Two quotations land on the same desk: one speed chain line, one powered roller line. Both meet a twelve-second takt on paper. What separates them is what happens between cycles, not during them.
Where the two types actually differ
Both conveyors index a carrier from station to station. A speed chain line runs a continuous chain under the carriers and engages a dog or a friction block to move them. A powered roller line drives rollers that carry a pallet or a fixture plate by friction. Until the carrier has to stop precisely, both behave the same.
The difference appears at three points: how the carrier is located at the station, how parts accumulate when a station is blocked, and how much of the line has to be rebuilt when the product changes.
Fixture repeatability
Speed chain lines position the carrier with a locating pin, a stop gate or a lift-and-rotate unit. Repeatability of plus or minus 0.3 mm is normal, which matters when a robot, a screwdriver spindle or a test probe has to engage the part without adjustment.
Roller lines locate the pallet against a pop-up stop or a centring unit. Repeatability is typically plus or minus 1 mm, and it drifts as rollers wear and as pallet bottoms pick up swarf. For manual assembly this is irrelevant. For automated fastening, vision or test probing, it becomes the constraint that forces a secondary locating station.
Accumulation behaviour
Speed chain lines accumulate with free-flow or low-pressure zones. Carriers queue without touching, which protects painted or plated parts. The chain keeps running, so the drive does not stop and start with every blockage.
Roller lines accumulate in zones with photoeyes and either zero-pressure or minimum-pressure logic. Zone length is fixed by the roller pitch and the sensor positions, so a pallet shorter than the zone leaves gaps that the logic has to tolerate. A pallet longer than the zone will straddle two zones and can be pushed by two drives at once.
For high-mix production the practical question is whether all variants fit inside one zone length. If they do not, the roller line needs either a longer zone or a different sensor arrangement.
Changeover and future models
This is where the cost difference usually reverses. A speed chain line carries fixtures that are product-specific. A new model means new fixture plates, new locating pins and sometimes a new station pitch. If the pitch changes, the chain and the station bases change with it.
A roller line carries pallets. A new model often means a new pallet top and a new fixture insert, while the conveyor stays untouched. Stations can be added or moved because the conveyor is modular and the drives are distributed.
| Criterion | Speed chain | Powered roller |
|---|---|---|
| Positioning repeatability | 0.2 to 0.5 mm with a locator | 1 mm, needs a lift-and-locate for automation |
| Accumulation | Free-flow, low back pressure | Zone logic, depends on pallet length |
| New model changeover | New fixtures, sometimes new pitch | New pallet top, conveyor unchanged |
| Heavy or hot parts | Limited by chain and wear strip | Limited by roller and bearing load |
| Line extension | Chain and frame must be re-tensioned | Modules bolt on, drives are local |
| Relative cost at 30 m | Higher | Lower by 15 to 25 percent |
The decision rule we use
- If the product is automated at two or more stations, start with a speed chain line and a locating unit.
- If the product mix changes more than once a month and the fixtures are simple, start with a roller line and pallets.
- If parts are heavy, hot or oily, neither is ideal; check chain plate or overhead before committing.
- If the line will be extended within three years, price the extension before choosing, not after.
What the quotation should state
Ask both suppliers for the same four numbers: positioning repeatability at the station, accumulation back pressure, the fixture cost per additional model, and the time to add one station. A quotation that omits these is comparing price, not capability.
On most high-mix electronics and appliance projects we specify a speed chain line for the automated core and a roller section for manual sub-assembly and packing. The hybrid is usually cheaper than forcing one technology across the whole floor.
Frequently asked questions
Can a roller conveyor hold a 12-second takt?
Yes, if the index time is under three seconds and the pallet is positively stopped at each station. Roller lines lose time in deceleration and in stop-gate release, so the practical limit is around eight seconds unless the stations are close together.
Does a speed chain line need more maintenance?
It needs chain lubrication and tension checks, typically monthly, plus wear-strip inspection every six months. A roller line needs bearing checks and roller replacement, which is easier to do but happens more often on dirty products.
