DLP 3d printer build details 1: Structure

The printer hardware consists of only a few assemblies the build plate/z axis assembly, the vat/tilt assembly, the projector mount, the housing and a light baffle (sucks up stray light when printing) all connected to a single vertical aluminum extrusion. There are two step motors, one for the z axis and one for the vat tilt, controlled by a dual step motor controller. The step motor controller takes commands over a ttl serial connection from an arduino.  The arduino interprets and executes commands sent to it over usb serial from theCreationWorkshop software running on the pc, it also controls the uv led relay (for the uv modified dlp projector) and a hobby servo that opens and closes a shutter (when using the white light projector). Step motor power comes from a 12V 30A power supply. The step motor controller is also able to supply regulated 5V for the shutter servo.

I make things as adjustable as possible. The main assemblies (the vat, build plate, z axis hardware, projector mount, light baffle) basically clamp on to the backbone extrusion and can be easily moved up and down in relation to each other. The vat because it is attached to a horizontal 1.5″ extrusion with carriage bolts can be slid “in and out” allowing for alignment with the projector and build plate. The projector mount is on a “shoulder and elbow” mount allowing for both height, lateral and rotational adjustments, it can also be moved in and out over a small distance by changing how it connects to the backbone extrusion. The tilt motor is mounted in a similar way to the vat which allows for in out adjustments. I have found in the past that if you make things as adjustable as possible one measurement or clearance mistake will not set back your project.

I’m a strong believer in the one big extrusion theory of building stuff. That is, get an aluminum extrusion and hang everything you need on it. My cnc router is built this way (It’s a cantilever design that gets it’s accuracy and rigidity from being built on a massive aluminum extrusion to which equally massive linear rails are attached), my robomagellan robot is also built this way. I am particularly fond of 1.5″ x 1.5″+ aluminum extrusions (series 15) , why, because 5/16th” carriage bolts from the local big box hardware store work perfectly for attaching things to those extrusions (the carriage bolt head and “square” are perfectly sized to the extrusions channel) and the hole at the center of the extrusion is also perfectly sized for tapping threads for 5/16 bolts. The major stuff on my printer build are held together/connected with 1.5″ aluminum extrusions and 5/16 carriage bolts I rarely use T nuts unless specifically called for. Also you may notice that I use a lot of polypropylene (which I machine on my cnc router) for structural parts, I use it because of availability but also because it is easily machined/sawed and in thick pieces (.5″+) it is structurally very strong (mdf would probably work well also). Also a neat trick to using a plastic like polypropylene (or mdf) is that when you use a 5/16″ carriage bolt through a 5/16″ hole the “square” on the carriage bolt seats into the plastic when a nut is screwed down and locks so that you can tighten and un-tighten the nut using only one wrench. My printer build uses a polaroid  mp4 photographic copy stand as the “backbone” extrusion for my printer build, why, because I had one, however, if I hadn’t had something like the copystand I would have probably used a 1.5″ X 3″ or a 1.5″ X 4.5″ extrusion for the backbone.

Next up:  z axis, build plate, vat and tilt mechanism



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