• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Skip to footer

Motion Control Tips

Automation • Motion Control • Power Transmission

  • News
    • Industry News
    • Editor Blogs
    • Video
  • Controls
    • HMIs
    • PC-Based Controllers
    • PLCs + PACs
    • Stand-Alone Controllers
    • Software
  • Drives
    • Servo Drives
    • Stepper Drives
  • Encoders
    • Absolute Encoders
    • Incremental Encoders
    • Rotary Encoders
  • Mechanical
    • Bearings
    • Brakes + Clutches
    • Belt + chain
    • Couplings
    • Gears + Gearing
    • Lubrication
    • Shock + Vibration Mitigation
    • Springs + Rings + Seals
  • Linear
    • Actuators
    • Linear Motors
    • Linear Encoders
  • Motors
    • AC Motors
    • DC Motors
    • Brushless Motors
    • Gearmotors
    • Piezo Motors
    • Servo Motors
    • Stepper Motors
  • Systems
    • Conveyors + linear transport systems
    • Gantries + Stages
    • Rotary Tables
    • Grippers + End Effectors
    • Robotics
  • Networks
    • Connections + Sliprings
    • Fieldbuses
    • I/O
    • Sensors + Vision
  • FAQs
    • Motion Casebook
    • Motion Selection Guides
  • Suppliers
You are here: Home / FAQs + basics / Power and free conveyors: Where do they excel?

Power and free conveyors: Where do they excel?

September 11, 2018 By Danielle Collins Leave a Comment

Power and free conveyors are designed for manufacturing environments where products need to be transported in a non-linear fashion — that is, where materials aren’t necessarily delivered in the order they were loaded or at the same pace. Traditional “linear” conveyors, on the other hand, lack the flexibility to handle manufacturing environments where different production processes run at different cadences or where various materials have different flow paths.


Because of their flexibility in handling and delivering products, power and free conveyors are also referred to as “asynchronous” or non-linear conveyors.


The defining feature of a power and free conveyor is that it consists of two tracks — an upper track and a lower track. The upper track is powered by a chain, and the lower track is unpowered. Trolleys, which carry the load, run on the lower track, supported by rolling wheels. Mechanical devices — often referred to as pusher dogs — on the powered track engage with the trolleys to move them and disengage with the trolleys to stop them.

The pusher dogs are engaged and disengaged by cam action caused by a trolley in front or by a stop blade positioned along the powered chain. Air-activated stops, triggered by switches, can also be used to control the movement of trolleys.

power and free conveyors
In a power and free conveyor, the upper track is powered by a chain and the lower track is unpowered. Trolleys (two of which are shown here) ride on the lower track and are driven by devices on the powered track called “pusher dogs” that engage and disengage with the trolleys. Image credit: Cisco-Eagle

Much like cars on a road, conveyor “traffic” can also be merged or diverted among multiple conveyor lines, and both sharp turns and elevation changes can be executed. And unlike traditional linear conveyors, power and free versions can allow products to accumulate, or “stack up” by holding trolleys stationary while other trolleys “catch up” and join them. The trolleys can then be released in the required sequence. All of this is accomplished through mechanical linkages via the pusher dogs and trolleys, without requiring complex automation.

To maximize space, especially during accumulation, trolleys can be connected via rigid load bars that set the spacing between trolleys at as little as 6 inches (depending on the size and shape of the load). And storage density can be maximized with trolleys that hold the load diagonally relative to the conveyor path.

power and free conveyors
Trolleys positioned diagonally can maximize space and increase storage density. Image credit: Ultimation Industries LLC

Circuits of conveyors up to 300 feet can be controlled with just one motor, and complex “traffic” patterns and timing sequences can be controlled via sensors triggered by a PLC or PC-based controller. In addition, bar codes or RFID tags on the trolleys can be used to identify individual loads and carry instructions for sequencing.


This video from Caldan Conveyor A/S demonstrates how power and free conveyors work, including their ability to accumulate, stage, merge, and divert products.


While most power and free conveyors are mounted overhead, above the working area, and carry products below the tracks, floor-mounted designs are available that carry the product above the tracks. This is especially useful when overhead space is a concern, or when potential contamination from the conveyor or product is an issue, as is often the case in cleanroom environments. And when overhead space is limited but floor-mounting is not an option, some manufacturers offer overhead versions with powered and non-powered tracks positioned side-by-side, rather than in a top-and-bottom configuration.

power and free conveyors
A floor-mounted power and free conveyor is useful when overhead space is limited, or when contamination from the conveyor or the product is an issue. Image credit: Richards-Wilcox

Power and free conveyors are custom-designed for each application and can carry loads from just a few pounds to several hundred pounds. They’re used extensively in the automotive industry, where robot cells are sometimes used to load/unload products from the trolleys or to perform work on the parts being conveyed as they’re held stationary. And power and free designs are available in heat and corrosion-resistant versions, so they can transport loads through processes such as washing and painting or through ovens.

You may also like:


  • Conveyors with backlighting + robotics automate outlet production

  • 12 Motion Trends articles offer engineering insight and technical 411

  • Top five conveyor trends — including new materials, drives, and…

  • Brakes and clutches: Top trends in IoT — and uses…

  • Customizing conveying systems: Review of options for pallet conveyors

Filed Under: Conveyors + linear transport systems, FAQs + basics, Featured

Reader Interactions

Leave a Reply Cancel reply

You must be logged in to post a comment.

Primary Sidebar

MOTION DESIGN GUIDES

“motion

“motion

“motion

“motion

“motion

POWER TRANSMISSION REFERENCE GUIDE

RSS Linear Motion Tips

  • Haydon Kerk Pittman launches compact Z-Theta motion platform
  • Three easy ways to specify application requirements for linear motion systems
  • Sourcing linear motion solutions from NSK’s global manufacturing sites
  • Ride the wave of electrification: Off-highway designs with linear actuators
  • What are capacitive sensors and where are they used?
Subscribe Today

RSS Featured White Papers

  • Identifying Best-Value Linear Motion Technologies
  • Learn how to reduce noise and distortion in encoders’ signals
  • Helical Planetary Gearboxes: Understanding The Tradeoffs
Tweets from https://twitter.com/Motion_Control/lists/motion-control-tweets

Footer

Motion Control Tips

DESIGN WORLD NETWORK

Design World Online
The Robot Report
Coupling Tips
Linear Motion Tips
Bearing Tips
Fastener Engineering

MOTION CONTROL TIPS

Subscribe to our newsletter
Advertise with us
Contact us
About us
Follow us on TwitterAdd us on FacebookAdd us on LinkedInAdd us on YouTubeAdd us on Instagram

Copyright © 2021 · WTWH Media LLC and its licensors. All rights reserved.
The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media.

Privacy Policy | RSS