Six Problems Must Not Be Ignored in Tool Grinding

Six Problems Must Not Be Ignored in Tool Grinding

Because of the complexity of tool application, the professional grindingcenter must modify the grinding scheme in time according to the failure form ofthe polished tool, and track the use effect of the tool. A professional toolgrinding center must continue to sum up experience, in order to tool grindingbetter, more specialized! From the point of view of tool material, grindingequipment, testing equipment and other hardware and grinding standards, grindingtechnicians and so on, this paper introduces six problems that tool grindingmust not be ignored! 1, the common tool materials in tool grinding are: highspeed steel, powder metallurgy high speed steel, cemented carbide and PCD,CBN,cermet and other superhard materials. High speed steel knife with sharp, goodtoughness, cemented carbide tool hardness is high but toughness is poor. Thedensity of cemented carbide tools is obviously higher than that of high speedsteel tools. These two materials are the main materials of drill bits, winches,milling cutters and taps. The properties of powder metallurgy high speed steelare between the above two materials, which are mainly used in the manufacture ofrough milling cutters and taps. High speed steel knife tools are not verysensitive to collision because of their good toughness. However, cementedcarbide tools have high hardness and brittleness, sensitive to collision, andeasy to jump at the edge. Therefore, in the process of grinding, we must be verycareful in the operation and placement of cemented carbide tools to prevent thecollision between cutting tools or tool fall. Because the accuracy of high speedsteel cutting tools is relatively low, its grinding requirements are not high,and its price is not high, so many manufacturers set up their own tool workshopsto repair and grind them. However, cemented carbide tools often need to be sentto the professional grinding center for grinding. According to the statistics ofsome tool grinding centers in China, more than 80% of the cutting tools arecemented carbide tools.

2. Because the tool material is very hard, the tool grinder can only changeits shape by grinding. In the manufacture of cutting tools, there are thefollowing common tool grinders in the manufacture and grinding of cutting tools:1. Slot grinder: the groove or back of a drill bit, end milling cutter, etc.two。 Grinding top angle machine: the conical top angle (or eccentric rear angle)of the grinding bit. 3. Repair machine: correct the cross edge of the bit. 4.Manual universal tool grinder: grinding outer circle, slot, back, top angle,transverse edge, plane, front knife surface, etc. It is often used in a smallnumber of tools with complex shapes. 5.CNC grinder: generally five-axis linkage,the function is determined by the software. It is generally used for cuttingtools with large grinding quantity and high precision, but not complicated, suchas drill bit, end milling cutter, reamer and so on. The main suppliers of suchgrinders come from Germany, Switzerland, the United States, Australia andJapan.

3, grinding wheel 3.1. Grinding wheels of different materials are suitablefor grinding tools of different materials. The size of abrasive particles usedin different parts of the tool is also different in order to ensure the bestcombination of edge protection and machining efficiency. Alumina: used to grindHSS tools. The grinding wheel is cheap and easy to modify into different shapesfor grinding complex cutting tools (corundum). Silicon carbide: used to correctCBN grinding wheel and diamond grinding wheel. CBN (cubic boron carbide): usedto grind HSS tools. The price is high, but it is durable. Internationally,grinding wheels are represented by B, such as B 107, where 107 represents thesize of the abrasive diameter. Diamond: used for grinding HM tools, high price,but durable. The grinding wheel is represented by D, such as D 64, where 64represents the size of the abrasive diameter. 3.2. In order to facilitate thegrinding of different parts of the tool, the grinding wheel should havedifferent shapes. The most commonly used are: parallel grinding wheel (1A1):grinding top angle, outer diameter, back and so on. Disc grinding wheel (12V9,11V9): grinding screw groove, main and auxiliary cutting edge of milling cutter,trimming edge, etc. After a period of use, the grinding wheel needs to bemodified (including plane, angle and fillet R). The grinding wheel must oftenuse clear stone to clean up the chips filled between the abrasive particles inorder to improve the grinding ability of the grinding wheel.

4. Whether the grinding standard has a good set of tool grinding standardsis a standard to measure whether a grinding center is professional. In thegrinding standard, the technical parameters of the cutting edge of differentcutting tools in cutting different materials are generally specified, includingthe inclination angle of the edge, the top angle, the front angle, the rearangle, the inverted edge, the chamfering edge and so on (in cemented carbidebit, the process of passivating the blade is called “inverted edge”. The widthof the inverted edge is related to the cutting material, generally between thecutting materials. The process of chamfering on the edge (tip of the knife) iscalled chamfering. Each professional company has its own grinding standardssummarized for many years. The difference between HM bit and HSS bit: the topangle is usually 118 degrees, sometimes more than 130 degrees; the blade issharp; the precision (blade height difference, symmetry, circumferential runout)is relatively low. There are many ways to practice the transverse blade. HM bit:the top angle is 140 degrees, the straight groove drill is often 130 degrees,and the three-edge drill is usually 150 degrees. Blade and tip (edge) are notsharp, often passivated, or inverted edge and chamfer; high precisionrequirements. The transverse blade is often modified into S-shape to facilitatechip breaking. Rear angle: the rear angle of the blade is very important to thetool. The rear corner is too large, the blade is empty and easy to jump, and therear corner is too small, the friction is too large, and the cutting isunfavorable. The rear angle of the tool varies with the cutting material, tooltype and tool diameter. Generally speaking, the rear angle decreases with theincrease of tool diameter. In addition, when the cutting material is hard, therear corner is smaller, otherwise, the rear corner is larger.

5, tool detection equipment tool testing equipment is generally dividedinto three categories: tool counter, projector and universal tool measuringinstrument. The tool alignment instrument is mainly used for tool preparation(such as length, etc.) of NC equipment such as machining center, and is alsoused to detect the parameters such as angle, radius, step length and so on, andthe function of projector is also used to detect the parameters such as angle,radius, step length and so on. However, the above two can not measure the rearangle of the tool. The universal tool measuring instrument can measure most ofthe geometric parameters of the tool, including the rear angle. Therefore, thetool professional grinding center must be equipped with a universal toolmeasuring instrument. But there are not many suppliers of this equipment, andthere are German and French products on the market.

6. Regrinding Mechanic The best equipment also requires the operation ofthe personnel, and the training of the grinding mechanic is one of the mostcritical links. Because of the relative backwardness of the tool manufacturingindustry in our country, and the serious shortage of vocational training, thetraining of the tool grinding technology can only be solved by the enterpriseitself.