Rib Knitting Machine vs. Interlock Knitting Machine: Which Should You Choose?

A cylinder, a dial and a cam box that looks identical from the aisle: rib and interlock machines are easy to confuse and expensive to confuse. Mills meet the mistake at the cutting table, when fabric grows past the pattern allowance or will not stretch where the seam needs it.

A rib knitting machine knits on both needle beds at every feeder, so alternate wales open under load and the fabric delivers strong widthwise extension with good recovery. An interlock knitting machine uses an offset gating in which only alternate needles knit at each feeder, so two feeds are needed to complete one course, and the result is a smooth, two-faced, dimensionally stable fabric. Choose rib when the garment depends on stretch and recovery; choose interlock when it depends on cover, opacity and stability.

Comparing a rib knitting machine vs interlock knitting machine comes down to needle set-out, cam tracks and feeds per course.

Rib Knitting Machine vs. Interlock Knitting Machine at a Glance

Both machines belong to the same double knit family, share a cylinder and dial, and are often built on identical frames, so the choice is not about quality but about which fabric architecture the business sells. Gating, feeds per course and the balance between extension and stability separate them.

Both are sold as variants of the same double jersey rib circular knitting machine platform, separated mainly by needle configuration.

How the Two Machines Differ in Needle Arrangement and Cams

Rib gating alternates cylinder and dial needles so that a face wale and a reverse wale stand side by side and knit in the same cycle. Interlock gating offsets the needles of a facing pair so that only one can knit at a given feeder, which forces two feeds per course and needs four-track cams to hold the idle needle while its neighbour knits.

Gating describes how the two beds are positioned; tracks describe how many cam paths each bed offers, and so how many needle actions can be selected at one feeder.

Rib Gating and Cam Tracks

In a 1x1 rib the needles alternate between beds, and the dial needle facing a cylinder needle knits in the same cycle, drawing a reverse wale beside its face wale. Every needle is active at every feeder, so one revolution produces one course.

A Double Rib Circular Knitting Machine is normally specified with two to four cylinder tracks and two dial tracks. Two tracks handle plain 1x1 and 2x2; four add selection of knit, tuck and miss at successive feeders, which makes Swiss ribs and racked effects possible.

The rib ratio is a needle decision, not a cam decision: moving from 1x1 to 5x3 means rebuilding the set-out and usually the butt arrangement that decides which cam path each needle follows.

Interlock Gating and Four-Track Cams

At feeder one only alternate cylinder needles knit while their dial partners hold; at feeder two the roles reverse. Needles that knit together are diagonal neighbours, so each bed builds a complete 1x1 rib, and sinker loops passing between them interlock the two.

That sequence explains the four tracks. At one feeder a needle must rise to clearing and stitch height while its neighbour stays at miss level, and at the next feeder they swap. Two tracks cannot express four positions reliably at production speed, so interlock machines carry four cylinder tracks and dial cams with knit, tuck, auxiliary knock-over and idle paths.

An interlock machine therefore cannot be built by bolting a dial onto a single jersey frame: the dial, its cams, the butt arrangement and the feeder timing all assume the interlock sequence.

What This Means on the Machine Floor

Double knit machines commonly run 2.4 to 3.2 feeders per inch at 20 to 30 revolutions per minute, with a speed factor of revolutions times diameter around 850. A 34 inch interlock machine at 3.2 carries 108 feeders; a rib machine at 2.4 carries about 82.

Gauge ties machine to yarn. Workable cotton count is roughly gauge squared divided by 18, so E24 points to about 30s and E18 to about 18s. Too coarse a gauge gives loose, transparent fabric; too fine leaves no room to reach the required weight. The trade-offs are in this guide to circular knitting machine gauge.

Stitch cam height, needle set-out, yarn tension and take-down tension decide whether the first roll matches the sample, and take-down is the usual cause of weight drift along a roll.

Fabric Properties: What Each Machine Actually Produces

Rib stretches because its wales open like a concertina across the width and recover once the load is removed. Interlock resists widthwise extension because two complete rib structures are interlocked loop for loop, so the columns cannot separate, and that same interlocking gives it cover, thickness and stability on both faces.

A knit fabric is built from courses and wales, and the way those columns are anchored decides how the fabric moves.

Elastane changes the numbers, not the logic: a rib with 3 percent elastane recovers a collar better than a heavier rib without it. Percentage alone proves nothing, because yarn count, loop length, feeding tension and finishing all move the result.

Stretch should therefore be measured rather than assumed. Methods such as ASTM D2594/D2594M quantify stretch under a known load and residual growth afterwards, the pair of numbers a collar or waistband needs.

Production Output and Cost per Kilogram

An interlock machine usually carries more feeders and a higher nominal speed, yet produces fewer kilograms per hour than a rib machine of the same diameter, because every course consumes two feeds. At comparable weight, expect roughly 20 to 30 percent less output from the interlock route, and compare machines on accepted kilograms per scheduled hour rather than on revolutions per minute.

Courses per minute equals revolutions multiplied by feeders, divided by feeds per course. At 25 rpm a 34 inch rib machine with 82 feeders completes about 2,050 courses a minute; an interlock machine with 108 completes about 1,350.

The figures assume a tubular frame, one yarn and steady running; real output also depends on yarn quality and humidity.

Working Out Cost per Kilogram

Cost per kilogram is built from six lines, and buyers who compare only machine prices miss four.

1. Yarn, at the consumption implied by loop length, fabric weight and waste rate.

2. Power, typically 5.5 to 7.5 kW for a 30 to 34 inch machine.

3. Direct labour, spread across the machines one operator attends.

4. Depreciation, from quoted price and realistic hours over seven to ten years.

5. Spares, dominated by needles, sinkers and cam wear.

6. Downtime, including changeover, first-piece approval and rejects.

Machine price varies with specification: basic tubular double jersey machines are commonly quoted between fifteen and thirty thousand US dollars, with open-width and computerised versions far above that.

Is the Investment Worth It?

A circular knitting machine earns its place when the order book keeps it loaded in the structure it was built for. A dedicated rib machine running cuffs pays back quickly on steady orders, because it produces more kilograms per hour at lower capital cost. An interlock machine earns its premium where cover and stability are the selling points.

The calculation weakens when styles fragment, since changeover time, trial rolls and rejects all cost money; for sampling rooms, a 4 to 12 inch machine is often the entry point.

Can One Machine Knit Both Rib and Interlock?

A double knit machine with a two-track dial and a four-track cylinder can be set for either structure, and interlock machines produce rib by taking dial needles out of action, but a genuine conversion is a documented production event rather than a switch on the panel. The machine can do it; the question is what the changeover costs and whether the rib matches a dedicated rib machine.

Changing between structures involves more than the cam setting: the set-out and butt arrangement must be rebuilt, cams exchanged, feeder timing rechecked and take-down reset for a different contraction. A realistic change takes half a shift to a full shift.

Three points belong in the contract: which change parts are standard; the changeover procedure in writing with a reproducible time reference; and boundary samples of each structure in the buyer's yarn.

Applications: Which Fabric for Which Garment

Rib is chosen where a garment must grip, follow the body or recover after stretching; interlock is chosen where it must cover, hold shape and look clean on both sides. The same mill often needs both, with rib as trim and interlock as body.

Rib as trim is a different product from rib as body fabric, and the specification should say which is being bought. A neckband needs a relaxed width that sits flat against the body cloth, enough extension to pass over the head, and recovery that returns it to shape.

Interlock suits polos, heavier T-shirts, underwear, loungewear, leggings, dresses and childrenswear, wherever a smooth surface on both sides matters. Its opacity at moderate weight is an advantage in light colours, and flat edges cut sewing time.

How to Choose: A Specification Checklist

Start from the finished fabric specification rather than the machine label, then let the fabric decide gauge, diameter, feeders and tracks. A machine chosen from a catalogue produces something; a machine chosen against a signed fabric standard produces what the buyer ordered.

1. Define the structure precisely, including the rib ratio, not just the family name.

2. Set finished weight, width, thickness, and the direction and amount of stretch.

3. Fix yarn count and fibre, then derive gauge from them rather than the reverse.

4. Choose diameter from finished open width and cutting plan, allowing for contraction.

5. Set feeder density from target output and confirm the frame and drive support it.

6. Decide whether changeover capability is required, and cost it honestly.

7. Confirm spares availability for needles, sinkers, cams and selection components.

8. Require documentation: gauge, feeders, speed, power, parts list and maintenance schedule.

Acceptance testing should go beyond hand feel: knit a full circumference, inspect both faces, measure relaxed width and weight across the roll, then wash and check dimensions against the standard. The same discipline explains why the difference between single jersey vs double jersey is best judged on samples.

FAQ

How do I match yarn count to gauge on a rib or interlock machine?

Use gauge squared divided by 18 as a starting point for cotton count, then adjust for structure. Interlock knits tighter than rib at the same gauge, so a count comfortable on an E20 rib machine may need E24. Confirm with a loop length measurement.

Can these machines run recycled and blended yarns?

Yes, with adjustments. Recycled blends carry more short fibre and lower tenacity, which shows up as fly around the feeders and then as barré and needle damage. Expect more cleaning, slightly lower speed and better tension control. Interlock is less forgiving of thick places, because a slub that sits in a rib valley becomes a mark on a flat face.

Do rib and interlock fabrics shrink differently after washing?

They relax differently. Rib contracts strongly in width as the wales close, moving a panel by several percent, while interlock moves more in length. Both depend on yarn, loop length, finishing and wash method, so name the test method and cut rib trims from relaxed fabric.