Part #	Description	Price	Purchase
KP-6-6-CS	KINEMATIC PLATFORM, 6" X 6", BASE PLATE WITH SPHERES	$59.00
KP-6-6-P	KINEMATIC PLATFORM, 6" X 6", PLAIN TOP PLATE	$73.00
KP-6-6-T	KINEMATIC PLATFORM, 6" X 6", DRILLED AND TAPPED TOP PLATE	$95.00

Mechanical Clamping of Kinematic Couplings
Mechanical Pre Loading of Kinematic Couplings

There is a very simple mechanical clamping technique for use on Kinematic couplings that can be used for fail-safe, high load carrying, off axis loading and vertical Kinematic couplings. This approach is very viable in high vibration environments.

The Pre Load Kit

The design consists of all of the components required for the Kinematic coupling as well as those for the clamping system. The system uses three of our standard, cylindrical post-mounted vee blocks (part number 75-VB-CBM) [3 pieces required] mounted on the lower platform. See Kinematic Catalog 105B , for the dimensions and full details. These are used with three pieces of one-quarter inch ( 1/4", 0.25", 6.35 mm) by 20 threads per inch, continuous threaded stock. This threaded stock projects up through the top of the Kinematic platform and down through the lower platform.

The vee blocks are held in position by standard one-quarter inch (6.35 MM) with 20 threads per inch heavy duty hex nuts and washers, that clamp the vee blocks rigidly to the lower platform from below (see sketch # 1).	An alternative tie down method using flathead screws can be used when the lower surface must be flush, (see sketch #2). As you can see, this design requires much more sophisticated machining.

Above the vee block the 1/4"-20 continuous threaded stock passes through a clearance hole in the upper three quarter inch ( 3/4", 0.75", 19 mm ) diameter Kinematic sphere (our part number 75-270-CH) [3 pieces required] and on through the upper platform. The two Kinematic platforms are held rigidly together by a one-inch (25.4 mm) diameter knurled clocking nut (our part number 250-20-CN) [3 pieces required]. This device is supplied with a heavy washer and a wing nut, to lock the clocking nut, for use in moderate vibrational environment. When situations of severe vibration are encountered a special clocking nut, fitted with our barn door clamping system may be required. Please contact our engineering department. This device includes a ball thrust bearing which decouples the torque of the clocking nuts rotation. This nut transfers the clamping force through a self-aligning three quarter inch (19 mm) diameter spherical tilt (our part number 75-ST-270) [3 pieces required]. The clocking nut has a timing line engraved on the face, so that the applied force can be repeated, by simply clocking the position of this engraved line.

A complete set of the Kinematic coupling hardware and the mechanical clamping kit, with all three sets of the components is available as (our part number FS-KIT-750), (see sketch #3).

Some advantages of using this clamping technique is that a much higher clamping force can be applied because three screws are utilized instead of one. These three clamps are placed far out towards the edges of the platform, leaving the center of the platform for mounting the payload.

The mechanical stability of the three-clamp platform is much better because the clamping force is applied as far out as possible. The downside to this design is that there are four lose pieces of hardware that must be assembled for each clamp.

Bottom Mount

The mechanical clamp can be mounted so that the clamping screw projects out the bottom side of the platform. This leaves the front face clear of any protrusions that would interfere with mounting the payload.

If the end of the clamping assembly is obscured by this inverted mounting, it may be advisable to use a hex “jam nut” instead of the usual wing nut supplied.

Clamping Small Platforms

On small platforms, a single clamp, located in the center of the platform may suffice. Using only one clocking nut with one spherical tilt and a single piece of 1/4-20 continuous threaded stock, located in the exact center of the Kinematic coupling good results may be achieved. (our part numbers 250-20-CN and 75-ST-270).

Spring Loading

Spring-loaded clamping may be desirable in some special applications. When this option is used it is only necessary to add a spring of the proper rate and a washer between the clocking nuts and the spherical tilt, or between the bottom of the spherical tilt and the upper platform.

Summary

The complete three piece set of Kinematic coupling hardware and the three-element fail-safe Kinematic clamping kit is available as (our part number FS-KIT-750). It consists of the following:

Mechanical Clamping

A mechanical clamping technique has been developed for this platform so that it can be used in off axis for fail safe, for high load situations and in high vibration environments.

This mechanical clamping kit consists of a 5/8-inch (16 mm) outside diameter plug with 18 threads per inch, (our part number 625-250-PLUG), that screws into the center hole in the lower platform. It has a 1/4-inch (6.3 mm) by 20 threads per inch, center hole that will accept a length of continuous threaded stock. A similar plug with a .280-inch (7.1 mm) diameter clearance hole, (our part number 625-280-PLUG), which screws into the upper platform. A rather long piece of continuous threaded stock passes through this hole and through a self-aligning spherical tilt (our part number 75-ST-270). This spherical tilt is used to isolate any X-Y or Z misalignment of the clamping force. The entire assembly is tied together by a clocking nut (our part number 250-20-CN). This clocking nut includes a ball thrust bearing that decouples the torque from the clamping. A wing nut and a washer are supplied to use as a jam nut, under conditions of moderate vibration. The entire kit including all of the parts required is (our part number KP-CLAMP).

Spring Load

When a spring-loaded force is preferred, for pre-loading, a very simple arrangement will suffice. By just insert a spring, of the desired stiffness, between the clocking nut and the spherical tilt or between the spherical tilt and the platform the job is complete.

Custom Versions

Custom versions of this platform will be quoted. The platforms can be supplied, hard anodized or nickel-plated and or with reference surfaces flat lapped.

The same basic design can be built with cemented tungsten carbide components that will give greater load carrying capacity, higher resonant frequency and more accurate repeatability.

It should also be noted that cemented tungsten carbide components will carry very heavy loads, with no signs of fretting.

Flexures

Many customers use the Kinematic Platform with flexure bearings. See our web page on flexures.

12" x 16" pre assembled Kinematic Platform

The 12 inch by 16 inch (304mm by 406mm) Kinematic Platform is a well-established design, with years of successful use.

This seasoned design is rugged, but at the same time it is lightweight.

A high stiffness is achieved through an integral ribbed structure. The cast aluminum design provides good damping and high stiffness.

The upper platform is one and one half inches (38 mm) thick but weighs only 16 pounds, (7.2 KG). The overall height from the bottom of the lower platform to the top of the upper platform is three and one quarter inches ( 3 1/4", 82.6 mm ).

The Kinematic couplings used on this platform are of a high load carrying design. It uses three spheres of three quarter inch ( 3/4", 19mm ) diameter on the base and three cylindrical vee's on the upper plate. The three spheres are not ordinary steel bearing balls; but are ultra fine grain, high chrome, high carbon stainless steel that is hardened to 58 HRC minimum and precision lapped to AFBMA instrument quality grade 10. Standard steel bearing balls used in competitive products are prone to rust and are very susceptible to fretting, which is one of the major problems of Kinematic couplings.

The Kinematic couplings in the upper platform consist of three pair of one-half inch ( 1/2", 12.7 mm) diameter cylinders that form three vees. These cylinders are securely glued into three precision-machined trenches, with a ceramic filled epoxy, that has a 3000-pound per square inch (535 kg per square cm) shear strength. These cylinders are made of exactly the same material and processed in the same manner as the precision balls. After hardening, these cylinders are ground and precision lapped to a surface texture that is below one microinch (25 nm) Ra. This contrasts with competitive products that use commercially ground only dowel pins, made of carbon steel that is prone to rust and very susceptible to fretting.

There are two standard versions of the 12"-16" upper platforms.

It is available with a plain flat top surface, so that our customer can provide any custom mounting facilities they desire; or we will bid machining the mounting features to your blue print or rough sketch. The top surface of this platform is ground flat. This plain configuration is the least expensive. It is part number KP-12-16-P.

The upper platform is also available in our standard breadboard configuration with four precision machined tee slots that use standard three eighths of an inch ( 3/8" ) or M10 Tee-nut hardware. This arrangement allows an infinite variety of mounting configurations. The top surface of this platform is ground flat. This is part number KP-12-16-S.

There are also two standard versions of the lower platform. The first version of the lower platform is built in a rugged triangular configuration. There are three slots that run the length of each leg of the triangle, that will accept either three eighths of an inch or M10 socket head cap screws, for holding this platform to its mounting surface. There is also a recessed ridge around the inside and outside rim of the triangle that will facilitate the use of hold down clamping. This lower platform is part number KP-12-16-CS.

The second standard version of the lower platform consists of three separate, one and one half inch ( 1 1/2", 38 mm) wide, by one inch ( 1", 25.4 mm) thick, by five-inches ( 5", 127 mm) long bars. Each bar has an instrument quality, grade 10, sphere rigidly mounted on one end and a four inch long recessed slot, that will accept a three eighths of an inch or M10 socket head cap screw to hold it down. This set of 3 pieces is part number KP-3-HEAVY-BAR.

With a symmetrical light load, the 12-16 platform can repeat in all six degrees of freedom within 4 microinches (0.1 micrometers).

This platform will carry up to 100 pounds ( 45 kg ) of load safely.

Mechanical Hold-Down

The substantial weight of the upper platform, at 16 pounds ( 7.2 kg ), usually precludes the need for additional preload; there are, however, circumstances that do require it.

Vertical Mounting

With it's very rugged construction this platform lends itself to vertical or even upside down mounting.

The facility for mechanical pre loading is built right into the design of the 12-16 Kinematic platform.

A special version of the three quarter inch ( 3/4", 19 mm ) diameter spheres used in both versions of the lower platforms can have a one-quarter inch ( 1/4", 6.4 mm) diameter clearance hole drilled through them. The three quarter inch ( 3/4", 19 mm) diameter Kinematic sphere with clearance hole drilled through it is (our part number 75-270-CH). Three of these parts are required.

Then a one-quarter inch ( 1/4", 6.3 mm ) by 20-threaded hole is drilled and tapped below these spheres. There is a one quarter inch ( 1/4", 6.3 mm) diameter clearance hole drilled through the upper Kinematic platform that allows a piece of continuous threaded stock to screw into the lower platform and pass up through the upper platform.

When mechanical clamping is used, it is important to isolate all of the potential X-Y and Z axial errors to prevent any cocking tendencies when the clamping force is applied. This is done by incorporating a spherical tilt between the clamping force and the top of the platform. This spherical tilt is (our part number 75-ST-270). The full mechanical clamp requires three of these parts.

The clamping force to hold the two platforms together is provided by three, one-inch ( 1", 25.4 mm) diameter knurled clocking nuts, ( part number 250-20-CN). These clocking nuts include a ball thrust bearing that decouples the torque generated by tightening these nuts. A wing nut and washer are supplied to be used as a jam nut, under conditions of moderate vibration. Three of these parts are required.

The clocking nut is a one-inch ( 1", 25.4 mm ) diameter knurled, stainless steel device, with a clocking line engraved on the top face, so that the clamping force generated by tightening it can be repeated time after time. This clamping force will have a major effect on the "Z" axis position as well as the pitch and roll of the upper platform.

Note: If mechanical clamping is going to be required, it must be ordered at the time the platform is purchased.

Spring Loading

Spring-loaded clamping may be desirable in some applications. When this option is used, it is only necessary to add springs of the proper rate and washers between the clocking nuts and the spherical tilts or between spherical tilt and the platform.

A 12-16 Kinematic platform that is provided with mechanical clamping can be converted back to a simple platform by just unscrewing the three pieces of 1/4-20 continuous threaded stock.

The complete mechanical clamping kit, with all three sets of components, installed on the platform is part number 12-16-FS-KIT-750.

Additional information on mechanical clamping of Kinematic couplings may be found in the addendum to our Kinematic Catalog 105B.

Custom Versions

Other features, such as hard anodize, nickel plated surfaces, or precision flat lapped reference surfaces can be supplied on special order.

This Kinematic platform can be supplied with cemented tungsten carbide component parts that will give higher load carrying capacity, a higher resonate frequency and much better repeatability.

The upper platform can also be supplied with a pattern of drilled and tapped holes of either English or metric diameter to suite the customer's requirements.

Three Dimensional Calibration Device
3D Ball Plate

The three-dimensional, 3D, ball plate is one of the oldest calibration devices for the evaluation of Coordinate Measuring Machines. It dates back to the beginning of the commercial use of C.M.M.'s, where it was used with hard probes (conical cups) to evaluate the machines' overall performance. There are three mating pairs of precision ground and lapped cylinders that are rigidly mounted in three precision-machined trenches in the bottom surface of the upper platform. These three pairs of cylinders form three Kinematic Vee Blocks. This upper platform containing the nine spherical masters can be removed and replaced any number of times, within less than one microradian. Building a practical three dimensional ( 3-D, 3D ) calibration artifact for modern Coordinate Measuring Machines is a tricky proposition. To be of any practical value, the artifact must be fairly large. It also must be rugged enough to be mechanically stable. This means that it must be able to withstand at least moderate handling and shipping abuse, but still be able to perform its task. It must remain dimensionally stable over long periods of time. The materials used must not twist or turn. They must not grow or shrink with time. This job is accomplished by erecting a series of nine very rigid vertical posts, of different heights, from the surface of a stiff, flat pallet. The standard post heights are 12 inches (305 mm), 6 inches (152 mm) and 2 inches (51 mm).

Base for Three Dimensional Ball Plate

On the top of each of the nine vertical posts is rigidly attached a very precise master sphere.

For use on machines with touch trigger, or other mechanical probes, a one-inch (25.4 mm) diameter sphere is normally used. These spheres are made of a very high chrome, high carbon, Martensitic stainless steel. This ultra fine grain material is hardened and thermal cycled to produce a minimum hardness of 58 HRC (Hardness on the Rockwell "C" scale). This special thermal cycle promotes long term dimensional stability.

All nine of the balls are precision lapped spherical and exactly same the diameter within five micro-inches (one hundred twenty five nanometers) tolerance.

When the C.M.M. probe used is a non-contact laser scanner of other optical device, the balls used are usually a satin finished white ceramic material. The reduced surface quality of these satin finished balls limits the sphericity and common diameter to twenty-five micro-inches (0.63 micrometers). Balls made of many other materials, and diameters, can be supplied on special order. Satin finished steel and titanium are two of the more common.

The rather large dimensions of the 3 D Ball plate, that are 12 inches (305 mm) by 16 inches (406 mm), requires an exceptional mounting method to avoid mechanical distortion. This is made more important, as any bending of the plate will cause serious first order errors in the spacing of the balls on the tops of the rather long posts.

In order to gain perfect repeatability of all the elastic deflections, the platform of the 3 D Ball plate is Kinematically mounted.

The base for this kinematic mount consists of a triangular aluminum casting that is rigidly attached to the CMM table. Three high quality, hard Martensitic stainless steel, spheres, are rigidly mounted at the corners of this triangle.

The Kinematically mounted upper platform is equipped with two sets of isolated handles to facilitate placing it in position on the triangular platform, without any personal contact with the metrology elements.

Even though the 3-D Ball Plate is rather large and very rugged, it weighs only 30.5 pounds (13.84 kilograms). This is well below the 44-pound O.S.H.A. limit, to be handled by a single technician.

The device can be custom built in other dimensional configurations. It can be configured with taller or shorter posts. It can also be built on a larger or smaller pallet. It can have a totally different aspect ratio, so that it is long and narrow.

Kinematic Clamping Component Pricing

Part #	Description	Price	Purchase
12-16-FS-KIT-750	KINEMATIC PLATFORM, 12" X 16", MECHANICAL THREE SWIVEL CLAMP KIT	$223.00
250-20-CN	KNURLED CLOCKING NUT FOR CLAMPING KIT	$19.00
250-20-TD	SCREWS FOR KINEMATIC PLATFORM TIE DOWN KIT	$17.00
3DBP12X16	THREE DIMENSION BALL PLATE, 12" ( 30 CM ) X 16" ( 41 CM )	$2500.00
625-11-MG-N	MAGNETICALLY PRELOADED KINEMATIC COUPLING	$24.62
625-11-MG-S	MAGNETICALLY PRELOADED KINEMATIC COUPLING	$24.62
625-18-HPD	HIGH MAGNETIC PERMEABILITY PLUG	$9.62
625-18-MG-KIT	MAGNET PRELOAD KIT, INCLUDES N/S MAGNET, PLUG	$55.80
625-18-MG-N	MAGNETIC PRELOAD KIT, NORTH	$24.62
625-18-MG-S	MAGNETIC PRELOAD KIT, SOUTH	$24.62
625-20-MG-N	MAGNETICALLY PRELOADED KINEMATIC COUPLING	$24.62
625-20-MG-S	MAGNETICALLY PRELOADED KINEMATIC COUPLING	$24.62
625-250-PLUG	PLUG FOR MECHANICAL CLAMP, KP-CLAMP, LOWER PLATE	$12.00
625-280-PLUG	PLUG FOR MECHANICAL CLAMP, KP-CLAMP, UPPER PLATE	$12.00
625-HPD	KINEMATIC COUPLING	$9.62
75-ST-270	SPHERICAL TILT, 3/4" DIAMETER	$32.00
CR-625-18-MG-N	MAGNETICALLY PRELOADED KINEMATIC COUPLING	$32.90
CR-625-18-MG-S	MAGNETICALLY PRELOADED KINEMATIC COUPLING	$32.90
CR-625-HPD	MAGNETICALLY PRELOADED KINEMATIC COUPLING	$18.00
KP-12-16-CS	KINEMATIC PLATFORM, 12" X 16", BOTTOM TRIANGLE	$124.00
KP-12-16-P	KINEMATIC PLATFORM, 12" X 16" PLAIN TOP PLATE	$148.00
KP-12-16-S	KINEMATIC PLATFORM, 12" X 16" TOP WITH T SLOT	$166.00
KP-3-3-CS	KINEMATIC PLATFORM, 3" X 3", BASE PLATE WITH SPHERES	$49.00
KP-3-3-P	KINEMATIC PLATFORM, 3" X 3", PLAIN TOP PLATE	$72.00
KP-3-3-P-4BAR	KINEMATIC PLATFORM, 3" X 3", TWO PIECE SET 3X3 PLAIN WITH FOUR BAR BOTTOM	$124.00
KP-3-3-P-CS	KINEMATIC PLATFORM, 3" X 3", TWO PIECE SET 3X3 PLAIN	$111.00
KP-3-3-T	KINEMATIC PLATFORM, 3" X 3", DRILLED AND TAPPED TOP PLATE	$92.00
KP-3-3-T-4BAR	KINEMATIC PLATFORM, 3" X 3", TWO PIECE SET 3X3 TAPPED WITH FOUR BAR BOTTOM	$160.00
KP-3-3-T-CS	KINEMATIC PLATFORM, 3" X 3", TWO PIECE SET 3X3 TAPPED	$127.00
KP-4-BAR	KINEMATIC PLATFORM, BASE FOUR PIECE BAR SET	$59.00
KP-4-HEAVY-BAR	KINEMATIC PLATFORM, 12" X 16", BOTTOM FOUR PIECE BAR SET	$89.00
KP-6-6-CS	KINEMATIC PLATFORM, 6" X 6", BASE PLATE WITH SPHERES	$59.00
KP-6-6-P	KINEMATIC PLATFORM, 6" X 6", PLAIN TOP PLATE	$73.00
KP-6-6-T	KINEMATIC PLATFORM, 6" X 6", DRILLED AND TAPPED TOP PLATE	$95.00
KP-CLAMP	KINEMATIC PLATFORM COMPLETE CLAMPING KIT	$75.00
SP-3-3	KINEMATIC PLATFORM, 3" X 3", SUB PLATE	$17.00
SP-6-6-P	KINEMATIC PLATFORM, 6" X 6", SUB PLATE	$19.00

Kinematic Components Price List	Return to Catalog 105-B
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