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What Is High-Speed Machining?
High-speed machining (HSM) represents a manufacturing procedure that makes quick but very light, low-pressure cuts to transform raw materials into desired shapes and geometries. HSM allows manufacturers to merge speed, efficiency, and precision to ensure increased material removal rates with lighter milling passes, high spindle speeds, and feed rates.
High-speed machining technology is embedded in most CAM (computer-aided manufacturing) software to achieve faster and easier machining tasks. Product designers often utilize HSM to produce prototypes, structural components, and molds with complex core and cavity geometries without compromising dimensional precision and quality.
Why High-Speed Machining Is Important?
Manufacturers across industries leverage high-speed machines’ high precision and repeatability in modern manufacturing for the vast benefits they offer. Some of the benefits of adopting high-speed machining include:
Superior Surface Finish and Dimensional Accuracy
Manufacturers embrace high-speed machining techniques because the high spindle speeds and feed rates ensure dimensional accuracy and high-quality finishes in machined parts. There is reduced heat generation at the cutting edge during the machining process due to the minimal tool engagement and high cutting speeds, mitigating the risks of thermal distortion.
Enhances Throughput and Efficiency
Increasing productivity is one of the numerous core strengths of high-speed machining. HSM facilitates increased throughput and helps manufacturers meet strict production schedules since it reduces machining time and creates higher amounts of parts with accelerated turnaround. Automating the process allows greater efficiency since tasks can be executed faster.
Minimizes Manufacturing costs
Although the HSM technology has an expensive initial investment, it provides overall cost efficiency to reimburse the investment. Manufacturers achieve a reduced cost per part with high-speed machining. It ensures reduced tool wear, a high production rate, and the ability to create superior-quality components with fewer defects.
Extends Tool Life
Contrary to the general conception, the high-speed conditions of HSM encourage better tool life because it minimizes the stress applied to the cutting tool and machine. Besides, machinists use advanced and precise tools with the proper coatings to minimize tool wear. It ensures optimized cutting parameters and reduces heat generation during high speed machining tasks.
Reduces Material Stress
This machining method reduces the risk of inducing stress or warping in the workpiece since high-speed machines exert less force on the raw material. Besides, it is crucial to ensure the structural integrity of parts when handling delicate or high-value materials that demand reliability and precision.
Common High-Speed Machining Techniques
We’ll explore some of the top techniques in high speed machining in this section:
Trochoidal Machining
Trochoidal machining is a cornerstone high-speed milling technique. It uses multi-fluted tools to create deep recesses, tight cavities, and confined grooves wider than the tool’s diameter. This process follows a series of circular cuts called trochoidal tool paths to maintain uniform chip thickness. It balances spindle speed and tool life by adjusting the tool path to achieve a constant chip load.
Trochoidal milling is a high-efficiency milling that leverages high speed while keeping a low radial depth of cut (RDOC) and a high axial depth of cut (ADOC). This machining technique operates primarily on the theory of chip thinning in machining. Machinists/designers often employ this method to maintain high-speed machining feeds and optimized workflow when cutting unusual or hard-to-machine materials like Inconel and titanium.
According to conventional thinking, cutting tools have an optimal chip load that determines the appropriate chip width and size produced during high-speed machining. Operators machine a workpiece with a chip load larger than “optimal” to ensure a constant maximum chip thickness, combating chip thinning.
Plunge Milling
Plunge Roughing CNC plunge milling, or z-axis milling, is a process where the machine feeds the cutting tool linearly into the material for high material removal rates in machining deep cavities or deep pockets. It is one of the most efficient high-speed CNC machining techniques and can handle more tool deflection.
Side Steps
Side steps represent the connection that produces an effective transition between adjacent tool paths, especially when feed rates are high. In recent years, parallel scan-line surface machining has been the most commonly used machining process to finish machine multi-surface models.
This machining technique can create sharp stepover moves at the end of each pass. An appropriate solution is to employ simple “looping” tool paths instead of sharper turns between scan passes at moderate feed rates (20-40 ipm). However, these simple rounded motions are too sharp at higher feeds. A “gulf club” stepover between passes is an alternative that has proven effective in some scenarios.
Radial Chip Thinning
The radial chip thinning technique occurs when radial-cutter engagement is less than 50 percent of the cutter diameter.
For instance, a ½”, 4-flute end mill feeding at 0.01 IPT (inch Per Tooth) with a ¼” or greater stepover (radial depth of cut) creates a chip thickness equal to the programmed inch per tooth feed rate, or 0.010-inch.
However, to achieve comparable chip thickness, experts recommend decreasing the stepover to 10 percent (0.050”) and the IPT value to 0.0167”.
Cornering
The feed rate of a CNC machine must drop to zero to create a sharp corner in the toolpath. This feature is complicated in high-speed machining because it demands high deceleration/acceleration rates near sharp corners. It also increases total machining time and may cause substantial path deviation (contour errors).
However, high-speed cornering strategies employ linear drives on all axes and high-speed spindles to maintain high deceleration and acceleration when the machine tool goes in and out of corners.
Smart machining
Feed rate optimization is critical to ensuring efficient machining and shorter machining times. Operators can predict and improve the performance of milling operations through autonomous machining systems and optimization. It is achieved by stimulating and analyzing the milling process in a virtual machining framework to extract cutter-workpiece engagement conditions. The machine operator evaluates the cutting force along the cutting segmentation based on the mechanical principles of milling.
Meanwhile, the manufacturer adopts a constraint-based optimization scheme to maximize the cutting force by determining acceptable federate levels as the optimization strategy. An autonomous machining system features an intelligent algorithm to enable numerically controlled programs to accommodate these new feed rate values.
Core Factors of High-Speed Machining Operations: Rigidity, Tool Balancing and Proper Clamping Methods
Rigidity, tool balancing, and proper clamping techniques are core factors that ensure repeatability, accuracy, and superior surface finishes, which guarantee a successful machining operation.
Rigidity
Rigidity is a critical necessity within high-speed machining because a rigid machine setup reduces the risks of tool deflection. Thus, it ensures the machine tool adheres to the programmed path with minimal deviation to achieve machined parts with accurate dimensions and superior surface finishes.
Most operators employ a stable workholding fixture and tailored toolholder designs for enhanced rigidity, minimizing vibration and resisting the bending forces that could affect the precision of the machining process. Consequently, machine rigidity reduces generated heat, lowers cutting forces, and ensures consistent adherence to precision engineering standards that maintain the machined part and the tool’s integrity.
Tool Balancing
High-speed machining tool alignment is essential in countering inefficiency and poorly delivered cuts. Excessive vibration can cause spindle damage and compromise the quality of machined parts, irrespective of the sophistication of the CNC machine used. Therefore, adjust tool holders to ensure smooth operation and extend the machine’s lifespan and tooling in high-speed machining. In addition, balancing tool holders to a finer degree is a key requirement in high-speed applications to ensure desired fits and quality surface finishes.
Proper Clamping Mechanism
Appropriate clamping methods are critical to creating a masterpiece with high-speed machines. Choose a clamping method based on the material and geometry of the workpiece and specific machining operation. From edge clamps to dovetail vises and grippers, the compatible clamping mechanism can secure the raw material during machining to prevent chatter and ensure superior surface roughness.
Real-World Applications of High-Speed Machining
HSM strategies with the integration into advanced CAM software packages enhance productivity in sectors including:
- Aerospace: High-precision machining technology provides the reliability and high durability necessary in aircraft components and designs. Aerospace CNC parts manufacturers leverage HSM techniques to produce precise and lightweight aircraft components like fuselage panels, landing gear, and engine components from different materials, including high-strength aluminum alloys.
- Automotive: In this sector, manufacturers rely on this invaluable modern manufacturing tool to mass-produce automotive components, including body panels, cylinder heads, and transmission components. It allows manufacturers to meet the high demands of consumers and help maintain efficiency in production runs.
- Defense: The defense sector leverages the high speed and precision of high-speed machining to create high-quality customized parts and devices, including weapon systems, aircraft parts, and military-grade vehicle components.
- Electronics: Electronic device manufacturers leverage the high precision of HSM techniques to handle the miniature of intricate components crucial to electronics manufacturing, including consumer electronics like casings for household appliances and toys.
- Energy: High-speed machining provides the efficiency and precision necessary for intricate aircraft components like turbine blades, solar panel mounts, and gas and steam turbines.
Best Practices and Considerations that Drive Efficiency in High-Speed Machining Operations
Implementing appropriate machining practices and leveraging the proper tooling help achieve desired results in high-speed machining. Here are helpful guidelines and strategies:
High-Speed Machining Tool Selection
A machinist must choose the perfect cutting tool for each high-speed machining operation, whether it is a simple roughing or complex finishing task. Choosing the right tool for each machining task depends on factors like the cutter’s geometry, holding mechanism, and the composition of the tool material. Each factor contributes to the quality of machined parts and the tool’s performance.
Geometry of High-Speed Machining Tools
The cutter geometry for high-speed machining determines the stability and longevity of the cutting process. For example, machinists achieve more effective stress dispersion with a larger radius on cutting tools.
A cutting-edge design with a slight rounding ensures better stability through uniform pressure distribution, particularly when machining materials such as nylon. More importantly, it helps achieve the desired depth of cut without affecting the tool’s performance.
Material Composition
The material composition of the tools used at high speed is as important as its form. For example, tungsten carbide is a typical material used to make HSD tools since it can handle high surface feet per minute and has an extensive work range. Polished carbide endmills significantly benefit HSM operations because chips slide off easily, ensuring a smooth, low-heat cut.
Silicon nitride and other ceramic materials are ideal for applications requiring a higher cutting speed of about 4000 sfm because of their high-temperature tolerance. Furthermore, CNC tools coated with Cubic Boron Nitride (CBN) and polycrystalline diamond can handle even higher thermal loads, exceeding cutting speeds of 4000 sfm.
Adjusting Chip Load
Knowing how to optimize chip load in high-speed machining operation allows you to increase the metal removal rate and expedite cycle time to achieve a more efficient machining process. Optimizing chip load helps machinists maximize cubic inches of removed material, offering a better economic sense and a more productivity-oriented approach.
Radial chip thinning is one critical factor to consider when adjusting chip load. It occurs when the cut’s width is less than half the diameter of the cutter, mandating an increase in feed rate to maintain the required chip load. However, experts recommend employing high-feed endmills to exploit axial chip thinning and increase the feed rates significantly in scenarios where the spindle speed limits productivity.
Material Considerations
When machining parts at high speed, a machinist must match the HSM strategies with the specific material to achieve optimal results. Machining techniques that work well with thermoplastics may not be ideal for composites, hence the need for a diverse approach to machining.
Besides technical requirements, the cost of materials can impact the machining process. Machinists often use less expensive materials for prototyping before machining parts from costly materials. The strength-to-weight ratio of high-performance plastics usually guides the ideal choice of the ideal material, especially in industries like aeronautics and space, where this ratio is critical.
Conclusion
High-speed machining is a game-changer in the fast-paced world of the modern manufacturing landscape, thanks to its high metal removal rate and accuracy in mass production of parts. This innovative machining concept pushes the boundaries of possibilities in machining, transforming your manufacturing operation through rapid cutting with minimal heat transfer and shop emissions.
AT-Machining is a top CNC machining expert with manufacturing capabilities and state-of-the-art technology that redefines the limits of production capabilities. Our team of experts can provide high-quality, accurate parts with superior surface finishes. Contact us for professional high-speed CNC machining services to boost your business!
