This is essentially a new design although it takes a lot of its heritage and style from Johan's Rostock design.
The most obvious change I have made are:
- to move the towers from 120° separation to 90° separation.
- to change from 8mm smooth rod and LM8UU to bearings running on a square stainless steel tube.
Moving the towers
The towers have been moved from the 120° separation used in Rostock. The Delta-Pi has the towers positioned 90° apart. This has its benefits and its drawbacks.
One benefit is that the build area becomes more square in shape instead of hexagonal or triangular. The result is that with the same arm length as the Rostock this design gives you a build area covering a full 205mm square and a 250mm diameter circle. The standard Rostock could not reach the corners of a 200mm square.
Aesthetically the Delta-Pi is cleaner with a completely open front. No front tower to get in the way of your viewing pleasure.
The downside shifting the towers is that the effective resolution is sacrificed slightly. Given the same steps per mm on the 3 towers the the Delta-Pi has about 50% larger steps in the x-y plane than the Rostock design. To compensate for that the design uses GT2 or S2M 20 tooth pulleys and 0.9° stepper motors.
Crossed-Roller Carriage Design
The other immediately obvious change is that the design does not use 8mm rod and LM8UU bearings. The Delta-Pi uses a live-loaded crossed-roller carriage design running on the corners of a 19mm square tube. The tube is a sanded finish stainless steel that should be easily available anywhere in the world. The carriage design contains 8 623ZZ bearings and another 2 are used for the idler pulley making 10 per tower and 30 total for the printer. The carriage design features a live hinge and spring beam that allows the bearing tension to be adjusted.
Current Project Status
As of 27 Jan 2013.
A prototype single tower has been built and tested and worked well. This resulted in a few design changes that have been done.
The design of all parts for the first full build is completed and the parts are printing. So this seemed like a good time to tell the world.
The design has been done using Solidworks and the source files will be published on GitHub in due course.
Assembly documentation, BOMs and drawings will be posted to GitHub too.
The STL files will be published to Thingiverse as soon as the prototype is successfully built.
Because the towers are arranged differently the Rostock firmwares will require modification to work on Delta-Pi. The changes are minor though and this will be my first priority once the prototype is built.