Introduction to the application range of metal mold high-speed processing technology
The main goal of roughing die roughing is to pursue the material removal rate per unit time and to prepare the geometric profile of the workpiece for semi-finishing.
During the cutting process, the metal area of ​​the cutting layer changes, causing the load to be changed by the tool, the cutting process is unstable, the tool wear speed is not uniform, and the quality of the machined surface is degraded. Many of the CAM software currently developed can maintain a constant cutting condition by the following measures, thereby obtaining good processing quality. Constant cutting load. A constant cutting area and material removal rate are obtained by calculation to balance the cutting load with the tool wear rate to improve tool life and machining quality. Avoid suddenly changing the tool feed direction.
Avoid burying the tool in the workpiece. For example, when machining the mold cavity, the tool should be prevented from being inserted vertically into the workpiece, but the inclined lower knife method should be used (the common inclination angle is 20° to 30°). It is best to use the spiral lower knife to reduce the tool load; when machining the mold core Should try to lower the knife from the outside of the workpiece and then cut it horizontally. When cutting and cutting out the workpiece, the tool should be cut and cut as much as possible by tilting (or arc) to avoid vertical cutting and cutting. Climbcutting reduces cutting heat, reduces tool force and work hardening, and improves machining quality.
The main goal of semi-finishing semi-finishing is to make the contour of the workpiece flat and the surface finishing allowance uniform, which is especially important for tool steel molds, because it will affect the change of the cutting area of ​​the tool and the change of the tool load during finishing. , which affects the stability of the cutting process and the quality of the finished surface. Roughing is based on a volume model and finishing is based on a surface model.
However, the previously developed CAD/CAM system has a discontinuous geometric description of the part. Since there is no intermediate information describing the machining model after roughing and finishing, the residual machining allowance distribution and the maximum remaining machining allowance of the roughed surface are not described. Both are unknown. Therefore, the semi-finishing strategy should be optimized to ensure a uniform residual machining allowance on the surface of the workpiece after semi-finishing.
The optimization process includes: calculation of the contour after roughing, calculation of the maximum residual machining allowance, determination of the maximum allowable machining allowance, and transformation of the profile division (such as grooves, corners, etc.) for the remaining machining allowance greater than the maximum allowable machining allowance. The radius is smaller than the radius of the roughing tool) and the calculation of the tool path during semi-finishing. The existing CAD/CAM software for high-speed machining of molds mostly has the residual machining allowance analysis function, and can adopt a reasonable semi-finishing strategy according to the size and distribution of the remaining machining allowance. For example, OpenMind's HyperMill and HyperForm software provide methods such as beam milling and residual milling to remove corners with large machining allowances after roughing to ensure a uniform machining allowance for subsequent processes. Local milling of PRO/ENGINEER software has similar functions. For example, the residual machining allowance of the local milling process is equal to the roughing. This process uses only a small diameter milling cutter to remove rough cut uncut corners. Then, semi-finishing is performed; if the remaining machining allowance value of the partial milling process is taken as the remaining machining allowance for the semi-finishing, the process can not only remove the uncut corners of the roughing, but also complete the semi-finishing.
The high-speed finishing strategy of a finishing tool depends on the point of contact between the tool and the workpiece, and the point of contact between the tool and the workpiece varies with the slope of the surface of the machined surface and the effective radius of the tool. For complex surface machining composed of multiple curved surfaces, continuous machining should be performed in one process as much as possible, instead of processing each curved surface separately to reduce the number of lifting and lowering. However, due to the change in the slope of the surface during processing, if only the sideover of the machining is defined, the actual step distance on the surface with different slopes may be uneven, which may affect the processing quality.
Pro/Engineer solves the above problem by defining the amount of knife on the side while defining the height of the machined surface (Scallopmachine); HyperMill provides an Equidistant machine to ensure uniform path between the passes. The amount of knife on the side is not limited by the slope and curvature of the surface, ensuring that the tool will always receive a uniform load during the cutting process. In general, the radius of curvature of the finished surface should be greater than 1.5 times the radius of the tool to avoid sudden changes in the feed direction. In the high-speed finishing of the mold, the feed direction should be changed by arc or curve as much as possible during each cutting and cutting of the workpiece, avoiding the use of linear transfer to maintain the smoothness of the cutting process.
Optimization of feed rate Many CAM softwares now have an optimized adjustment of the feed rate: in the semi-finishing process, the feed rate is reduced when the cutting layer area is large, and the feed rate is increased when the cutting layer area is small. The optimized adjustment of the feed rate can make the cutting process smooth and improve the quality of the machined surface. The size of the cutting layer area is completely calculated automatically by the CAM software, and the adjustment of the feed rate can be set by the user according to the processing requirements.
4 Conclusion Mold high-speed machining technology is the integration of a variety of advanced processing technology, not only involves high-speed machining technology, but also high-speed machining machine tools, CNC systems, high-speed cutting tools and CAD / CAM technology. The high-speed mold processing technology has been widely used in the mold manufacturing industry in developed countries, and the application scope and application level in China still need to be improved. We will vigorously develop and promote the application of high-speed mold processing technology to promote the overall technical level and economy of China's mold manufacturing industry. The improvement of benefits is of great significance.
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Tag: High-speed machining Machining allowance Cutting process Machining quality Tool
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A ball check valve is a check valve in which the closing member, the movable part to block the flow, is a spherical ball. In some ball check Valves, the ball is spring-loaded to help keep it shut. For those designs without a spring, reverse flow is required to move the ball toward the seat and create a seal. The interior surface of the main seats of ball check valves are more or less conically-tapered to guide the ball into the seat and form a positive seal when stopping reverse flow.
Ball check valves are often very small, simple, and cheap. They are commonly used in liquid or gel minipump dispenser spigots, spray devices, some rubber bulbs for pumping air, etc., manual air pumps and some other pumps, and refillable dispensing syringes. Although the balls are most often made of metal, they can be made of other materials, or in some specialized cases out of artificial ruby. High pressure HPLC pumps and similar applications commonly use small inlet and outlet ball check valves with both balls and seats made of artificial ruby, for both hardness and chemical resistance. After prolonged use, such check valves can eventually wear out or the seat can develop a crack, requiring replacement. Therefore, such valves are made to be replaceable, sometimes placed in a small plastic body tightly-fitted inside a metal fitting which can withstand high pressure and which is screwed into the pump head.
There are similar check valves where the disc is not a ball, but some other shape, such as a poppet energized by a spring. Ball check valves should not be confused with Ball Valves, which is a different type of valve in which a ball acts as a controllable rotor to stop or direct flow.
A diaphragm check valve uses a flexing rubber diaphragm positioned to create a normally-closed valve. Pressure on the upstream side must be greater than the pressure on the downstream side by a certain amount, known as the pressure differential, for the check valve to open allowing flow. Once positive pressure stops, the diaphragm automatically flexes back to its original closed position.
A swing check valve or tilting disc check valve is check valve in which the disc, the movable part to block the flow, swings on a hinge or trunnion, either onto the seat to block reverse flow or off the seat to allow forward flow. The seat opening cross-section may be perpendicular to the centerline between the two ports or at an angle. Although swing check valves can come in various sizes, large check valves are often swing check valves. The flapper valve in a flush-toilet mechanism is an example of this type of valve. Tank pressure holding it closed is overcome by manual lift of the flapper. It then remains open until the tank Drains and the flapper falls due to gravity. Another variation of this mechanism is the clapper valve, used in applications such firefighting and fire life safety systems. A hinged gate only remains open in the inflowing direction. The clapper valve often also has a spring that keeps the gate shut when there is no forward pressure. Another example is the backwater valve (for sanitary drainage system) that protects against flooding caused by return flow of sewage waters. Such risk occurs most often in sanitary drainage systems connected to combined sewerage systems and in rainwater drainage systems. It may be caused by intense rainfall, thaw or flood.
A stop-check valve is a check valve with override control to stop flow regardless of flow direction or pressure. In addition to closing in response to backflow or insufficient forward pressure (normal check-valve behavior), it can also be deliberately shut by an external mechanism, thereby preventing any flow regardless of forward pressure.
A lift-check valve is a check valve in which the disc, sometimes called a lift, can be lifted up off its seat by higher pressure of inlet or upstream fluid to allow flow to the outlet or downstream side. A guide keeps motion of the disc on a vertical line, so the valve can later reseat properly. When the pressure is no longer higher, gravity or higher downstream pressure will cause the disc to lower onto its seat, shutting the valve to stop reverse flow.
An in-line check valve is a check valve similar to the lift check valve. However, this valve generally has a spring that will 'lift' when there is pressure on the upstream side of the valve. The pressure needed on the upstream side of the valve to overcome the spring tension is called the 'cracking pressure'. When the pressure going through the valve goes below the cracking pressure, the spring will close the valve to prevent back-flow in the process.
A duckbill valve is a check valve in which flow proceeds through a soft tube that protrudes into the downstream side. Back-pressure collapses this tube, cutting off flow.
A pneumatic non-return valve.
Multiple check valves can be connected in series. For example, a double check valve is often used as a backflow prevention device to keep potentially contaminated water from siphoning back into municipal water supply lines. There are also double ball check valves in which there are two ball/seat combinations sequentially in the same body to ensure positive leak-tight shutoff when blocking reverse flow; and piston check valves, wafer check valves, and ball-and-cone check valves.
Check Valves, Water Check Valves, Brass Check Valves, Sanitary Check Valves
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