Practical application of UG in KONKA small precision mold processing

Traditional processes have always used EDM as the final finishing process for precision tooling. Its advantage is that the detection of the electrode before processing can better control the dimensional accuracy of the machined part, there is no hard interference during the processing, the heat distribution is small, and the surface finish is better than that of the ordinary CNC machine tool. However, it also has some shortcomings, which makes it difficult to produce precision molds, especially those that are extremely important in appearance. First, the processing and inspection of the rough electrode will take a long time. Second, the molding of the mold requires two polishing processes, and it has been difficult to ensure the required angularity of the plastic parts. In modern mold processing, high-speed CNC machine tools are used to directly mill high-quality smooth surfaces, and small diameter tools are used for deep cavity or clear angle high-speed machining to reduce EDM, high-speed and low-load cutting, and low-speed high-load cutting. It is a general trend to cut materials faster, reduce thermal deformation, and improve mold production efficiency. It can be called a revolution in the machining industry.

As we all know, high-speed machining (HSM) requires very high requirements for machine tool performance, tool clamping system, tool quality, machined parts, and CAM software. All aspects require good quality to complete the machining. The most influential one is CAM software. HSM puts forward extremely high requirements for CAM software: full automatic over-cutting processing capability and automatic tool holder interference inspection, rich processing strategy in line with high-speed machining requirements, high calculation programming speed, and powerful intelligent operation. UG has a perfect interpretation of the above requirements, processing software is changing with each passing day, and Unigraphics CAM has always danced to the top of the industry, which is the main reason we choose UG.

From our company to buy UG13 to UG NX2, UG CAM has improved through several eras, and now it has achieved greater advantages in the field of high-speed machining. In 1999, our company introduced two state-of-the-art high-speed CNC machining centers, which can reach 20,000 RPM. The stable FANUC 16i-m system, advanced oil mist cooling method, and solid cast iron gantry machine structure provide a good guarantee for the precision mold production of our factory. High-speed processing equipment is a very expensive equipment. Any accident will cause immeasurable losses to the enterprise. The CAM system must ensure the absolute safety of the NC command, which is a basic requirement for high-speed processing equipment. In addition, the smooth and smooth path of the tool should be ensured to ensure the quality of the part and the life of the machine tool spindle and the load uniformity of the tool during the cutting process. However, in the past actual processing, due to lack of experience and traditional process concepts, we have been unable to meet the high quality requirements we need. In order to maintain our leading position in the fierce competition in the industry, we need a new improvement in processing efficiency and quality. With the strong support of the company, we have carried out a series of high-speed processing and application, and achieved some results. . Among them, the excellent Unigraphics NX software provides us with the best CAM solution:

First, rough processing:

The strategy adopted for rough machining of high speed machining is: high cutting speed, high feed rate and small cutting amount. UG keeps the tool load as stable as possible, reduces sudden changes in any cutting direction, and maintains maximum and stable cutting speed. We use hardened materials that are quenched to 50-55HRC. The traditional processing method is first roughing and then quenching, and then finishing, the process is longer. Now there are guarantees for high-speed machine tools, titanium-coated alloy tools and UG CAM, which can reduce the previous redundant links.

1. Tool motion control:

UG has a very rich strategy in tool motion control that can control every movement of the machine. The circular arc or oblique line of the knife and the retracting knife, the various connection modes of the tool between the layers and the layer, can be selected in the program to avoid damage or even breakage of the cutting edge of the tool caused by the straight lower knife, reducing the frequent cutting in and out. The impact. At the corner of the knife, plus the equal radius connection, smooth cutting, greatly improve the actual feed rate, avoiding discontinuous and sudden acceleration changes. UG rich cut-in and connection methods meet the requirements of high-speed machining to a great extent. In addition, UGCAM also has a unique area filtering function. For a beef nose knife without central cutting force, UG can use this function to filter out some processing blind areas. Path and warn to avoid a knife break. Although UG CAD utilizes the powerful Direct Modeling parametric tool to modify or simplify model features that do not require milling, it is undoubtedly an option for efficiency and processing safety.

Excessive free-range movement in the tool path is also a big taboo for HSM. UG can choose the offset path of follow periphery in the roughing process to reduce many unnecessary jumps, usually than follow part{follow the workpiece} The parallel machining path is preferred, which greatly reduces the opening time, and the tool maintains a constant cutting force and prolongs the service life.

2. Residual roughing (secondary roughing) is necessary before semi-finishing, and it is necessary to select a tool smaller than roughing. The reference tool function has been introduced from UG NX, which can intelligently and quickly identify the uncut of the upper tool. The step left in the process workpiece, the cost of the secondary cutting blank is set, and the residual margin can be automatically removed according to the setting, and the layer processing is performed to keep the balance uniform, and the next process is prepared. It is necessary to pay attention to the overlap area option to set the appropriate value according to the ratio of the two knife diameters, so as to avoid the knife under the solid.

3. In high-speed milling, it is necessary to avoid the knife being completely embedded during milling and the cutting being blocked or even broken. In order to meet such requirements in UG roughing, a unique machining function is proposed: Tronchorial. Cycloidal machining is to use the movement of the tool along a rolling circle to make the surface of the part high-speed, high-efficiency and small. Very smooth cutting of the cut. Combined with the UG efficient process blank identification, the efficiency of roughing is maximized.

Second, the basic requirements of finishing <br> <br> finishing is to obtain high accuracy, a smooth surface quality of parts, easily fine processing region. The tolerance can be adjusted appropriately during semi-finishing to save calculation time. In our experience, the tool selected is preferably smaller than the tool used for finishing, or the root is removed in advance to avoid collision of the tool at the corner during finishing. If you are sure, you can leave less cutting allowance to extend the life of the finishing tool.

1. We are used to semi-finishing when using the area-milling method in fixed-contour, the on part function is especially suitable. It maintains a very consistent cutting line spacing along the surface and completely removes the tool marks from all surface roughing operations to ensure the stability of the finishing load.

2. In the actual machining process, it was found that when using the fixed axis milling in the past, if the UG default circular interpolation method {circular-perp to TA} is selected, the output PTP file capacity will be larger, especially the 45 degree finishing. On a machine with a slightly poor read-ahead ability, if a higher feed rate is used, the surface of the workpiece will have a different degree of knife-shaving, which will greatly reduce the surface finish. In the repeated experiments, we found a suitable solution, and chose another circular interpolation method provided by UG [circular-perp/par TA}. In this way, the processed ptp file is greatly reduced. Small, the machine's read-ahead load is reduced, and it is easy to maintain a very high finish and surface quality at higher feed rates.

3. In traditional machining, the geometric model is basically approximated by a combination of straight lines and arcs. For complex advanced surfaces and curves, this interpolation will greatly increase the data, increasing the time and difficulty of data transmission. Moreover, the machining accuracy and surface quality are often difficult to meet the requirements, and the high-speed machining will have adverse effects. When outputting machining data, UG not only supports standard linear and circular interpolation, but also has NURBS interpolation. UG/Nurbs Path

The Generator Spline Trajectory Generator module allows toolpath data based on Nurbs non-uniform rational B-splines to be generated directly in the UG software, allowing for a series of curved motions rather than a large number of short linear motions for finishing. The trajectory has higher precision and smoothness, and the machining program is 30%~50% less than the standard format. The actual machining time avoids the waiting of the machine controller, because each NURBS movement is longer and the speed adjustment is less. The controller can look farther forward and the machining time is greatly reduced.

4. In machining, due to the large diameter or rounded corner of the selected tool, the angle between the corners of the part is too large, so that a smaller tool is needed to perform special machining on these areas, using a small diameter tool. Place the roots of the steps or the small R corners. In general, these areas are just the roots and corners in the cavity. The flow cut function in UG CAM is a solution specially designed for the above situations. It can automatically find the area on the part to be machined that meets the “double tangency condition”, and can flexibly adopt the separation of the tool path. Various methods such as deletion and fusion are used for tool path calculation processing, and the rooting program of one or more passes is automatically generated.

Third, the impact of CAD on high-speed machining

The impact of CAD on the quality and stability of high-speed machining is undoubtedly significant, and UG is a CADCAM integrated software with a single data source and relevance, which fundamentally eliminates the impact of data exchange on accuracy. . It is usually designed by a CAD system and then converted to another CAD system for additional design and processing preparation. Every time data is transferred, it is necessary to convert the geometry from one format to another, often at the expense of reduced accuracy. Some CAM software must also convert solids into curved surfaces, causing even damage and loss of the surface. The trade-off between accuracy and completeness is something we don't expect to see.

UG has a unified solution, with a single user interface, data structure, and tight integration to make the model interoperable and relevant, so that design changes can be quickly reacted, can handle complex models, directly process scan data, and support parallel engineering. Therefore, the production efficiency is greatly improved.

Fourth, the conclusion

According to the author's understanding of high-speed machining and some experience in practical work, I personally believe that the safety of high-speed machining is the first priority. Generally speaking, we can see that in the high-efficiency and high-quality safety production, UG, as our trustworthy software, can always meet our various needs for high-speed machining, and is suitable for a wide variety of processing environments. , bringing high efficiency to our production.

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Tianyi Chemical Engineering Material Co., Ltd. ,