Six problems that must not be ignored in the grind

Six problems that must not be ignored in tool grinding

due to the complexity of tool application, the professional grinding center must timely repair the grinding scheme according to the failure form of the tool to be repaired, and track the use effect of the tool. A professional tool grinding center must also constantly sum up experience in order to make the tool grinding better and more professional

I. tool materials

common tool materials in tool grinding include: high speed steel, powder metallurgy high speed steel, cemented carbide, PCD, CBN, cermet and other superhard materials. High speed steel tools are sharp and tough, while cemented carbide tools have high hardness but poor toughness. The density of cemented carbide tools is significantly higher than that of high-speed steel tools. These two materials are the main materials of drill bits, reamers, milling cutters and taps. The properties of powder metallurgy high speed steel are between the above two materials, which are mainly used to manufacture rough milling cutters and taps

high speed steel tools are not sensitive to collision because of their good toughness. However, cemented carbide tools are high hardness and brittle, and are very sensitive to collision, and the cutting edge is easy to jump. Therefore, in the grinding process, we must be very careful about the operation and placement of cemented carbide tools to prevent the localization of film making raw materials between tools and the performance characteristics of film group digital display electronic tensile testing machine and the usual protection of the equipment. Do you know? Next, the technicians of our company will introduce the collision or tool fall of bar technology

due to the relatively low accuracy of most high-speed steel cutting tools, their grinding requirements are not high, and their prices are not high, many manufacturers set up their own tool workshops to grind all the items in 7.2.2 type inspection, including technical requirements. However, cemented carbide tools often need to be sent to a professional grinding center for grinding. According to the statistics of some domestic tool grinding centers, more than 80% of the tools sent for repair are cemented carbide tools

II. Tool grinder

because the tool material is very hard, generally, only grinding can be used to change its shape. In the manufacturing and grinding of cutting tools, there are several common tool grinders:

1 Grooving machine: it is used to grind the groove or back of cutting tools such as drill bits and end mills

2. Grinding vertex angle machine: grinding the conical vertex angle (or eccentric back angle) of the drill bit

3. Horizontal edge trimming machine: correct the horizontal edge of the drill bit

4. Manual universal tool grinder: grinding excircle, groove, back, vertex angle, transverse edge, plane, rake face, etc. It is often used for cutting tools with small quantity and complex shape

c grinder: generally, it is five axis linkage, and the function is determined by the software. It is generally used for grinding tools with large quantity and high accuracy requirements, but not complex, such as drill bits, end mills, reamers, etc. The main suppliers of such grinding machines come from Germany, Switzerland, the United States, Australia and Japan

III. grinding wheel

1 Abrasive pair 1 specific system

grinding wheels of different materials abrasive grains are suitable for grinding tools of different materials. Different parts of the tool need to use different sizes of abrasive particles to ensure the best combination of edge protection and processing efficiency

alumina: used for grinding HSS tools. The grinding wheel is cheap and easy to modify into different shapes for grinding complex cutting tools (corundum)

silicon carbide: used to modify CBN grinding wheel and diamond grinding wheel

cbn (cubic boron carbide): used for grinding HSS tools. High price, but durable

internationally, the grinding wheel is represented by B, such as b107, in which 107 represents the size of abrasive particle diameter

Diamond: used for grinding HM tools, which is expensive but durable. The grinding wheel is represented by D, such as d64, where 64 represents the size of abrasive particle diameter

2. Shape

in order to facilitate the grinding of different parts of the tool, the grinding wheel should have different shapes. The most commonly used are:

parallel grinding wheel (1A1): grinding vertex angle, outer diameter, back, etc

dished grinding wheel (12v9,11v9): grinding spiral grooves, main and auxiliary cutting edges of milling cutters, trimming edges, etc.

after a period of use, the shape of the grinding wheel needs to be modified (including plane, angle and fillet R). The grinding wheel must often use a cleaning stone to remove the chips filled between the abrasive grains in order to improve the grinding ability of the grinding wheel

IV. grinding standard

whether there is a set of good tool grinding standard is the standard to measure whether a grinding center is professional. In the grinding standard, the technical parameters of the cutting edge of different tools when cutting different materials are generally specified, including edge inclination, vertex angle, front angle, back angle, chamfer, chamfering and other parameters (in cemented carbide bits, the process of passivating the edge is called "chamfer", and the width of the chamfer is related to the material being cut, generally between 0..25mm. The process of chamfering on the edge (tip point) is called "chamfer". Each professional company has its own grinding standards summarized over the years

the difference between HM bit and HSS bit:

HSS bit: the vertex angle is generally 118 degrees, sometimes greater than 130 degrees; The blade is sharp; The requirements for accuracy (blade height difference, symmetry, circumferential runout) are relatively low. There are many ways to fix the horizontal blade

hm bit: the vertex angle is generally 140 degrees; Straight slot drills are often 130 degrees, and three edge drills are generally 150 degrees. The blade and tip (on the edge) are not sharp, and are often passivated, or called chamfer and chamfer; High accuracy requirements. The horizontal blade is often trimmed into an S-shape to facilitate chip breaking

the back angle of the blade is very important for the tool. The back corner is too large, and the blade is weak, which is easy to jump and "stab"; If the rear angle is too small, the friction is too large and the cutting is unfavorable

the back angle of the tool varies with the material being cut, the type of tool, and the diameter of the tool. Generally speaking, the back angle decreases with the increase of tool diameter. In addition, if the material to be cut is hard, the back angle is smaller, otherwise, the back angle is larger

v. tool detection equipment

tool detection equipment is generally divided into three categories: tool setting instrument, projector and universal tool measuring instrument. The tool setting instrument is mainly used for tool setting preparation (such as length) of CNC equipment such as machining center, and also used to detect parameters such as angle, radius, step length, etc; The function of the projector is also used to detect parameters such as angle, radius and step length. However, the above two generally cannot measure the back angle of the tool. The universal tool measuring instrument can measure most of the geometric parameters of the tool, including the back angle

therefore, the professional tool grinding center must be equipped with a universal tool measuring instrument. However, there are not many suppliers of this kind of equipment. There are German and French products on the market

VI. grinding technicians

the best equipment also needs personnel to operate, and the training of grinding technicians is naturally one of the most critical links. Due to the relative backwardness of China's tool manufacturing industry and the serious lack of Vocational and technical training, the training of tool grinding technicians can only be solved by enterprises themselves

VII. Conclusion

with hardware such as grinding equipment and testing equipment and software such as grinding standards and grinding technicians, the grinding of precision tools can begin. Due to the complexity of tool application, the professional grinding center must timely repair the grinding plan according to the failure form of the tool to be repaired, and track the use effect of the tool. A professional tool grinding center must also constantly sum up experience in order to make the tool grinding better and more professional