DLP Printing pt. 2: The projector

The projector is the most important component to a DLP printer. DLP stands forDigital Light Processing, and is a technology developed by Texas Instruments to project light. I'm not going to go into many details about the technology, as it doesn't really matter for the printer. All that is important is that there is a filter that blocks UV light from being projected, and we need to fix that. The projector replaces both the X and Y axis of a typical FDM printer by projecting the desired layer shape onto the build plate. The projected image is black and white, and the white region is where the resin cures. A simple way to visualize this process is to think of an MRI or CATScan. An objected is "sliced" like deli meat into many thin layers. The printer recreates each layer on top of each other sequentially until the object has formed.

(LEFT: the desired shape. RIGHT: the sliced version. source: Wikipedia: Rapid Prototyping) 

After a week of eBay hunting, I came across a used Optoma EP716 DLP Projector for only $40. This projector is capable of resolutions up to 1400x1050, and has a 200W UHP (Ultra High Performance) mercury- arc bulb. It came with a working bulb, which is strangely difficult to come across on eBay, and the only thing missing was the remote. The projector arrived yesterday and is in decent condition, with only a couple of scratches. After watching an episode of Late Night with Jimmy Fallon on my ceiling while lying down, I decided it was time to get to work.

(my baby! source: eBay listing)

Optoma datasheet

Key components for a good Projector:

• MUST be DLP (a Texas Instruments technlogy. Read more about it here)
• A high wattage lamp. The higher the wattage, the stronger the light and the faster the cure time
• Avoid LED. These are harder to get enough UV light from. It seems as though it is possible to use a LED projector, but there will be much more work.
• A high resolution. The build area and resolution of your prints is directly proportional to the projector resolution. The projected image is the X and Y axis, while the lead screw moving the build plate is the Z axis.