Introduction

In addition to the trifecta of demands for high quality, short delivery times, and low costs, manufacturing sites are facing increasingly apparent challenges such as labor shortages and the difficulty of skill succession. Fastening components, though small, are the “final quality gate” that influences equipment operating rates and yield.
In recent years, evolution has been accelerating in three main areas:
(1) higher-functioning ball screws that elevate machining accuracy,
(2) special-shaped screws that reduce workload and errors
(3) IoT smart bolts that visualize fastening status.
When combined with torque management (the practice of reproducing a specified tightening force) and traceability (history tracking), these technologies form a quality assurance platform that spans from design and procurement to manufacturing and maintenance.
This article provides a practical explanation of the key points of each technology, tips for selection and implementation, and an implementation strategy for the Vietnamese manufacturing industry.

New-Generation Ball Screws for Higher Precision

NSK’s next-generation ball screws for high-precision machine tools suppress the friction fluctuations that tend to occur when the feed axis reverses its direction of motion, reducing the quadrant glitches that are a problem in machine tools. This stabilizes positioning during contouring corners and at minute pitches, enabling high-quality surface finishing. A practical advantage is that they are designed to be compatible for installation on existing machines, making it easy to achieve phased performance improvements through retrofitting.

Why do quadrant glitches occur?

During motion reversal, the contact state between the balls and the screw groove changes temporarily, and errors are amplified by a combination of friction, backlash, and control system delays. If friction fluctuations can be smoothed out, the compensation load on the control system is reduced, which directly leads to stabilization of contouring accuracy and surface roughness (Ra).

Key Points for Measurement and Effect Verification

• Ballbar measurement: Visualize quadrant glitches through deviations in circular motion to quantify the difference before and after retrofitting.
• Machined surface quality: Evaluate using Ra/Rz values and waviness indicators for mirror finishes and fine groove machining.
• Energy: Reduced friction lowers the power consumption of the spindle and feed drives, and by suppressing heat generation, thermal displacement is also reduced.

Application Areas and Design Tips

• Effective for processes requiring µm-order positioning, such as in molds, semiconductors, and medical parts.
• For existing machines, the effects can be maximized by simultaneously planning for feed screw compatibility and the re-tuning of control parameters (gain/feed-forward compensation).

Special-Shaped Screws for Improved Work Efficiency

Accurate’s Totsupra Screw®, with its unique design featuring a 0° bit tip angle, suppresses the upward component of force (bit lift) that occurs during rotation, thereby preventing cam-out. The wide drive area ensures stable torque transmission, reducing screw recess damage and bit wear.

Chasing Two Rabbits: Productivity and Quality

• Reduced pressing force: Eliminates the need for strong pushing, enabling reliable tightening even in unstable postures or in high or confined places.
• Reduced work variability: The bit is less likely to slip, resulting in high reproducibility of reaching the target torque.
• Extended tool life: Bit wear is reduced, curbing tool replacement losses and indirect costs.

Comparison with Conventional Screws (From a Shop-Floor Perspective)

Key Points for Application and Introduction

• Effective for multi-process, multi-posture assembly lines and for high-mix, low-volume production.
• Verifying the driver’s set torque and the quality limit (lower limit of fastening force) in accordance with ISO 16047 (Fasteners—Torque-clamp force testing) beforehand facilitates failure analysis after startup.

Evolving Fastening Status Monitoring with IoT

Smart bolts/nuts with built-in sensors acquire data such as clamping force (axial force), temperature, and vibration. This data is transmitted to a gateway via Bluetooth/LoRa/NB-IoT, then aggregated and analyzed in the cloud. This allows the status to be grasped without waiting for equipment to stop, making it a core data source for predictive maintenance.

Basic Formula and Measurement Concept

• The approximate relationship between torque and axial force is T = K × F × d
  (where T: torque, F: clamping force, d: nominal diameter, K: torque coefficient).
• In actual equipment, the coefficient K varies with surface treatment and lubrication. Therefore, it is important to conduct an evaluation based on ISO 16047 and perform mutual verification with the measured values from smart bolts.

Example of Data Architecture

1. Edge: Data is collected by strain and temperature sensors embedded in the bolt.
2. Communication: Use Bluetooth for short distances and LoRa/NB-IoT for wide-area or outdoor applications.
3. Platform: Visualize data on a cloud-based dashboard, monitor thresholds and trends, and issue alerts.
4. Integration: Link with MES/CMMS to automate work instructions and parts ordering.

Tips for Alert Design

• Monitor using two conditions: a sharp decrease in clamping force (%/hour) and an absolute lower limit, applying temperature compensation.
• Using relative comparison among a group of bolts (distribution under the same conditions) helps suppress the effects of sensor errors and external disturbances.

Power Supply and Protection Design

• In addition to long-life batteries, the maintenance cycle is extended through energy harvesting, which utilizes vibration or temperature differences.
• IP-rated waterproof/dustproof and shock-resistant designs enable operation even in outdoor or high-vibration environments.

Sample Calculation of Introduction Effects (Model)

• Continuously monitor 200 critical bolts → Transition from biannual periodic disassembly to condition-based maintenance (CBM).
• Assuming a 20% reduction in downtime, a 30% reduction in inspection labor, and a 10% reduction in consumables, the return on investment is estimated to be in the range of 1.5 to 2.5 years.

Introduction Strategy in the Vietnamese Manufacturing Industry

In Vietnam, as foreign investment and technological upgrades advance, standardization to international quality control norms is an urgent task. GIS OHTA Vietnam provides end-to-end support for local procurement, inspection, and implementation.

Procurement and Standards Compliance

• We can arrange everything from standard products by domestic and international manufacturers to custom-made items. We support the unification of drawing numbers, materials, and strength classes based on JIS/ISO standards.
• When sourcing alternatives, we ensure the reproducibility of the clamping force by checking for specification consistency, including the torque coefficient K and seating surface conditions.

Quality Assurance and Traceability

• We establish inspection plans for incoming, in-process, and outgoing quality control (IQC/IPQC/OQC).
• Smart bolt data is accumulated in the cloud and visualized by linking it to lots, equipment, and operators.

Recommended Introduction Roadmap

1. PoC (Proof of Concept): Select 20 to 50 critical joints and acquire baseline data.
2. Pilot: Simultaneously implement a ball screw retrofit, replacement with Totsupra Screws, and IoT monitoring on a single line.
3. Full-scale Rollout: Expand to other processes with high cost-effectiveness and reflect the changes in standard operating procedures and training materials.

Case Studies (Summary)

• Adopted Totsupra Screws on an assembly line, resulting in a 40% reduction in pressing force and an 8% reduction in takt time. Zero screw recess damage has been maintained.
• Replaced the feed system of a molding die with high-precision ball screws, achieving a 20-30% improvement in machined surface Ra and shortening the finishing process.
• Implemented IoT for critical bolts in plant equipment, transitioning periodic disassembly to CBM and achieving an approximate 30% reduction in annual maintenance costs.

Value Provided by Ohta Vietnam

• Local inventory and short lead-time support, with integrated assistance from prototyping to mass production.
• Hands-on support covering torque management training, fastening failure analysis, and dashboard design.

Reference: Our company’s support case studies (internal data), JIS B 0205-1/ISO 68-1, ISO 898-1, ISO 16047, etc.

 

Summary

Next-generation screw technology demonstrates its true value as a trinity:
(1) elevating contouring accuracy and surface quality with high-precision ball screws,
(2) suppressing work variability and errors with special-shaped screws
(3) enabling visualization and predictive maintenance with smart bolts.

When introducing these technologies, a “measure – compare – connect” sequence is effective:
① measure the current torque, axial force, surface roughness, and energy consumption.
② conduct comparative tests with alternative solutions.
③ connect to the cloud and integrate into standard operations.
Short-term benefits include reduced takt time and fewer defects, while long-term prospects include the transition of maintenance to CBM and energy optimization. We recommend starting by identifying critical joints for a PoC and incorporating data-driven fastening management into your company’s quality assurance process.

Sources: NSK product information / Accurate product page / Various ISO and JIS standards.

Conclusion

For inquiries regarding samples or materials, please respond to this email or contact our sales representative!

At Ohta Vietnam, we not only provide ready-made products such as screws and bolts, but also support activities in the manufacturing field such as cutting, inspection, assembly, packaging…
Our equipment list is here

As a “specialized support” for the manufacturing industry in Asia. If you have any related questions, feel free to contact Ohta Vietnam for detailed support!
URL: https://ohtavn.com/en/contact/

List to Column page