Part.three
Failure mode of cutting tools:
The main failure modes of cemented carbide cutting tools are brittle failure and plastic failure
A small gap is created in the cutting edge, the size is equal to or slightly larger than the feed, and the blade can continue cutting.
B. Small pieces break or large pieces break on the cutting edge, so it is impossible to cut normally.
C peeling off a layer of debris on the front and back knife surfaces almost parallel to the cutting edge, and often peeling off the cutting edge together, especially when the knife has chip adhesion on the front knife surface to cut again, it is more obvious.
D crack damage caused by fatigue during a long period of intermittent cutting.There are thermal cracks caused by thermal shock, or mechanical cracks caused by mechanical shock.When these cracks grow and combine, they cause the cutting edge to fracture or fracture.
E plastic damage under the action of high temperature and high pressure, at the front and back cutter surface and the workpiece contact layer, the tool surface material plastic flow and loss of cutting ability.The damage form of cutting tools is a typical random phenomenon. The cemented carbide material is made of powder metallurgy sintering, and contains randomly distributed microscopic defects and inclusions. Under different cutting conditions, the cutting tools may be damaged due to the impact load of different sizes and positions.
How to reduce tool wear:
A. The installation of the tool shall ensure that the tool holder is clean and free of foreign matters, so as to ensure the installation accuracy of the tool;
B. When selecting tools, choose tools with good rigidity (large diameter or handle diameter) as far as possible;
C tool installation, hanging length should be as short as possible;
D. At the beginning of use, the tool should be used at a low speed. The speed should be 50% of the normal speed.
E rough machining, should be used as far as possible;
F in the process of processing, in case of intensified vibration, it should be suspended in time to reduce the rotating speed and cutter speed;
G. Use cutting fluid to fully cool and lubricate, and do not refilling or closing during the process;Clean the cutting area in time.
Set reasonable cutting parameters:
Reasonable cutting amount, is to make full use of the cutting performance of the tool and machine tool performance (power, torque), in the premise of ensuring quality, to obtain high productivity and low processing costs of cutting amount.
Machining is generally divided into rough machining, semi - finishing machining and finishing machining.
When roughing, remove as much allowance as possible.When the margin is large, to determine the cutting parameters to consider the machine power and tool strength, to avoid causing a large vibration, so that the tool was broken by a large impact.
When finishing, the limitation of machining accuracy and surface roughness is mainly considered.If you can't meet the requirements, you should consider adding a semi-finishing order.So that the finishing before the balance is even, so as to achieve satisfactory results
Determine cutting parameters to consider machine power and tool strength, as well as process system rigidity.
Ways to improve cutting parameters:
1. Use tool materials with better cutting performance;
2. Improve the workability of workpiece materials;
3. Improve tool structure and choose reasonable tool geometric Angle;
4. Improve the cutting tool grinding and manufacturing quality;
Adopt the cutting fluid with better performance and the high efficiency consistent method.
Common errors in tool grinding
The following common mistakes should be noted in the steps of sharpening knives:
1. The cutter cutting half plane is not parallel with the cutter rod axis, which will cause difficulty in tool measurement. If the front part is big and the back part is small or the front part is small and the back part is big, the measurement position is different, and the size is different.Open half is not accurate, resulting in tool quality instability.
2) open half taper too fast speed, grinding tools open half taper too fast speed, grinding of cutting tool material, hardness will not result in a greater impact, but when the speed is too fast, position of grinding temperature rise quickly, before and after the tool temperature difference is bigger, especially easy to form the micro crack (that is, the temperature crack), the cutting tool is very easy to produce collapse edge, in use process cause damage.
3 tool eccentric sharpening machine pipe is not straight, will make the tool diameter appear larger or smaller, it is difficult to use 40X magnifying glass to measure the accurate value.Slant small, tool chip discharge is not good;Larger, tool strength, easy to break
4. pointy questions
The problem of the tool's point point is mainly the Angle point.The corner point of the edge will make the tool not chip, the bottom surface is not smooth, debris stuck in the groove;The corner of the edge is too large, and the bottom residue is too much and uneven.
Vice back corner point has two kinds of situation, too large will make the tool and workpiece violent friction, cutting resistance increased, the tool is very easy to break;When the point is small, the processing of the metal bottom surface of the effect of non-metal bottom surface uneven, there will be molten chips adhere to the material.
Auxiliary back Angle is too big, cutting tool is sharp, easy to wear, low life.
The above problems often appear in the process of sharpening knives, especially the pointwise process, which is difficult for beginners to master. In order to ensure the accuracy of the pointwise Angle and dimension, the grinding method of the sharpening machine can be used, referring to the repairing method of the noose cutting tools, so as to ensure the accuracy of the cutting tools.
The above is all about the choice of knives and matters needing attention, thank you for watching!To learn more about the product, please visit our website:
https://www.acctekgroup.com
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