Selection of cutting tools for CNC machine tools

1、 Selection of blade (cutter)

The following aspects should be considered when selecting a blade or cutter

1. The workpiece materials are steel materials (carbon steel, low alloy steel, tool steel, stainless steel). And other complex materials, such as copper, iron and non-metallic materials.
2. The material properties of machined parts include properties, toughness, microstructure, etc.
3. The categories of cutting technology include turning, milling, boring, drilling; machining, superfinishing; inner hole, outer circle, plane, groove; cutting flow state, tool displacement time interval, etc.
4. The geometric shape of the workpiece affects the continuous cutting or intermittent cutting, the cutting in or out angle of the tool. Part accuracy (dimensional tolerance, geometric tolerance, surface roughness) and machining allowance.
5. Cutting parameters of blade (tool) (back feed, cutting speed)
6. Production site conditions (operation interruption time, feed rate, cutting speed)
7. Processing of workpieces and production batch. Economic life of blade (cutter)

2、 Selection of boring tools:

In the selection of boring tools, the main problem is the rigidity of the tool bar, and the vibration should be prevented or eliminated as far as possible. The main points for consideration are as follows;

1. The diameter of the reverse bar should be as large as possible, close to the boring diameter.
2. Select the short arm (working length) as far as possible. When the working length is less than 4 times the diameter of the tool bar, steel tool bar can be used. When machining holes with high requirements, cemented carbide tool bar is best used. When the working length is 7-10 times the diameter of the arbor, the small hole is made of cemented carbide arbor, and the drilling is made of shock absorber arbor. When the working length is 7-10 times the diameter of the cutter bar, the damping cutter bar should be used.
3. The main deflection angle is more than 75 ° and close to 90 °
4. Select the blade without coating to reduce the radius of cutting arc and tool tip.
5. The positive cutting edge (positive rake angle) blade and tool are used for finish machining, and the negative cutting edge (negative rake angle) blade and tool are used for rough machining.
6. When boring deep through holes, cooling measures should be taken. Compressed air (air cooling) or cutting fluid (chip removal and cooling) can be used.
7. Choose the right and fast boring tool holder.

3、 Selection of milling cutter:

1. Indexable carbide milling cutter should be used when milling plane on CNC machine tool. It can be divided into two steps. One rough milling and one finish milling. When continuous cutting. The diameter of rough milling cutter should be reduced. The diameter of the finishing cutter should be larger, and it is better to contain the whole width of the surface to be machined. When the machining allowance is large and the machined surface is uneven, the tool diameter should be selected smaller. Otherwise, when rough machining, it will affect the machining quality due to the deep tool mark.
2. High speed steel end mills are mostly used to process boss and groove, so it is better not to use them to process blank, because there are hardening layer and cracks in the blank. It will accelerate the tool wear.
3. The machining allowance is small and the surface roughness is required to be low, so the CBN end mill or ceramic end mill should be used.

The end milling cutter with carbide insert can be used for machining groove, concave surface, convex surface and blank surface.

5. The end milling cutter with cemented carbide can be used for powerful cutting. Milling the surface of the blank and rough machining the hole.
6. When machining the groove with high accuracy requirements, the end milling cutter with diameter smaller than the groove width can be used. Firstly, the middle part of the groove is milled, and then the two sides of the groove are milled by using the radius compensation function of the cutter until the accuracy requirements are met.
7. When drilling on CNC milling machine, the drill die is generally not used. When the depth of the hole is about 5 times of the diameter, it is easy to break the drill bit. Fixed cycle program can be used to advance and retreat automatically for many times to facilitate cooling and drainage. Before drilling, it is better to drill a central hole with a central drill or to drill the bottom hole with a section drill with good rigidity for positioning

When drilling on the milling machine, the drilling die is not generally used. When the depth of the hole is about 5 times of the diameter, it is easy to break the drill bit, and fixed circulation can be used

ken.tang @ chengcg.com