SLA 3D Printer Log 1: Projection, Projection...

In between dreaming of a house where model trains bring me pre-mixed Robinson's squash and keenly observing the cathartic tidal wave of backlash against Dungeon Keeper Mobile I have received a 720p projector from Ebay, costing £250.  Before launching into the specifics of how to use it, let's examine the unit itself.

The book is A4 width (and 2cm shorter lengthways) for comparison, and the unit weighs 1.13kg

The unit is actually 206 x 162 x 75mm (lxwxh), feels like a quality implementation despite it's low weight and is highly intuitive to operate; this isn't surprising when we learn that this model (Nobo X22PW) is simply a rebranded Optoma TW330, which is going for £410 at time of writing.  That is excellent value for money given that most projectors in that range will be 1024x768 native at most, not 1280x800 native (keep an eye out for native resolution, most projector sellers claim their model will "handle" 1080p, but this is done through upscaling and will make your movie look anything but sharp).

*Review Interlude*

The unit is surprisingly quiet in spite of the fan having to keep a 2200 lumen lamp from exploding (not a hint of facetious here), and that lamp gives plenty of brightness even on std-mode with 1700 lumens.  It is audible, but it quickly fades away during gaming since the noise has no irritating frequency (that goes out the window in bright mode, I suggest just turning up the brightness in windows).  Having played Medal of Honor: Airborne on it I can say that it eco-mode might not be to everyone's taste but with lamps costing around £90 I think most can sacrifice 29% brightness for 66% more lamp life.  This is also a Single-Chip DLP model so it suffers from a little colour separation during fast motion (highly noticeable when you shake your head viewing a black background); finally I would like a better contrast ratio than 2000:1 for more defined extremes in the colours, but I'm rapidly disappearing down a rabbit hole here.

*End Review Interlude*

Back to the point at hand, 1280x800 will allow for a detail level of 0.1mm per pixel for a build area of 12.8cm x 8.0cm; I'm looking for a minimum resolution of 0.05mm seeing as I design for FUD on Shapeways (0.1mm Resolution), giving a build area of 6.4cm x 4.0cm.  One of my ideas up to this point was to traverse the projector along a vertical rail, utilizing a redundant RAMPS axis to adjust the build area/resolution balance, but I forgot to account for projector focus; what's worse is that the minimum distance I could get the projector to focus was around 28cm, which gives an image of 197.5mm x 124mm - well above the 64mm x 40mm required.

Despite this, the brightness of the resultant screen area was highly encouraging.

In order to attain this build area, I need to add an adjustable lens with at least 3.0x magnification.  DSLR lenses can be had used for around £50, given that a UV filter is a common accessory it may be that the lens can transmit UV without hindrance, but apparently DSLRs have UV filters of their own and there may be some in the lens too - an optical testbed will be required to fully investigate the matter, as well as some actual 3D resins (no VOCs, please).

Free Ideas Bucket 1.0

I intend this project to be completely open-source, that means any and all STLs and diagrams related to the build will be available royalty-free and not on my Shapeways Shop; if *you* would like to sell it, go ahead but be prepared for a hard time making money given that the models are free and Shapeways can be used by a Bonobo.  Anyhoo, I present my current list of ideas:

• A standalone built-in computer, either a Raspberry Pi, it's more powerful compatibles or even a full-on x86 PC.  This is to allow the printer to run without having to keep either my PC or Laptop running with it all night.
• An ultrasound sensor to detect the resin level in the bath and adjust the build platform starting point to suit, this is only relevant to top-down designs.
• A touchscreen on top of the machine, adjustable to either face outwards (for desk use) or upwards (for floor use).
• Gullwing doors...  just because...

That concludes the first of hopefully many buildlogs to the SLA 3D Printer Project.  The ultimate aim is to largely free me from having to use Shapeways for every.  single.  solitary.  step.  in the R&D Process for Tawe_TMD.  It's always the way when you make something that you trip up on things you couldn't have predicted, but even if I flounder and fail, I can always watch Zero Punctuation across my wall.