CandyFab Mechanical Design

From CandyFabWiki

[edit] CandyFab 6000

The CandyFab 6000 is the current revision CandyFab hardware reference platform. (See also: RoadMap) The design is all new, and uses off-the-shelf parts wherever possible, e.g., for the motion control systems. Additionally, effort has been made to use components and materials that are accepted for use with food where possible and/or necessary. The structural design is based on high-end 6 mm plywood which can be cut to shape with a CO2 laser cutter.

The motion control systems in the three axes are based on servo motors and timing belts. The Z axis is driven by a single servo motor that drives a timing belt that turns four 3/8-12 acme screws to lift the piston. The X axis, which moves the Main Carriage, or Gantry, that includes the whole Y axis, is driven by dual timing belts on either side of the machine, which are in turn driven by a single timing belt from a servo motor. The Heater Carriage, which holds the heating element ("oven"), is attached directly to the a timing belt driven by a smaller servo motor. The Heater Carriage position is constrained by an off-the-shelf dust-resistant linear slide.

Most bearings in the CandyFab design are plain bearings made from high performance composite materials and are particularly immune to high-dust environments.

The build volume is 8.5" x 11" x 7" deep. A washable cotton "culinary" liner is used to provide a food-safe seal around the edges of the piston. Food-safe UHMW HDPE funnels (gutters) around the edge of the piston return unused media to a storage tray beneath the unit. Unlike the previous versions of the CandyFab, the CandyFab 6000 is designed as a "benchtop" fabricator, not a floor-standing fabricator.

[edit] CandyFab 5000

The CandyFab 5000 was the 2008 revision CandyFab hardware reference platform. (See also: RoadMap) The design was a complete departure from the CF4k, using new off-the-shelf parts wherever possible. Additionally, effort was made to use components and materials that are accepted for use with food where possible and/or necessary. The structural design was based on 1/2" plywood and 1/4" MDF which can be cut to shape with a CNC router. This design was abandoned late in 2008 due to manufacturing difficulties.

The motion control systems in the three axes were based on stepping motors and timing belts. The Z axis was driven by a single stepping motor that drives a timing belt that turns four acme screws to lift the piston. The X axis, which moves the Main Carriage, or Gantry, that includes the whole Y axis, was driven by dual acme lead screws on either side of the machine, which are in turn driven by a single timing belt from a stepping motor. The Heater Carriage, which held the heating element, was attached directly to the a timing belt driven by a smaller stepping motor. The Heater Carriage position is constrained by two linear shafts.

The build volume was 8.5" x 11" x 17". The piston walls were constructed of high-temperature UHMW polyethylene and the piston floor was topped with a gum-rubber surface that made a tight seal against the four walls.

[edit] CandyFab 4000

The CandyFab 4000 was the first prototype CandyFab machine, which launched the CandyFab Project. It was built in a garage by the Evil Mad Scientist Laboratories staff between August 2006 and May 2007.1 The X and Y axis motion control systems were taken from old HP pen plotters, where the original industrial servo motors in those axes were controlled to drive the motion. The Z axis drive was a modified automotive jack, where the position was encoded by a 10-turn potentiometer. The structure itself was constructed of plywood, 2x4's and other basic lumber, and was built primarily with a jig saw and a hand drill.

The build volume of the CandyFab 4000 is 24 x 13.5 x 9 inches (61 x 34 x 23 cm). In order to contain the sugar, a flexible canvas liner was constructed that included a pleated piston area (that unfolds as the build progresses).

Weaknesses of the CandyFab 4000:

• Constructed from surplus parts-- cannot easily be reproduced without finding old HP plotters.
• The X-axis (which moves the Y carriage) is controlled and constrained on one end only, which leads to significant backlash and slight deviation from square fabrication.
• Excessively large floor footprint