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Rails can be cut to any length using an abrasive cutting method. Consider graduated shallow cuts to keep heat down and avoid warp potential. Some folks prefer to mount the rail to spare extrusion which can also help with warp mitigation. What is a Z1 preload? Dynamic load (C) is the maximum continuous load applied to the bearings and raceways that doesn’t compromise the service life of the rails beyond the nominal rating (which is 50km for MGN/HG rails and other ball-type rails).
Tip: three-wheel gantries are preferred over four-wheel gantries to avoid overconstraint issues. Linear rails vs smooth rods Z1 preloaded rails will not slide as freely by hand when compared to a Z0 rail. Any imperfections in the machining process become twice as apparent when higher preloads are involved with an absence of real load. Want to feel your Z1 rail's true characteristics? Lay the rail on a clean, flat, and hard surface - then push down on the face of the carriage with light force while moving the carriage around. This better simulates real-world behavior. This makes it easy to shop for cheap Chinese rails as long as you’re familiar with Hiwin’s naming system (as described in their catalogue ). Z1 commands a higher preload between the rail and carriage than a more typical Z0 preload. Preload occurs after all space between two components (in this case the rail and carriage) is closed. Any further interference becomes preload, as these materials are too hard to physically compress.On the other hand, linear rail carriages are designed to have raceways with slightly oversized balls. This “negative clearance” is known as preload.
V-wheels are the main alternative to linear rails in the hobby space, and are widespread in 3D printers and budget laser cutters (like some variants of the K40 laser cutter). V-wheels are designed to ride on V-shaped grooves of aluminum extrusions. Because of this, they are extremely cost effective for large machines since parts of the frame also act as linear guides. The other issue with smooth rods is deflection, which is how much the rod bends when a load is applied. Deflection is the main weakness of unsupported rods, and the reason why supported rods are always preferable for moderate and heavy load applications. MGN vs HGR linear rails If you compare smooth rods to linear rails side-by-side, the first thing you’ll notice is their play, or rather clearance, as linear bearings designed for smooth rods tend to be fit quite loosely. This makes them particularly poor at withstanding loads that cause the bearing to “yaw” or tilt perpendicularly to the axis of travel. This is why they are rarely used outside of low-load applications like 3D printers and laser cutters.However, V-wheels need to be carefully tightened with a small wrench, and require maintenance as they loosen and wear out over time. V-wheels are very much a “save now, worry later” solution. Still, when properly installed, they do provide good accuracy. According to Hiwin’s official lubricating instructions , these are the recommended grease lubricants for standard applications: Manufacturer Having a higher preload is a benefit for our use case, but does change the way that rails feel when move by hand. What to expect: Linear rails and carriages have been prohibitively expensive for a long time, but in recent years their price has fallen considerably. It’s worth noting that MGN9 carriages are the only ones out of the three sizes that do not overhang a 2020 extrusion. This means that the carriage can ride right next to a panel, or that two MGN9 rails can be mounted 90 degrees apart onto the same 2020 extrusions like this:
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