A. G. Davis
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Standard Rotary Table Features
A. G. Davis-AA Gage Rotary Tables
The Precision Rotary Tables are designed for use in Metrology, Inspection, and other precision applications. The Rotary Tables can be supplied with stand-alone or rack-mounted controllers, or can be interfaced to your operational Rotary Axis Control. The control is a solid-state, closed-loop system incorporating the latest State-of-the-Art concepts and can include IEEE or RS232 interface for remote program control.
Air Float Capstan Servo (AFCS) Rotary Tables
The Air Float Rotary Table consists of hardened steel faceplate, which is floated on air in the thrust plane and centered by preload ball bearings radially during rotation. After an index move is completed the Air float is shut off allowing the faceplate to rest on the base of the rotary table producing excellent wobble characteristics. This action also friction locks the Air Float Rotary Table. A high-grade meehanite base casting is used to support the faceplate. Standard faceplate mounting pattern is by threaded hole patterns with other configurations available. The Air Float Type Precision Rotary Table can only be used with the faceplate in the horizontal plane.
The Rotary Table radial ball bearing is permanently lubricated with high quality grease.
General (AFCS) Specifications
| Horizontal Face Plate (Vertical Axis of Rotation) |
Accuracy Grades | ||
| 30 | 50 | 100 | |
Radial Motionat 1.0 in. (25.4mm) |
0.000030 (.0008 mm) |
0.000050 (.00127 mm) |
0.000100 (.0025 mm) |
Radial Motionat 12.75 in. (323.8mm) Above Face Plate |
0.000050 (.00127 mm) |
0.000075 (.00191 mm) |
0.000150 (.00381 mm) |
Axial Motion |
0.000020 (.0005 mm) |
0.000040 (.0010 mm) |
0.00080 (.0020 mm) |
Tilt Motion(Arc Second Band) |
0.5 | 1 | 2 |
| Note- Geometry Specifications apply when the Air Float Rotary Table is locked. (Air Float off) | |||
Ball Bearing Capstan Servo (BBCS) Rotary Tables
The Ball Bearing Rotary Table consists of hardened steel faceplate supported by a maximum diameter preloaded angular contact ball bearing. The large diameter ball bearing produces excellent wobble characteristics. The preloaded ball bearing along with the closed loop servo system provides for continuous as well as point-to-point measuring. A high-grade meehanite base casting is used to support the ball bearing. Standard faceplate mounting pattern is by threaded hole patterns with other configurations available.
The Rotary Table's preloaded angular contact ball bearing is permanently lubricated with high quality grease.
General (BBCS) Specifications
| Horizontal Face Plate (Vertical Axis of Rotation) |
Accuracy Grades | ||
| 15 | 30 | 60 | |
Radial Motion(25.4mm) Above Face Plate |
0.000015 (.00038 mm) |
0.000030 (.00076 mm) |
0.000060 (.0015 mm) |
Radial Motionat 12.75 in. (323.8mm) |
0.000030 (.00076 mm) |
0.000060 (.0015 mm) |
0.00120 (.0030 mm) |
Axial Motion |
0.000004 (.00010 mm) |
0.000008 (.0002 mm) |
0.000016 (.0004 mm) |
Tilt Motion(Arc Second Band) |
0.45 | 0.85 | 1.7 |
Air Bearing Capstan Servo (ABCS) Rotary Tables
The Air Bearing Rotary Table consists of hardened and stabilized stainless steels and/or high-grade steels with corrosion resistant coatings. The base is made from high-grade meehanite castings. The Rotary Table employs a fully trapped gas bearing for both radial and thrust planes. The gas bearing jets are manufactured of precision machined gemstones. The air bearing along with the closed loop servo system provides for continuous as well as point to point measuring. Standard faceplate piece part hold down consists of threaded hole patterns, or special configurations are optionally available.
Air bearings require small clearances between rotating members. The possibility of these surfaces contacting each other during rotation is a major concern of air bearing users. Typically when this touch down does occur conventional air bearings will seize up and require major repairs. A.G. Davis-AA Gage has eliminated this possibility. The air orifice manifold detail is constructed from hardened stainless steel. The opposing surfaces are constructed from high-grade hardened steel and coated with a proprietary material. This construction permits the air bearing to lose air pressure while rotating even under maximum rated load and not damage the air bearing thrust and radial precision surfaces. After the air pressure is reinstated the bearing will freely operate as before.
General (ABCS) Specifications
| Horizontal Face Plate (Vertical Axis of Rotation) |
Accuracy Grades | ||
| 2 | 4 | 8 | |
Radial Motionat 1.0 in. (25.4mm) Above Face Plate |
0.000002 (.00005 mm) |
0.000004 (.00010 mm) |
0.000008 (.00020 mm) |
Radial Motionat 12.75 in. (323.8mm) Above Face Plate |
0.000004 (.00010 mm) |
0.000008 (.00020 mm) |
0.000016 (.00040 mm) |
Axial Motion |
0.000002 (.00005 mm) |
0.000004 (.00010 mm) |
0.000008 (.00020 mm) |
Tilt Motion(Arc Second Band) |
0.07 | 0.10 | 0.14 |
Zero Backlash Servo Drive
The servo drive utilizes a capstan type friction wheel drive system. This drive system eliminates backlash (lost motion) between the servo motor and the Rotary Table it must position. The zero backlash condition provides an excellent foundation for a servo system which positions accurately without instability over a wide range of payload conditions.
Non-Influencing drive
The drive is constructed to eliminate any side loading of the rotary table bearings. Tangential loading only. This is accomplished by mounting the entire capstan drive package on a pivot which is tangent to the table drive rim. The main capstan drives on the O.D. of the drive rim while an opposing wheel bearing runs on the I.D. of the drive rim. The drive force required to engage the main capstan is provided by the opposing wheel bearing which creates a pinching action on the drive rim. This pinching action along with the pivot allow the drive to follow the drive rim's motion without imparting any force to the rotary tables precision bearings. Note -unwanted side loading of the rotary table bearing will cause an increase
Optional Base Air Ride (Float) System
The base of the rotary table can be provided with air jet pads. These pads when actuated allow the rotary table to float on a level continuous flat surface. This feature is particularly convenient to CMM users who often move the rotary table to other locations on the CMM for various applications. The Air Ride is actuated by a dead man switch (automatically turns off when released). The switch is located adjacent to the drive cover.
Optional Zero Home Switch
A micro switch can be provided to close approximately 10° to 15° before the encoder's marker pulse. The approach direction can be either clockwise or counterclockwise. Specify the desired approach direction when ordering. The encoder marker pulse will be located within 5° of the rotary tables zero position (the RT outline drawing shows the rotary table at it's zero position).
Optional Freewheel Switch
A switch (DISENGAGE/ENGAGE DRIVE) can be provided adjacent to the drive cover. This toggle switch actuates a cylinder that alternately disengages and/or engages the drive. This switch also turns the Air Float Bearing on and off. This permits freewheel rotation of the face plate for faster centering and complete manual operation.
Optional Hiedenhain EXE or IBV Mounting Location
The Hiedenhain EXE or IBV can optionally be mounted internal to the Rotary Table or externally. Or can be provide for separate mounting by the user.
Encoder Options
| Description | Resolution Multiplier | Encoder Options | ||||
| Heidenhain Encoder P/N | RON-886 (36,000 Lines) | RON-806 (36,000 Lines) | RPN-886 (180,000 Periods) | ERP-880 (180,000 Periods) | RON-905 (36,000 Lines) | |
| Maximum available thru hole | 2.00[50.8] | 2.00[50.8] | 2.00[50.8] | 2.10[53.3] | None | |
| Incremental Signals | 1 Volt pp | 11 m Amp pp | 1 Volt pp | 1 Volt pp | 11 m Amp pp | |
| *Coupling Elasticity (Arc Second Band) | .30 | .30 | .30 | None | .30 | |
| *Signal period Error (Arc Second Band) | .36 | .36 | .072 | .072 | .30 | |
| *Once per revolution Accuracy (Arc Second Band) | 1.64 | 1.64 | 1.64 | 1.64 | 0.5 | |
| *Total Accuracy (Arc Second Band) | 2.0 | 2.0 | 1.7 | 1.7 | 0.8 | |
| Heidenhain Servo Resolution Extension Electronics P/N | IBV-660B | EXE-660B | IBV-660B | IBV-660B | EXE-660B | |
| Resolution | x 100 | .0001o | .0001o | .00002o | .00002o | .0001o |
| x 200 | .00005o | .00005o | .00001o | .00001o | .00005o | |
| x 400 | .000025o | .000025o | .000005o | .000005o | .000025o | |
| x 800 | .0000125o | .0000125o | .0000025o | .0000025o | .0000125o | |
| x 1600 | .00000625o | .00000625o | .00000125o | .00000125o | .00000625o | |
| Angular Positioning Repeatability (6 Sigma) (Arc Second Band) | x 100 | 0.51 | 0.51 | 0.22 | 0.10 | 0.44 |
| x 200 | 0.33 | 0.33 | 0.33 | 0.07 | 0.26 | |
| x 400 | 0.24 | 0.24 | 0.20 | 0.05 | 0.17 | |
| x 800 | 0.20 | 0.20 | 0.17 | 0.04 | 0.12 | |
| x 1600 | 0.17 | 0.17 | 0.17 | 0.035 | 0.10 | |
| Angular Positioning Accuracy per NMTBA (Arc Second Band) | x 100 | 3.02 | 3.02 | 2.44 | 2.20 | 1.67 |
| x 200 | 2.66 | 2.66 | 2.66 | 2.14 | 1.31 | |
| x 400 | 2.48 | 2.48 | 2.40 | 2.10 | 1.13 | |
| x 800 | 2.39 | 2.39 | 2.34 | 2.08 | 1.04 | |
| x 1600 | 2.35 | 2.35 | 2.34 | 2.07 | 1.00 | |
| The Angle encoders normally produce sinusoidal scanning signals either 11uApp or 1Vpp. The Subsequent electronic EXE or IBV boxes convert them into a square-wave pulses (digitizing). They can be switched between 25,50,100,200 and 400 fold interpolation of the signal and with the help of a 1,2 and 4 fold evaluation to yield the desired servo resolution. | ||||||
| *Note – See Measuring Accuracy section in Heidenhain’s Angle Encoders Catalog | ||||||
| Note - Repeatability and Positioning Accuracies shown are typically expected values and are dependent on the quality of the servo control system. | ||||||