The Use of Frequency Drives for Smooth Control in Bottling Machinery

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A device on the conveyor is only worth its cost if the line stops when it stops, or the defect rate rises when it is off. The ability to program complex sequences and logic functions in the PLC allows for efficient communication with the VFDs, enabling precise motor control and optimal performance throughout the bottling line.
Key facts at a glance
What is includedPrinters, coders, cap feeders, nitrogen dosers, detectors
FunctionSupport the filler without changing its rating
Key controlPosition, timing, consumable cost
IntegrationSignals from the filler PLC or a standalone sensor
Key decisionWhether the device earns its cost per 1,000 units
Typical positionAfter the filler, before the packer

Where does it sit in the line sequence?

Position follows the signal. A coder needs the bottle presented at a fixed gap; a cap feeder needs a buffer before the capper; a detector needs a clear view and a reject gate downstream. Moving any of them changes the timing and the reject logic.

The ability to program complex sequences and logic functions in the PLC allows for efficient communication with the VFDs, enabling precise motor control and optimal performance throughout the bottling line.

What consumable cost does it add per 1,000 units?

Ink, solvent, laser power, nitrogen, caps and labels all carry a per-unit cost that does not appear in the machine price. A device with a low purchase price and a high consumable cost can be the most expensive item on the line over five years.

By gradually increasing or decreasing the motor speed, VFDs prevent sudden torque spikes that can damage equipment and lead to costly repairs.

DeviceWhat it controlsConsumable
Coder or printerDate and batch codeInk, solvent or laser power
Cap feederCap supply to the capperNone, but a buffer is needed
Nitrogen doserHeadspace oxygenNitrogen per 1,000 units
Fill level detectorReject decisionNone, but a reject gate is needed

Rated output, change parts and services are listed on the Accessory page.

How is it integrated with the filler?

Either through a discrete signal from the filler PLC, which is simple and reliable, or through the line network, which allows recipes and reporting. Discrete signals are easier to commission; network integration is easier to audit. Choose based on who will maintain it.

By connecting VFDs to PLCs, bottling plants can achieve a high level of synchronization and coordination between different stages of the production process.

The specification sheet for the Conveying carries the figures quoted here.

How is a coder synchronised with the conveyor?

Through an encoder on the conveyor, so the print position follows the actual speed rather than a set value. Without the encoder, the code stretches when the line accelerates and lands off-centre.

The same question is worked through from another angle in Cap and Fill Level Detection: What the Camera Checks.

What does a cap sorter need to run reliably?

A consistent cap, a correct chute angle and a hopper that is never empty. Most cap jams are the chute and the level, not the sorter. A low-level sensor that stops the line before the hopper empties prevents most of them.

How to read the numbers. The BPH figures quoted are reference ranges on the product specification. Setup, adjustment and upstream stops sit outside a rated rate, so plan on 0.65-0.85.

Frequently asked questions

Does a nitrogen doser increase line speed?

No. It does not change the filler rating. It reduces headspace oxygen, which protects shelf life. Its value is measured in shelf life and rejects, not in BPH.

Why does a cap feeder run out?

Because the hopper is sized for a shift rather than for the line rate, or because the elevator runs slower than the capper consumes. Size the hopper on caps per minute at the filler rating, with margin.

How does a laser coder differ from an inkjet coder?

A laser marks the surface and needs no consumable ink, but it needs a clear line of sight and a consistent bottle position. An inkjet prints on most surfaces and carries ink and solvent cost.

Why does a cap feeder jam?

Caps arrive out of orientation, the elevator runs faster than the chute can release, or the chute angle is wrong for the cap. Most jams are a chute and speed setting, not a cap defect.

Does a fill level detector need a reject gate?

Yes. Detection without a reject gate only records the defect. The gate needs a shift register so it rejects the bottle that was measured, not the one behind it.

Key takeaways
  1. Support equipment removes a task or a defect; it does not add capacity.
  2. Position follows the signal path, not the convenience of the layout.
  3. A device without a reject gate only records the defect.
  4. Consumable cost per 1,000 units belongs in the comparison.
About the author
Written by the Sunswell engineering team - led by Howie SUN, Founder & CEO, with 14 years in filling and blow-moulding equipment R&D and turnkey project delivery across 71+ countries.
Last reviewed: 2026-08-28 . Reviewed by Sunswell engineering team
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