Forged Beam or Cast Beam? How to Read Warp Knitting Beam Sizes

August 1, 2026

A warp knitting beam code such as 30″x21″ is two dimensions in inches: flange diameter first, barrel width second. Choosing between a forged beam and a cast beam is a separate decision, and it turns on how the beam is loaded and handled in your mill rather than on which process word the seller prints on the page.

We opened the pages currently ranking for beam terms before writing this. Not one of them explains the size code. One catalogue puts 30″x21″(HD) in the product title and never says what either number refers to. Another separates a conventional casting beam from a high tension bearing forging beam in a single line, then lists no flange diameter, no barrel width and no material grade at all — getting a number out of it means opening WhatsApp.

Reading the size code: flange diameter x barrel width

The codes you meet across supplier catalogues are 14″x21″, 21″x21″, 30″x21″, 40″x21″ and 42″x21″. The first number is the flange diameter, and one arithmetic check settles it.

One supplier publishes a 42″x21″ aluminium beam at 1060 mm flange diameter and 180 kg. Forty-two inches converts to 1066.8 mm. The first number tracks the flange; the second cannot, because it stays at 21 right across the range while the beam grows.

The millimetre figures above are conversions of the inch code, not measurements published by anyone, with the single exception of the 42″x21″ row. Treat the second figure as nominal as well: the usable width between flange faces is what your warp actually occupies, and none of the pages we opened publish it. Measure it on a beam you already run instead of assuming the code is the machined dimension.

Matching a size code to our own forged beam models

Size codes are market shorthand. Our own beams are published model by model instead: the spec table on our forged beam page lists the J-006 and J-008 forged beams with a flange diameter and a finished weight against each model number. Read your requirement off measurements and match it to that table, rather than ordering against the code stamped on a beam that has already been in service.

The order that works:

1. Measure the flange outside diameter of the beam you run now, in millimetres, across two axes at ninety degrees. A beam that has been dropped reads differently on the two axes, and that difference is itself the answer to why it is being replaced.
2. Measure the usable barrel width between the flange faces. The 21 in the code stays at 21 across the whole range, so it tells you nothing about the width your warp actually occupies.
3. Take the finished weight of the beam you are replacing and compare it with the weight column against J-006 and J-008. Weight is the figure your hoist, trolley and beam rack care about, and it is the one buyers most often discover after delivery.
4. Check the shaft and chuck interface last, and treat it as a veto. A model that matches on flange diameter and weight is still the wrong beam if the drive end does not match.

If your measured flange diameter falls between two published models, send us the two measurements, the finished weight and the machine model number and we will say which one applies. Do not round to the nearer figure yourself; the gap between codes is larger than the tolerance your chucks will accept.

This section is about matching an existing installation. If your machine builder names a beam type or flange material in the machine manual, that specification wins over any supplier table, ours included.

Forged or cast: what supplier pages state, and what they verify

Construction detail is thin but consistent where it exists. One catalogue specifies high-strength aluminium alloy flanges, a heat-treated aluminium extruded tube for the barrel, CNC machining and ISO 9001 certification. That was the most complete description on any page ranking for these terms.

The strength claims are a different matter. Forging refines the internal grain structure and yields a part stronger than a cast or welded equivalent, and forged beams spread yarn tension more evenly — both statements appear on supplier pages, and neither is supported on those pages by third-party test data, tolerance figures, runout limits or allowable tension values. Read them as vendor positioning until someone puts a report behind them.

There is also a contradiction worth knowing before you sign anything. The supplier page carrying the fullest size table states in one place that flange and barrel are both forged, and in another that the flange is cast aluminium and the barrel is centrifugally cast. Same page, same product.

When a cast beam is enough, and when it is not

If your beams stay on one machine type, sit in the lower half of the published range (14″x21″ to 21″x21″) and are moved by trolley or an automatic loading system rather than lifted by hand, then a cast beam whose construction the supplier will document in writing does the job, and the forged premium buys nothing you can measure.

If you are ordering at the top of the range, handling load starts to dominate. The 42″x21″ aluminium beam runs 1060 mm across the flange at 180 kg. At that diameter and mass a dropped or badly racked beam is the realistic damage path, so it is reasonable to press the supplier on how the flange is made and to get the answer written into the order confirmation.

This guideline does not apply in two cases. If your machine builder specifies a beam type or flange material in the machine manual, that specification wins. And if beams are already failing in your mill, the failure you actually have — flange cracking, runout, a bent barrel, chuck wear — decides the replacement rather than any general rule. Diagnose it before you re-order.

Measure these before you order a replacement beam

1. Machine family and model number. Supplier compatibility lists say Tricot and Raschel, and name Karl Mayer, LIBA and Benninger followed by etc. No page we opened carried a model-by-model table, so match against your actual machine.
2. Flange outside diameter, measured, in millimetres — compared against the converted code rather than trusting the code.
3. Usable barrel width between the flange faces, measured.
4. The shaft and chuck interface: how the beam is driven and clamped. A correct diameter with the wrong interface is still the wrong beam.
5. Finished weight, checked against your hoist, trolley and beam rack rating.

Some of this gets easier when the changeover is mechanised; our beam auto-installation system takes over the lifting and alignment that hand loading tends to get wrong. What happens upstream matters too, because a beam only holds what the warping stage wound onto it — see how the split warping machine solves superfine yarn challenges.

Five questions that get a real answer out of a beam quote

1. Which parts are forged and which are cast — flange, barrel, or both? Ask in writing, given that at least one supplier page answers this two different ways.
2. What is the flange outside diameter in millimetres, and the barrel width between faces in millimetres, for the exact code you quoted?
3. What is the finished weight of that code?
4. Which machine models by number, not by brand family?
5. Is there test data behind the strength claim, or is it a description of the process?

Our own range is split the same way the market is, so you can specify instead of accepting a default: forged beams and cast beams, with the surrounding hardware — chucks, shaft connectors, flanges — under warp knitting spare parts. The same beams sit on our group site at grandstarcn.com.

Send us the size code you run, the machine model number and a photograph of the flange face, and we will tell you which beam matches before anyone quotes anything — start on our contact page.

Frequently Asked Questions

What does 30×21 mean on a warp knitting beam?

Two dimensions in inches: flange diameter first, barrel width second. A supplier-published 42″x21″ aluminium beam with a 1060 mm flange confirms the reading, since 42 inches converts to 1066.8 mm. The codes in common circulation are 14×21, 21×21, 30×21, 40×21 and 42×21.

Which forged beam do I need, the J-006 or the J-008?

Both are published on our forged beam page with a flange diameter and a finished weight against the model number, so the match is made on measurements rather than on the size code. Measure the flange outside diameter of the beam you run now in millimetres, take its finished weight, and check the shaft and chuck interface before you decide between the two.

Is a forged beam really stronger than a cast beam?

Suppliers say so: the claim is that forging refines the grain structure and produces a part stronger than a cast or welded one, with more even tension distribution. None of the supplier pages we opened publish test data, tolerances or allowable tension values behind that claim, so treat it as vendor positioning and ask for evidence in writing.

Will a 21×21 beam fit my Karl Mayer machine?

Brand compatibility alone will not tell you. Supplier pages list Tricot and Raschel machines and name Karl Mayer, LIBA and Benninger, but none of them publish a model-by-model table. Measure your current beam’s flange outside diameter and the barrel width between flange faces, and check the shaft and chuck interface, before ordering.

How do I measure my old beam before ordering a new one?

Measure three things and record one: flange outside diameter in millimetres, usable barrel width between the flange faces, and the shaft and chuck interface; record the machine model number. Size codes are nominal, so measured figures beat the code stamped on the old beam.