Precision Gear Fitting Using Cryogenics
Our recent project involved the refurbishment and precise fitting of gears for a Krauss Maffei Twin Screw Extruder Gearbox, showcasing our capability in handling highly specialised mechanical assemblies.
The Challenge: Zero-Tolerance Gear Fitting
The gearbox in question is a high-performance, heavy-duty unit used in demanding industrial processes. The gears had no keyways, meaning that the torque is transferred solely via the interference fit between the shaft and the gear bore – leaving absolutely no room for error.
Achieving this type of fit requires extreme accuracy. Even the slightest dimensional variance can compromise the mechanical integrity and lead to premature failure under load.
The NET Solution: Cryogenic Shrink Fitting
To meet this precision challenge, NET utilised cryogenic shrink fitting, a method that involves freezing the gearbox shaft with liquid nitrogen to approximately -200°C. This causes the shaft to shrink, allowing it to be effortlessly inserted into the gear bore. Once the shaft returns to room temperature, it expands to form a tight, interference-based fit – with no need for keys or splines.
This method not only ensures the highest level of torque transfer reliability but also eliminates stress concentrations that traditional keyed designs may introduce.
Step-by-Step Process
Preparation – The gear is heated or kept at ambient while the shaft is submerged in liquid nitrogen.
Assembly – Once the shaft reaches the cryogenic temperature, it is swiftly aligned and inserted into the gear.
Stabilisation – The shaft expands as it warms, locking into place with a perfect interference fit.
Industry-Leading Expertise
With decades of experience, NET is trusted by leading manufacturers and processors across the UK and beyond. Our workshop is equipped to handle everything from legacy units to cutting-edge systems – whether it’s mechanical, electrical, or a complex mechatronic integration.