The twin-strand pallet-transfer conveyor has long been the go-to transfer system for asynchronous automated assembly lines. But, it’s not the only game in town.

In some cases, flexible chain conveyors, like the modular VarioFlow plus from Bosch Rexroth, are a better alternative for transporting small assemblies or moving larger objects over complex routes or through limited-space environments.

The VarioFlow plus employs a single strand of flat-top chain to convey a puck or pallet or to directly support a workpiece, box or tote. While these systems don’t offer the same inherent positional stability as their twin-rail counterparts, they can be equipped with guide rails to keep product in position.

A major advantage of the VarioFlow plus is its ability to transport product up and down inclines and to negotiate sharp turns, both are a plus in settings where space is an issue. These durable systems are also fast. The belts can travel 60 feet per minute in some applications. High-performance variable-speed drives allow for maximum efficiency in operation and reduce energy costs.

The motor mounting position can be selected on-site. Smart connection technology saves time during assembly and allows for easy conversions and system extensions. Slide rails with lateral mounting minimize wear and ensure reliable assembly and quiet operation. Ascending and inclined conveyor sections can easily be built thanks to a holder with centering lugs. Reversible operation is possible.

The conveyor is available in a basic aluminum version and a stainless steel model for applications with higher hygiene demands. The conveyor comes in six standard widths: 65, 90, 120, 160, 240 and 320 millimeters.

Conveyor components subject to constant friction are made from FDA-compliant materials. Stainless steel ball bearings are sealed on both sides and lubricated with special FDA-compliant grease.

A variety of chains are available to suit different applications. Improved sliding characteristics and low-friction materials result in a quiet working atmosphere. Fewer joints and rolling friction in the horizontal curves ensure low wear and reduce downtime. Chains are available with tensile strengths of 1,250 newtons.

Gray conveyor chain is mainly used to transport products via metal pallets. The gray color hides any marks that might be produced by rubbing against the pallet. Cleated chain or static friction chain are used to transport products on ascending or descending sections. Roller chain is for horizontal applications requiring accumulation.

Assemblies can ride directly on the chain or on a puck or pallet. Pucks are pallets are needed when:

  • The product has no static stability due to its geometry.

  • Transport can cause a change in position of the product.

  • The process requires it.

  • The product surface is sensitive.

  • Accumulation is required and the product geometry does not allow for accumulation.

  • Exact positioning of the part is required.

  • The process is controlled via an automatic identification system.

Pucks or pallets can be supplemented with an RFID system for identification, data storage and material flow control. Standard pallets are available in widths of 135 and 160 millimeters and any length up to 500 millimeters. The conveyor can position pallets with an accuracy of ±0.15 millimeter.

If products are transported directly on the chain, it’s important that the center of the product is as close as possible to the center of the chain and that it has high inherent stability.

To simplify conveyor module selection and layout, engineers can use MTpro planning software to quickly select components, design single- or multi-conveyor systems, and output the results to a CAD file.

In the end, deciding between a twin-strand conveyor and a single-chain system comes down to precision. A single-chain system like VarioFlow is good at moving product, but it doesn’t offer the same precision that can be obtained with a dual-rail approach. The reason for this is that, in a twin-rail system, the locating station can actually engage the pallet from below with the help of mechanical stops and locating pins. This kind of precision isn’t possible when engaging a pallet from the sides, as is necessary when using a single chain.

For more information on VarioFlow plus, visit