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As the competition in China's auto industry continues to intensify, the automotive mold industry is gradually expanding toward a high starting point and a high investment direction. Various large-scale high-precision equipments have been introduced in large quantities. Here, how to make better use of these devices, high-quality, high-efficiency, low-cost manufacturing of first-class mold products has become a focus of general attention.
1. The status of automobile mold processing in various countries (1) The United States Faced with the influx of low prices and high quality molds in Japan and Asia, the whole industry is facing a very serious situation. How to shorten the delivery cycle has become a key issue for enterprises. In order to reduce the purchase cost of the blank, and to give play to the geographical advantage in the delivery period, the insert structure design mold is often used. In addition, due to the constraints of the trade unions, in addition to the BIG3 related large manufacturers have opened 2 classes, some Japanese factories have 3 classes down, the rest of the manufacturers are basically only one class. Therefore, in a limited time, how to process faster, that is, to improve production processability is the top priority. Compared with Japan, the United States is relatively harsh in terms of cutting conditions. In general, the cutting speed is high, about 1.5 times that of Japan, and the feed is 2 to 3 times. The depth of cut is similar to that of China, which is 2 to 5 times that of Japan.
From the perspective of the stamping die industry, rough machining, due to the extremely slow update of equipment, takes the gantry machine tool of about 10 years as the mainstream. Casting and roughing tools are mainly ball-end milling cutters, and the tool holders are mostly in the form of side solids. Therefore, the tool is required to have extremely high chipping resistance. At the same time, it pays more attention to high chip discharge and efficient processing performance.
Finishing is also generally based on old equipment, and the speed and feed rate are relatively low. Recently, some high-speed processing machines (maximum speed 25000r/min) produced in Japan and Europe have been used, and high-speed machining is performed by means of KM holders and thermal expansion clamping of carbide shanks. Its purpose is to "cancel the grinding" process and shorten the processing cycle.
The plastic mold industry still mostly uses EDM for finishing. Most of the electrodes are made in-house, so the high-speed machining center of 20,000 to 40,000 r/min for electrode processing is gradually optimistic, and the tools are mostly made of diamond coating. Recently, Yan Jie's overall sintered diamond "dream" milling cutter is very popular. In addition, investment in rough/finishing equipment directly used for high-hardness processing is also becoming active. A large number of manufacturers using a large number of machining centers of about 15,000 r/min have appeared, and the processed materials are mostly P20 pre-hardened steel. Roughing tools are generally preferred to use multi-functional and efficient machining tools. The finishing tool is the same as the stamping die, and the high-speed machining achieves the goal of “cancel grinding†directly into a mirror effect.
(2) Europe The grim situation is similar to that of the United States, but the mutual supply relationship in the EU circle is very strong, and its mold manufacturing has its certain closedness, so the industry's sense of crisis is not very strong.
The stamping die is mostly made of castings. The deep die and blanking die are generally made of GGG70 (QT700), and also cast steel and high hardness materials. Relatively speaking, it pays more attention to the durability of the mold. The same pair of molds have a single function, but the rigidity is very good, and the mold body is very large. From the processing equipment, they all have more advanced machine tools, and the large-scale automobile factory affiliated mold factory has an FMS production line (with ATC+AWC+AGV). Guaranteed to run unattended from 1PM on Sunday to 7PM on Saturday.
The roughing and finishing equipment are equipped separately, and the equipment is equipped with the MT tool holder as the mainstream. The tool is gradually transferred from the ball cutter to the fillet cutter. Although the depth of cut once is not large, but the number of blades is large, a higher feed can be obtained. At the same time, the burden on the machine tool is relatively small.
For finishing, the 5-axis high-speed machining center (HSK63, the highest speed 25000r/min) is used in Europe. The actual processing is 10000r/min, F=12000mm/min processing conditions, as well as the thermal expansion shank and carbide knives. The rod, through high-speed machining, achieves the purpose of “cancel grindingâ€.
The plastic molds are mostly processed from the square blanks, mainly P20 pre-hardened steel, and the equipment is mostly about 12000~15000r/min. Rough finishing is done in the same setup on the same equipment. Roughing tools are mainly rounded inserts, while finishing are dominated by ball-end cutters and rounded end mills. It is also expected to use high-speed machining to achieve “cancel grinding†and directly process into a mirror surface.
Forging and die-casting molds are mainly pre-hardened steel (45-55HRC). Most of them use machine-clamped round-end milling cutters for high-speed direct machining. K03+TiAL coated blades are used for tool materials.
(3) Japan's automobile stamping die mainly consists of castings, and the materials are mostly FC300 (HT300) and GM (alloy cast iron). With the recent use of high-tensile steel plates on the surface of the car body, the material of the mold is gradually using HPM. /NAK/SKD and other mold steel. They are all applied to the casting base in the form of inserts. However, whether it is a whole piece of casting or a block, its production level is much better than that of other countries. Even if it is a large margin, its quantity is relatively uniform. Machining programming control and increasing the speed of the pass are relatively easy.
The processing equipment is mainly gantry machine tools, and the rough finishing is equipped separately. Rough processing mostly uses older equipment, especially Russian and Czech equipment, which is low in price and high in rigidity, and is favored by customers. The finishing process uses the Japanese-made gantry machining center. The maximum speed is around 10,000 to 12000r/mm. There is a big difference compared to Europe. This is mainly due to the consideration of tool life and reliability of machining accuracy.
Most of the plastic molds are processed from the square material, and the materials are mainly pre-hardened steel such as NAK. The equipment is mostly processing centers of 15000-25000r/min. Rough finishing is performed on one piece of equipment, requiring low cutting resistance and fast feed to improve machining efficiency. The roughing tool is mainly made up of a large feed square angle cutter, and the depth of cut is not large, but the feed is very fast. The finishing process mainly consists of a ball-end knife and a round-end end mill, and most of them process the mold directly into a mirror surface.
Forging molds and die-casting molds are mostly processed from square materials. The materials are mainly SKD, NAK, HPM hardened steel (HRC45-55), and the equipment is mostly 15000-25000r/min. Rough finishing is performed on one piece of equipment, requiring low cutting resistance and fast feed to improve machining efficiency. Die-casting mold: The roughing tool is mainly made up of large feed cutters. The finishing is mainly based on the large-feed integral round-end milling cutter, supplemented by the ball-end cutter. Most of them are directly processed into mirrors. Forging die: rough finishing uses the same knife, mostly for the newly developed large feed integral round end mill. It is usually processed directly under high hardness. The actual goal is to achieve "cancel grinding" with high speed machining.
In general, the biggest difference between Japanese molds and Europe is their diverse functions and compact structure. The manufacturing cycle and processing costs are very tightly controlled during the mold processing. Therefore, the selection of equipment, tools and their interface equipment by various manufacturers is more rationalized than other countries. For the connection between the tool holder and the machine tool:
The traditional method is to use the BT standard (MAS 403/JIS 6399) holder for the general machine tool spindle. The clamping method includes a spring collet, a flat tailband screw to lock the Mob, and a composite handle (C508).
Then, for the purpose of improving the connection rigidity and improving the positioning accuracy of the shank and the service life of the tool, the shank is positioned by the tapered surface and the end surface. Commonly available are BBT, NC5 and other tool holders. The latest BTS (SuperBT) tool holder adopts a different design from BBT, so that the end face of the tool holder directly fits with the end face of the ordinary machine tool spindle, and no special spindle is needed, which represents the development direction of the tool holder technology in the future.
In addition, it is in the form of a tool holder for tool holders. The clamping form of the roughing tool is generally a MO-handle (MT). This is due to the better centering performance of the Mo-handle. The handle straight is thinner than the composite handle (C508), and the interference in use is less affected. For roughing ball end mills, side-mounted or straight-handle shanks are generally not used. Mainly to minimize the tool eccentricity and the influence of the axial cutting force in the Z direction on the tool. For the selection of the finishing tool shank type, the φ50 machine-clamping cutter is also fixed by thermal expansion. Tool life can generally be increased by more than 1 time.
Finishing with small diameter milling cutter to clear the root, when using ordinary jacketed shank, the tool needs to hang 50~80mm to avoid interference, the feed speed can only reach 200~300mm/min, and the rigidity of the tool during machining Not good, it is easy to break. The thermal expansion shank has now formed a series of standard specifications according to the processing needs. The rigidity of the shank is improved, the tool only needs to be hung 20mm, and the feed speed can be increased to 1000-1500mm/min, resulting in a total machining time reduction of more than 15%. .
2. The main configuration method of Japanese mold industry tools: Traditional processing methods:
(1) Generally, Ñ„50 rough milling ball end milling cutter is used for rough machining, including contouring and corner allowance;
(2) Semi-finishing with Ñ„30 ball-end milling cutter;
(3) Finishing is done using Ñ„30 or Ñ„25 finishing ball end mill.
Automated unmanned processing:
(1) Firstly, the high-infeed SKS new trunk milling cutter or the Ñ„50 rough milling "Sven" ball-end milling cutter is used for contour processing of rough blanks to remove most of the margin;
(2) Use Ñ„40 rough milling "Sven" ball end milling cutter to carry out large-scale clearing and partial clearing, equalizing the machining allowance and minimizing the influence of uneven margin on semi-finishing;
(3) High-speed semi-roughing (feed rate 3500-4000 mm/min) in a profiling manner using a Ñ„50 (3-blade) milling cutter;
(4) Semi-finishing First use Ñ„30 "Sven" ball-end milling cutter to remove corners and roots to make the balance uniform;
(5) Contour semi-finishing with Ñ„25 "Sven" ball end milling cutter (feed rate 3500 ~ 4000mm / min);
(6) Finishing using Ñ„30 mirror ball end mill for high-speed profiling of the entire shape (feed rate 10000mm/min), and finally using a small diameter (Ñ„4 ~ Ñ„16) integral or mirror ball end mill for local clearing finishing.
Japanese mold processing auxiliary tool configuration:
· Roughing and cutting large margins often require the use of BT handle corn milling cutters;
·The cutting edge of the cutting die is processed by a back milling cutter;
·The guide post hole roughing is a rotary milling cutter that can perform three-dimensional cutting;
·The punching and inserting hole finishing is performed by the mirror fillet milling cutter in the form of circular interpolation (larger hole). For the standard size, the bushing holes are “reamed†according to the tool size directly by a tool such as a mirror-finished milling cutter;
·The insert base is processed by high feed milling cutter or drilling and milling cutter;
·The mold base is installed with fixing groove and the end face is processed by the T-shaped corn blade compound machine clamp type milling cutter;
· Guide plate surface processing: within 250mm depth, layered cutting with mirror fillet milling cutter. More than 250mm is processed by a plunge cutter.
Processing of high hardness parts:
Roughing application:
·Mold edge, surfacing, repair welding, residual amount after heavy hole inlaying and machining when trimming the mold, using φ50 or φ30 "Sven" ball end milling cutter with special blade machining.
Finishing application:
· After the quenched air-cooled steel insert is mounted on the mold, the φ30 mirror mirror ball head S-milling cutter is used to remove the residual stress, and the depth of cut is about 0.2 mm;
·Fracture processing of φ30 mirror ball end mill for finishing. Example of tool configuration and processing conditions for automated unmanned production line in a mold factory in Japan:
(1) Contour line and profiling processing with φ50mm Sven ball end milling cutter: Ap=10mm, Ae=9mm, leaving 1mm for semi-finishing allowance;
(2) Using φ40mm Sven ball end milling cutter for roughing and roughing, leaving 0.3~0.5mm for finishing allowance (the above processing is performed on roughing machine);
(3) Contour semi-roughing with φ50mm, 3 blade good yield Qiba SHC type: Ap=0.7mm, Ae=3mm, leaving 0.3mm for finishing allowance;
(4) The φ30mm mirror ball end mill BNM type is used for contour finishing and semi-finishing. The roots of the Qing Dynasty do not leave a margin;
(5) 25mmC-body Sven ball end milling cutter for profiled semi-finishing: Ap=0.5mm;
(6) Contour finishing with φ30mm mirror ball end mill BNM type: Ap=0.1～0.3mm, Ae=0.7mm;
(7) Partial rooting and finishing with φ16mm, φ10mm, φ8mm, φ6mm, φ4mm million chopping head milling cutters;
Hardness is 60HRC mold processing example:
(1) Performing the semi-finishing of the mirrored ball head BNM type to remove the residual stress on the surface of the hardened material: Ap = 0.2 mm, Ae = 1.4 mm;
(2) Contour finishing with mirror ball head BNM type: Ap = 0.05 ~ 0.1 mm, Ae = 0.7 mm.
Features of automated unmanned machining tools:
In today's increasingly competitive form of the machining industry, automated unmanned production methods are increasingly being adopted. Unmanned machining has the following features in tool usage and machining programming:
(1) According to the approximate life of the tool, the program is segmented and sliced. The roughing tool life is generally determined according to the operating field experience data; when the finishing program is programmed, the general tool life standard is set to 600m according to the processed steel material; the processed ductile iron is set to 800m; the processed gray cast iron is set to 1200m.
(2) Processes such as roughing and semi-roughing are subdivided, and the tool is multi-functional.
(3) Adding a rooting process between the various conventional processes to make the entire mold allowance as uniform as possible. Special attention should be paid to local roots.
(4) Long life of the tool. Avoid unnecessarily high line speeds and use cutting conditions with tool life of at least 5000m. For example, φ30mm mirror ball end mill BNM type finishing alloy cast iron, after cutting 5080m with the speed of 6000r/min, feed rate 5000mm/min, depth of cut 0.1mm, step size 0.7mm, the blade flank wear width is less than 0.2mm .
In automated unmanned production methods, the use and management of tools is very important. In the tool management process, the geometrical parameters of the tool (type, diameter, blade length, overhang, etc.) are generally determined according to the customary usage according to their respective processing experience. For example, when using the Ñ„50 roughing ball end mill, some users configure the tool's lower tool depth by 100/150; others use 120/170.
The tool preparation department installs and calibrates the tool and the tool holder according to the tool standard, and then transfers the integrated data information of the tool to the process programming department, which is directly set by the programmer in the machining program. The machining program is modularized, and the machine operator can select according to the machining requirements during actual machining. At the same time, the standard of the tool is also brought directly to the machining process by the programmed value. The cutting conditions when the tool is used are mostly adjusted by the machine operator according to the program setting and the specific processing conditions.
Tool application in international automotive mold processing technology
This paper combines the current status of processing technology in Europe, America and Japan, and explains the manufacturing of automotive molds from the perspective of the setting of processing conditions and the selection of processing tools.