To ensure the production of high-quality rotary files, four core manufacturing processes are crucial to product quality: welding process, concentricity control, heat treatment process, and tooth grinding process. This article will introduce the key technical points, industry pain points and optimization solutions of these processes in detail, providing professional references for buyers to accurately select high-quality rotary file.
1. Rotary File Welding Process
Carbide rotary files usually adopt a combined structure of Tungsten carbide head + alloy steel shank. The physical properties of the two materials are quite different, so welding quality directly determines the overall strength and use safety of the tool, which is a basic core process.
There are two common welding methods in the industry: high-frequency induction brazing and vacuum brazing.
High-frequency induction welding: It is the mainstream process for mass production. It uses a high-frequency induction coil to quickly and evenly heat the welding seam locally, and completes metallurgical bonding with special solder. It has the advantages of high heating efficiency, precise temperature control, good weld formation and strong mass production stability. It is suitable for large-scale production of most general industrial rotary files.
Vacuum welding: It is the preferred process for high-end precision rotary files. The welding operation is completed in an oxygen-free vacuum environment, which completely avoids defects such as weld oxidation, slag inclusion and air holes. The strength of the welding joint is increased by more than 30%, and it has excellent high temperature resistance, vibration resistance and fatigue resistance. It is suitable for the production of high-precision rotary files for high-end scenarios.
Key Points of Rotary File Welding Process
To avoid common industry problems such as false welding and head detachment, it is necessary to conduct refined control over the entire welding process. The core control points include:
Pre-welding pretreatment: Before welding, the joint surface of the file head and shank is precision turned, ground to remove rust, and cleaned by ultrasonic to remove oil. Ensure the flatness error of the joint surface is ≤0.02mm, reducing the hidden dangers of gaps and false welding.
Solder and temperature control: Strictly match special copper-based and silver-based brazing solder, and strictly control the welding heating rate, peak temperature and heat preservation time. Avoid overheating of the tungsten carbide head leading to coarse grains and reduced performance, and prevent the alloy steel shank from annealing and softening, losing torsion resistance.
Post-welding slow cooling and inspection: After welding, adopt a stepped slow cooling process to eliminate welding internal stress and avoid weld cracking. 100% of the products pass torque test and ultrasonic flaw detection after welding.
- Concentricity Control
Concentricity is a key indicator to measure the dynamic accuracy of rotary files, referring to the coincidence degree between the axis of the file head edge and the shank. It directly affects the grinding effect and operation experience. The concentricity of high-quality rotary files is not controlled by a single process, but by systematic control throughout the production process. The core control nodes include:
Raw material pretreatment control: The shank steel adopts high-precision cold-drawn round steel, and precision straightening is performed after cutting to ensure the straightness error of the raw material is ≤0.01mm/100mm, avoiding eccentricity hidden dangers from the source.
Precise welding positioning control: Use high-precision integrated positioning fixtures to limit the coaxial position of the file head and shank. The positioning concentricity error is ≤0.005mm, and it is fixed throughout the welding process to avoid displacement deviation during high-temperature welding.
Post-welding secondary correction: After welding and cooling, 100% inspection is carried out with a high-precision coaxiality detector. Products with slight deviations are corrected by cold pressing to eliminate concentricity errors caused by welding thermal deformation.
Finishing closed-loop control: The tooth grinding process uses high-precision 5-axis CNC grinders, and adopts one-time clamping processing based on the shank clamping position to avoid reference deviation caused by secondary clamping. After the finished product is completed, 100% dynamic balance detection and radial runout test are carried out to ensure the factory products meet the precision standards.
The concentricity error of high-quality industrial rotary files is controlled within a very small range (≤0.02mm), running stably without vibration. It is suitable for precision processing such as precision mold trimming, fine carving and high-precision weld cleaning, balancing grinding efficiency and workpiece surface quality.
- Heat Treatment Process
Heat treatment is the core process to balance the hardness, wear resistance and toughness of rotary files. Differentiated treatment schemes are adopted for alloy steel shanks and cemented carbide file heads to solve the problems of easy cracking due to excessive hardness and easy bending due to insufficient toughness.
Shank heat treatment process: The core requirement of the shank is high torsion resistance, high bending resistance and high toughness to avoid bending and breaking during operation. The industry generally adopts the overall heat treatment process of “quenching and tempering + high-temperature tempering”. After treatment, the hardness of the shank is stably controlled at HRC 38-42, balancing high strength and excellent toughness, and it is not easy to bend or break during long-term heavy operation.
Carbide file head heat treatment process: The core requirement of the Tungsten carbide head is high hardness, high wear resistance and high temperature resistance, while avoiding chipping caused by excessive brittleness. The high-end process adopts the heat treatment scheme of “low-temperature vacuum setting + aging treatment”, which retains the high hardness and wear resistance of Tungsten carbide itself, and improves the impact resistance and high-temperature wear resistance of the edge. After treatment, the hardness of the file head is stably controlled at HRA 89-92, suitable for high-intensity continuous cutting operations.
Rotary files after standardized heat treatment can achieve a perfect balance of hardness and toughness, with greatly improved wear resistance and service life.
- Tooth Grinding Process
Tooth grinding process directly determines the sharpness, cutting efficiency, chip removal performance and processing surface finish of the product, which is the core dividing line between ordinary rotary files and high-end rotary files.
The tooth grinding of rotary files consists of multiple refined processing procedures. The core procedures include:
Rough grinding and shaping: Use diamond grinding wheels to perform rough processing according to the product tooth shape, complete the basic shaping of tooth grooves and tooth tops at one time, ensure the basic consistency of tooth pitch and tooth depth, and reserve grinding allowance.
Precision grinding and tooth trimming: Use high-precision 5-axis CNC grinders with micron-level diamond grinding wheels to complete the precision processing of the tooth shape according to the preset trajectory, strictly control the tooth profile error, and ensure the size and angle of each tooth are uniform.
Edge passivation and chamfering: Perform micron-level passivation and precise chamfering on the precision-ground edge to eliminate micro burrs and micro cracks on the edge, avoid edge curling and chipping in the initial use, and improve the impact resistance and service life of the carbide burrs.
Mirror polishing and deburring: Finally, perform mirror polishing on the tooth surface and chip removal groove to remove fine burrs left by processing, reduce the friction coefficient of the tooth surface, improve chip removal performance, and avoid chip adhesion and blockage during processing.
Tooth Grinding Process Adaptation for Different Processing Scenarios
High-quality rotary files will customize differentiated edge grinding process schemes according to the target processing scenarios to achieve the optimal cutting performance.
Heavy-duty rough processing scenarios: For large-margin cutting scenarios such as casting deburring and weld grinding, adopt coarse tooth type and strong edge grinding process, increase edge passivation amount, improve impact resistance, and avoid chipping under large feed rate.
Precision finishing scenarios: For small-margin and high-precision scenarios such as precision mold trimming and mirror processing, adopt fine tooth type and micron-level mirror grinding process, strictly control edge profile error, and ensure the processing surface finish is free of scratches and waves.
Soft material processing scenarios: For soft materials such as aluminum alloy, plastic and wood, adopt sharp edge and large helix angle grinding process to reduce cutting resistance and avoid chip adhesion.
In general, the quality of rotary files is determined by the above four processes. The lack of control in any link will lead to product quality defects. When selecting rotary files, in addition to paying attention to basic parameters such as material, specification and tooth shape, we should focus more on the standards and control of these four core processes.
As a manufacturer committed to producing high-quality rotary files, we have established a full-process process control system, implemented standardized and refined control over these four core processes, introduced high-precision 5-axis CNC processing equipment and full-inspection testing system, to avoid process defects from the source and improve the core competitiveness of products.
