Delta-Pi

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Delta-Pi

Release status: Working Prototype

Overall Assy1.JPG
Description Delta-Pi is a Rostock style Delta printer with a new carriage design.
License GPL
Author MikeP-NZ
Based-on Rostock
Categories Delta
CAD Models GitHub
External Link


Contents

Introduction

This is essentially a new design in that it does not reuse any parts from an existing design. It does however take a lot of its heritage and style from Johan's Rostock design. A huge thanks to all of those whose hard work, knowledge and innovation have brought things this far. Now I hope that I can add my own little increment to the development of the Reprap concept. Mike Paauwe

History

The first iteration of this machine featured the vertical towers separated by 90° instead of the normal 120°. The reason for this was that it gave a better shaped build area. The build area was more square than hexagonal or triangular. After building the prototype it became obvious that the concept was seriously flawed. In theory the three towers kept the centre platform fully constrained but in practice the platform was relying on the torsional stiffness of the arms whenever one set of arms was near horizontal. The result wasn't really usable over a large portion of the intended build envelope. So the 90° tower angles were dropped and the design reverted to being a more standard Rostock Delta style 3D printer.

Design Changes

Photo of the prototype after completing its first ever print
Close-up of prototype carriage showing live hinge, spring beam and a couple of the 623ZZ bearings visible
Hot end platform with a variant of the Kiss hot end and fan cooling
Another view of the carriage design.

Crossed-Roller Carriage Design

The 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 3/4"/19mm or a 20mm square tube. The tube is a sanded finish stainless steel that should be easily available anywhere in the world. The carriage design contains 8 pieces of 623ZZ bearing and another 2 pieces 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. The inside of the tubes is open so that it can be used to run wires between the top and bottom of the printer.

Arm Design

The arm design has been changed slightly from the Rostock design. The arms use a 6mm carbon fibre tube and the tube is glued inside a clevis. That's not too different but the yokes at each end of the arm assembly are intended to simplify assembly and reduce the number of fasteners required. It also give a larger range of motion than the commonly used ball joints.

Belt connection

The belt can be either S2M or GT2 belt and is 6mm wide. The belt is connected to the carriage by looping a short length back on itself. The belt teeth interlock and a small piece of rod (3mm filament) stops the loop from pulling out. The belt is tensioned by moving the stepper motor.

Design Files

The design has been created using SolidWorks and the source files have been published on GitHub.
Assembly documentation, BOMs and drawings are hosted on GitHub.
github.com/Makershop/DeltaPi
The STL files for printed parts are published on Thingiverse:
www.thingiverse.com/thing:53708

Firmware

The prototype was originally run using the Marlin firmware and later switched to the Repetier firmware.

Current Project Status

As of 6 January 2014. After a lengthy hiatus there has been some progress. The prototype now incorporates the E3D hot end and a derivative of the Air Tripper filament drive. I attempted to incorporate the bed leveling probe and switched to Marlin firmware briefly. It worked but not as well as I hoped so I've changed back to Repetier F/W.

Known Issues

  • The bowden extruder used in this setup can make prints a little stringy if retracts are slow.
  • Calibrating the delta geometry can be "tricky".
  • Any play in the linkages makes operation very noisy and detracts from the positioning accuracy. This could be a problem as the printer ages and wears.

External Links

Photos of the prototype here:on flickr.com
Video of the prototype here: on YouTube