In the processing of automotive transmission gears, the increase in market demand makes the number of product changeovers also increased. Reasonable production organization management and maintenance management of grinding gears in multiple varieties of mixed flow production conditions can reduce the frequency of product changeovers. , Improve equipment utilization, make production more equalized, and better ensure processing quality and efficiency.
In the car gearbox gear processing machine, for the gear molding process, often using the gear-shaved gear, hobbing - shaving or hobbing - grinding and grinding teeth, precision forging, enamel and other processing technology. Among them, the hobbing-hot post-grinding process can correct various errors caused by gears during pre-processing and heat treatment, reduce tooth surface roughness, and obtain gears with higher precision and better tooth surface quality. With the continuous improvement of the worm wheel grinding machine technology, the grinding tooth efficiency has also been greatly improved, and it has been more and more widely used in mass production.
FAW-Volkswagen Automotive Co., Ltd., in the transmission workshop, used hot front hobbing gears for the production of the new product MQ250 gearbox (the five-speed manual gearbox was applied to Sagitar and Magotan manual box models). After the hot grinding grinding process, the purchased Gleason HURTH 245TWG gear grinding machine is used for input shaft, ring gear, and gear grinding of second, third and fifth gears to improve the quality of gearbox manufacturing. The worm wheel grinding process used in car gearboxes (see Figure 1) is less widely used in China, and is relatively unfamiliar to the transmission workshop. The characteristics and use of gear grinding machines are still being explored and studied. In actual production, due to the relatively high cost of a single grinding machine, the high cost of cutting tools, maintenance and maintenance, the transmission workshop is facing the contradiction of insufficient production capacity and multiple varieties of mixed-flow production, making the grinding machine face production in the initial stage of its use. Organization, maintenance, tool wear, and frequent line change problems. How to solve these problems systematically, reasonably and quickly is a big challenge for the workshop, and it is also the purpose of this article.
Figure 1 Example of a Gleason HURTH Worm Grinding Wheel and Corresponding Process Gear
Technical improvements and breakthroughs can solve the problems encountered in actual production, but how to use limited resources to complete production tasks, improve production efficiency, and reduce production costs, we must consider the grinding machine under the conditions of mixed production Production organization management.
Balanced production and difficulties faced
The gear grinding machine of the gear segment needs to produce 5 kinds of gears of different types of boxes. The production must be changed frequently to meet the needs of gearbox assembly. Under the original planned production capacity, the factory can basically meet the production requirements. However, with the increase of the market demand for MQ250, the originally planned production capacity can no longer meet the current production demand. The market for multiple varieties and small batches needs to increase the frequency of program updates, increase the number of changeovers, and change the tools, jigs, trays, and programs for each type of conversion, and spend a lot of time on the machine for changing lines. Adjustments and wheel corrections. Therefore, this slows down the production cycle and greatly limits the market's demand. In addition, the gear grinding machine is a device with high precision requirements. Frequent line changing will inevitably have a serious impact on the accuracy and service life of the machine tool. At this time, according to the planned production, the use of JIT's production management methods will make the production face great risks and cannot complete the task.
In order to reduce the frequency of line changes and increase equipment utilization, it is necessary to increase the reserve of work-in-process products. However, due to the tight production tasks, there is little time available for the construction of storage, and when equipment is used, it is necessary The reserves soon consumed up. The simple idea of ​​constructing storage can no longer meet the requirements, so it is necessary to consider the issue of equalization of production.
1. About reasonable reserves
A reasonable reserve, similar to the role of the reservoir, can release the production capacity under the conditions of frequent changes in the plan and abrupt increase in production requirements, giving sufficient time for buffering the grinding teeth, and avoiding surprise line change due to changes in the tasks, so as to achieve Improve the purpose of equipment utilization.
Graphically speaking, the entrance to the pool is the capacity of the equipment. The pool is divided into several small pools according to each breed. Each small pool is continuously flowing, and the continuous flow of water is the daily consumption. The valve that controls the water flow distribution at the inlet is a line change, and the speed of water discharge from each small pool is different. If the water flow in a pool is too fast and below the warning water level, the pool should be filled with water, that is, it should be changed for production.
However, how many reserves can be changed? Determining a reasonable WIP stock is not as easy as you think. This requires changing the processing method of the gear grinding machine. The original gear processing is based on the needs of the assembly plan production, belongs to the downstream pull upstream, the advantage of this approach is to reduce work in progress, reduce production costs. However, its disadvantage is that it is subject to the production of upstream processes and the elasticity of planned changes is reduced. In order to increase the elasticity of this resistance to change, the grinding machine can fully release the production capacity. Therefore, the way of listening to the plan work must be changed, and the method of producing parts in accordance with the plan quantity should be changed to the mode of autonomous production of parts according to the time. Grinding machines have different machining times for each part. If they are all manufactured according to the assembly plan, there will be some work involved in the processing of some parts, and some have insufficient time and need additional overtime. If the processing is measured according to time, this time waste and artificial distribution problem can be effectively reduced. For example, the five-speed gears have a shorter processing cycle and the second gear has a longer beat. In the initial stage, the second and fifth gears will be allocated roughly the same amount of time. Then, the number of fifth gear processing can be more, and it will flow into the reserve pool. By continuously counting and comparing the length of time, a reasonable processing period can be determined and the different reserves of different parts can be determined.
2. Effective implementation, with regard to visual management
Smooth communication can increase efficiency and reduce errors. The information of production and conversion becomes visual information that can be seen at a glance, which is also a very important management tool.
Taking a reservoir as an example, a histogram of changes in response can be made at the production site (see Figure 2). The horizontal axis of the chart is a variety of parts. The top of the histogram is the quantity of work-in-process reserves for each part, and the lower part is the amount consumed in the day. For each part, there are two control lines, one for the highest reserve and one for the lowest reserve. What the operator needs to do is to add the entered variety and output to the following table and slide the label on the histogram. For these two lines of control, the person responsible for the production plan is responsible for adjusting the position on a regular basis.
Figure 2 Visual board example of part reserve in production
In fact, in addition to the processed product in-process reserves, it is also necessary to coordinate the rough reserves at the entrance. For the gear grinding machine, its blanks come from the heat treatment and thermal pre-processing steps. It is not a bottleneck and the difficulties are relatively few. We will not repeat them here.
Improve the operating rate of equipment
Reducing the number of stoppages of equipment can minimize the interference of uncertainties and reduce the reserves that are raised due to the effect of preventing stoppages.
Here we first advocate rapid response during preventive maintenance and repair. The implementation of preventive maintenance can effectively reduce the chance of equipment stopping and eliminate hidden dangers in the bud, which has a good effect on increasing the rate of equipment operation. However, blindly pursuing preventive maintenance is also unrealistic. Regular inspections and maintenance and planned arrangements for maintenance cannot fundamentally solve the problem of the suspension of the station. From another perspective, it is inevitable that the suspension will be suspended. However, there are some ideas for reference on how to quickly repair faults, shorten downtime, and ensure the operation of production.
The strategy and organization of gear grinding machine maintenance
For newer equipment such as gear grinding machines, it is necessary to rapidly improve the maintenance knowledge reserve. The experience and attempts of maintenance personnel alone cannot meet the needs of production. At the initial stage of equipment introduction, maintenance personnel should intervene in the planning and procurement process of the equipment, request equipment manufacturers from the perspective of equipment ease of use, interchangeability, and maintenance, and participate in equipment operation and maintenance training at the beginning of project operation. If the conditions permit, it is best to learn from the manufacturers who are using the device to learn about the existing experience and skills.
During the installation and inspection of the equipment, the maintenance department must also actively participate in the inspection. For parts where the equipment is prone to problems, consider the spare parts, training, and document acceptance in advance, and use the preventive maintenance system at the equipment use stage. , promptly find and feedback questions. For specific and targeted operations, questions can be asked in a form, brainstorming, and problem groups.
After the fault occurs, the process of initial problem determination requires a process of brainstorming, because the original personal experience is often not enough for treating a new student problem, and there is not enough time for theoretical analysis from the source. Therefore, it is best to develop people. The advantages of many are composed of technical teams, discussion of problem groups, and raising the possibility of problem solving.
In the maintenance of faults, it is necessary to prevent many people from working together. Because people have more hands and miscellaneous items, the trainee's train of thought is vulnerable to interference. At the same time, there are certain security risks and it is not conducive to the resolution of the fault. For the solution to the problem, it is necessary to analyze after-effects to avoid recurrence of the problem.
summary
In short, from the early introduction of equipment, to the preventive maintenance in the normal production process, to the rapid response when the fault occurs, and finally to the analysis of the problem after the conclusion of the summary, a variety of maintenance strategies should be comprehensively used, reasonable coordination, reduce Stop loss. In addition to gear grinding machines, perfect maintenance strategy for other equipment is a strong guarantee for smooth production.
In modern enterprises, the scope and depth of mutual integration of technology and management is increasing. Good technologies must reflect good values ​​through good management. Good management must also rely on good technologies to be effective, and both must develop harmoniously. It is the cornerstone of the steady development of manufacturing companies.
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