Assembling resistors and capacitors requires extreme precision due to their small size

Rotary motor positioning requirements call for accuracy of ±0.1 degree or better. Rod runout must be less than 10 microns and the diameter of the motor must be less than 15 mm, and that is moving toward 8 mm. These demand constraints put pressure on motor and encoder manufacturers to improve their design and manufacturing methods. To meet demands, manufacturers can do several things: Improve the electrical design of the motor. This can be accomplished in a couple of ways. Use printed coil technology rather than winding coils using wire and electromechanical winders. Motor wire for these types of small motors is very thin, which makes precision winding a challenge. A printed coil is basically a flexible printed circuit. The “wire” is replaced by printed circuits on a strip. “Printed” wire is like square wire used in high-end speakers. The wire width and height are not tied to set gauge sizes, which means higher torques can be achieved, especially because speed is not critical. This strip is then wound and formed into a resulting coil. The process is very precise as it is essentially the same as that used in circuit boards. The coil resistance is very repeatable and, since there is no wire fed from a spool or tensioning to worry about, is a factor of 10 tighter than conventionally wound coils. A significant side benefit is greatly reduced cogging effect compared with that seen in conventionally wound brushless motors. A further benefit is that there is no special tooling cost. Circuit board manufacturing is highly automated, so the setup cost is built into the price of the board. It is also faster to get started as the time from design release to production is a couple of weeks.

SMAC uses printed coil technology for its rotary motors. The coil is basically a flexible printed circuit which requires no additional cost for tooling. Use molded soft laminations, which are rapidly replacing stacks of stamped lamination rings. Again, the effect on cogging and the cost of production are drastically reduced.