Power Transmission

From CandyFabWiki

The CandyFab mechanical design employs a few different means of transmitting kinetic energy from the motors to the actuators that they control.

[edit] Lead Screws

A lead screw with a nut converts rotary motion of the screw into linear motion of a nut on the screw that is not free to rotate. While lead screws are not particularly power efficient, they are a very common and low-cost technology. The CandyFab 5000 uses plain steel 1/2-10 Acme lead screws in cases where lead screws are needed. Acme thread is a relatively coarse and well-controlled thread design with low to moderate friction and backlash. The thread shape on both the screw and nut is a clean trapezoid. For applications requiring high transmitted power, acme screws are usually operated greased or oiled. For low-power applications such as in CandyFab, greasing the screw may provide more friction than benefit. Although a bit more expensive, a good alternative may be to use a plastic nut and a teflon-coated lead screw.

The much more expensive but more power efficient alternative to the standard lead screw is a ball screw and nut.

[edit] Timing belts and pulleys

A timing belt efficiently transmits synchronized rotary motion between two or more shafts that have timing pulleys mounted on them. It can also be used to convert rotational motion to linear motion by clamping an actuator ("carriage") to the belt at a fixed point.

The CandyFab 5000 uses open-ended MXL (0.080" pitch) timing belt for the Y axis drive. The two acme lead screws for the X-axis drive are synchronized by a timing belt, and the Z axis lead screws are also driven by a timing belt. The X and Z timing belts are endless XL (0.200" pitch) timing belts; the Z axis belt is double sided.