RF Bent Plywood

What RF bent plywood is

RF bent plywood is a curved plywood part made by stacking glue-spread veneers in a shaped form and curing the adhesive with a radio frequency field rather than with heated platens. It is also called radio frequency bending, and outside the US it is usually called high frequency or HF bending. The underlying physics is dielectric heating: an alternating field, typically somewhere in the 2–30 MHz band, agitates polar molecules in the adhesive and in the wood's moisture, and the assembly heats from the inside out.

That distinction is the whole point. A hot press has to conduct heat from its surfaces inward, so a thicker stack takes disproportionately longer to cure and the outer plies sit at temperature far longer than the middle ones need. A cold press does not heat at all — it simply holds the part in the form until the glue cures on its own, which can mean hours or an overnight. RF deposits energy through the whole lay-up at once, so the glue lines reach cure temperature together and a part can come out of the form in a couple of minutes.

RF bending versus cold press and steam bending

	RF bending	Cold press	Steam bending
Time in the form	Minutes	Hours to overnight	Bend is quick; drying in the form takes far longer
Springback	Lowest — the adhesive is fully cured before the part leaves the form	Low, but depends on full cure	Highest and least predictable
Part-to-part repeatability	High	High, but the form is tied up all day	Varies with species and moisture
Tooling	Forms can be plywood or MDF, because the tool does not have to conduct heat	Simple forms, but you need many of them to get throughput	Male former plus a steel strap
Best suited to	Repeat production runs	Prototypes, one-offs, very large parts	Solid wood, craft and restoration work

The economics are easier to see in form turns than in unit price. A cold-press form yields roughly one or two parts a day because it is occupied while the glue cures. The same geometry on an RF press, at a two-to-three minute cycle, can turn over and over in a shift — and several parts can often be stacked in one press load. That is why RF wins on production runs and loses on ones and twos.

Where induction pressing fits

The real alternative a serious buyer will raise is not cold press, it is induction heat pressing. The trade generally splits the work this way: upholstery-grade parts and simpler curvature go to RF, while large one-piece exposed-grade shells, multi-thickness parts and big panels tend to go to induction, which is gentler on large exposed faces. If your part is a big visible-grain shell, say so on the form and we will route it accordingly rather than forcing it onto the wrong press.

Molded plywood or bent lamination?

Two different products share the shelf, and the difference matters when you quote.

• Molded plywood (also formed plywood) has its plies crossed at 90°, the same as flat plywood. It is dimensionally stable across the part, which is why seats, backs and one-piece shells are built this way.
• Bent lamination runs every ply's grain in the same direction, along the curve. It gives higher tensile strength along the length, which is what you want in an armrest, a chair spar or a cantilever side frame.

A third thing gets confused with both: flexible sheet stock sold as bending plywood, wiggle board or wacky wood. That is a material you buy by the sheet and glue up yourself. RF bent plywood is a finished, pressed component made to your drawing. If what you actually need is the sheet stock, tell us — it is a different conversation and a much faster one.

The specs that decide the job

These are the variables that drive whether a bent plywood part is straightforward, expensive or impossible. Exact capability depends on which press the work lands on, so we confirm each one against a real drawing rather than publishing a blanket number.

Inside radius	The governing constraint, and the one most often given wrong. Radius is a function of veneer thickness — thinner plies bend tighter. Tight radii mean thin special veneer and a higher price. Give us the inside radius, not the diameter.
Veneer and ply count	Plies commonly fall in the sub-millimetre to roughly 2.3 mm range, with thinner stock reserved for tight radii. Ply count follows from finished thickness and how hard the part has to work.
Finished thickness	Drives ply count and press cycle. Thickness affects RF cycle time far less than it affects a hot press, which is part of why the process suits thicker curved parts.
Part size	Press platen size is a hard ceiling. Width in particular runs out well before length on most curved plywood presses, so an oversized panel may need a different press or a second operation. Worth checking before anything else if your part is large.
Core species	Birch, beech and hard maple are the usual cores. Species affects both bend radius and the finished surface under a clear coat.
Face and back	Sliced hardwood veneer, HPL or CPL laminate, decorative paper, primer foil, or paint grade. Construction should be balanced — an unbalanced lay-up cups.
Grain direction	Crossed plies for stability, parallel plies for strength along the curve. See above.
Tolerance	Machining tolerances on trimmed and bored features are tight. Shape tolerance is a different animal — opening angles move with ambient humidity, so tolerance gets quoted against the actual part rather than promised in the abstract.
Secondary operations	Parts come off the press oversize. CNC trim, edge sand, drill and bore, edgeband or solid-wood edge, and sanding to grit are all normal and usually quoted together with the pressing.
Compliance	TSCA Title VI and CARB Phase 2 are the usual asks on panel products, along with FSC where the program requires it. Tell us what your customer demands.

Tooling, quantities and lead time

Every RF bent plywood part needs a form — a shaped male and female pair, with the outer member called a caul, that distributes clamping pressure evenly across the glue line instead of pinching it at a few points. RF is kinder here than heated pressing, because the tool does not have to conduct heat, so forms can be cut from plywood or MDF rather than machined from aluminium. That keeps the one-time cost down and makes design changes survivable.

Tooling is quoted as a separate one-time line item ahead of the first article, and it is the reason quantity is the first thing we ask. Below roughly a few hundred pieces, the tooling usually dominates the unit price and you are often better served by cold press or by a CNC stack-cut part. Above that, the press cycle takes over and RF starts to look very good. If a matching form already exists for your geometry, tooling can drop out of the quote entirely — which is exactly why it is worth asking.

Lead times vary too much by shop, tooling status and finish spec for a published number to mean anything. We quote it with the price, against your drawing.

What these parts end up as

• Seating — chair backs, seat pans, one-piece shells, backrests, armrests, spars and cantilever side parts
• Case goods and cabinetry — curved doors and drawer fronts, radius end panels and gables, corner cabinets, curved toe kicks
• Store fixtures — curved valances, display panels, column covers, wrapped counter and reception desk fronts
• Beds and casegoods — bed rails, slats and headboards
• Architectural millwork — curved wall panels, ceiling elements, radius trim blanks
• Transportation and marine interiors — curved lining and trim panels

Why buy through Supply Tie

We are an industrial supply distributor, not the press. What that buys you is a straight answer about which process and which shop your part belongs at, instead of a quote from whoever happens to own one machine. If your part is a large exposed-grade shell that really wants induction, or a run of twelve that really wants cold press, we will tell you that rather than quoting you RF for the sake of it. Send the drawing and we will come back with questions and a number.

Common questions

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