Quebra-cavacos – Necessidades, Princípios, Tipos de quebra-cavacos

Chipbreakers – Needs, Principles, Types of chipbreakers

Chipbreakers – needs, principles and types of chipbreakers

Necessity and purpose of chip breaking

Continuous machining such as turning ductile metals, unlike brittle metals such as gray cast iron, produces continuous chips, which leads to handling and disposal problems. Problems become acute when ductile but strong metals such as steels are machined at high cutting speed for high MRR by carbide or ceramic inserts with flat rake face. The hot continuous chip with sharp edges that comes out at very high speed

• becomes dangerous for the operator and other people working nearby

• may harm the finished surface by becoming entangled in rotating work

• creates difficulties in chip disposal.

Therefore, it is essentially necessary to break such continuous chips into small regular pieces to

• worker safety

• prevention of product damage

• easy chip collection and disposal.

Chip breaking is done properly also with the additional purpose of improving machinability by reducing the chip-tool contact area, cutting forces and crater wear of the cutting tool.

Chip cracking principles

In terms of convenience and safety, short-length closed coil chips and half-turn coma chips are ideal for high-speed machining of ductile metals and alloys.

Chip breaking principles and methods are generally classified as follows:

• Self-break

This is done without using a separate chipbreaker as an accessory or an additional geometric modification of the tool.

• Forced chip breaking by additional tool features or geometric devices.

Principle of forced chip breaking (embedded type) Principle of forced chip breaking (embedded type)

Chipbreakers are basically of two types:

• Built-in type

Built-in circuit breakers are in the form of a step or groove on the slope surface near the cutting edges of the tools. These chip breakers are provided

  • After manufacturing – in the case of HSS tools such as drills, milling cutters, broaches, etc. and brazed carbide inserts
  • During their manufacture by the powder metallurgical process – for example, disposable inserts made of carbides, ceramics and cermets.

The basic principle of forced chip breaking is shown schematically in Fig. When the strain-hardened and brittle chip reaches the heel, the cantilever chip is forcibly bent and then breaks.

  • Fixed type chipbreaker

Fixed-type chipbreakers basically work on the principle of stepped-type chipbreakers, but have the possibility of varying the step width and/or heel angle.

Fixed types of chipbreakers Fixed types of chipbreakers

The figure schematically shows three of these chip breakers in common use:

• With fixed additional sash distance and angle – effective only for a limited parametric combination domain

• With variable width (W) only – not very versatile

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