America's Cutting Edge (ACE)’s Post

Let’s talk about the number of teeth on an endmill. The top left panel shows the frequency response function, or FRF, for an endmill. This describes its natural frequency, stiffness, and damping. We obtain it from a tap test, where we excite the tool with an instrumented hammer and measure the response with an accelerometer. The other three panels show the stability maps for 25% radial immersion down milling in aluminum using an endmill with the displayed FRF (800 Hz natural frequency). The only difference is the number of teeth. We see that the best spindle speed-axial depth combination (green circle) changes with the number of teeth. As we add teeth, the stability peaks tend to squeeze together at lower spindle speeds. The simple equation shows the approximate relationship between the best spindle speed, natural frequency, and number of teeth. To learn more, register for our ACE CNC machining course. The related metrology course describes manufacturing measurements and measurement uncertainty. https://lnkd.in/dWnixj6c

Have you seen analogy questions on standardized tests? An example is: drip is to gush as… (dent is to destroy would be a plausible answer). I have another analogy for you. Microscope is to fingerprint as tap testing is to frequency response function (FRF). This analogy is demonstrated in the figure. While one finger may look like another, when we use the microscope to image the fingerprint, we can clearly differentiate one finger from another. In the same way, while one tool-holder-spindle-machine may look like another, when we use the tap test to measure the FRF, we can clearly differentiate one combination from another. Given the FRF, we can make the best use of that tool-holder-spindle-machine by calculating the associated stability map. If you'd like to learn more about the relationship between vibrations and milling parameter selection, register for our online, no-cost CNC machining course. To learn more about measurement of machined parts, register for our metrology course. https://lnkd.in/dWnixj6c

Let’s talk about memory in milling. Did you know that one tooth knows about the behavior of the previous tooth? The picture demonstrates the situation. We see that the vibration of the current tooth is imprinted on the part surface. This is the solid line in the figure (the scale is exaggerated). There is memory because vibration of the previous tooth (dotted line) also affects the current chip thickness, h. This chip thickness is defined in the surface normal direction, n, which changes with the cutter angle. Because the cutting force is scaled by the chip thickness (as h increases, the force increases), the new cutter vibration, which depends on the force, is affected by this memory as well. The result is that chatter in milling is caused by memory! The good news is that this effect is understood and modeled. If we know the frequency response function (structural dynamics) for the tool-holder-spindle-machine, we can predict stable machining conditions. If you'd like to learn more about machining dynamics, register for our no-cost, online CNC machining training. https://lnkd.in/dWnixj6c #ace #cncmachining #dynamics #education #workforcedevelopment

Let’s talk about cutting forces in milling. The top plot shows results for up (conventional) milling and the bottom plot shows results for down (climb) milling. The radial depth of cut is one-fourth of the endmill diameter (25% radial immersion) in both cases, but the forces look quite different. In up milling, the force is smallest when a tooth enters the cut and largest just before the tooth exits the cut. This is because the chip thickness increases with the endmill clockwise rotation and translation to the right. In down milling, the force is largest when a tooth enters the cut and smallest as the tooth exits the cut. This is because the chip thickness decreases with the endmill clockwise rotation and translation to the right. If you'd like to learn more about milling forces, register for our no-cost, online ACE CNC machining training. https://lnkd.in/dWnixj6c #cncmachining #force #ace #mtrc

Let’s talk about indexable endmills. The top left picture shows a structured light scan for a selected endmill with three teeth and five rows (15 total inserts). The top right figures displays the location of the cutting edges around the steel body periphery for all 15 carbide inserts. We see a 14.7 deg helix angle for each insert, but a larger rake angle of 62.6 deg between rows 1 (top) and 2 and 55.5 deg for rows 2 to 5 (bottom). The lower collection of plots shows the cutting force (x is the feed direction) for four different axial depths of cut. In each figure, the red line indicates the measurement and the blue line the prediction from our time domain simulation. For 5 mm, we are cutting with only the first row of inserts, so the force profile is simple: each insert enters and exits the cut individually (5% radial immersion). The differences in magnitude from one to the next are due to runout. As the axial depth increases, the profile becomes increasingly complicated as multiple rows are engaged. Once we can model the force, we combine this with the structural dynamics to predict the stability behavior. If you'd like to learn more about milling force, register for our no-cost online CNC machining training. https://lnkd.in/ejFqkhtH #cncmachining #dynamics #mtrc #ace

Let’s talk about tap testing. This is a technique that is used to measure the frequency response function, or FRF, for a tool-holder-spindle combination. With this information, we can select optimized milling parameters. The figures identify the key elements of the test. The lower left photograph shows a hammer being used to tap a tool tip and an accelerometer being used to measure the vibration response. The top row displays the time responses for the force and vibration. We see that the tap produces a short duration force input. Due to this impulse, the tool vibrates with a decaying amplitude (due to damping). The middle row shows the conversion of these signals to the frequency domain. The bottom row displays the FRF. From this plot, we can identify the natural frequency, stiffness, and damping ratio for each vibration mode. If you'd like to learn more about selecting milling parameters using the FRF, register for our online, no-cost ACE CNC machining course. To learn more about measuring parts after machining, register for our ACE metrology course. https://lnkd.in/dWnixj6c

LightGRIND LT10 Single-laser Grinding Machine √The single piece machining can ensure the consistency of finished products; √ The customized fixture allows for quick clamping and automatic transformation; √ The integrally cast machine can ensure high rigidity, high accuracy and high stability; √ The PCD tool blade can realize thinning and finish machining; √ The average machining time of a single piece is about 5 minutes, and one piece can be installed at a time (the efficiency is subject to the actual test result due to differences in material properties and dimensions); √ As for the finished product accuracy, the height difference at the front surface is 0.005, ensuring a convexity of 0.005 in the middle, as well as deformation in subsequent grinding. 😃

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❓ What's the best helix angle for efficient chip removal in aluminium CNC machining? 🌀 The helix angle in cutting tools is crucial. A higher angle speeds up chip removal but raises friction and heat, risking chip welding during high-speed aluminium CNC machining. Conversely, a lower angle reduces heat but may not clear chips efficiently. Optimal helix angles for aluminium CNC machining are around 35°-40° for roughing and 45° for finishing. 📰 Discover more about aluminium CNC machining tooling strategies: https://zurl.co/maQh

LightGRIND LT10 Single-laser Grinding Machine √The single piece machining can ensure the consistency of finished products; √ The customized fixture allows for quick clamping and automatic transformation; √ The integrally cast machine can ensure high rigidity, high accuracy and high stability; √ The PCD tool blade can realize thinning and finish machining; √ The average machining time of a single piece is about 5 minutes, and one piece can be installed at a time (the efficiency is subject to the actual test result due to differences in material properties and dimensions); √ As for the finished product accuracy, the height difference at the front surface is 0.005, ensuring a convexity of 0.005 in the middle, as well as deformation in subsequent grinding.