How to ensure the machining accuracy in the process of die machining?

In the process of mold machining, it is necessary to ensure the machining accuracy from many aspects, including accurate design, high-quality equipment and tools, stable process system, accurate measurement and testing, strict quality control, etc. The following is a detailed introduction:

Design link

Accurate drawing design: use professional CAD/CAM software to design the mold, accurately draw two-dimensional and three-dimensional drawings of the mold, and mark the technical requirements such as size, tolerance and surface roughness in detail. In the design process, we should fully consider the use requirements of the mold, processing technology, subsequent assembly and debugging and other factors to avoid the machining accuracy problem caused by unreasonable design.

Reasonable tolerance distribution: according to the final use requirements of the mold, the tolerance of each part and each processing part is reasonably distributed. For the parts that affect the key dimensions and properties of stamping parts, give smaller tolerances; For non-critical parts, the tolerance can be appropriately relaxed to reduce the processing difficulty and cost.

Equipment and tool selection

High-precision machining equipment: choose high-precision and stable machining equipment, such as high-precision CNC milling machine, machining center, EDM machine tool, etc. These equipments have advanced control systems and transmission devices, which can ensure the accuracy and stability in the machining process. For example, the positioning accuracy of some high-end machining centers can reach within 0.01 mm.

High-quality tool: Choose a tool with good quality and high precision, and the precision and rigidity of the tool directly affect the machining accuracy. For different processing materials and processes, it is necessary to choose appropriate tool materials and tool types. For example, when processing die steel with high hardness, cemented carbide cutter or CBN cutter can be selected; In high-precision milling, precise ball-end milling cutter or end milling cutter can be selected to ensure the accuracy and roughness of the machined surface.

Process system stability

Reasonable process planning: make a detailed and reasonable processing route, taking into account the processing sequence, cutting parameters, clamping methods and other factors. Follow the machining principle of roughing first, then refining, first and then secondary, and rationally distribute the machining allowance of each process to reduce the deformation and stress in the machining process. For example, after rough machining, arrange appropriate aging treatment or tempering treatment to eliminate internal stress, and then finish machining to ensure the dimensional accuracy and stability of parts.

Stable clamping and positioning: adopt reliable clamping mode and positioning device to ensure that the workpiece does not shift and deform during machining. For mold parts with complex shapes, special fixtures can be designed for clamping to ensure the clamping accuracy within 0.05 mm. At the same time, we should pay attention to the size and action point of clamping force to avoid workpiece deformation caused by excessive clamping force.

Optimization of cutting parameters: according to the processing materials, tools and processing requirements, reasonably select cutting parameters, including cutting speed, feed rate and cutting depth. Optimizing cutting parameters can reduce tool wear, cutting force and cutting heat, thus improving machining accuracy. For example, when milling die steel at high speed, the cutting speed is generally between 1000 and 3000 m/min, the feed rate is 0.05-0.1mm/z, and the cutting depth is generally between 0.5-2mm depending on the cutter and workpiece.

Measurement and detection

On-line measurement: In the process of machining, the on-line measurement system is used to monitor the size of the workpiece in real time, and the machining error is found and adjusted in time. For example, a laser measuring system or a contact probe is equipped on the NC machining center, which can automatically measure the size of the workpiece during machining and compare it with the programmed size. If there is any deviation, the system can automatically correct the tool path to ensure the machining accuracy.

Off-line inspection: After machining is completed, the key dimensions, shapes and position accuracy of the mold are comprehensively inspected by using precision measuring equipment such as coordinate measuring instrument and profilometer. The measuring accuracy can reach ±0.01mm or even higher, which ensures that all indexes of the die meet the design requirements. For the out-of-tolerance parts, analyze the reasons and take corresponding measures to correct them, such as re-processing and adjusting process parameters.

Personnel skills and quality control

Operator skills: Operators should have rich experience and professional skills in mold processing, be familiar with the performance and operation methods of processing equipment, and be able to correctly compile processing procedures and adjust processing parameters. Regularly train and examine the operators, improve their operation level and quality awareness, and ensure that all operations in the processing process meet the process requirements.

Quality control system: establish a perfect quality control system, from raw material procurement, processing control to finished product inspection, every link must be strictly controlled. Formulate detailed quality inspection standards and procedures, inspect and record all stages of mold processing, find and solve quality problems in time, and ensure mold processing accuracy and quality stability.