In the braking system of passenger cars, the brake disc serves as the core friction component, and its double-sided parallelism, end face runout, and friction surface roughness directly determine the braking response speed and driving safety (the national standard GB/T 34872-2017 requires the double-sided parallelism of brake discs to be ≤ 0.05mm, end face runout to be ≤ 0.08mm, and friction surface roughness to be ≤ Ra1.2 μ m); If the machining accuracy does not meet the standard, it is easy to cause brake eccentric wear, brake abnormal noise, and in extreme working conditions, it may lead to a braking distance extension of more than 15%.
A leading domestic manufacturer of passenger car brake systems once faced a bottleneck in brake disc processing: for the Φ 280-380mm brake discs (made of HT250 gray cast iron, FC250 ductile iron, including ventilation groove structure), traditional processing requires four processes: "horizontal lathe rough turning on one side → flipping rough turning on the other side → vertical milling machine milling ventilation groove → rocker arm drilling machine drilling positioning hole", with a single piece processing cycle of up to 28 minutes; Due to multiple flipping and clamping, the parallelism of both sides of the brake disc often exceeds 0.09mm, and the end face runout error reaches 0.1-0.15mm, resulting in an uneven adhesion rate of brake pads of 18% during braking; At the same time, the chips generated by high-speed cutting of gray cast iron are prone to adhere to the ventilation groove, requiring an additional 12% manual cleaning. Moreover, the tool wears out quickly due to vibration, with a lifespan of only 60-80 pieces per blade, and the cost of a single disc tool exceeds 22 yuan.
Customer usage site
To solve this dilemma, the company introduced the Taiyun CNC locomotive CK525 CNC vertical lathe and built an exclusive manufacturing system for brake discs with "dual column synchronous machining+one-time clamping full process". The equipment adopts an integral high-strength cast iron bed body (with a casting wall thickness of 70mm), which has undergone dual stress relief treatment of "natural aging for 6 months+vibration aging for 48 hours". Combined with a symmetrical box type sliding table structure, the rigidity distribution is optimized through finite element analysis. The radial cutting stiffness reaches 30kN/mm, which can stably withstand the 14kN radial cutting force during gray cast iron cutting; Equipped with the Fanuc 0i MF Plus CNC system and fully closed-loop control of the grating ruler (resolution 0.1 μ m), it achieves a positioning accuracy of ± 0.008mm and a repeatability accuracy of ± 0.005mm, accurately matching the tolerance requirement of ± 0.03mm for the double-sided parallelism of the brake disc. In response to the double-sided processing requirements of brake discs, the equipment is equipped with dual columns and bidirectional tool towers, high-performance spindle (spindle speed 100-1000rpm/min), high-pressure external cooling system (cooling pressure 1.0MPa, flow rate 30L/min) and magnetic chip removal machine (chip removal efficiency ≥ 60L/h), effectively suppressing chip accumulation and tool chip tumors. At the same time, AlTiN coated hard alloy cutting tools (WC Co content 94%, hardness HRA93) are selected to improve cutting wear resistance.
In terms of technological innovation, the equipment has achieved a dual breakthrough of "process integration+double-sided synchronous shape control" in brake disc processing: integrating a 21 inch three jaw linkage chuck (with a clamping force of 75kN, suitable for Φ 500mm-700mm brake discs), an 8-station servo tool holder+cutting tool (with a tool change time of 1.4 seconds), and a ventilation groove dedicated forming tool holder. It can complete the double-sided turning of brake discs (friction surface flatness ≤ 0.04mm), outer circle precision turning (tolerance IT7), ventilation groove milling (groove width tolerance ± 0.1mm, depth tolerance ± 0.05mm), and 4-5 positioning hole drilling (hole diameter tolerance H9, position tolerance ≤ 0.12mm) in one go. In response to the difficulty of controlling the parallelism of the brake disc on both sides, an innovative "dual column synchronous compensation process" is adopted. By collecting the cutting force (accuracy ± 0.5%) and speed deviation of the left and right spindles in real time, the feed rate (compensation accuracy 0.001mm) is automatically adjusted to ensure stable control of the parallelism of both sides within ≤ 0.04mm. In view of the high toughness and high cutting resistance of ductile iron (FC250), the equipment has a built-in material and process database, which automatically matches cutting parameters (spindle speed 1500-2000r/min, feed rate 40-70mm/min, back cutting amount 1.5-2.5mm) to avoid tool breakage; For multi vehicle brake disc replacement (such as differences in specifications between sedans and SUVs), the equipment supports one click adjustment of process parameters (with 35 sets of brake disc processing templates built-in), reducing the replacement time from traditional 1.2 hours to 10 minutes.
Brake drum clamping once
The implementation results fully comply with the safety standards for passenger car braking: the single piece processing cycle has been reduced from 28 minutes to 16 minutes, and the daily production capacity has been increased from 320 sets to 580 sets; The double-sided parallelism of the brake disc is stably controlled at ≤ 0.04mm, the end face runout is ≤ 0.06mm, and the friction surface roughness reaches Ra0.8 μ m, fully meeting the requirements of GB/T 34872-2017 "Passenger Car Brake Discs" and the EU ECE R90 standard; The uneven fitting rate of brake pads during braking has decreased from 18% to 2.5%, and the complaint rate of abnormal braking noise from customers has decreased by 92%; The tool life has been extended by 50% (up to 90-120 pieces/blade) due to cooling optimization and parameter adaptation, reducing the cost of a single disc tool to 14 yuan. At the same time, the manual chip cleaning process has been cancelled, reducing the labor cost of a single disc by 8 yuan; The intelligent diagnostic module equipped on the equipment can collect real-time data such as spindle temperature (resolution 0.1 ℃), current load (accuracy ± 0.8%), etc. Combined with tool wear prediction algorithm, the comprehensive utilization rate of the equipment has been increased from 78% to 95%, and the annual downtime has been reduced by 320 hours.
CK525 has completely resolved the core contradiction between 'double-sided precision synchronous control and mass production efficiency' of brake discs. ”The manufacturing director of the company stated, "Now our brake discs have not only passed the PPAP (Production Part Approval Process) certification of top car companies such as Volkswagen and Toyota, but also meet the ultimate requirements of new energy vehicles for 'low noise, long life' braking systems. This has laid a key foundation for us to win annual matching orders from mainstream car companies. ”This case confirms that the CNC vertical lathe has become the core equipment for breaking through the bottleneck of "safety accuracy and cost efficiency" in the field of passenger car brake disc manufacturing through the deep collaboration of "dual spindle rigid architecture+double-sided synchronous shape control+material and process customization".
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