The milling machine has two kinds of milling methods, forward milling and reverse milling. When forward milling, the effect of the cutter on the workpiece is the same as the feed direction of the cutter in the feed direction. Reverse milling is the opposite direction.
1. Advantages and disadvantages of circular forward milling
When the forward milling is done, the force on the workpiece is reduced by the force of the workpiece, the milling is smooth, it is suitable for the workpiece which is not easy to be clamped and the slim parts are slim. Cutting edge and the machined surface of the extrusion, friction is small, high quality processing surface. Consume less power. However, when cutting the cutting edge into the workpiece, easy to accelerate the tool wear and damage. Milling force Ff and workpiece feed the same direction, when the table feed screw and nut gap and bearing the axial clearance is large, the milling machine table will produce intermittent movement, resulting in tooth damage, knife The rod is bent and the workpiece and the fixture are displaced. As the picture shows.
2. Advantages and disadvantages of circular reverse milling
In inverse milling, cutting edge along the machined surface of workpiece, surface crust on the cutting edge of small damage. The Ff is opposite to the feeding direction of the workpiece without the movement of the milling machine table. But the Fn is always upwards and requires greater clamping force. The extrusion and friction of the cutting edge and the workpiece surface are serious, which accelerates the cutting edge wear, reduces the life of the milling cutter, and produces a hardened layer on the machined surface of the workpiece, thus reducing the processing quality of the workpiece surface. The power consumed in feed motion is greater.
Reverse milling is generally used when milling a circle on a milling machine. When the screw nut transmission pair, the axial clearance is 0.03~0.05 mm, Ff is less than the friction between the rail milling machine, milling is not easy to thin and slender workpiece, also can choose forward milling.
3. Forward milling and reverse milling in end milling
According to the relative positions between the milling cutter and the workpiece, end milling is divided into two kinds, symmetrical milling and asymmetrical milling. End milling also has forward milling and reverse milling.
(1) Symmetrical milling
In the end milling, the center of the workpiece is in the center of the milling cutter. In symmetrical milling, half is reverse milling, half is forward milling. Symmetrical milling is used when the side knife is close to the cutter diameter.
(2) Asymmetric milling
According to cut into the edge and cut out the side of the amount of knife to eat the ratio is divided into asymmetric forward milling and asymmetric reverse milling. Asymmetric forward milling along the milling part of the proportion of large, end milling generally do not use this method. In the milling machine milling plasticity and toughness is good, hardening of hardening materials, such as stainless steel, heat-resistant alloy steel, etc., the use of the method. The proportion of the counter-milling part of the asymmetric inverse milling is larger and the method is generally used for end milling.