| Established in 1952 | |
Page: 1790 |
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A Ball Bar (Dumbbell) is the major tool for functional "Performance Evaluation of Coordinate Measuring Machines" According to ANSI B89.4.1-1997. A Ball Bar (Dumbbell) consists of two very round spheres of exactly the same size firmly attached to opposite ends of a rather long rigid bar. The accuracy of a Ball Bar (Dumbbell) has a single major limitation. A conventional free standing Ball Bar (Dumbbell) will bend when the contact force of the measuring probe is applied to it. The longer the Ball Bar (Dumbbell), the greater the bending. With all of the automatic error correcting computer power, it should be easy enough to compensate for these Ball Bar (Dumbbell) deflections. However, these corrections turn out to be a good deal more complex than they first appear. The resulting deflection of the Ball is a rather complex vector function of gravitational sag, some simple bending and a large twisting moment. This is all complicated by the fact that there is no deflection at all on the very ends of the Ball Bar (Dumbbell). The end result of this complexity is that the C.M.M. and its software see two much smaller diameter spheres with the distance between their centers much further apart then the true dimension. |
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Cantilever Ball Bar shown with stand and
collar
( priced separately ) |
For C.M.M.s of ordinary quality, these shortcomings are of little or no consequence. The bending is fairly repeatable and the limited resolution and accuracy of ordinary machines presented little challenge for the free standing Ball Bar (Dumbbell).
With the advent of the new generation of high end C.M.M.s, a new higher accuracy Ball Bar (Dumbbell) is required.
An advance in Ball Bar (Dumbbell) technology now corrects these errors by providing two additional spheres just behind the master spheres.
These two hardened steel spheres are rigidly attached to the Ball Bar (Dumbbell) shaft.
The additional spheres are used to Kinematically support the Ball Bar (Dumbbell) in a very rigid manner, while leaving the full surfaces of the master spheres exposed for measurement.
These two kinematic couplings that support the Ball Bar (Dumbbell) are mounted near the very ends of a robust aluminum supporting structure that resists all bending.
The very rigid aluminum structure is only used as a support mechanism for the Ball Bar (Dumbbell). Its high rate of thermal expansion does not in any way influence the inter ball dimension of the steel Ball Bar (Dumbbell) itself.
The kinematic coupling that holds the first support sphere consists of three precision spheres located in a circle and rigidly mounted to the aluminum structure. The other coupling consists of two precision lapped cylinders rigidly mounted to the aluminum structure, to form a Vee-Block, that locates the second support sphere. There is a powerful rare earth magnet just below each of the couplings that pulls the support spheres solidly down against the kinematic couplings.
The Way Out Ball Bar ( Dumbbell ) support is often used with the Cantilever Ball Bar ( Dumbbell ).
| Part # | Description | Price | Purchase |
| WO-1-2 | WAY OUT RAIL 100 STANDARD BALL BAR; 200 CANTILEVER BALL BAR | $605.71 |  |
| WO-2-3 | WAY OUT RAIL 200 STANDARD BALL BAR; 300 CANTILEVER BALL BAR | $547.55 | |
| WO-3-4 | WAY OUT RAIL 300 STANDARD BALL BAR; 400 CANTILEVER BALL BAR | $547.55 | |
| WO-3.5-4.5 | WAY OUT RAIL 350 STANDARD BALL BAR; 450 CANTILEVER BALL BAR | $547.55 | |
| WO-4-5 | WAY OUT RAIL 400 STANDARD BALL BAR; 500 CANTILEVER BALL BAR | $440.63 | |
| WO-4.5-5.5 | WAY OUT RAIL 450 STANDARD BALL BAR; 550 CANTILEVER BALL BAR | $441.00 | |
| WO-5-6 | WAY OUT RAIL 500 STANDARD BALL BAR; 600 CANTILEVER BALL BAR | $571.05 | |
| WO-5.5-6.5 | WAY OUT RAIL 550 STANDARD BALL BAR; 650 CANTILEVER BALL BAR | $547.00 | |
| WO-6-7 | WAY OUT RAIL 600 STANDARD BALL BAR; 700 CANTILEVER BALL BAR | $564.13 | |
| WO-6.5-7.5 | WAY OUT RAIL 650 STANDARD BALL BAR; 750 CANTILEVER BALL BAR | $580.00 | |
| WO-7-8 | WAY OUT RAIL 700 STANDARD BALL BAR; 800 CANTILEVER BALL BAR | $649.20 | |
| WO-7.5-8.5 | WAY OUT RAIL 750 STANDARD BALL BAR; 850 CANTILEVER BALL BAR | $660.00 | |
| WO-8-9 | WAY OUT RAIL 800 STANDARD BALL BAR; 900 CANTILEVER BALL BAR | $688.40 | |
| WO-9-10 | WAY OUT RAIL 900 STANDARD BALL BAR; 1000 CANTILEVER BALL BAR | $697.95 | |
| < CMM-16 Page 1, Cantilever Ball Bar (Dumbbell) | ||
http://www.precisionballs.com |
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