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Build Your Own SLA/SLS • Top down and bottom up DLP
Page 1 of 1

Top down and bottom up DLP

Posted: Sat Aug 01, 2015 11:01 am
by igorkvartuh1
Hi!
I am doing research for school and I am wondering if anyone has any good articles which describe each type of printing (bottom up and top down)? Advantages and disadvantages of each type for example.

Any help and any article is welcomed!
Thank you.

Re: Top down and bottom up DLP

Posted: Tue Sep 22, 2015 10:29 am
by Terah
As a new member to 'BuildyourownSLA' and pretty new to the whole concept of 3D printing using resins, I'm going to venture a guess as to why this question has not been answered yet.

While thoughts like 'Research does not mean having other people do your homework' have crossed my mind, when looking at several working designs on Youtube, Google Image search, etc, the prevailing though is that there ís no concise answer to your question, as a whole bunch of things depend on questions like 'what do you want to print, what materials do you have to work with (in terms of building the actual printer), how much room to you have', etc, etc.

What might be a limitation of top down printing in one design might not be an issue in another, and the same goes for bottom up printing.
Of course, one immediate difference is that with bottom down printing, your UV source is pretty close to the build plate, a distance that will remain the same regardless of the size of the object you want to print, ensuring an consistent, and presumably higher, amount of (UV) light for every layer.
Since with top down, a projector is positioned above the object you want to print, there is a limit to the size of that object. Of course you can position your projector a greater distance above the build plate, but then other laws kick in, such as the one that says that the intensity of light is reduced by the square of the distance (not sure I'm describing this well, lacking the correct words in english, but in short, if you move the projector from eg. 50cm to 1m, a doubling of the distance, light intensity is reduced by a factor 4. Go from 1 meter to 2, and the build plate will receive 8 times less light than it receives at 50cm). Needless to say, this has a huge impact on printing speeds (and presumably on the overall quality of the final product)

Another typical disadvantage of top down, related to the size of the object, is that a taller object needs a deeper container with resin, whereas a bottom up printer just needs 1 single container (as far as height is concerned) for all object sizes. All you need is to refill the container so that it doesn't run dry. The only limitation here is the height of your ceiling.

These are just 2, 3 things to consider from the top of my mind after having been looking at several ways to build my own SLA in the near future, so I'm by no means an expert (heck, I'm not even a beginner yet :P) at this, but my advise would be as already mentioned above: Look at youtube video's, check out Google Images for (diy) designs of other people, and apply common sense as to their specific limitations, and I'm sure you'll have plenty to write about for your research :).

EDIT:
I realize you asked for articles, but what I aimed to imply (unsuccesfully, in retrospect), is that what articles you find will always be influenced by personal preference, requirements, budget, etc, so rather than use what essentially are other's people's opinions, try to reach your own conclusions for your research :) It'll be a learning experience!


Good luck,

Terah

Re: Top down and bottom up DLP

Posted: Tue Sep 22, 2015 1:42 pm
by sodium

Re: Top down and bottom up DLP

Posted: Wed Sep 23, 2015 5:02 am
by Terah

Re: Top down and bottom up DLP

Posted: Thu Sep 24, 2015 5:12 pm
by sodium
this is the place to get info about building a printer. read as much as possible and will learn a lot ... specially the build subforum. nice ideas around.