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In the world of linear transmission, the MGN Series is synonymous with micro guides. Among them, MGN3—as the smallest and most difficult to manufacture specification in the series—represents the pinnacle of "miniaturization" in mass-produced linear guides.
When your design space is calculated in millimeters, yet you cannot compromise on accuracy, MGN3 is often the only choice.
The number "3" in MGN3 represents a rail width of only 3mm. To give you a visual reference, it is narrower than a standard USB-C plug.
Rail Width (W): 3mm
Assembly Height (H): Typically between 4mm - 4.5mm (including the block).
Mounting Holes: Extremely minute, usually requiring M1.6 or smaller micro screws.
Material: Because the size is too small for standard bearing steel to be effectively rust-proofed, reputable MGN3 rails and blocks almost always come standard in Martensitic Stainless Steel (e.g., SUS440C) for corrosion resistance.
Despite its tiny volume, the MGN3 retains the core structure of a precision guide.
Gothic Arch Contact Design:
It utilizes a 2-row ball circulation design. The contact interface between the balls and the raceway forms a Gothic arch, creating a 45° angle 4-point contact.
Why is this important? This design allows the guide to withstand equal loads from all four directions (up, down, left, right) while maintaining high rigidity in an extremely small space.
Ball Circulation System:
The block contains microscopic steel balls (diameter usually less than 0.8mm), end caps, and return paths. This is the most challenging part of the manufacturing process; even the slightest burr can cause jamming.
MGN3 is not built for heavy load-bearing; it is built for precision movement under space constraints.
Medical Devices: Endoscope drive mechanisms, end-effectors for minimally invasive surgical robots, and micro-injection systems in blood analyzers.
Semiconductor & Optics: Micro-lens focusing modules, chip testing probe stations.
Micro Robotics: Bionic robot finger joints, gimbal control for micro drones.
Portable Devices: Sliding mechanisms in certain high-end handheld precision measurement tools.
If you decide to use MGN3 in your project, strictly adhere to the following points. These are lessons learned from countless engineering failures:
Handling an MGN3 is like performing mechanical "surgery."
Never remove the block casually: MGN3 balls are microscopic and lack the strong retainers found in larger guides. Once the block slides off the rail, the balls will almost certainly scatter and are nearly impossible to reinstall manually.
Must use a "Dummy Rail": If disassembly is necessary, you must use the provided plastic insert tool (dummy rail) to hold the balls in place.
Due to its low inherent rigidity (because it is so thin), MGN3 relies heavily on the precision of the mounting base.
If the mounting surface is not perfectly flat, tightening the screws will force the rail to bend and deform, causing the block to run with high friction or even seize up.
Lubricant Choice: Do not use high-viscosity grease. For MGN3, thick grease creates massive viscous drag due to the tiny size of the balls. It is recommended to use low-viscosity precision instrument oil.
Preload Impact: At this scale, the effect of preload on friction is amplified. It is generally recommended to choose ZF (Micro Clearance) or Z0 (Zero Preload) grades. Unless there is an extreme rigidity requirement, avoid high preload classes.
| Feature | MGN3 | MGN7 / MGN9 | MGN12 |
| Rail Width | 3mm | 7mm / 9mm | 12mm |
| Common Use | Micro-medical, Precision Optics | 3D Printers (Voron0), Small Automation | 3D Printers, Desktop CNC |
| Load Capacity | Very Low (Motion only) | Medium | High |
| Install Difficulty | Extremely High (Micro-surgery level) | Medium | Easy |
| Price | High (Premium for manufacturing difficulty) | Affordable (Mass production) | Affordable |
The MGN3 micro linear guide is a masterpiece of precision manufacturing. Although it has limited load capacity and is extremely picky about its installation environment, it is an irreplaceable solution for achieving linear guidance within ultra-compact spaces.
Advice for Designers: Unless your space is truly compressed to the limit (e.g., total device thickness must be less than 10mm), it is usually recommended to prioritize MGN5 or MGN7, as they offer significant improvements in operational convenience and load robustness.
