The importance of mechanical cutting tool edge passivation

Mon Jul 04 14:40:50 CST 2022

Why do you want to do edge passivation

After grinding with ordinary grinding wheel or diamond grinding wheel, the cutting edge of the tool does have different degree of micro notch (that is, micro chipping edge and saw edge). The former can be observed with the naked eye and ordinary magnifying glass, the latter can be observed with 100 times (with 0.010mm carving line) microscope, its microscopic gap is generally in 0.01-0.05mm, the severity of up to 0.1mm or more. In the process of cutting, the micro-notch on the cutting edge is easy to expand, which speeds up the cutting tool wear and damage.

Modern high speed cutting tool and automatic machine tools have put forward higher requirements on tool performance and stability, especially coating tool must be passivated before coating, in order to ensure the fastness and service life of coating. The cutting tools used in CNC machine tools and production lines imported from abroad have all been passivated. There is a lot of information to show that the cutting edge passivation can effectively extend the tool life of 200% or more, greatly reduce the tool cost, to bring huge economic benefits to users. Therefore, it is very important to study and practice the knowledge of tool passivation. Today we mainly discuss the importance of edge passivation from the following two aspects:

1. Select the cutting edge type and parameters

Sharp edge: a tax edge formed naturally when the cutting surfaces intersect before and after grinding, with sharp edge, poor strength and easy to wear.

Chamfering edge: on the front edge near the edge, the edge has a narrow negative front edge, which greatly improves the edge strength. Used for roughing and semi-finishing tools.

Damping edge edge: a very narrow negative rear Angle edge is grinded on the rear tool surface near the cutting edge to increase the contact area between the tool and the workpiece during cutting and eliminate vibration in the cutting process. Single-edge tool used when the process system is not rigid enough.

White edge: there is a narrow edge or edge belt with a 0° back Angle grinded on the back edge near the edge, which can play the role of supporting guide and extrusion and finishing. It is used for multi-edge tools such as reamer and broach.

Inverted round edge: it is a kind of indexable cutting tool used for rough and semi-finish machining.

Blade passivation geometry has a great impact on cutting tool life:

Arc cutting edge:

 symmetrical arc is formed at the corner of the cutting edge, accounting for more than 80% of the tool used, suitable for rough and finishing machining.

Waterfall edge:

 the top and side ratio at the edge corner is generally 2:1, which is an asymmetric arc and suitable for harsh impact processing. Tool edge passivation technology, its purpose is to solve the above grinding tool edge micro notch defect, reduce or eliminate its edge value, to smooth, sharp and durable purpose. According to the different processing conditions, reasonable selection of blade type and parameter, and closely combined with counterparts, the selection of passivation parameters, properly handle tool "sharp" and "solid", the relationship between "sharp" is the characteristic of cutting tool machining must have at the same time, considering the edge "solid" is also in order to more effective for machining, improve tool life, reduce consumption of cutting tool costs.

2. Edge passivation technology and parameters

Manual passivation:

The first passivation tools started with leather and oil, such as a shave at the barber shop, and a couple of purses from the purses to make the blades sharper and more durable. And we have a lot of experience in the purses for machining, and the effect is very significant. Examples are as follows:

During rough processing, a newly ground and purses knife can reduce the wear value in the primary wear stage, and also extend the normal wear stage at the later stage of normal wear stage, and the service life of the general cutter can be increased by more than 0.5 times.

When the reamer is processed, the surface of the inner hole can not meet the requirements of the drawings without the purses knife. After the purses knife, the surface roughness can be stable ra1.6-0.8 , and the cutting tool life can be increased about 1 times.

Precision planer machine guide, the use of negative front Angle wide blade pressure smooth knife, its front and back blade surface must be carefully grinded through the plate, improve the surface quality to ensure sharp and straight edge, guide processing surface roughness can be stable to Ra0.8 or less.

Due to the high toughness and strength of the processed material, the tool wear is fast, and even the chips are stuck, we have to arrange a couple of experienced veteran workers and a couple of knives to complete the processing.

The printing machine wall board is processed with floating boring knife, and the purses knife tool with magnifying glass is developed, and the edge is sharp and straight. The feed rate increased from 1mm/r to 4mm/r.

The crankshaft of an internal combustion engine is processed in a factory. Its equipment and cutting tools are introduced from abroad. The original cutting tool can be processed 50-60 pieces, and only 15-16 pieces are processed after using domestic blade. After the blade passivation and the selection of reasonable passivation parameters, a plate of knife can also process 50-60 pieces.

Mechanical passivation:

In order to improve the passivation efficiency and quality, most mechanical passivation methods are adopted. Such as the use of vibration passivation, media passivation, passivation of grinding pulp, passivation of rubber wheel containing abrasive, dry or wet sandblasting passivation, rolling passivation and passivation of nylon brush containing abrasive etc.. Ixm-50 Conicity Technologies LLC, the latest development of the IXM-50 cone passivation machine, is controlled by a CNC program, by the operator to enter a few simple commands, it can be the same tool on the different surface, passivation for different sizes. Can be passivated slot cutter and thread comb cutter. From the introduction of a number of domestic blade production line can be seen, both coated blade or non-coated blade production line with blade edge passivation machine, become an indispensable important process in blade production, this is also one of the reasons why the performance of foreign tool is good and high life.

Cutting tool edge passivation technology is a very important problem which is not paid attention to by people generally. It is important because: after the passivation of the tool can effectively improve the edge strength, improve the tool life and the stability of the cutting process. You know machine tool is the "teeth", the main factors influencing the cutting performance and life of tools, in addition to cutting tool material, cutting tool geometry parameter and cutting tool structure and cutting parameter optimization, etc., through a lot of cutting tool edge passivation practice experience: there is a good blade type and quality of blade passivation is how fast tool can save the precondition of machining. Therefore, the cutting edge condition is also a factor that can not be ignored.