CN102107376B - Process chain method for realizing optimal grinding efficiency and quality - Google Patents

Abstract

A process chain method to realize the optimization of grinding efficiency and quality, including: under the same machine tool and the same type of grinding wheel, perform high-speed or ultra-high-speed grinding for the purpose of obtaining higher grinding efficiency and certain processing accuracy High-speed grinding process test; analyze the relationship between grinding efficiency, workpiece surface quality, sub-surface damage and each grinding condition; combine each optimized grinding condition for processing, and then carry out grinding depth of Zero light grinding process, on the premise of ensuring the final processing quality of the parts, makes the grinding efficiency the highest; determines the optimal process route, and realizes rough machining and finishing machining of the workpiece with one clamping and positioning on the same grinding machine. Based on the precise analysis of grinding conditions and grinding surface/subsurface quality, it obtains a grinding process route with optimized efficiency and quality, which can greatly improve the grinding process efficiency and reduce the cutting process and processing cycle of parts , Improve equipment utilization.

Description

A Process Chain Method for Optimizing Grinding Efficiency and Quality

technical field

The present invention relates to a process chain method that can optimize the efficiency and quality of material grinding, especially the cutting process that needs to use grinding to remove material, or other cutting methods, such as turning, milling, etc., to cooperate with grinding material cutting process.

Background technique

Many parts require multiple cutting processes to achieve the required shape and dimension accuracy and surface quality. Grinding is a finishing method that can obtain high machining accuracy and surface quality, but the machining efficiency is extremely low. Therefore, parts with high machining accuracy and large removal allowance are usually rough processed by turning, milling or rough grinding, then semi-finish grinding, and finally fine grinding to achieve the final processing accuracy and surface quality of the parts. Require. Such processing often needs to go through multiple clamping and positioning on multiple machine tools to complete. This undoubtedly increases the consumption and processing cycle of equipment and fixtures, and the processing accuracy is also affected in different clamping processes. At the same time, because of the processing procedures of multiple equipment, it needs to occupy more workshop area. For example, engineering ceramic parts usually need to be turned by diamond turning tool, and then diamond grinding wheel is rough grinding, semi-fine grinding and fine grinding.

Contents of the invention

The technical problem to be solved by the present invention is to propose a process chain method to optimize the efficiency and quality of grinding processing in view of the defects existing in the prior art, which can realize the rough machining of workpieces with one clamping and positioning on the same grinding machine And finishing, improve the processing efficiency of the workpiece, reduce processing procedures and processing equipment.

The technical solution of the present invention is that the process chain method for realizing grinding process efficiency and quality optimization includes:

(1) Conduct a high-speed or ultra-high-speed high-efficiency grinding process test on the workpiece material under the same machine tool and the same type of grinding wheel; the test consists of two parts: the first part, in order to obtain a higher grinding efficiency test, allow damage to occur; the second part The second part is the fine grinding test aimed at obtaining a certain machining accuracy; high-speed or ultra-high-speed high-efficiency grinding refers to grinding with a grinding wheel speed of 50m/s-200m/s and a grinding depth of 0.1-30mm; workpiece materials include various Hardened metals, strong toughness and hard and brittle difficult-to-machine materials;

(2) Analyze the relationship between grinding efficiency, workpiece surface quality, subsurface damage and each grinding condition; grinding condition refers to the grinding wheel linear speed, workpiece feed rate and grinding depth in surface grinding etc.; grinding wheel linear speed, headstock speed, feed depth and feed speed, etc. in external circular and non-circular profile grinding;

(3) Combine the optimized grinding conditions for parts processing, and then perform smooth grinding with zero grinding depth, so as to ensure the highest grinding efficiency under the premise of ensuring the final processing quality of parts;

The optimal grinding condition is the grinding condition when the surface quality of the workpiece is good, the subsurface damage is the least, and the grinding processing efficiency is the highest;

(4) Determine the optimal process route, and realize the rough machining and finishing machining of the workpiece in one clamping and positioning on the same grinding machine.

The present invention is further described below.

Grinding is a cutting process with a large negative rake angle, and its damage forms mainly include thermal damage and damage caused by normal force, including various burns, residual tensile stress, surface/subsurface damage, and cracks. Under certain machine conditions and cooling conditions, the damage depth has a regular relationship with the grinding conditions. That is to say, the grinding damage can be effectively controlled by changing the grinding conditions. The present invention is based on extensive technological tests, and has a detailed understanding of the grinding surface roughness, surface morphology and surface/subsurface damage of workpieces under different grinding conditions (parameters). For example, for hard and brittle materials such as engineering ceramics, it is necessary to grind, polish and corrode the side of the vertical processing surface to understand the depth of subsurface damage and microcracks under various grinding conditions (parameters); for metal materials such as hardened steel, it is necessary to By detecting the microhardness of the grinding subsurface or metallographic observation, the situation of the tempering burn and the depth of the secondary quenching burn can be understood. Only a detailed understanding of the surface or sub-surface of the workpiece under different working conditions can ensure that the quality of the workpiece processed according to the optimized process chain is qualified.

As can be seen from the above, the present invention is a process chain method for realizing the optimization of grinding process efficiency and quality. It is based on the precise analysis of grinding conditions and grinding surface/subsurface quality, and obtains the grinding process with optimized efficiency and quality. The grinding process route can greatly improve the grinding efficiency, reduce the cutting process and processing cycle of parts, and improve the utilization rate of equipment.

Description of drawings

Figure 1 is a schematic diagram of the optimized process chain; where, the total removal depth of the part is H, and it is removed in n times of feeding, and the grinding depth of each time is a _pi (i=1, 2, 3...n) , the depth of the damaged layer is h _i (i=1, 2, 3...n), and the last time is smooth grinding with zero feed.

Figure 2(a)(b)(c) is the surface roughness value of the camshaft under different working conditions;

Figure 3(a)(b)(c) is the surface microhardness of the camshaft under different working conditions;

Fig. 4 is a scanning electron micrograph of zirconia at different grinding depths; wherein, (a) is the grinding depth a _p = 1mm,

(b) is the grinding depth a _p = 3mm, (c) is the grinding depth a _p = 4mm, (d) is the grinding depth a _p = 6mm; workpiece feed speed v _w = 20mm/s, grinding wheel linear speed v _s =120m/s;

Figure 5(a)(b) is the transverse crack of the subsurface damaged layer of partially stabilized zirconia; where, v _s =160m/s, v _w =1200mm/min., a _p =6mm;

Detailed ways

Embodiment 1: Take the widely used 45 ^# hardened steel camshaft as an example.

The structure of hardened steel is tempered martensite, the microhardness reaches HV700kgf/mm ² , and the plasticity and thermal conductivity are extremely low. Since the feed rate of traditional grinding semi-finishing and finishing of hardened steel is generally only a dozen microns to tens of microns, the existing processing method of hardened steel camshaft is usually to use a white corundum grinding wheel on an ordinary grinding machine. It is roughly ground at a line speed of 30m/s, and then semi-finishing and fine-grinding are performed on a CNC grinding machine with a CBN abrasive wheel. The invention takes 45 ^# hardened steel camshaft as object, and adopts 120 ^# vitrified bond CBN grinding wheel on an ultra-high-speed non-circular contour cylindrical grinding machine to perform high-speed/ultra-high-speed grinding.

In order to test the grinding quality, the surface roughness of the workpiece was measured; in order to evaluate the grinding burn, the surface microhardness of the workpiece was tested; the results are:

It can be seen from Figure 2 that the surface roughness values of the machined camshafts all meet the requirements, and R _a is not greater than 0.4 microns; the surface roughness value decreases with the increase of the grinding wheel linear speed, and except for the working condition of 60m/s, the surface roughness The change of the value is not large; the base circle speed and unilateral feed have little effect on the surface roughness;

It can be seen from Figure 3 that under the working condition of the grinding wheel linear speed of 60m/s, the workpiece is tempered and burnt during the grinding process, and the surface hardness decreases, which will lead to a decrease in the wear resistance of the part. The microhardness of the rest of the working conditions showed that no burns occurred and the condition was good.

From the above experimental results, it can be known that the selection of grinding wheel linear velocity v _s , base circle rotational speed n, unilateral feed rate (grinding depth) a _p is that v _s = 60m/s, n = 100rpm, a _p = Any grinding parameters outside 0.1mm, such as using v _s = 120m/s, n = 100rpm, a _p = 0.2mm or v _s 1200m/s, n = 200rpm, a _p = 0.1mm Machining and semi-finishing, using v _s = 120m/s, n = 100rpm, a _p = 0.05mm for fine grinding, and finally smooth grinding without feed.

Embodiment 2: Take a partially stabilized zirconia ceramic block sample as an example.

Partially stabilized zirconia ceramic block is a typical hard, brittle and difficult-to-machine material. The traditional grinding technology has a very low grinding efficiency, generally maintained at about 10mm ³ /mm·s. The present invention uses a 120 ^# resin bonded diamond grinding wheel to grind yttrium oxide partially stabilized zirconia ceramics on an ultra-high-speed surface grinding test bench. And evaluate the quality of the machined surface and sub-surface to optimize the grinding process. turn out:

It can be seen from Figure 4 that the ground surface of zirconia is mainly composed of plastic grooves, smooth areas, coating areas and brittle fracture areas, and the plastic removal marks decrease with the increase of grinding depth, but the change is not obvious;

Figure 5 shows the transverse cracks in the subsurface damage layer of partially stabilized zirconia. In the observation of the subsurface damage of partially stabilized zirconia specimens, only occasional subsurface transverse cracks were seen, and the depth of subsurface residual cracks was not greater than 10 μm, and there is no obvious change under different working conditions.

Therefore, ultra-high-speed and high-efficiency grinding can be performed on partially stabilized zirconia, with a grinding depth of up to 6mm and a removal rate of 120mm ³ /mm·s, followed by finishing with a grinding depth of about a dozen microns. Realize the high-efficiency precision grinding of the ceramic parts, and complete the processing of the parts in one clamping on the same machine tool.

Claims (1)

1. A process chain method for realizing grinding efficiency and quality optimization, characterized in that the method comprises: (1) Conduct a high-speed or ultra-high-speed high-efficiency grinding process test on the workpiece material under the same machine tool and the same type of grinding wheel; the test consists of two parts: the first part, in order to obtain a higher grinding efficiency test, allow damage to occur; the second part The second part is the fine grinding test aimed at obtaining a certain machining accuracy; high-speed or ultra-high-speed high-efficiency grinding refers to grinding with a grinding wheel speed of 50m/s-200m/s and a grinding depth of 0.1-30mm; workpiece materials include various Hardened metals, strong toughness and hard and brittle difficult-to-machine materials; (2) Analyze the relationship between grinding efficiency, workpiece surface quality, subsurface damage and each grinding condition; grinding condition refers to the grinding wheel linear speed, workpiece feed rate and grinding depth in surface grinding , the linear speed of the grinding wheel, the rotational speed of the headstock, the depth of feed and the feed speed in external circular and non-circular contour grinding; (3) Combine the optimized grinding conditions for processing, and then perform smooth grinding with a grinding depth of zero, so as to ensure the highest grinding efficiency under the premise of ensuring the final processing quality of the parts; The optimal grinding condition is the grinding condition when the surface quality of the workpiece is good, the subsurface damage is the least, and the grinding processing efficiency is the highest; (4) determine the optimal process route, and realize the workpiece clamping and positioning on the same grinding machine rough machining and finishing machining.

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