Automated product filling and packaging require conveyor systems that provide precision product placement. Although traditional flat-belt conveyors can deliver some degree of precision placement,
they are a poor choice for managing product accumulation, such as is required for staging and spacing
product into these automated systems. The result is product jam ups, product damage, misfires on
wrapping, wasted packaging materials such as shrink wrapping film, and resultant line slowdowns and
Fortunately, the solution for effectively managing product staging and spacing, and eliminating these
production line difficulties comes in the form of smarter roller technology. One system in particular
which is in broad use, and has been in a continual state of refinement over the past several decades, is
called Slip-Torque®, which was developed by Shuttleworth.
Slip-Torque is very interesting, in that it utilizes individually-powered, stationary rotating roller shafts
covered with loose, segmented rollers, which become the conveyor surface. It is powered by a
continuous chain to control the drive force of the conveyed products. When the products stop on the
surface of the conveyor, the segmented rollers beneath them also stop, generating low back-pressure
accumulation, and minimizing product damage. It is the weight of the product being conveyed,
combined with the coefficient of friction between the shafts and the inside diameter of the rollers that
provides the driving force. As the weight of the product increases, there is a corresponding increase in
the driving force supplied.
Slip-Torque’s low line-pressure provided throughout the continuous-motion accumulation conveyor
allows for precise product placement on the conveyor while it continues to take product flow from an
upstream line for a period of time, where other conveyors would have stopped well before. A lowpressure
accumulation buffer absorbs irregularities in the production flow and provides a smooth, even
flow on the line.
The system allows the same conveyor to be split into multiple, independently-operating lanes if desired.
For example, the middle lane can accumulate, while at the same time the right lane and the left lane can
both convey, or even run in opposite directions. Each lane can act independently, but is powered by
only one common motor, which also reduces energy costs.
Conveyors with Slip-Torque have the ability to modulate the speed of different sections of the conveyor
via a central control PLC and HMI. As products are moving down the line, the rollers at the back end of
the conveyor can be moving faster than the ones at the front end of it. The products can be moving at
variable speeds on different sections of the conveyor as dictated by throughput requirements. This
controls the product spacing on the conveyor, keeping items such as delicate cheesecakes or fragile
pharmaceutical products separated, and equally spaced, from each other to minimize product contact
and facilitate infeed into packaging equipment such as shrink wrappers.
Such motorized rollers like Slip-Torque can also be used to minimize product contact while steering
products into desired locations, such as employing rollers with herringbone patterns to orient products
without the use of guardrails, or setting up a series of sequentially smaller roller heights to direct food
products into the center of the conveyor for packaging induction, without touching any other conveyor
parts. And motorized rollers with tapered corners can be used to maintain product orientation, gently and safely, as it is transported through 45-degree and 90-degree conveyor turns.
Slip-Torque technology can be used in elevated temperature applications such as hot products coming
out of ovens up to 500° F (260° C) and in low temperature applications as low as -20° F (-29° C) such as
for refrigerated and frozen foods and pharmaceuticals.