Product Details

The Kinematic Quarter Round

The Quarter Round is a different approach in kinematic design. A different reality is unlocked by simply thinking in different terms. How do you describe the surface of a Kinematic Platform?

Is it the top of the physical plate orcould it be better defined as the central plane of thekinematic system? What this changes is the very nature ofthe kinematic system. In order to achieve veryhigh levels of mechanical perfectioni.e. geometry and surface texture in the kinematicelements, they are produced as separateentities that are then attached to the platform.In order to get enhanced physical properties, i.e.hardness, stiffness and corrosive resistance in kinematicelements that are better than the material of theplatform itself, the same approach is used. By simply burying these enhanced kinematicelements in self supporting trenches that are machined intoplatform proper, the rigidity and the resonatefrequency of the platform can be raised by orders ofmagnitude.

The Quarter Round

A high quality Vee Block is one of the mostdifficult pieces of kinematic hardware to produce. For thisreason, two parallel cylinders have become apopular Ultimate Round for the flat angled facets of a Vee Block. Although very high qualitycylinders are easy to produce, it is difficult to rigidlyattach them to the Kinematic Platform. Cylinders of largediameter have a high profile, are heavy, and quiteexpensive

By splitting a precision lappedcylinder of rather large diameter into quarters, weproduce components that can be rigidly glued into a simple slotor trench machined into the Kinematic Platform.

The Ultimate Quarter Round

The "Ultimate Quarter Round" is the zenith ofperfection in kinematic components. When used in combinationwith grade 2.5 quality tungsten carbide spheres, thesecomponents will challenge present capability of errorevaluation. When used in a well-designed kinematic system, the errorbudget will be measured in nanometers and microradians.

How is this extraordinary performance achieved? We start with the choice of materials. The stiffness of tungsten carbide, measured in compression, ison the order of one hundred and twelve million pounds persquare inch. This is only surpassed by diamond in readilyavailable materials.The hardness of tungsten carbide is 91 HRAor 1500 Vickers. Abrasion tests rate it at 20 to 30 timeshard steel.

Now we compound these qualities by producing the materialwith a particulate grain diameter that is less than onemicron. As if this isn't enough, the material hot isostatic pressedto achieve 100% density, virtually eliminatingany porosity. The original cylinders that are used to produce the"Ultimate Quarter Round" are first centerless ground using adiamond wheel. They are then ring lapped to correct anyPolylobular condition. Next they are machine lapped with threeprogressively finer diamond compounds, toachieve a surface quality that is below 0.1 microinches Ra, 2.5nanometers.

The normal mounting technique is to glue the component quarter rounds into a machined trench with a highstrength ceramic filled epoxy. If the epoxy glue is objectionable, for vacuum or otherreasons, a threaded hole can be provided atthe apex of the triangular back mounting surfaces. Thismounting method has been well proven in high-endoptical applications. Unique Quarter Round components will be custommanufactured to meet any customer requirement. These mayinclude corrosion resistance and special magnetic or electricalproperties.

See here for Kinematic Cylinders prices.