What are the main factors that affect the successful milling of CNC parts?

There are many factors that need to be considered in order to ensure the efficiency of the milling operation, such as using the correct milling tool, using the correct diameter and the correct number of teeth, and using the correct speed, feed rate, axial depth of cut and radial cut width. However, in order to ensure the effectiveness of tool application, there are many more important but often overlooked factors. CNC precision machining factory comprehensively considers five milling factors that determine production efficiency and profitability: entering angle, tooth pitch, milling cutter position, milling cutter bite amount and arc cutting skills.

Leading angle

The influence of different entering angles on the milling effect is very significant. If a 90° milling cutter is used as a face milling cutter, it is often just because it is easy to use, but its production Not as efficient or cost effective as a 45° cutter. Face milling parts with a 90° cutter instead of a 45° cutter reduces productivity by 30%, which in turn directly affects profitability.

Mainly, the entering angle affects the metal removal rate and tool life. Also, as the entering angle decreases, the chip thickness becomes thinner, and as such, there is an opportunity to increase the feed rate to compensate. More and more shops are now using small depths of cut and high feed rates to increase productivity, usually with milling cutters with a small entering angle (eg 10°), or with round inserts for chip thinning concept. Compared to the 45° face mill, the 10° face mill has an increased feed rate because the chips are thinned to almost one-sixth the size of the 90° face mill. If this strategy results in an insufficient depth of cut, a high feed rate can be used to compensate for the loss of efficiency.

High-feed milling cutters with a 10° entering angle can use very high table feeds due to the thin chips formed. In addition, high axial cutting forces ensure spindle stability and limit vibration, making these cutters more suitable for long tool overhangs and/or unstable clamping applications.

For 45° cutters, these are usually the choice for face milling because they balance radial and axial cutting forces well, and the engagement is very smooth. These milling cutters have low vibration and are suitable for short-chipping materials (such as gray cast iron), which are prone to edge chipping if the radial force is too large due to less and less workpiece allowance at the end of the pass.

If a 90° milling cutter is used as a face milling cutter, it is often just because it is easy to use, but its productivity or cost efficiency is not as good as a 45° milling cutter. A high-feed milling cutter with a 10° entering angle can also use a very high table feed due to the thin chips formed.

The main application of 90° milling cutters is shoulder milling. In this application, radial forces are mainly generated in the feed direction and are suitable for milling vibration-prone parts. In addition, the surface is not subjected to large axial pressure, which is good for milling structural parts or thin-walled parts that are not strong. It must be noted that 90° cutters cannot form thin chips, and the programmed feed rate per tooth for large cutting widths is equal to the actual large chip thickness.

So, what about round inserts? Round inserts are suitable for efficient heavy-duty roughing and general-purpose milling.

Round inserts are especially suitable for machining titanium alloys and HRSA materials, but the effect is not very good when the pursuit of high-quality surface accuracy. This is because the entering angle changes in the range of 0~90°, which causes the cutting force to change with the arc cutting edge, and thus the pressure changes. Round inserts are unique in that the thickness of the chips formed varies with the depth of cut - the smaller the depth of cut, the thinner the chip. Therefore, if the depth of cut is small, the feed rate must be increased to ensure a suitable chip thickness and improve production efficiency.

Pitch

By increasing the number of cutting edges, the table feed can be increased while keeping the cutting speed and emit more heat). However, the denser the tooth pitch, the less space for chip evacuation. In addition, increasing the number of inserts in a milling cutter has the disadvantage of negatively affecting vibration if the clamping is not sufficiently rigid. Using unequal pitch milling cutters optimizes the application, and choosing the correct pitch is also important as it affects productivity, stability and power consumption.

Generally speaking, there are three pitches of sparse teeth, dense teeth and super dense teeth. Rough-tooth milling cutters have fewer blades. Since they transmit low cutting forces, they are the choice for unstable operations. Full slot milling operations and long-chip ISO N materials are suitable for coarse-pitch milling cutters.

The number of inserts of the fine-pitch milling cutter is medium, and the design of equidistant or non-equidistant can be used. They are the choice for general roughing in stable conditions. The benefits also include efficient machining of all materials without worrying about chip space.

Wow, this sounds like a bit of a cruel question, but it is a vitally important question to ask yourself if you are struggling with your sheet metal manufacturing and you would like to stop the custom metal parts problem.
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