Pancake motor from PMW helps digitise film heritage

pmw-film-transfer-pancake-motorThe increasing popularity of Ultra HD television is generating a growing
need for ultra high definition content. Fortunately there is a readily
available source in the millions of hours of existing 35mm film.

Transferring these many decades of film heritage onto digital media is a big
task, which has now been made easier by a new pancake motor developed by
Printed Motor Works for a state-of-the-art film scanner.

To guarantee faithful reproduction, the film has to be driven at a precise
and absolutely constant speed through the scanner’s optomechanical transfer
head. This requirement for precise speed control is very similar to that for
the tape drives once common in computer storage systems, and for this reason
PMW used the same type of pancake motor technology.

Its iron-free printed armature with over 100 commutator paths per revolution
enables it to produce no ripple or cogging torque, and it can maintain the
extremely smooth speed required across a very wide range of speeds.

The powerful motor can accelerate from stationary to top speed in less than
one revolution and can decelerate just as quickly. It can also run as
smoothly in either direction of rotation.

As with all PMW’s larger diameter motors, the company had to be certain it
could carry the load without the risk of shaft deflection causing touchdown
of the armature onto the magnets.

The shaft was therefore strengthened and the bearings supporting the radial
load were recessed within strengthened aluminium housings on both ends of
the motor. Bearings were chosen to a high specification fit and clearance,
and axial preload was increased to ensure positional accuracy under load.

The motor’s very low inductance also ensures long brush life due to the
absence of arcing during commutation.

This type of motor is suitable for a wide range of other applications
requiring rapid stop-start, zero cogging, low inductance, precise electronic
motor control, low thermal time constant or just an axially flat profile.

Printed Motor Works can be found at