Linear guides
MGN rails and SBR supported shafts with carriages for CNC machines, 3D printers and automation. Linear guides turn a motor's rotation into accurate travel along a straight line. Sizes from MGN7 to MGN15 in lengths from 100 to 800 mm and supported shafts SBR12–SBR20 in sets from 800 to 2200 mm, carriages in types C and H.
Linear guides
Every machine that moves along an axis — a CNC router, a 3D printer, a plotter or a piece of one-off automation — needs something to hold that movement in a straight line and take the forces acting across the direction of travel. The accuracy of what comes out therefore rests not just on the motor but above all on how little play the guide has. Play on an axis writes itself straight into the dimension of the workpiece or into the walls of a print.
MGN rails are profile guides with a carriage in which balls recirculate. The number in the designation is the width of the rail in millimetres: MGN7 and MGN9 suit the light axes of 3D printers and small mechanisms, while MGN12 and MGN15 carry more and get used where material is being cut. The rails have mounting holes at a fixed pitch, so the frame needs holes in matching places and, above all, needs to be flat — a profile guide will not forgive an uneven base, it passes that unevenness straight into the travel.
Carriages in types C and H differ in length. Type C is the shorter one and the standard choice where space is tight. Type H is longer, has more balls in circulation and therefore a higher load rating and better resistance to tipping — it earns its place on long brackets and wherever the carriage carries mass well away from the rail.
SBR supported shafts are a different design: a round shaft carried along its whole length by an aluminium profile, with an open bearing block running on it. They cost less, are more forgiving of an inaccurate frame and, thanks to that continuous support, have no sag to fear on longer axes. What you pay for it is lower accuracy and greater sensitivity to dirt.
When choosing, start from the travel you need and the forces that arise on the axis, and leave yourself some room for mounting the carriage. Every guide wants lubricant and cleanliness — swarf and dust in the ball track will destroy a carriage faster than years of use ever could.