Ortman Key

A low-profile method for joining two concentric cylinders. It has a low part count, and is fairly simple, but the undercuts are annoying from a DFM standpoint.

From aerocon systems.

Patent: https://www.google.com/patents/US3027631

Ortman Key


Broaching is a process for steadily removing material to create a positive or negative feature in a workpiece. In this sense, broaching is similar to milling or drilling, but it is different in the sense that it is intended to happen in one pass with one tool, and is often used to create non-circular features. This is the main advantage of broaching – it is a process that can quickly and (when done properly) precisely produce a complex feature for production. There are two different ways to categorize broaches: internal and surface, and rotary or linear.

Internal broaches are meant for expanding a pilot hole to the desired geometry of the broach, whereas a surface broach is used to create a feature on the outside of a part.

Linear broaches use a long rod with progressively deeper teeth to progressively make many cuts in the material in one pass. Linear broaches begin with roughing teeth, and end with precise teeth that match the shape of the final feature at the end.

Rotary broaches match the shape of the desired feature, but sit at a roughly 1 degree angle off-axis form the axis of rotation for the tool. This off-axis rotation causes each of the edges of the rotary broach to slightly oscillate back and forth. Since those edges have a small relief behind them, the back and forth motion takes small cuts out of the material, creating the shape of the broach. These rotary broaches can be very simple, but can also leave a slight spiral in the shape of the cut.





High Speed Magnetic Rotary Encoder

Primarily made by Austrian MicroSystems, these encoders use an array of hall effect sensors to accurately sense the angular position of a shaft (or anything that rotates with a magnet). This technology is cheap, continuous, and provides an absolute position – meaning that the motor controller has much better information to work with when magnetizing the windings.


Figure 1: from directindustry.com


Some example product details: AS5134_Factsheet_v1_7, http://ams.com/eng/Products/Magnetic-Position-Sensors

High Speed Magnetic Rotary Encoder

Belleville Springs

Belleville springs are conical washers that rely on the curvature of the shell to provide stiffness as it is compressed.

Bi-stable: Their geometry means that belleville spring can have a bi-stable snap-through behavior. This behavior can be very useful in mechanisms that we want to fail in a stable position, like this poppet valve: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090016268.pdf

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From Fundamentals of Machine Elements by Schmid, Hamrock, and Jacobson


Hysteresis: Unlike helical springs, Belleville springs also generate friction as they deform because there is a coupled radial and axial motion at the outer and inner rim. This friction creates hysteresis in the spring’s force-deflection curve that (although it can inhibit repeatability) can also act as a damper if that is needed.

Figure 12. Isothermal load–deflection curve of the Belleville spring at T t = 323 K and subsequent thermal cycle. 

From NiTi Belleville washers: Design, manufacturing and testing, by Maletta et al.


Compact: Due to the non-linear nature of Belleville springs, it is possible to get a very large stiffness in a small volume. Additionally, Belleville springs can be stacked in series (like a bellows) to reduce their stiffness, or in parallel to increase their stiffness.


From Raymondasia

Information also taken from: https://en.wikipedia.org/wiki/Belleville_washer

Belleville Springs