EMS (electrified monorail system) and power and free are the two most common overhead conveyor technologies in industrial production. They solve similar problems in very different ways.
The core difference: how carriers are driven
In an EMS conveyor, every carrier has its own electric drive and controller. Power and control signals come through a conductor rail built into the track. Each carrier can move, stop and change speed on its own.
In a power and free conveyor, a single chain runs continuously in the power track. Dogs on the chain push passive trolleys that run in a separate free track. A trolley stops when a mechanical stop disengages it from the chain.
Side-by-side comparison
| Criteria | EMS | Power & Free |
|---|---|---|
| Speed control | Individual and variable | Fixed chain speed |
| Positioning accuracy | High, suits automation | Moderate, uses stations |
| Accumulation | Software controlled | Mechanical, very economical |
| Cost per carrier | Higher (drive on every carrier) | Lower (passive trolleys) |
| Heat and harsh environments | Limited by onboard electronics | Well suited, including ovens |
| Noise and lubrication | Quiet, no chain lubrication | Chain needs lubrication |
| Re-layout | Easy to extend and re-route | More effort to change |
When to choose EMS
- Automated stations need precise, repeatable stop positions
- Different zones need different speeds, or work content varies by model
- Products must be lifted or lowered along the line
- The area must stay clean and quiet, such as final assembly
- You expect the layout to change in the coming years
When to choose power and free
- The line runs through pretreatment, paint booths or curing ovens
- You need long, low-cost accumulation buffers
- Loads are heavy and the line is long with many carriers
- A constant line speed fits the process
Combining both
Many plants use both: power and free through the paint shop and ovens, and EMS in assembly. Transfers between the systems hand over the product, and one control concept tracks it end to end. See our customized conveyor systems.
Next step
Send us your layout, product weight and target jobs per hour. We will recommend the technology and give a first concept. Contact our engineers.