A sliding window profile set is not one section. It is a frame, a sash, an interlock, a track, a glazing bead and a mullion, and the window only closes because those six fit each other to within a tenth of a millimetre. We extrude the set from 6063 or 6061, hold the interlock slot at ±0.1 mm, powder coat it on our own line and, where the project asks for timber without the maintenance, run the wood paper transfer in the same plant. Minimum order 500 kg, cut to your cutting list, shipped FOB Shenzhen or Guangzhou.

What a sliding window section set contains

A two-panel slider needs eight profiles before any hardware; miss the interlock or the sill upstand and the window can be built but not drained.

A two-panel slider needs eight profiles before hardware: outer frame (head, sill, jambs), two sashes (top, bottom, stiles), one interlock where the sashes meet, and a mullion where a fixed panel sits beside the sliding one. Buyers who order only the frame and then look for a sash discover that the sash bottom must match the sill's track spacing, and the interlock must match the sash stile's pocket. That is the reason we quote a window as a set rather than by the metre of one attractive section.

Two tracks or three

The third rail buys a third sliding leaf and costs frame width, aluminium per metre, and sash weight that the track and rollers must carry.

Two tracks give one fixed panel and one sliding panel in the same opening. Three tracks give two sliding panels and one fixed, or three sliding panels in a wide opening. The extra rail is worth it when the opening is wide enough that a two-panel window leaves each sash too heavy to move smoothly, or when the design wants two panels to open from the middle. It is not worth it when a two-track window already gives a clear opening wide enough for the use. Ask for the clear opening width, not the frame width, when you compare the two.

Mullion and transom

A mullion carries a glazing pocket on one side and a sliding frame rebate on the other; without the mating bead groove the fixed panel will not clip.

A mullion is the vertical member between openings; a transom is the horizontal one above a door or between a fixed and an opening panel. Neither is a generic bar. A mullion for a sliding system has to take a glazing pocket on the fixed side and a track pocket or frame rebate on the sliding side, and it has to be deep enough that the two do not meet in the middle of the web.

This is where most replacement orders go wrong: the buyer sends a photo of a mullion, we cut a die to it, and the fixed panel's bead no longer clips because the photo lacked the bead groove. Send the section drawing, or a 100 mm cut piece, and the mating bead with it. On curtain wall and shopfront work the same member is called a mullion; on a window it is called a centre post. Same function, same tolerance problem — see our thermal break window and door profiles where the same logic runs through a two-part section.

Powder coating on our own line

Coating on our own line means one spray batch per project, 26 presses feeding it, and no truck ride between the coating and the transfer.

We powder coat in-house. That changes three things a buyer feels. Colour holds across a project and across a repeat order, because the batch is sprayed in one run. Lead time does not sit in someone else's queue in the season when every coater in the region is full. And the profile goes from the press to the line to the transfer without a journey in between, which is where coated faces pick up the handling marks that later show through a film.

The coating is the base for the wood grain, not a separate product. Wood paper transfer works by wrapping printed film around a cured powder surface, drawing it down under vacuum and holding it in heat until the print transfers into the coating. If the powder is under-cured, the film releases unevenly and the grain goes patchy at the corners. Because both steps happen here, that failure is caught before packing, not at your assembly bench.

Wood paper transfer

Wood paper transfer gives oak, walnut or teak colour with no swelling and no repainting; it gives no grain texture and no covered cut end.

The transfer gives an aluminium window the colour of timber without the swelling, the painting cycle or the rot. It does not give the texture of timber, and it does not give a sawn end. Three things follow, and all three are decided before the order runs.

First, the seam. Printed film comes on a roll, so the pattern has to be joined somewhere on every profile. We fix the join on one face at the press and mark which face it is, and by default we put it where a joint, a bead or a wall normally covers it. After that the bar is yours: you cut it and assemble the window, or you sell the bar on and your customer cuts it. Where the joint actually lands is decided by that cut and that assembly, so the seam has to be planned on your side of the saw as well as ours.

Second, the grain direction. The print runs along the extrusion, so the grain follows the length of every profile and turns ninety degrees at a corner where a horizontal head meets a vertical jamb. On a light oak that break reads clearly; on a dark walnut it almost disappears. Third, the ends. Every cut leaves bare aluminium, whether it is made on our saw or on yours — the close-up on this page is a cut end. Nothing in the transfer covers a mitre, so end caps or a touch-up stick belong on the packing list, not on a list of problems found at the bench.

Exterior life depends on film grade, the powder beneath it and the exposure: a north-facing wall under an overhang is not a west-facing parapet at the coast. We quote the film grade for the project and state it in the offer, rather than putting one number on every window.

Tolerances that decide whether the sash closes

The interlock slot is held to ±0.1 mm, walls start at 0.8 mm, and mating faces are machined after extrusion to GB/T 5237 high-precision grade.

The interlock is the joint that decides how the window feels. Hold it at ±0.1 mm on the slot that receives the sash stile, and two sashes made a month apart will still meet. Let it drift and the gap opens, the brush seal stops touching, and the window whistles.

Our extrusion runs to GB/T 5237 high-precision grade, which is the tighter grade of the same table, not a separate standard. Wall thickness starts at 0.8 mm. Where a face has to mate, we machine it after extrusion instead of asking the die to be perfect: a machined face is a known surface, a die face is a distribution of metal flow. Twist and bow matter more than the outside diameter on a 6 m length, because a sash made from a bowed stile binds at one end of its travel. The classes behind these numbers are set out in aluminium extrusion tolerances.

Cutting list, order size and container

Minimum order 500 kg, new die or not; a 20 ft container takes 5.85 m and a 40 ft takes 6.0 m in two lengths; below 5 m sawing is charged separately.

There is no standard length. Profiles are cut to your cutting list, and the list decides the packing. Below 5 m, sawing is charged separately. For a wood-grain order, packing is part of the product: profiles are wrapped so faces do not rub, and the film side is protected rather than laid against a bare extrusion.

Mixed loads are normal: mill finish frames, anodised sills in AA10 or AA15, and wood-grain sashes in one container, as long as the total weight and the longest bundle fit. Weight is calculated from the drawing and certified on the mill certificate, within ±10% of theoretical — worth checking before you compare two suppliers by the kilo. Powder-coated frames that do not need the wood grain are covered under powder coated window and door profiles.

Where our scope ends

We extrude, cut, coat and transfer; glass, rollers, locks and gaskets we can buy in on request, and assembled windows we do not ship.

Cutting, machining the joints and building the window is your work, or your customer's if you resell the bar. Glass, rollers, locks and gaskets are not extruded here either, but they do not have to come from a second supplier: we can buy them on your behalf or introduce the accessory suppliers we already work with, so one container can leave with frames, sashes and the hardware that fits them. If you take that route, name the system and the hardware brand on the order; mixing a mullion from one system with hardware from another is where the fit fails.

Fluoropolymer and liquid paint are not our standard finishes. Anodising in AA10 or AA15, powder coating and wood paper transfer are. Alloys are 6063, 6061, 6463 and 6082, with 6005A and individual 5xxx or 7xxx grades produced on request.

Send the section drawing in DWG, DXF or PDF with wall thicknesses and slot dimensions, the finish and the colour reference, the cutting list in metres per profile, and the destination port. If your drawing is a photo of an existing window, send a 100 mm cut piece with it — that answers in one look what a photo argues about for a week.