Circular Knitting Machine Cams: Types, Functions & Maintenance (2026)

Introduction

The cam system is the heartbeat of a circular knitting machine. It controls every needle and sinker movement, determining how yarn becomes fabric — stitch by stitch, at speeds exceeding 1,000 revolutions per minute. When cams wear or go out of adjustment, the symptoms show up immediately: dropped stitches, uneven loops, fabric bars, or complete production stoppages. This guide covers the types of cams in a circular knitting machine, how they function, and the maintenance practices that keep them running cleanly for years.

What Is a Cam in a Circular Knitting Machine?

A cam is a precision-machined track — usually made from hardened steel or alloy — that guides the movement of needles and sinkers. As the cylinder rotates, the butts of needles and sinkers follow the cam profile, which dictates exactly when each element rises, falls, and loops yarn.

The cam profile is not a simple circle. It’s a carefully engineered path with specific heights, slopes, and dwell points that correspond to each stage of the knitting cycle: yarn feeding, loop formation, clearing, and knock-over (or sinker withdrawal).

In a modern 30″ single jersey machine running at 30 RPM, the cam system completes 30 full knitting cycles per minute. At 2,500 needles per cylinder, that’s 75,000 precise needle movements per minute — all dictated by cam geometry.

Types of Cams in Circular Knitting Machines

Circular knitting machines use two primary cam systems, each serving a distinct function.

Needle Cams (Cylinder Cams)

Needle cams control the vertical movement of needles in the cylinder. They determine:

• Clearing height: How far the needle rises to clear the old loop
• Feeding position: The exact height at which yarn is presented to the needle hook
• Knock-over depth: How far the needle drops to form the new loop through the old one
• Dwell time: How long the needle stays at specific positions during the cycle

Needle cams are mounted in cam segments arranged around the cylinder. Each feeder on the machine has its own set of needle cams. A 30″ single jersey machine with 90 feeders has 90 sets of needle cams working in unison.

Sinker Cams

Sinker cams control the horizontal (radial) movement of sinkers, which perform several critical functions:

• Holding down: Sinkers press against the fabric to hold loops in place while needles rise
• Loop formation: Sinkers guide yarn into the needle hook during feeding
• Knock-over: Sinkers push the newly formed loop over the latch or push it clear during weft insertion

Sinker cams sit in a sinker ring (sinker dial) above the cylinder. Their timing relative to needle cams is critical — even 0.1mm of misalignment causes fabric defects.

Jacquard Cams (Pattern Cams)

In jacquard-equipped machines, additional cam systems control individual needle selection for pattern knitting:

• Selector cams: Guide interactive or piezo-electric selectors
• Pattern drum/chain cams: Provide mechanical pattern input in older machines
• Electronic servo cams: In modern machines, servo motors replace mechanical cams for pattern selection

Cam Segment Configurations

Most modern circular knitting machines use modular cam segments rather than one continuous ring:

• Single-system machines: 1 set of needle cams per feeder (plain jersey)
• Double-system machines: 2 sets per feeder (rib, interlock)
• Jacquard machines: Needle cams plus selector mechanism per feeder

This modular design allows operators to change cam configurations for different fabric structures without replacing the entire cam ring.

How the Cam System Works

Understanding cam function requires following a single needle through one complete knitting cycle.

The Four Stages of the Knitting Cycle

1. Clearing

• Cam lifts the needle from rest position to clearing height
• The old loop slides down the needle blade, below the latch
• Sinker holds down the adjacent loops to prevent them from lifting

2. Yarn Feeding

• Cam lowers needle to feeding position (below clearing, above knock-over)
• New yarn is laid into the open needle hook by the feeder
• Sinker advances to create space for yarn placement

3. Loop Formation (Lapping)

• Cam continues lowering the needle
• The new yarn catches in the needle hook
• Old loop begins to close the latch over the new yarn

4. Knock-Over

• Cam drops needle to knock-over depth
• Old loop is pulled through the new loop (intermeshing)
• Sinker withdraws to release the newly formed loop

This entire sequence occurs in approximately 1/30th of a second (at 30 RPM). At production speeds, each needle completes this cycle 30 times per minute.

Cam Profile Terminology

Higher pressure angles give sharper needle action but increase wear. Manufacturers balance speed capability against cam life in their profile designs.

Understanding cam costs is part of the bigger picture — see our Circular Knitting Machine TCO Guide for full lifecycle cost analysis.

Cam Materials and Manufacturing

Material Selection

Manufacturing Processes

Modern cams are manufactured using:

• CNC profile milling: For prototype and short-run cams
• Wire EDM (Electrical Discharge Machining): For high-precision cam profiles in hardened steel
• Grinding: Final finishing to achieve surface finish below Ra 0.4μm
• Surface treatments: DLC (Diamond-Like Carbon) or TiN coatings can extend cam life by 30-50%

Cam Wear Patterns and Replacement Timelines

Normal Wear

Cams wear gradually at contact points with needle/sinker butts. The wear pattern depends on:

• Machine speed: Higher RPM = more contact cycles per hour
• Yarn type: Abrasive yarns (cotton, some synthetics) accelerate wear
• Needle/sinker butt condition: Worn butts act like files on cam surfaces
• Lubrication quality: Inadequate oiling dramatically increases wear rates

For a comprehensive breakdown of machine pricing and specifications, see our Circular Knitting Machine Price Guide 2026.

When to Replace Cams

Replacement Intervals

Under normal operating conditions:

• Needle cams: Replace every 5-8 years (standard steel) or 8-12 years (high-speed steel)
• Sinker cams: Replace every 5-8 years
• Complete cam overhaul: Every 10-12 years (all cam segments, reset timing)

These intervals assume 4,000+ hours/year operation at moderate speeds. High-volume mills running 6,000+ hours/year at 30+ RPM should shorten intervals by 20-30%.

Cam System Maintenance

For a detailed maintenance schedule covering all circular knitting machine components, see our Circular Knitting Machine Maintenance Guide.

Daily Checks

• Visual inspection: Look for oil splatter accumulation on cam surfaces (can indicate over-lubrication or oil leak)
• Listen for changes: New clicking or grinding sounds often indicate cam or butt wear
• Fabric quality check: Dropped stitches or bars appearing in output are early cam wear indicators

Weekly Maintenance

• Clean cam surfaces: Remove lint and oil residue using compressed air and lint-free cloth
• Check oil flow: Ensure oil cam system nozzles are flowing properly
• Inspect needle/sinker butts: Worn butts accelerate cam wear — replace worn needles/sinkers promptly

Monthly Maintenance

• Measure cam track clearance: Use feeler gauges to check clearance between cam plates and needle/sinker butts. Spec is typically 0.05-0.10mm. Beyond 0.15mm, replacement is due.
• Check cam segment locking bolts: Ensure segments are firmly seated and haven’t shifted
• Inspect for chips or cracks: Any damage to cam profile edges will cause immediate fabric defects

Annual Overhaul

• Remove and inspect all cam segments: Check wear patterns against manufacturer specs
• Measure cam height at critical points: Compare to original profile specifications
• Replace any cam that’s worn beyond tolerance: Don’t mix new and worn cam segments in the same machine — it causes uneven fabric
• Reset cam timing: Verify that needle cam and sinker cam timing is per factory specification

Common Cam-Related Problems and Solutions

For help finding reliable suppliers, see our guide on How to Source Circular Knitting Machines from China and our Best Circular Knitting Machine Manufacturers in China comparison.

Frequently Asked Questions

How often should cam segments be replaced?

Under normal conditions, every 5-8 years for standard steel cams. High-speed steel or carbide cams last 8-12+ years. Replace sooner if fabric quality degrades or noise increases.

Can cam segments be repaired instead of replaced?

Minor wear can sometimes be restored by re-grinding the profile, but this is only economical for expensive carbide cams. Standard practice is replacement.

What happens if I mix old and new cam segments?

Fabric quality becomes inconsistent. New cams hold needles at precise heights while worn cams allow excess movement. Always replace all cam segments in a system at the same time.

How do I know if the problem is cams or needles?

Start with needles — they’re cheaper to replace. If new needles don’t solve the problem, inspect the cam profile for wear or damage. Chipped cams cause distinct defect patterns that track to specific feeder positions.

Is there a difference between OEM and aftermarket cams?

OEM cams are manufactured to the machine maker’s exact specifications and surface finish. Quality aftermarket cams from reputable suppliers can perform similarly, but ensure material hardness and profile tolerances match the original.

References

1. Yuanda — Understanding the Crucial Role of Cams in Circular Knitting Machines — Technical reference on cam function, types, and selection criteria
2. LinkedIn — Circular Knitting Machine Parts and Functions — Practical overview of cam system components and their functions
3. Scribd — Circular Knitting Machine Maintenance Guide — Maintenance procedures including lubrication, air circulation, and cam system servicing
4. iFactory — Knitting Machine Maintenance Circular and Warp Knit Guide — Preventive maintenance protocols for circular knitting machines
5. Fabrico — Best Maintenance Software for Knitting Machines 2026 — Modern approaches to cam system monitoring and predictive maintenance using OEE and stop-motion sensors