abouts are you?
I have been developing an LCD based 3d printer for the last 6 months, While my thread has been quiet for some time, rest assured ive been plugging away at it.. Its not been a simple matter. Ive done a lot of testing with different resins, LCD's, Light sources, Lenses, and Electronics.
I am hoping to release a DIY kit for others to build their own LCD 3D printer. Im working with Chris Marion and we are developing a great machine, I will be using a custom version of Chris's software.
Dont waste your time with color LCD, you will need a monochrome LCD no matter what.
My current setup is using a custom 400w MH bulb on a digital ballast, this bulb has a small arc and a very high output in the 390-420nm range and has a large spike at 450nm and not much of the spectrum after that, its a very nice purple/blue color. Optics are very important, and dealing with the heat of the 400w MH bulb must also be address.
I havent had much success with any other bulbs, I was testing with a 150w MH and a regular 400w MH but they didnt work out.
The nice thing about the LCD printer is the large build area, I hope to be able to print the entire structure of the printer with the prototype in a reprap style. Print panels, add hardware and electronics and you got a printer. Ive been designing printable panels but there is much to deal with before I even begin printing other machines.
You will have to deal with all the issues youve listed and more, and its a big task. I encourage you to experiment and try. To start off save you money and dont bother with color LCD's get a monochrome or greyscale LCD used for medical purposes, x-ray imaging.
If you wait a couple more months I hope to have a working printer and I can spend some time getting a DIY kit out there and write up all that ive learned from my testing ao rhat others can make their own.
I wish you luck!
--- In email@example.com, "apu_16" <ali.punjani.groups@...> wrote:
> 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.