Básico de fresamento – fresamento ascendente e fresamento descendente

Milling basics – up milling and down milling

June 25, 2024 Roberto Magalhães

Milling basics – up milling and down milling

Milling is a process of producing flat, complex shapes using multi-point (or multi-tooth) cutting tools. The axis of rotation of the cutting tool is perpendicular to the feed direction, whether parallel or perpendicular to the machined surface. Milling is generally an interrupted cutting operation, as the cutter teeth move in and out of the workpiece during each rotation. This interrupted cutting action subjects the teeth to a cycle of impact force and thermal shock with each rotation. The tool material and cutter geometry must be designed to withstand these conditions. The figure shows two basic types of milling operations: down milling, when the rotation of the cutter is in the same direction as the movement of the part being fed, and up milling, in which the part moves toward the cutter, opposing it. to the direction of rotation of the cutter. .

See more information; Milling Machine Basics Interview Questions and Answers

In downward milling, the cutting force is directed towards the work table, which allows the machining of thinner parts without susceptibility to breakage. Better surface finish is obtained in down milling, but the stress load on the teeth is abrupt, which can damage the cutter. The backlash eliminator must be used in this operation. In up milling, the cutting action tends to lift the part and therefore proper clamping is required in this operation.

Up-cut or conventional milling

This is shown in Fig. You can see that the work is fed towards the cutter in the opposite direction of rotation.

• This prevents work from being drawn into the cutter if there is any play in the feed mechanism.

• Unfortunately, this technique causes the cutting edges to rub together as each tooth begins to cut, which can cause chatter and blunting of the cutting edge.

• The cutting action tends to lift the work off the machine table.

• For safety, this is the technique you should always adopt, unless your instructor advises you otherwise, because he or she knows that your machine is equipped to operate safely using the following technique.

Down or up milling

This is shown in the direction of Fig. while the cutter is rotating.

Safety: The up milling technique can only be used on machines equipped with a 'backlash eliminator' and which are designed for this technique. If it can be used safely, this technique has a number of advantages, particularly for heavy cutting operations.

• The cutter does not rub when each tooth starts to cut. This reduces the risk of vibration and extends the life of the cutter.

• Cutting forces keep the part pressed against the machine table.

• The action of the cutter helps advance the work and takes most of the load off the feed mechanism.