Abstract
Thread inserts are key components in mold manufacturing and are widely used in plastic injection molding, die casting and other molding processes to form internal or external threads on products. Due to their complex structure and high precision requirements, they often face difficulties in material selection, processing deformation, tool wear, and precision control during processing. This article discusses the processing difficulties of mold threaded inserts in detail and proposes corresponding optimization solutions to improve processing efficiency and product quality.
1. Application and processing requirements of threaded inserts
Thread inserts are usually made of high-hardness, wear-resistant materials (such as tool steel, high-speed steel, cemented carbide, etc.) to ensure that they maintain dimensional stability during long-term use of the mold. Its main processing requirements include:
High precision: The thread tolerance usually needs to be controlled within ± 0.02 mm to ensure matching with the molded product.
High surface quality: Burrs and knife marks need to be reduced to avoid affecting demolding and thread function.
Wear resistance: Heat treatment (such as quenching, nitriding) is required to increase service life.
2. The main processing difficulties of thread inserts
2.1 The material has high hardness and is difficult to process
Threaded inserts usually adopt high-hardness materials (such as H13, SKD61, tungsten steel, etc.), and after heat treatment, the hardness can reach HRC 50-60, resulting in large cutting force, rapid tool wear, and affecting the processing efficiency.
Main problem:Cutting tools are prone to chipping and wear, resulting in a decline in the quality of the machined surface.
High cutting temperature may cause local annealing or deformation of the material.
2.2 Difficulty in controlling thread processing accuracy
The accuracy of thread inserts directly affects the demoulding performance of the mold and the fit of the product thread. common processing difficulties include:
Cumulative pitch error: In multi-thread thread processing, pitch error may cause thread misalignment.
Deviation of thread profile angle: Tool wear or insufficient machine tool rigidity may cause inaccurate thread profile angle.
Thread median diameter control: Accurate measurement is required to avoid over-tightening (resulting in demoulding difficulties) or over-loosening (resulting in thread loosening).
2.3 Deformation problem of slender thread inserts
Slender thread inserts (such as diameter <3mm, aspect ratio >5) are easily affected by cutting force during processing, resulting in bending deformation, which leads to:
The thread axis is offset, affecting the assembly accuracy.
The processing vibration is aggravated and the surface roughness is deteriorated.
2.4 Tool selection and wear management
Thread processing usually adopts turning, milling or grinding. Different processing methods have different requirements for tools:
Thread turning: Carbide tools are easy to wear, and cutting parameters need to be optimized (such as reducing feed and increasing speed).
Thread milling: Suitable for small batches and complex threads, but the tool cost is high.
Thread grinding: Suitable for high hardness materials, but low efficiency and high cost.
2.5 Cooling and chip removal issues
When machining deep holes or tiny threads, it is difficult for the coolant to enter the cutting area, causing the tool to overheat.
Chip accumulation may scratch the machined surface and affect the thread qualit
3. Solutions for optimizing processing technology
3.1 Reasonable selection of tools and cutting parameters
Tool materials: Use CBN (cubic boron nitride) or PCD (polycrystalline diamond) tools to process high-hardness materials.
Cutting parameter optimization:
Reduce feed rate (f ≤ 0.05mm/r) to reduce cutting force.
Increase cutting speed (Vc ≥ 100m/min) to reduce built-up edge.
Use minimal quantity lubrication (MQL) to reduce cutting temperature.
3.2 Use high-precision processing equipment
Use high-rigidity CNC lathes or machining centers to reduce vibration.
Use thread grinders for precision finishing to ensure the accuracy of pitch and tooth angle.
3.3 Reduce machining deformation
For slender parts, use a tool rest or center rest to improve rigidity.
Divide the rough machining and precision processing stages to avoid deformation caused by cutting too deep at one time.
Use stress relief annealing to eliminate internal stress in the material.
3.4 Optimize cooling and chip removal
Use high-pressure internal cooling tools to ensure that the coolant reaches the cutting area directly.
Use compressed air to assist chip removal to avoid chip entanglement.
3.5 Precision inspection and compensation
Use thread gauges and coordinate measuring machines (CMM) to inspect key dimensions such as pitch and center diameter.
Use tool wear compensation function to adjust processing parameters in real time.
4. Conclusion
The processing of mold thread inserts involves many factors such as materials, tools, machine tools, and processes. The core difficulty lies in the cutting, precision control, and deformation management of high-hardness materials. By optimizing tool selection, cutting parameters, processing technology, and testing methods, the processing quality and efficiency of thread inserts can be significantly improved, providing reliable guarantees for mold manufacturing. In the future, with the development of superhard tools and intelligent processing technology, the processing of thread inserts will develop in the direction of higher precision and higher efficiency.
