Blum Legrabox: Why Soft-Close Drawers Outlast Metabox on a 60kg Pull-Out

A broom-cupboard base drawer carrying a Henry vacuum, spare filters, a folded step stool and a box of light bulbs puts its highest demand on the runner at full extension. At that point the carriage has to carry the mass while the open drawer acts as a lever. Blum publishes a dynamic load rating of 40kg for standard Legrabox and 70kg for the heavy-duty version running on Movento-derived carriages. Metabox tops out at 30kg on its double-walled steel box with side-mounted epoxy rollers.

Where Metabox starts to wear

Metabox uses partial-extension or full-extension roller runners. The drawer side is a double-walled steel box, and the running action comes from nylon rollers moving inside a stamped steel channel screwed to the cabinet side.

At a 30kg load, that arrangement can work well for years. At 45 or 50kg, the contact patch between each roller and its channel becomes the stressed point in the system. The full drawer weight is concentrated onto two small rolling contacts, and repeated cycles change the way the drawer sits in the opening.

The wear pattern is familiar in older roller drawers. The nylon begins to flat-spot, the steel channel polishes where the roller bears on it, and the front of the drawer starts to dip near the outer part of the travel. The user feels it when the drawer is about three-quarters out and the front edge drops slightly.

Legrabox and the Movento platform use a captured ball-bearing carriage instead of nylon rollers. A row of hardened steel balls runs in a machined raceway, spreading load across a much larger contact area than two roller points. That wider bearing path helps the runner hold its geometry under heavy extension loads, which is why Blum can rate the heavy-duty version of the same broad rail architecture to 70kg.

Blumotion damping under a heavy front

Soft-close on Legrabox is handled by Blumotion, an integrated hydraulic damper built into the carriage. It is a small oil-filled cylinder that meters roughly the last 60mm of the closing stroke. The heavier the drawer, the more energy the damper has to absorb before the front reaches the cabinet.

Blumotion is tuned across a load range, so a 5kg cutlery drawer and a 55kg pan drawer can both arrive quietly. Metabox soft-close, when fitted, is usually a bolt-on Blumotion clip-on unit. Its damping envelope was designed around the lighter loads used on roller-runner drawers.

A 60kg drawer on an under-specified damper can still travel shut, then rebound. The oil cannot absorb the kinetic energy quickly enough, the drawer front bounces a millimetre or two away from the cabinet, and a magnetic or mechanical latch may fail to seat fully. On the integrated Legrabox damper matched to the 70kg carriage, the metering orifice and bearing friction are engineered together, so the same mass decelerates in a controlled way.

A loaded 900mm drawer in numbers

Start with the drawer weight. A 900mm wide, 500mm deep Legrabox at 128mm height in the standard steel finish weighs roughly 3.5 to 4kg empty after the base panel and back are added. Against a 60kg working figure, that leaves about 56kg for contents.

Cookware reaches that figure faster than many showroom tests suggest. A cast-iron Le Creuset 28cm casserole weighs about 5.5kg. Four of them bring the contents to roughly 22kg before anything else is added.

Add a 6kg stockpot, a set of steel baking trays and assorted lids, and the contents are already past 40kg. The drawer can still look half empty at that point because dense metal cookware consumes load capacity before it consumes volume.

Specifying standard 40kg Legrabox because an empty display drawer felt solid would leave the installed drawer above its dynamic rating once that cookware load is reached. The dynamic figure is the load Blum tests over its cycle count. Once the loaded drawer moves beyond that figure, the tested lifecycle should no longer be assumed.

With the 70kg heavy-duty carriage, the same 56kg payload sits inside the published envelope. It also leaves margin for a common abuse case: someone resting weight on the open drawer front while reaching into the back.

The loaded weight has to include the box, the base, the back and the contents. In a wide drawer used for pans, tools or cleaning equipment, the payload estimate can climb from harmless to excessive before the drawer looks visually full.

Cabinet fixing sets the installed limit

A 70kg carriage loses that rating if it is fastened into 15mm MFC with three coarse-thread chipboard screws per rail and the rear holes have little material behind them. Runner ratings assume that the fixings stay put. On a heavy pull-out, the rear cabinet fixing takes much of the extraction load, and a stripped rear screw hole in melamine-faced chipboard is a common real-world failure before the bearings themselves are worn out.

For a genuine 60kg installation, the cabinet side wants to be at least 18mm thick. Ideally, the rear runner fixing lands in solid timber or a hardwood insert rather than raw chipboard core. Blum supplies the Zamak locking devices and the front fixing brackets that clip the box to the carriage, so those components are controlled parts of the system.

The variable is the carcass and the screw work. Understairs storage often tempts installers to fix runners to whatever framing is already behind the plasterboard. An angled screw driven into the edge of a stud holds far less than a square fixing into an 18mm carcass side.

Parallel mounting matters as well. Two runners that are out of parallel will bind, and binding on a ball-bearing carriage under 60kg generates heat and premature bearing wear. Blum sells the EASYASSEMBLE jig and mounting plates because both rails need to be coplanar to within about a millimetre. At 60kg, that tolerance matters far more than it did on a light Metabox drawer, where roller slop could hide small alignment errors.

Where Metabox still fits

Metabox remains a sensible specification for a bedroom fitted-wardrobe internal drawer holding folded shirts. That load rarely clears 12kg, and the lower unit cost across a run of eight drawers adds up.

The 60kg example leaves Metabox’s lighter load band intact. Its weak point appears when it is asked to carry a mass well beyond the published 30kg rating.

Drawer depth changes the load case

Runner length changes how the same mass acts on the cabinet. A 550mm Legrabox carriage at full extension places the payload centre of mass a long way from the rear fixing, so the moment arm on the rear screw is large. The same 60kg in a 400mm drawer sits closer to the cabinet and loads the fixings less severely.

Blum quotes the dynamic rating for the full nominal runner length. A shorter runner therefore gives some unadvertised headroom because the drawer does not project as far from the cabinet side.

This matters in understairs storage. The triangular void pushes designs toward very deep pull-outs under the higher part of the stair. A 650mm-plus pull-out carrying 60kg places a heavy combined demand on the rear fixing and the carriage cantilever. Splitting the storage into two shallower stacked drawers, or using a 500mm drawer with a shelf behind it, keeps each runner closer to a load-and-length combination Blum has actually tested. That leaves a real trade-off between using the deep part of the stair void and keeping the rear fixing inside a tested load path.