Compared to ordinary machine tools, CNC milling machines offer significant advantages in the production process.
With its flexibility and adaptability, CNC milling handles complex contours and size-sensitive parts like molds and shells.
CNC milling is capable of processing parts that ordinary machines cannot, including complex curves and 3D surface parts.
The parts that need to be processed in multiple procedures after one clamping and positioning are processed.
CNC milling machines provide high accuracy and stable quality, with pulse equivalents of 0.001mm and up to 0.1µm in high-precision systems.
By reducing operator errors, increasing automation, and lowering labor intensity, CNC milling supports better production management.
Efficiency is enhanced in CNC milling through the elimination of special fixtures, quick program recall, and tool adjustments that shorten production cycles.
CNC milling machines integrate milling, boring, and cobalt bed functions, centralizing processes and improving production efficiency.
With capabilities that ordinary machines can’t replace, CNC milling machines simplify operations and significantly boost efficiency.
Overcutting phenomenon in CNC Milling
In modern industrial parts processing, CNC milling machine has been widely used by virtue of its simple operation process and high efficiency.
However, in the actual processing, processing materials and so on may lead to CNC milling machine overcutting phenomenon.
Overcutting occurs when excessive material is removed, causing accuracy deviation. It can happen at any step in the machining process.
Overcutting when machining corners
In industrial part cutting, overcutting at the inner corner occurs due to two main reasons.
As the milling cutter moves to the inner corner, the contact area and cutting force increase.
After the milling cutter passes the inner corner, the contact area and cutting force decrease.
Changes in cutting force cause elastic deformation, affecting cutting accuracy and leading to overcutting.
Sudden changes in feed speed can cause overcutting due to inertia, leading to inaccuracies in the milling process.
For the above two situations, the solution measures are as follows:
Short-shank milling cutters improve rigidity and reduce overcutting, preventing part damage despite higher costs.
Make full use of the hierarchical programming of feed speed.
Overcutting when machining right angles
In right-angled part processing, matching the route with the orthogonal axes can cause the servo system to stop at a specific position coordinate.
The other axis servo system reaches its position, allowing the first axis to accelerate instantly to the specified speed.
Instruction changes may cause the second axis to accelerate while the first axis experiences hysteresis, leading to overcutting.
For the above situation, the solution measures are as follows:
Use graded speed reduction for the first axis to enable automatic acceleration or deceleration, minimizing hysteresis.
Use a proper clamping method to avoid overlapping machining paths and ensure orthogonal coordinate axis overlap.
In addition, the programming can be modified so that it can pause slightly when running to the corner position to avoid overcutting.
Remediation of overcutting
Overcut phenomenon in the process of establishing or withdrawing tool compensation
Currently widely used CNC milling machines are able to manipulate and execute automated tool radius compensation function of this command.
At the tool-part intersection, the machine struggles to quickly establish or cancel the milling tool’s patch.
Therefore, strict control and selection of the tool’s cut-out and cut-in modes are required at the tangent or tangent extension of the tool to the part.
Using a radial cut-in tool can change the tool’s movement direction and cutting size, causing a brief pause on the workpiece surface.
Changes in the tool or part’s elasticity coefficient can cause scars on the surface, affecting accuracy and lifespan.
Utilize digital technology to enhance the level of automatic operation of milling machine processing
Digital technology in milling automation should enhance automation, improve system functions, and conduct simulation tests for effective operation.
Digital technology in milling automation progresses towards integration, informatization, and openness, starting with equipment and simulations.
Milling machine automation combines independent modules that require ongoing adjustment and management for efficient operation and broader adoption.
overcutting phenomenon control factors
Reasonable selection of tools and other related supplies
The tool is crucial in CNC milling, where external friction causes high temperatures and pressure on the blade.
CNC milling machine must check and control the materials used in the process of controlling overcutting.
The cutter must have high friction resistance, hardness, toughness, and good high-temperature performance to prevent damage during use.
High-speed steel tools offer superior cutting speed and heat resistance (~540 °C), outperforming high-carbon and alloy steels.
High-carbon and alloy tool steels don’t meet CNC milling machine speed requirements, directly affecting heat during cutting.
This material isn’t suitable for CNC milling or high-speed cutting but is easier to sharpen than high-speed steel.
The scope of application of the control of the amount of cutting
CNC milling involves fixed cutting parameters, including cutting speed, tool length, depth, and feed rate.
The cutting speed must match the tool’s wear and heat resistance, with durability being the key measure of this critical index.
In addition, the cutting rate must also be in line with the feed of the CNC milling machine, and the last element is the cutting depth and thickness of the workpiece.
In CNC milling, cutting amount closely relates to tool durability, so technicians assess both when selecting processing parameters.
Technicians prioritize CNC machines with high efficiency, long tool life, and high cutting capacity.
In order of effect, the tool durability comes first, then a large feed is selected, and the last factor considered is the appropriate cutting run rate.
If the tooling used by the skilled laborer in the finishing process is worn out, this will usually have a significant impact on the accuracy of the machining.
Before each CNC milling operation, technicians check the tools to ensure their material, wear resistance, heat resistance, and durability meet requirements.
It’s also crucial to maintain optimal chipping speed and select the proper chipping amount.
Scientific processing technology
Overcutting can occur due to poor processing route or machining allowance selection, making careful process choice essential.
For non-straight contour cuts, ensure the tool follows the tangent direction smoothly into the arc, avoiding a normal cutting approach.
After completing the cut, the tool should exit along the tangent direction to prevent overcutting and ensure the operation is not canceled.
When cutting arc-shaped objects, the tool must enter and exit along the tangential direction.
For high-precision machining, use roughing followed by finishing to test the milling machine’s cutting technology.
Choose a 0.2mm to 0.5mm finishing allowance and use a small-diameter end mill for groove cuts, starting from the center.
Next, apply cutting compensation and use milling tools with an appropriate tool radius.
Conclusion
CNC milling machine in the cutting process, will be affected by a variety of factors that lead to the phenomenon of overcutting.
During part design, follow the processing mode in the drawings to minimize errors and prevent inaccuracies.
Correct CNC milling machine operation is essential, so technicians must check the machine before use to minimize errors.
