Thursday, September 24, 2020
Machining Methods

# How to correctly handle the reamer feed and rotation of CNC machining center

How to correctly handle the reamer feed and rotation of CNC machining center

## Reamer speed and feed speed selection:

The principle of reasonable choice of cutting amount is that when grinding is usually increased about productivity, economic cost and processing must also be considered; in semi-finishing and finishing, the cutting efficiency must be considered on the premise of ensuring the processing quality. Economic and processing costs. The specific value should be based on the machine manual, cutting volume manual and experience.

### 1. Cutting depth

In this machine tool, the rigidity permit of the workpiece and tool, t is equal to the china cnc machining tolerance, it is an effective measure to improve productivity. In order to ensure the machining accuracy and the roughness of the surface of the parts, it is usually necessary to leave a certain margin for finishing. The finishing allowance of CNC machine tools may be slightly smaller than ordinary machine tools.

### 2. Cutting width L.

Generally, L is proportional to the diameter d of the tool and inversely proportional to the depth of cut. In economical CNC machining, the general range of L is: L=(0.6~0.9)d.

### 3. Cutting speed

Increasing v is also a measure to increase productivity, but v is more closely related to tool durability. With the increase of v, the durability of the tool drops sharply, so the choice of v mainly depends on the durability of the tool. In addition, the cutting speed is also closely related to the processed material. For example, when grinding only the alloy 30CrNi2MoVA with the final grinder, v may be about 8 m/min; when grinding the aluminum alloy with the same laminator, v may be greater than 200 m/min. .

### 4. Spindle speed n (r/min)

The spindle speed is usually selected according to the cutting speed v. The calculation formula is: where d is the diameter (mm) of the tool or piece. The control panel of CNC machine tools is usually equipped with a dressing switch (increased) screw speed, which can adjust the spindle speed during processing.

### 5, vF feed speed

Ventricular fibrillation must be selected according to the requirements for machining accuracy and surface roughness of the workpiece and tool material and workpiece. The increase in vF can also improve production efficiency. When the surface roughness of the processed surface is low, a larger vF can be selected. During processing, audio can also be adjusted manually by setting a switch on the control panel of the machine, but the maximum feed rate is limited by the rigidity of the equipment and system performance power.
With the wide application of CNC machine tools in production practice, CNC programming has become one of the key topics in CNC machining. In the process of programming NC programs, it is necessary to select tools and determine the amount of cutting in the state of human-computer interaction. Therefore, the programmer must be familiar with the method of selecting tools and the principle of determining the cutting amount to ensure the processing quality and the processing efficiency of the parts.

Selection of reaming amount

• 1. Reaming hole distribution Reaming hole tolerance is the cutting depth reserved for reaming. Generally, the reaming allowance is smaller than the reaming or drilling allowance. Too much reaming allowance will increase cutting pressure and damage the reamer, which will result in rough surfaces. When the edge is too large, thick hinges and thin hinges can be used to ensure technical requirements. On the other hand, if the remaining amount of white is too small, the reamer wears prematurely and usually cannot be cut, and the surface roughness is also poor. Generally, the reaming margin is 0.1~0.25 mm. For larger diameter holes, the margin should not be greater than 0.3 mm. An experience shows that the thickness of the reamer is 1~3% as the edge of the reaming hole (diameter value). For example, a reamer of Φ20 plus an aperture of Φ19.6 is sufficient: 20-(20 * 2/100)=19.6 For hard materials and some aerospace materials, the reaming hole margin is usually small.
• 2. Feeding speed of reaming hole The reaming speed of reaming hole is faster than that of perforation, generally 2~3 times. The purpose of using a higher feed rate is to let the reamer cut the material instead of rubbing the material. However, the roughness Ra of the reamer increases as the advance speed increases. If the feed rate is too small, the radial friction will increase and the reamer will wear quickly, which will cause the reamer to vibrate and roughen the hole surface. For steel parts with standard steel reamer, if the surface roughness Ra0.63 is obtained, the feed speed should not exceed 0.5mm/r. For cast iron parts, it can be increased to 0.85mm/s.
• 3. The reaming of the spindle speed of each element has an effect on the roughness of the reaming surface, which has the greatest impact on the reaming speed, such as steel reaming, with a good roughness Ra0.63m, for medium carbon steel parts, reaming The speed should not exceed 5 meters/minute, because it is not easy to produce cumulative rims at this time, and the speed is not high; when reaming the cast iron, the chips will break into particles and will not form. Built-in edge, the speed can be increased to 8~10m/min. Generally, the speed of the reaming shaft can be selected to be 2/3 of the speed of the drilling shaft in the same material. For example, if the speed of the drilling shaft is 500r/min, the speed of the reaming shaft is set to 2/3500*0.660=330r/min of its fair value.