Considerations for Choosing the Right Capping Technology
Bottle capping machines basically come in two categories: inline cappers and rotary chuck-style cappers. These two machines differ from each other in their core designs, as well as in the techniques they apply for closures, such as torque control and the use of a magnetic brake.
Inline capping machines have side gripping belts that grip the outer edges of the bottles that travel along the conveyor. The gripping belts are speed-matched to the conveyor so that no bottle escapes. As the bottle passes under the cap dispenser, a cap is stripped out by its neck finish. Then, a series of cap tightening wheels spin the cap onto the threaded neck finish as the closure resting on the finish passes through them. Finally, a pair of wheels equipped with friction clutches delivers the desired torque to the capped bottle. The bottle, now tightly capped, is released from the gripping belts.
Rotary chuck-style capping machines
Rotary chuck-style capping machines have what is called a cap transfer device, which picks out the cap chute and places it in the capping head’s capping chuck, or gripping chuck, if you like. There are two types of pick-and-place mechanisms: a rotary star-wheel with pockets or individual pegs associated with each capping head station.
An in-feed timing screw separates the bottles traveling on the conveyor to match the capping head’s pitch and then transfers them to an in-feed star wheel. They are then transferred to the turret star wheel and placed directly under the capping heads. Then, a rotating capping head holding a cap in its gripping chuck applies the cap to the desired torque. Each capping head has a magnetic clutch that controls the torque. After the cap is applied, the bottle is then released and transferred to the exit conveyor.
That was a brief description of how bottle capping equipment works. Now, let’s talk about the considerations that should be made when choosing the right capping technology for your application.
A list to consider
Inline capping machines are much less costly than rotary chuck-style capping machines.
The cost of additional change parts:
Inline capping machines have a lower cost for additional change parts that are required to run different sizes of closures and containers. The cap handling equipment consists of only three parts: a sorter, a chute, and a dispenser. There are no cap transfer mechanisms or individual chucks. Changes in cap diameters are made by adjusting the spacing of the tightening wheels.
Inline capping machines take less floor space than rotary capping machines.
This is where chuck-style capping machines beat inline capping machines hands down. They are faster — a lot faster, actually. Chuck clappers use as many as 40 heads and are able to achieve speeds of up to 1,200 bottles per minute (bpm). In comparison, inline cappers have a maximum speed of 200 bpm.
The diameter of the cap that inline cappers can use ranges from 28 millimeters to 70 millimeters. Inline cappers work best with closures of a diameter smaller than 53 millimeters. Rotary cappers, on the other hand, can be used for caps of any diameter since they provide 360 degrees of contact with the cap’s sidewalls. Additionally, they have machined pockets to help maintain the round shapes of the bottle’s neck finish.
Inline cappers are good for round-shaped caps only. Rotary chuck-style cappers can be used for any cap shape: round, oval, square, rectangular, tapered, and reversed tapered.
Rotary chuck-style cappers have precision torque mechanisms, which allows them to apply torque far more accurately than inline cappers, especially in narrow range applications.
Since inline clappers rely on the neck finish to pick off the cap from the cap dispenser, they are limited to caps that are easy to pick off. Rotary cappers have no such limitation.
Since inline cappers have only side gripping belts they can rely on to keep the container from rotating while applying a cap, there are greater chances of faulty capping. Rotary cappers have no such problem.
Tamper Evident (TE) bands:
Rotary cappers have a huge advantage when it comes to applying closures with Tamper Evident (TE) bands.
Thus, as you can see, rotary chuck-style capping machines have many advantages over inline capping machines. However, if inline cappers can serve your purpose, then you should use them. Lastly, make sure a bottle capping machine has passed a tork test before buying it. Call us, we’d love to answer any questions.