MGN vs MGW Miniature Guides

MGN and MGW are the same miniature guide in two rail widths. The block internals, the ball circuit and the accuracy grades are the same; the MGW rail is wider, and the block is wider with it. The choice comes down to how much overturning moment the carriage has to take without the load sitting directly over the rail.

Width is the difference

At 9 mm the standard block is 20 mm across the body and the wide block is 30 mm; the rail goes from 9 mm to 18 mm. The height barely changes, which is the point: the wide version fits into the same vertical space and only asks for lateral room.

When MGN is enough

Use MGN when the load is centred over the rail and the carriage is symmetric: printer gantries, laser heads, dispensing axes, small inspection slides. The narrow profile saves weight on a moving gantry, and on a belt-driven printer that weight is the limiting factor for acceleration. Two MGN rails are usually cheaper than one wide rail carrying the same load.

When MGW earns its space

Use MGW when the load hangs to one side of a single rail, when the carriage is cantilevered, or when the design has room for one rail only. The wider rail raises the resistance to overturning moment without going up a size, so the height and the hole pattern stay where the rest of the machine expects them. On a single-rail Z axis with a spindle offset to one side, that is often the difference between a smooth axis and one that rocks.

What does not change

Accuracy C / H / P, preload ZF / Z0 / Z1, the C and H block lengths, and the stainless construction are common to both families. Both use the same wiper arrangement and the same mounting practice. The load ratings differ because the rail width changes the moment capacity, not because the block is built differently — compare the C values in the table rather than assuming the wide version is “stronger”.

A note on the numbers

The miniature range is catalogued in kgf in the printed manual, so the pages here show both: the catalogue figure and the converted kN. That is why a 9 mm block reads 280 kgf (2.75 kN) rather than a round kN number. Do not mix the two units when comparing with another supplier's catalogue.

Models

MGN: MGN7, MGN9, MGN12, MGN15. MGW: MGW7, MGW9, MGW12, MGW15. Rails: HGR / miniature rails. Selection help: selection guide.

Overturning moment, in practice

Take a single-rail Z axis with a 2 kg spindle offset 60 mm from the rail centreline. The static moment is about 1.2 N·m, small in absolute terms but applied in the same direction every time the axis accelerates, so the block sees a reversing moment rather than a steady load. A standard miniature block resists that with its ball rows spaced across a narrow body; the wide version spaces them further apart on the same height, which is why it rocks less at the same nominal load.

Two MGN rails side by side can achieve the same effect, and often cheaper, but they double the alignment work: two rails have to be parallel within the running tolerance, while one wide rail needs only its own straightness. On a machine built in volume, that assembly time is the deciding cost, not the part price.

Mounting the two rails close together

When two MGN rails sit close, check the wrench clearance for the rail bolts before the design is fixed. The narrow profile leaves little room between the rails, and a bolt head that cannot be reached is a design that cannot be assembled. MGW has the same problem at the block end: the wider body needs clearance for the flange ears on both sides.

On a two-rail gantry the wide version is not automatically better. Two narrow rails already resist overturning through their spacing, and the extra width of MGW can push the gantry mass up without adding stiffness where the machine needs it. Judge each axis separately: the Z head may want MGW while the X gantry is better on MGN.

If the choice is still open, order one of each and measure the rocking on the bench before committing the design.

FAQ