Cost-effective high-speed container capping

Is the lack of high-speed container capping a production bottleneck you could do without? SMAC manufactures a unique range of precision electric moving coil actuators. They are unique in that force, position and speed are programmable. Markedly, they operate and verify accuracy at the same time, then feedback the data to improve quality (for FDA approval).

Current technology

Most high-speed capping takes place on continuous motion equipment using a capping chuck with a clutch mounted on a vertical shaft. As the chuck moves around the dial, it spins as it meets a stationary friction band or surface. The chuck winds the cap onto the container as it travels down the vertical shaft. On reaching the approximate on-torque, the clutch disengages the chuck from spinning.

The height of the final cap placement is commonly checked downstream of the capping equipment. Here one sensor checks for the presence of the cap and another sensor checks its height does not exceed a set limit. Too high indicates not screwing the cap on all the way or cross-threaded. This design usually requires four sensors, a PLC and a stand-alone reject device. Alternatively, the inspection takes place with sensors on the capping dial, but this can be complex and more expensive.

A recent trend to reduce bottle packaging costs had been by reducing the height/profile of the cap. Unfortunately, this has complicated on-torqueing a cap and validating the off-torque to remove. Consumers have more problems removing lower profile caps and this increases customer dissatisfaction. It was a barrier for limiting the height of a cap until recent economic pressures forced manufacturers to push through this barrier. The combination of a low-profile cap and excessive torque to remove it may be enough to drive them away


Using a clutch and chuck is bulky and involves a lot of components and processes. This method has wide variations in on-toque forces and no off-torque validation. Clutches make it difficult to detect cross-threaded caps, needing inspection and reject equipment downstream. The design also needs manual adjustments to accommodate different size containers. This results in which equates to further downtime and lost productivity.

Innovative high-speed container capping

SMAC’s LAR Series linear-rotary actuators are ideal for improving capping quality. Moreover, they are cost-effective and provide 100% real time on-and off-torqueing validation. Built-in force, torque, speed and stroke control and feedback optimize the process without external sensors and checking stations. They also provide the flexibility to perform push-button changeover for different height containers.

Unlike a servo motor, each SMAC actuator contains both a linear axis and rotary axis in a single unit controlled by an easy to set up controller. All at a life-cycle cost less than the current approach.

Improved On-Torque Process

Each station on the dial has a SMAC linear-rotary actuator. The linear axis lowers the cap onto the container threads. As the rotary motion spins the cap onto the container, the actuator monitors both the torque and stroke. This validates that they both match the thread profile. Once the actuator detects a spike in torque associated with seating the cap or cross threading, the rotational motion stops.

Having torqued the cap on, the application of a small reverse torque indicated correct fitting for every cap. This reverse torque can be small enough to prevent damage to the tamper evident band. The cap is then rotated back to the exact position before the off-torque was measured.

Because of the built-in force, torque, speed and stroke feedback on each actuator, proper on-and off-torqueing are all performed and validated using the same SMAC actuator. All validation is on the dial and needs no extra downstream inspection station.

Difficult Capping Process
Because of the complete control of both the rotational and vertical axis, difficult to thread caps can be easily handled. The actuator first counter-rotates the cap until detecting the drop-in force associated with the start of the threads. Then the cap is rotated forward.

Benefits of precision electric moving coil actuators

– High speed direct electric drive with life expectancy of over 100 million cycles.

– Faster line changeover

– Reduces downstream inspection


See SMAC Cost-effective high-speed container capping on YouTube