In the time-consuming CNC finishing process, how to improve the processing efficiency is a particularly meaningful topic. If I tell you that there is a processing method that can reduce the finishing time of parts from 60 minutes to 4 minutes, you may think it is a joke! Today, I will introduce you to the superstring finishing technology, which uses innovative tools and processing strategies to greatly improve the finishing efficiency and fully release the extraordinary potential of CNC processing.
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▲ Schematic diagram of the finishing tool path
The purpose of finishing is to ensure the final dimensional accuracy and surface quality of the workpiece. To improve the efficiency of finishing, we must consider these two aspects in depth.
New programming ideas: superstring finishing
Taking our commonly used processing programming software Mastercam as an example, superstring finishing technology is an efficient finishing programming solution:
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▲ Actual cutting case
In this case, if process 1 uses a ball cutter for finishing, the time is: 30 minutes, and if a circular tool + superstring finishing is used, the time is: 3 minutes.
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In process 2, if ball cutter finishing is used, the time is: 60 minutes; while if arc cutter + superchord finishing is used, the time is: 4 minutes.
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Why can such an effect be achieved? This starts with the determinants of our finishing surface quality.
Determinants of finishing: residual ridge height
The surface quality of finishing depends largely on the residual ridge height left after processing. So what is the residual ridge height? The residual ridge height refers to the maximum height of the protruding part of the residual material after the tool passes through two adjacent tool paths during processing.
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How to reduce the residual ridge height
One feasible method is to reduce the step distance and reduce the distance between adjacent tool paths. But this means increasing the number and density of tool paths per unit area and increasing the finishing time. So in 3D surface finishing, everyone will feel that the choice between "surface quality" and "processing time" seems to be a dilemma, because: better surface quality = longer processing time.
Another feasible method is to use a larger tool. Because the larger the tool radius, the larger the arc at the contact point when it contacts the material. Under the same tool path density, the smaller the residual ridge height is obtained.
For example:
Use a 10mm ball cutter and set the step length to 4mm;
The resulting residual ridge height is 0.432mm.
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Use a 25mm ball cutter and set the step length to 4mm;
The resulting residual ridge height is 0.152mm.
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Comparison of residual ridge heights of two tools of different sizes using the same step length.
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Use a tool with a larger arc to reduce the residual ridge height.
Use a tool with a large radius or a tool with a small radius
Use a tool with a large radius to reduce the residual ridge height and achieve better surface quality. But a new problem arises: many workpieces need to be finished where the gap is small and cannot be processed with a tool with a large radius.
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Finishing with a large radius tool:
Advantages: smaller residual ridge height; shorter cycle time.
Disadvantages: cannot process small gap areas; easy to interfere, complex programming.
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Finishing with a small radius tool:
Advantages: easy programming; can process small gap areas.
Disadvantages: To achieve better surface quality, it is necessary to reduce the step distance and increase the tool path density; the processing time is longer.
What programming strategy to use
Superchord finishing technology is a programming solution for efficient finishing using arc tools. For large arc tools of various shapes, based on the tool shape, special tool path algorithms can be used to dynamically compensate the tool contact points during the processing process, and the shape of the arc tool can be fully utilized for high-precision and high-efficiency finishing.
If you want to use large arc tools for finishing in superchord finishing, what tool path strategy should be selected for programming?
3-axis machining:
In ordinary 3-axis machining, because the machine tool axis movement is simple, superchord finishing can be used for finishing of some side walls and steep areas or flat areas on the top surface. It is recommended to use barrel-shaped and taper-shaped arc tools, and use the equal height strategy and parallel strategy in Mastercam 3D finishing for superchord finishing.
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3+2 fixed surface machining:
In the 3+2 fixed surface environment, it is also recommended to use the equal height and parallel strategies for superchord finishing. Unlike simple 3-axis machining, in 3+2 fixed surface machining, it is necessary to select a suitable tool plane so that the arc of the tool contacts the material at a stable tangent point in the tool path.
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Five-axis linkage machining:
Five-axis linkage machining has flexible machine tool movement angles and is the main application area of superchord finishing. In five-axis machining, it is recommended to use parallel and gradient machining strategies.
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The key point of superchord finishing in five-axis linkage is to control the tool axis so that the tool contacts the material at a stable and appropriate arc tangent point.
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Comprehensive comparative analysis
Is there a way to integrate the advantages of the two and avoid the disadvantages of the two? The answer is yes. A careful analysis of the formation process of the residual ridge height shows that the residual ridge height is actually related to the arc radius of the contact point between the tool and the material, and has little to do with the tool radius itself. If we only increase the radius of the effective machining part of the tool while keeping the radius of the tool body unchanged, we may be able to achieve both the goals of improving surface quality and shortening finishing time.
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Take the large radius arc milling cutter of the taper form as an example. The height of the residual ridge left by the effective machining arc of the tool for finishing is equivalent to the height of the residual ridge left by a ball cutter with a diameter of 187 times.
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The surface quality of finishing completed by a 16mm taper form large arc milling cutter at the same step distance and the same time is equivalent to the surface quality achieved by a ball cutter with a diameter of nearly 3000mm (3 meters).
Changing the shape of the tool, increasing the arc of the contact point between the tool and the material during processing, and reducing the height of the residual ridge left by finishing can greatly reduce the number and density of tool paths required in the finishing area, which greatly reduces the processing time and improves production efficiency.
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But a new problem arises: the effective machining arc of this type of large arc milling cutter has a complex shape. In the tool path, corresponding compensation must be made based on the complex shape of the tool to make the large arc of the tool accurately fit the machining position and meet the surface quality requirements in the finishing process. How should such a tool path be programmed?
Using superstring finishing technology on the CAM software Mastercam, you can dynamically compensate for the tool contact points during the machining process for large arc tools of various shapes based on the tool shape through special tool path algorithms, and make full use of the shape of the arc tool for high-precision and high-efficiency finishing.
This superstring finishing technique has really improved efficiency in finishing, but it also has the problem of slightly higher programming costs. The specific analysis still needs to be carried out according to the product processing conditions. What do you think of this solution? Will you use it? Welcome to discuss with everyone in the comment area below~
