Packaging Glossary: 36+ Technical Terms for Cappers and Caps

Packaging technical dictionary, alphabetically ordered. Each entry has a practical definition, production-line context and, where applicable, a link to the blog article that goes deeper into the problem. Use the index below to jump straight to the term.

Anti-Rotation Insert

Rubberized or textured part mounted on the star-wheel rear guide that holds the bottle against rotation while the head turns the cap. Without it, the bottle would spin with the cap and the cap would not thread.

The rear guide should be 1 to 1.5 mm below the inserts. Worn inserts, contaminated with oil/grease, or worn anti-rotation bases/belts are a frequent cause of under-application.

Application Angle

Degree of cap rotation until full application onto the finish. It is a tool complementary to torque for evaluating seal integrity. The big advantage is not being influenced by friction — it is a mathematical conversion of rotation into vertical movement, based on known thread pitch. That makes the angle a more consistent measure than torque alone.

Typically measured with a 360° graduated protractor fitted over the cap. For continuous thread on 28/38 mm, the final reading adds +360° (one full turn). See the detailed 7-step procedure.

Bottle Finish

Upper threaded region of the bottle neck that receives the cap. Includes the external thread, the sealing surface (top of the neck), the lock ring (where the tamper-evidence band engages) and the support ring (used by transport stars).

Common finish defects: misalignment, dimensional excess (verified with "go/no-go" gauge), parting-line flash, microcracks in the sealing zone.

Broken Band

Cap with complete horizontal band separation before consumer use. The tamper-evidence band ruptured all the way around during application or transport. The symptom compromises the band's primary function (showing the package was opened) and typically stems from excessive vertical load, high sorter speed, or cold caps. Full diagnosis here.

Cap In Head (C.I.H.)

Capping system where the cap enters the head directly, retained by a ball ring with O-ring. Transfer of the cap to the head happens through a transfer plate synchronized with the turret. Advantages: mechanically simple design, fewer moving parts outside the head, maintenance concentrated on a few components.

Exclusive C.I.H. defect causes: misadjusted transfer plate, worn balls/O-ring, broken ejector pin spring.

Cap Pallet

Cap storage and transport unit, typically cardboard boxes stacked on a wooden pallet. Storage rule: cap pallets must not be stacked more than 2 pallets high — weight compresses the lower caps, deforming bands and causing systematic defects when the lot reaches the line.

Cap Sorter

Equipment upstream of the capper that receives bulk caps, orients them in the correct position (thread down) and feeds the down chute. Comprises reservoir, sorter disc, misoriented-cap ejection system and feeder (Jet Flow or similar).

Ideal speed: 22-25 rpm for up to 8 heads, 28-30 rpm above 8. Cap level in the reservoir between 1/4 and 1/3 of capacity.

Capping

Industrial process of applying a cap on a package (bottle, jar, container) to close it hermetically. On high-speed packaging lines, it is done by rotary cappers with multiple heads in parallel. Critical variables: static torque, vertical load, turret position, star wheel sync. The two dominant systems are C.I.H. (Cap In Head) and P.O. (Pick-Off).

Capping Head

Main capper component that applies the cap onto the bottle. Combines vertical movement (vertical load) with rotational movement (torque) to thread the cap. Each capper has multiple heads — typically 6 to 16 — mounted on a rotating turret.

Modern models use magnetic coupling (Magna Torq) to control static torque without mechanical clutches. The head includes chuck, spindle, spring, and in C.I.H. systems, the ejector pin and ball ring.

Chuck

Capping-head component that receives the cap and transmits rotational torque. Has internal splines that grip the cap shell (at the external thread height). Wrong chuck for cap type or worn splines generates multiple defects: under-application, cocked cap, bottle without cap.

Practical test: if a chuck is suspect, install it in another head — if the defect follows, that's confirmation.

Cocked Cap

Cap applied tilted on the finish, with thread roots deformed toward the liner. Causes leakage. 17 causes at the capper, 3 at the bottle, 2 at the cap.

Cocked Closure

Technical term for a tilted cap — applied at an angle on the finish, causing leakage. Diagnosed by the thread deformation pattern: deformation toward the liner indicates tilt at the moment of application. See the complete diagnosis with 17 capper causes.

Continuous vs Multi-Start Thread

Cap thread can have 1 start (continuous) or multiple starts (2 or 3). Continuous is the traditional — a single helix covering the circumference. Multi-start has 2-3 parallel helices, enabling cap application in a fraction of a turn (180° or 120° instead of 360°+).

For application-angle control, multi-start requires extra care: when removing the cap for measurement, maintain the correct pairing between threads, or the reading will be incorrect.

Graduated Protractor

Application-angle measurement instrument. Disc with 10° graduations and a splined central hole sized for the specific cap diameter under analysis. Reading precision close to 5°. Combined with marker pens (blue and red), it enables the 7-step procedure to measure the angle. Procedure here.

High Cap

Cap stopped above the sealing point — cannot be hand-threaded on the finish (opposite of under-application). The liner does not touch the sealing surface. Immediate leakage. Causes: wrong cap for the finish, bottle finish out of spec, excessive vertical load. Complete diagnosis.

Incremental Torque

Difference between peak removal torque and the "plateau" torque after the band breaks. Indicator of tamper-evidence band integrity: very low increment suggests fragile band; very high suggests band that does not break correctly.

Jet Flow

Air-jet feeding system that pneumatically transports caps from the reservoir to the sorter. Air carries the caps through curved tubing. Advantages: high speed, low mechanical maintenance, continuous flow.

When Jet Flow has excessive flow, it creates defects: caps that hit the channels with force and break bands. The fix is to reduce the flow to the minimum possible without affecting feeding.

Liner

Internal sealing material of the cap in direct contact with the finish sealing surface. Typically a soft polymer (TPE, PVC, foam) injected or pre-formed in the cap. When the liner is incomplete, missing, deformed or in excess, it causes leakage (when missing) or high torque (when in excess). It is the cap component where factory defects appear most often.

Magnetic Capping Head (Magna Torq)

Capping head with magnetic coupling instead of mechanical clutch to limit static torque. Adjustment is done by rotating the internal magnet set, changing the magnetic force up to the desired "slip" point. Advantages: continuous adjustment, lower wear, repeatability across heads.

The Magna Torq reference line must match the upper edge of the housing — essential adjustment to avoid cocked cap or under-application.

Missing Band

Cap that arrives at the line already without a tamper-evidence band. The band separated and was lost in transport, feeding or sorting. Shares causes with broken band and smiley band — all stem from cap temperature, pull test, capper setup or sorter speed issues. Full diagnosis here.

PCO 1810 / PCO 1881

Plastic Closure Only (ISBT) standard specifications for PET bottle finishes intended for carbonated soft drinks. PCO 1810 was the dominant standard for decades; PCO 1881 is the lighter version, with reduced finish height, saving ~1 g of PET per bottle.

Migration from PCO 1810 to 1881 requires cap change and capper adjustment (turret reference, transfer plate, cams). Mixing the two types is a cause of systematic high cap.

PET Bottle

Bottle made of polyethylene terephthalate, a thermoplastic widely used for beverages (soft drinks, water, juices). Lightweight, transparent, recyclable. The industry standard finish for carbonated soft drinks is PCO 1810, gradually replaced by PCO 1881 (lighter, same performance).

Typical PET packaging defects: poor material distribution in the walls (causes leakage by microcrack in the sealing zone), dimensional excess on the finish, chipped finish.

Pick-Off (P.O.)

Capping system where the cap passes through an external launcher with pre-torque before the head. The launcher "picks off" the cap from the sorter and positions it, with light pre-torque, on the bottle, before the head completes application. Advantages: better control over the initial cap orientation.

Exclusive P.O. defect causes: wrong launcher air pressure, serrated arm spring, pre-torque adjustment, misaligned launcher.

Pre-Torque

Partial application of torque on the cap before final application by the head, exclusive to the Pick-Off system. Performed by a serrated arm that engages at mid-height of the cap while the bottle passes. Pre-torque takes the cap from neutral and leaves it "seated" before final threading.

The serrated arm must be in the package path; its spring must have proper tension — neither too high (creates cocked cap) nor too low (no pre-torque).

Pull Test

Destructive test that measures the force needed to separate the tamper-evidence band from the cap. Measured in N (newton) or lb by the cap supplier. Low pull test causes broken band, smiley band and missing band on the line. High pull test creates the opposite defect: the band does not break when the consumer opens the package, making the tamper indicator fail.

Removal Torque

Force needed to open the cap for the first time, measured in in.lb or kgf·cm with a bench torque tester. Low torque = leakage. High torque = consumer cannot open. Comparison between the two extremes.

Returnable Bottle

Package (typically glass or thick PET) designed for multiple use cycles. Each cycle includes return, washing, inspection, refilling and capping. Since the bottle wears with each cycle, microcracks in the sealing zone are a frequent cause of leakage on returnable bottles — different from single-use bottles, where the defect comes from initial manufacturing.

Smiley Band (Partial Rupture)

Cap with partial horizontal separation of the tamper-evidence band — the band hangs over part of the circumference, forming a characteristic "smile" that gives the defect its name. Sits between broken band (complete rupture) and intact cap. Causes and corrections.

Sorter Disc

Rotating component of the cap sorter that orients caps in the correct position (thread down) before feeding the chute. Works by geometry — caps only descend through the gap between discs if in the expected orientation.

Critical adjustments: speed (22-25 rpm for up to 8 heads, 28-30 rpm above), gap between plates, rotation direction, and automatic stop when the chute is full.

Spindle

Rotating shaft of the capping head that transmits torque from the turret motor to the chuck. Excessive radial play on the spindle (worn central bearing or bushing) causes threading imprecision, generating cocked cap and torque variation between heads of the same machine.

Star Wheel

Star-shaped component with individual pockets for each bottle, responsible for transferring the bottle between the conveyor and the capper turret. Maintains exact spacing and positioning so each bottle is aligned with the corresponding head.

A misadjusted star wheel is one of the most frequent causes of cocked cap. The bottle must be perpendicular to the head, centered in the pocket, with equal clearance on each side.

Static Torque

Torque limit defined at the head by mechanical clutch or magnetic coupling (Magna Torq). When reached, the head "slips" and stops applying torque. Typical range: 10 ± 2 in.lb. Very low static torque causes under-application; very high causes cracked cap and broken band.

Tamper-Evidence Band

Lower ring of the cap that breaks on first use, indicating the package has been opened. On PET beverage caps, the band stays connected to the cap body by small plastic bridges that snap when the consumer opens it. It is a regulatory requirement in several packaging categories: beverages, pharmaceuticals, infant foods.

When the band fails to work, the problem can be broken band, smiley band or missing band. See the full diagnosis of band defects.

Thread Roots

Internal helical protrusions of the cap and external ones of the bottle finish that engage during threading. The direction of thread deformation is the main diagnostic signal in application defects: deformation toward the liner indicates cocked cap; deformation toward the band indicates excessive application force.

Under-Application

Cap left loose after capping — you can hand-thread it and it tightens further. The capper should have tightened it and didn't. Causes: turret too high, low vertical load, low static torque, wrong chuck. 10 detailed causes here.

Vertical Load

Vertical force, measured in pounds (lb), that the head applies on the cap during threading. Typical operating range: 20 to 40 lb. Below it generates under-application. Above it generates multiple defects: cocked cap, broken band, cracked cap, high cap.

It is the equipment adjustment with the greatest impact on cross root cause — a single correction can solve several problems at once.