A hollow rotary table brings clear advantages to rotary indexing. Its through-hole routes wiring, air, and vacuum lines directly through the rotation axis. Servo-driven positioning accuracy rivals solid tables, with repeatability in the arc-second range and measurable space savings over setups that need external rotary unions. An indexing hollow rotary table wins on integration and clean routing; solid tables still suit high-moment, large-diameter loads.

Key Takeaways

• Hollow rotary tables route cables and air lines through a center hole, saving space and reducing clutter.
• They match solid tables in accuracy and load capacity when sized correctly, with repeatability within arc-seconds.
• Choose hollow tables for through-axis needs; choose solid tables for high-moment, large-diameter loads.

Rotary Indexing Fit: Where Hollow Rotary Tables Earn Their Place

Defining Rotary Indexing Motion

Rotary indexing converts a uniform drive movement into a cyclical output movement. Rotary indexing tables, also called cycling tables, repeat this pattern with each cycle. A barrel cam indexer produces accurate, repeatable intermittent motion through two cam sections:

• The index cam section moves the fixture into its process position.
• The dwell cam section holds the part in-station with no movement.

A constant lead cam changes this model. A servo motor sets the index period and dwell period electronically, and the drive reads the encoder and corrects position continuously. Pneumatic designs deliver fixed steps with mechanical hard stops, so error does not accumulate.

Hollow Rotary Table Application Case: Through-Hole Routing

A hollow rotary table application case often centers on the central bore. Cables, air tubes, vacuum lines, and sensors pass directly through the axis. This routing stays compact and organized, and it avoids twisting and extra cable management devices. The center can also stay open for tooling access or an inspection light path. A hollow rotary table application case in a fourth machining axis shows the same benefit. Engineers must still check connector envelope, bend radius, clearance, and bore sizing. Continuous rotation may require a slip ring or rotary union.

Matching Table Type to Load and Duty Cycle

A hollow rotary actuator suits rotary motion occasions requiring high precision and compact structure, such as 4 stations precision positioning or 8 stations rotary positioning on an automatic production line. A hollow rotating table and a hollow rotating platform both support precise angular positioning. A servo rotary platform delivers positioning accuracy that rivals solid tables. The hollow rotary actuators family fits light-to-medium loads with through-axis needs. Solid tables remain the choice for high-moment, large-diameter loads. Duty cycle and load moment decide the fit.

Hollow Rotary Table Performance, by the Numbers

Speed, Accuracy, and Repeatability Data

Performance specifications separate a capable indexing hollow rotary table from a marginal one. Manufacturers publish three core figures: allowable plate speed, positioning accuracy, and repeat positioning. These numbers tell engineers whether a table can meet cycle time targets and hold part tolerance across thousands of cycles.

The TMR series illustrates a consistent performance band across four frame sizes. Every model in this family reaches an allowable plate speed of 200 r/min, a positioning accuracy of ±0.5 arcmin, and a repeat positioning of ≤10 arcsec.

A second specification set shows a wider performance envelope. One hollow rotary table platform rates a permissible table surface speed of 120 rpm, a positioning accuracy of ≤2 arcmin, and a repeatability of ±5 arcsec (0.001°). The tighter repeatability figure matters most for rotary indexing. Repeatability describes how consistently the table returns to the same commanded angle. A ±5 arcsec band equals roughly 0.0014 degrees of scatter, which supports high repetitive positioning accuracy in multi-station processes.

The hollow structure of servo rotary table designs enables this performance. A servo motor drives the table through a single-stage helical gear deceleration mode, and an encoder closes the position loop. The ac servo motor corrects for small errors on every cycle. This closed-loop control delivers precise angular positioning without the cumulative drift that open-loop mechanisms can develop.

Rigidity and Load Capacity Compared

Rigidity and load capacity determine whether a table survives the cutting forces, payload weight, and moment loads of a given process. The cross roller bearing of the rotary table carries both axial and radial loads in a compact envelope. Precision cross roller bearings spread load across the full raceway, which supports high rotation accuracy under combined loading.

Load ratings scale with table diameter. The TMD series shows a steady climb from small to large frames.

The TMR series follows the same pattern with different values. The TMR60-30 rates 400 N radial and 400 N axial, with a 400 N allowable axial load. The TMR120-30 jumps to 9000 N radial and axial, with a 3000 N allowable axial load. The TMR165-30 reaches 18000 N radial and axial, with a 7000 N allowable axial load. The TMR240-30 lists a 12000 N allowable axial load. One heavy-duty model, the ZCM260-L1, rates 29600 N allowable axial load and 29600 N allowable radial load.

A direct comparison at equal diameter answers the hollow-versus-solid question. At 100 mm, the solid-core AY110-100-SC and the hollow-core AY110-100 both rate 45 kg of load capacity. The solid-core advantage appears in rigidity and payload support, not in a higher rated load. Hollow-core models span 1 kg to 100 kg depending on size. The largest capacities, 55 kg to 100 kg, appear in 200 mm to 400 mm hollow units. A 200 mm hollow model with a 60 mm aperture reaches 100 kg. A 400 mm hollow model with a 180 mm aperture reaches 75 kg.

These figures show that a hollow rotary table can match a solid table on rated load when engineers size it equivalently. The cross roller bearing provides the stiffness that indexing and positioning demand. Engineers should still check moment load separately. A large-diameter load hung far from the table face creates a moment that axial and radial ratings alone do not capture.

Space Savings and Integration Benefits

Space savings drive table selection in most automated systems. Compact installation ranks as a key selection requirement for rotary positioning products. A hollow rotary table delivers this benefit through its center bore. Cables, hoses, and vacuum lines pass through the hollow center, which frees space where installation room is limited.

Integration benefits extend beyond footprint. The hollow center reduces clutter and potential failure points in automated systems. A stable table surface with a central through-hole supports fixtures and part orientation. Servo integration fits within constrained installation space. Advanced transmission systems built into the unit deliver smooth, efficient operation. The result is a compact precision drive unit that combines rigidity, transmission efficiency, and positioning accuracy in one module.

A hollow rotary table application case in a multi-station line shows the practical effect. An eight-station indexing dial routes all sensor and air lines through the center bore. The design eliminates an external rotary union and the cable carrier that a solid table would need. Fewer moving parts mean fewer wear points and a cleaner machine layout.

Custom machines often combine compact installation, hollow center access, fixture support, servo positioning, indexing, and part orientation in a single station. A hollow rotary table or platform fits this role when the design needs a stable table surface with a central through-hole. The table handles rotary indexing and holds precise angular position while the through-hole carries services to the tooling. Engineers who weigh space, routing, and positioning together usually find the hollow design covers all three.

Hollow vs. Solid: Compliance, Cost, and Selection

Regulatory Compliance Considerations

Compliance requirements shape table selection as much as performance data does. A hollow rotary table introduces a large open bore, and that opening changes how a machine meets ingress protection and safety standards. Dynamic sealing across a rotating aperture is harder to achieve than sealing a solid face. Engineers who specify a hollow unit for washdown, outdoor, or dusty environments should plan for additional sealing design, validation testing, and non-recurring engineering cost. A solid table reaches IP67 or IP68 protection with mature, low-cost seal designs.

Safety standards add another layer. Machines with continuous rotation need guarding that accounts for cables passing through the axis. A hollow design that routes lines internally simplifies this guarding because the cables never sweep through the work envelope. Risk assessment teams often find fewer pinch and catch hazards on a hollow installation. The trade-off is that the internal passage must still meet bend radius and strain relief rules for the cables it carries.

Supplier qualification belongs in the compliance plan. Hollow units come from a smaller pool of specialized vendors. A second source protects against supply interruptions and keeps compliance documentation current. Solid tables remain widely available from hundreds of suppliers, which eases qualification for standard indexing tasks.

Total Cost of Ownership Data

Purchase price tells only part of the cost story. A hollow unit typically carries a 30 to 60 percent price premium over a comparable solid table, so the buying decision must rest on total cost of ownership. The table below breaks down the major cost factors.

The cable management line often decides the case. A solid table forces external routing, and external cables wear, snag, and fail. Each field failure carries replacement cost, downtime, and warranty exposure. A hollow rotary table application case on a high-cycle line can repay its price premium through fewer cable-related stoppages alone. The encoder and bearing lines push the other way. Off-axis ring encoders and thin-section bearings cost more and demand careful handling during assembly.

Maintenance access affects uptime and total cost as well. Ease of inspection, lubrication, calibration, and part replacement all feed into the ownership equation. Buyers should ask how quickly a technician can reach the encoder, the bearing, and the cable passage on each design. A table that is cheap to buy but slow to service can cost more across a ten-year life.

Where Each Table Type Fits Best

The two designs serve different jobs, and the right choice follows the application. The comparison below summarizes the practical differences.

A hollow rotary table fits best when lines must cross the rotation axis. Multi-station dials, fourth-axis machining, robotics with continuous panning, and inspection stations all benefit from internal routing. The servo motor and cross roller bearing inside a quality hollow unit deliver positioning accuracy and repeated positioning accuracy that match solid tables at equal size. Rotary indexing on an eight-station line becomes cleaner when every air line and sensor cable passes through the bore.

A solid table fits best when the load is large in diameter and heavy, or when moment loads dominate. Solid construction puts more material where stiffness matters, and the design reaches high ingress protection with simple seals. Standard rotary indexing tasks with no through-axis need rarely justify the hollow premium. Basic setups also install faster with a solid unit.

Selection should follow four checks. First, confirm whether the process needs a through-hole for wiring, air, or vacuum. Second, set the accuracy target and compare it against published positioning and repeatability figures. Third, calculate the load moment, not just the axial and radial ratings. Fourth, review the duty cycle and the service access plan. A hollow unit wins when the first check passes and the other three stay within its ratings. A solid unit wins when moment loads are high and routing needs are low. Both paths lead to reliable rotary indexing when the data drives the decision.

Data confirms that an indexing hollow rotary table delivers integration, positioning accuracy, and total cost gains for through-axis work. A hollow rotary table suits rotary indexing with clean routing. Solid tables still fit high-moment, large-diameter loads. Check four items: through-hole need, accuracy target, load moment, and duty cycle.

FAQ

Can a hollow rotary table match a solid table on accuracy?

Yes. Servo-driven hollow units reach ±0.5 arcmin positioning accuracy and ≤10 arcsec repeatability. Closed-loop encoder correction holds that band across thousands of cycles at equal frame size.

When does the hollow premium pay back?

The premium pays back on high-cycle lines. Internal routing removes cable carriers and rotary unions, so cable-related stoppages and warranty claims drop. Low-cycle, low-routing jobs rarely recover the 30–60% premium.

How do engineers size the center bore?

Engineers measure the connector envelope, bend radius, and line count first. The bore must clear all routed services with margin. Continuous rotation also needs a slip ring or rotary union.