加入好友
Home
1
Information
2
Uncategorized
3
Knowledge Sharing Issue #3 Understanding Rotational Accuracy - Repeatability and Backlash4
https://www.herbao.com.tw/en/ HER BAO MACHINERY CO., LTD.
HER BAO MACHINERY CO., LTD. 1 F., No. 10-59, Yuangang, 2nd Neighborhood, Yuangang Vil., Yuanli Township, Miaoli County 35852, Taiwan (R.O.C.)
  Installation and Technical Key Points ofA Large 4th-Axis Rotary Table In CNC machining, a 4th-axis rotary table is an essential component that enables efficient multi-face machining of complex parts. It not only enhances angular flexibility but also determines machining speed, precision, and overall stability. In this article, we present a real-world case study showing how we replaced and integrated a heavy-duty 4th-axis unit on a CNC machining center with a 1.4-meter travel. We dive into the technical reasoning and precision requirements behind each step, guiding you through the complete installation process and helping you understand the key principles of 4th-axis integration. Why Replacing the 4th Axis Is Necessary: The Impact of Precision Degradation The customer’s original 4th-axis rotary table had been in service for many years and had developed significant issues, including severe loss of repeatability, increased positioning errors, and brake system failure.Once the precision of a 4th axis deteriorates, it directly leads to several machining problems：• Amplified angular errors during multi-face machining• Reduced surface quality of machined parts• Increased vibration or wobble during long-part rotation• Machine compensation unable to resolve the root cause of inaccuracy Electrical Integration Test: Ensuring Compatibility Between the CNC and 4th Axis  Before installing the new 4th axis onto the machine, it is essential to verify that the CNC controller can properly drive it.All control cables must be connected, followed by electrical tests including rotation direction, speed response, brake engagement, and servo feedback.Performing these checks in advance prevents issues such as mismatched parameters, unrecognized signals, or brake malfunction after installation. Worktable Flatness Preparation: The Foundation of High-Precision Installation The machine's worktable serves as the fundamental reference surface for all subsequent machining.To ensure accuracy, we carefully scrape the table surface with an oil stone to remove burrs, tool marks, tiny high spots, and machining debris.A clean and perfectly flat surface is the first and most critical step in maintaining the geometric accuracy of the newly installed 4th axis. Installing the Positioning Key: Ensuring the 4th Axis Returns to the Exact Reference After applying anti-rust oil to the base of the new 4th axis, a positioning key is installed.This small but essential component establishes a fixed reference between the rotary table and the machine table.It prevents positional shifts caused by long-term machining vibrations and allows the 4th axis to return to its original precise location even after future removal or maintenance.  Tailstock and 4th-Axis Positioning: Establishing a Complete Rotational Support System  The 4th-axis body and the tailstock must be placed on the machine table simultaneously. Initial measurements are taken to estimate the fixture plate location and the alignment of all contact surfaces. After cleaning the tailstock, we again use an oil stone to refine its mounting surface. This ensures that the center height of the 4th axis and tailstock are perfectly matched, providing balanced support for long workpieces during rotation and preventing vibration or runout caused by eccentric loading.  4th-Axis Parameter and Operation Testing  Before final tightening, we test all operating conditions of the 4th axis, including:• Rotational speed• Direction accuracy• Brake positioning precision• Smoothness of movement and absence of abnormal noiseThese checks verify that the system is functioning correctly prior to final installation.  Parallelism Calibration: Maintaining Geometric Consistency with the CNC Machine  The rotational axis of the 4th axis must be perfectly parallel to the CNC machine’s Y-axis. Using a dial indicator, we perform multi-point measurements and repeatedly adjust until the deviation falls within the required tolerance. After tightening the mounting bolts, the calibration is performed once more to ensure no positional shift occurred during fastening.  Fixture Plate Installation  Before installing the fixture plate, both the machine table and fixture plate mounting surfaces must be rechecked with an oil stone to ensure flatness. Once the fixture plate is pre-mounted, we adjust four critical geometric parameters—concentricity, center height, parallelism, and perpendicularity. These precision alignments determine whether the 4th axis can reliably support workpieces and maintain accurate positioning during future machining operations.  Test Run and Actual Machining: The Final Verification of the Entire System  After completing all precision adjustments, a full test run is conducted to verify system performance.We ensure that the entire rotary table assembly operates smoothly, without abnormal noise, vibration, or irregular motion.Once these conditions are confirmed, the integration of the large heavy-duty 4th axis is officially complete, and the machine is ready for real machining applications.  Conclusion: Installing a 4th Axis Is a Complete Precision Engineering Process  The installation of a 4th-axis rotary table is not simply a mechanical replacement—it is a comprehensive precision engineering task.It involves evaluating worktable conditions, ensuring electrical compatibility, synchronizing hydraulic systems, performing geometric calibration across multiple axes, and adjusting fixture plate flatness and parallelism.Every step must be executed correctly and every measurement verified to ensure that the CNC machining center can fully leverage the capabilities of the 4th axis.When done properly, the machine achieves high precision, high efficiency, and exceptional stability across multi-angle and multi-face machining tasks.If you are considering upgrading to a 4th axis, integrating a heavy-duty rotary table, or facing challenges in precision calibration, Herbao Machinery is ready to provide professional assistance and help you enhance your production capabilities.  Common Questions About Large 4th-Axis Installation (FAQ)  Q1：When should a 4th-axis rotary table be replaced?A：A 4th axis will naturally wear over long-term use, leading to reduced repeatability, increased positioning errors, weakened brake performance, or abnormal noise.If these issues begin to affect machining accuracy or can no longer be corrected through adjustment, replacement becomes necessary.Q2：Why is it necessary to remove burrs and high spots on the worktable with an oil stone?A：Any remaining metal chips or tiny high spots on the worktable can cause misalignment during installation.This may lead to angular errors or parallelism issues during 4th-axis rotation.Oil stone scraping ensures a smooth, accurate reference surface for installation.Q3：What is a positioning key?A：A positioning key is a reference slot or key used to lock the 4th axis into a precise mounting position.It ensures that the rotary table returns to the exact same location after removal or maintenance, preventing positional drift caused by vibration or thermal deformation.This greatly reduces recalibration time and improves machining consistency.Q4：What happens if the center height of the 4th axis and tailstock does not match?A：If their center heights are inconsistent, the workpiece will experience uneven forces during rotation, resulting in vibration, chatter, irregular tool marks, or even deformation.Therefore, precise measurement and alignment of center height are essential.Q5：Is a test run required after installation?A：Yes.A test run checks for abnormal noise, binding, vibration, or delayed hydraulic response.It ensures the entire system is functioning correctly before real machining begins.Q6：What machining benefits does a 4th axis provide?A：Installing a 4th axis significantly enhances:• Multi-angle machining flexibility• Capability for spherical, angled, and curved-surface machining• Machining speed and efficiency in multi-face operations• Workpiece consistency• Overall production throughput Herbao Machinery continues to drive technology innovation, providing professional and reliable machining solutions.If you have any technical questions or application challenges, feel free to contact us anytime! https://www.herbao.com.tw/en/hot_526942.html Knowledge Share #11 – Installation and Technical Key Points of a Large 4th-Axis Rotary Table 2025-12-23 2026-12-23
HER BAO MACHINERY CO., LTD. 1 F., No. 10-59, Yuangang, 2nd Neighborhood, Yuangang Vil., Yuanli Township, Miaoli County 35852, Taiwan (R.O.C.) https://www.herbao.com.tw/en/hot_526942.html
HER BAO MACHINERY CO., LTD. 1 F., No. 10-59, Yuangang, 2nd Neighborhood, Yuangang Vil., Yuanli Township, Miaoli County 35852, Taiwan (R.O.C.) https://www.herbao.com.tw/en/hot_526942.html
https://schema.org/EventMovedOnline https://schema.org/OfflineEventAttendanceMode
2025-12-23 http://schema.org/InStock TWD 0 https://www.herbao.com.tw/en/hot_526942.html
Information
others
TMTS 2026 即將登場！3/25–3/28 在【臺中國際會展中心】與您相見！歡迎蒞臨禾寶機械【攤位 H0211】！一同探索最新精密加工技術！
Home Information Knowledge Sharing Issue #3 Understanding Rotational Accuracy - Repeatability and Backlash [2024-06-19]

 

 

 

The Science Behind Accurate Positioning

Rotational positioning accuracy plays a crucial role in manufacturing processes. It ensures the alignment accuracy between different machining operations, achieving consistency and coherence in multi-process manufacturing. Precise rotational positioning also reduces material waste and production costs while improving production efficiency and quality control.

 

Unidirectional Positioning Accuracy

Unidirectional positioning accuracy is one of the key parameters in evaluating the performance of a rotary positioning platform. It pertains to the platform's positioning accuracy in a single direction. This concept is measured by rotating from the starting position to the end position, selecting multiple data points along the rotational circumference. High unidirectional positioning accuracy impacts the platform's precision in single-direction tasks such as precise machining, engraving, and cutting. Detailed measurement and analysis of unidirectional positioning accuracy ensure that the platform meets the required precision standards, guaranteeing product quality and efficiency in related applications.

 

Unidirectional System Positioning Error

Unidirectional system positioning error refers to the accuracy of the rotary positioning system in a single direction, considering the error produced during the rotation from the starting position to the end position. When designing and manufacturing rotary positioning systems, it is essential to consider these factors, optimize the design and production processes to minimize unidirectional system positioning errors, and ensure the system meets the expected positioning accuracy requirements during operation.

Unidirectional Repeatability Accuracy

Unidirectional repeatability accuracy refers to the ability of the rotary positioning system to consistently return to the same position in a single direction over multiple positioning operations. This metric measures the system's performance in maintaining accuracy in a specific direction, crucial for applications requiring high consistency and precision.

 

 

Bidirectional Positioning Accuracy

Bidirectional positioning accuracy is a key indicator of the rotary positioning platform's positioning precision, measuring the consistency of the platform's positioning in both directions. It evaluates the platform's accuracy in rotating from the starting position to the end position and then returning from the end position back to the starting position. This ensures the platform can accurately and stably rotate and position in both directions.

 

Bidirectional System Positioning Error

Bidirectional system positioning error refers to the accuracy of the rotary positioning system in both directions, assessing the positioning precision from the starting position to the end position and then returning to the starting position. Errors may arise from various factors, including the mechanical structure's precision, the drive system's performance, and the control system's accuracy.

Average Bidirectional System Positioning Error Range

The average bidirectional system positioning error range indicates the mean value of positioning accuracy in both directions, typically expressed as a range encompassing maximum and minimum positioning errors. This range is calculated based on a series of measurements, covering all possible scenarios from the system's maximum to minimum positions.

Bidirectional Repeatability Accuracy

Bidirectional repeatability accuracy measures the rotary positioning system's ability to return to the same position in both directions consistently over multiple operations. This metric is essential for ensuring the system's reliability and precision in applications requiring accurate bidirectional positioning.

 

 

Backlash

Backlash refers to the gap or play within the rotary positioning system due to the mechanical structure or material properties. This gap allows rotary components to move slightly when changing direction without immediately following the new direction. The presence of backlash causes a delay or lag when the rotary positioning system changes direction until the system fully reacts and follows the new direction.

 

Average Backlash

Average backlash, also known as the mean backlash, indicates the average value of all axial backlashes within the rotary positioning system. This metric is calculated by measuring multiple backlash values and averaging them, serving as an indicator of the overall backlash level of the rotary positioning system. It helps evaluate the system's performance and precision.

Previous Back to List Next