01>>The concept of multiple varieties and small batches
Multi-variety, small-batch production refers to a production method in which there are many types of products (specifications, models, sizes, shapes, colors, etc.) as the production target during the specified production period, and a small number of products of each type are produced. .
Generally speaking, compared with mass production methods, this production method has low efficiency, high cost, is not easy to realize automation, and the production plan and organization are more complicated. However, under the conditions of a market economy, consumers tend to diversify their hobbies, pursuing advanced, unique and popular products that are different from others.
New products are emerging in endlessly, and in order to expand market share, companies must adapt to this change in the market. The diversification of enterprise products has become an inevitable trend. Of course, we should see the diversification of products and the endless emergence of new products, which will also cause some products to be eliminated before they are outdated and still have use value, which greatly wastes social resources. This phenomenon should arouse people’s attention.
02>>Characteristics of multiple varieties and small batches
1. Multiple varieties in parallel
Since many companies’ products are configured for customers, different products have different needs, and the resources of the company are in multiple varieties.
2. Resource Sharing
Every task in the production process requires resources, but the resources that can be used in the actual process are very limited. For example, the problem of equipment conflicts often encountered in the production process is caused by the sharing of project resources. Therefore, the limited resources must be properly allocated to meet the needs of the project.
3. Uncertainty of order result and production cycle
Due to the instability of customer demand, the clearly planned nodes are inconsistent with the complete cycle of human, machine, material, method, and environment, etc., the production cycle is often uncertain, and projects with insufficient cycle time require more resources. , Increasing the difficulty of production control.
4. Changes in material requirements have caused serious purchase delays
Due to the insertion or change of the order, it is difficult for external processing and procurement to reflect the delivery time of the order. Due to the small batch and single source of supply, the supply risk is extremely high.
03>>Difficulties in multi-variety, small batch production
1. Dynamic process path planning and virtual unit line deployment: emergency order insertion, equipment failure, bottleneck drift.
2. Identification and drift of bottlenecks: before and during production
3. Multi-level bottlenecks: the bottleneck of the assembly line, the bottleneck of the virtual line of parts, how to coordinate and couple.
4. Buffer size: either backlog or poor anti-interference. Production batches, transfer batches, etc.
5. Production scheduling: not only consider the bottleneck, but also consider the impact of non-bottleneck resources.
The multi-variety and small-batch production model will also encounter many problems in corporate practice, such as:
>>>Multi-variety and small batch production, mixed scheduling is difficult
>>>Unable to deliver on time, too many “fire-fighting” overtime
>>>The order requires too much follow-up
>>>Production priorities are frequently changed, and the original plan cannot be implemented
>>>Inventory continues to increase, but key materials are often lacking
>>>The production cycle is too long, and the lead time is infinitely expanded
04>>Multi-variety, small batch production and quality management
1. High scrap rate during the commissioning phase
Due to the constant change of products, product change and production debugging must be carried out frequently. During the change, the parameters of the equipment need to be modified, the replacement of tools and fixtures, the preparation or calling of CNC programs, etc., are slightly inadvertent. There will be errors or omissions. Sometimes workers have just finished the last product and have not yet fully grasped or remembered the relevant operating essentials of the new product, and are still “immersed” in the operation of the last product, resulting in unqualified products and product scrapping.
In fact, in small batch production, most of the waste products are produced in the process of product remodeling and debugging equipment. For multi-variety and small-batch production, reducing scrap during commissioning is particularly important.
2. Quality control mode of post-inspection check
The core issues of the quality management system are process control and total quality management.
Within the scope of the company, product quality is only regarded as a matter of the production workshop, but various departments are excluded. In terms of process control, although many companies have process regulations, equipment operation regulations, safety regulations and job responsibilities, they are due to poor operability and It is too cumbersome, and there is no monitoring means, and its implementation is not high. Regarding operation records, many companies have not conducted statistics and have not developed the habit of checking operation records every day. Therefore, many original records are nothing but a pile of waste paper.
3. Difficulties in implementing statistical process control
Statistical Process Control (SPC) is a quality management technology that applies statistical techniques to evaluate and monitor all stages of the process, establish and maintain the process at an acceptable and stable level, and ensure that products and services meet specified requirements.
Statistical process control is an important method of quality control, and control charts are the key technology of statistical process control. However, because traditional control charts are produced in a large-volume, rigid production environment, it is difficult to apply in a small-volume production environment.
Due to the small number of processed parts, the collected data does not meet the requirements of using traditional statistical methods, that is, the control chart has not been made and the production has ended. The control chart did not play its due preventive role and lost the significance of using statistical methods to control quality.
05>>Multi-variety, small-batch production quality control measures
The production characteristics of multiple varieties and small batches increase the difficulty of product quality control. In order to ensure the steady improvement of product quality under the conditions of multiple varieties and small batch production, it is necessary to establish detailed operating instructions, implement the principle of “prevention first”, and introduce Advanced management concepts improve the management level.
1. Establish detailed work instructions and standard operating procedures during the commissioning phase
The work instruction should include the required numerical control program, fixture number, inspection means and all parameters to be adjusted. Prepare work instructions in advance, you can fully consider various factors, through compilation and proofreading, gather the wisdom and experience of multiple people to improve accuracy and feasibility. It can also effectively reduce the online changeover time and increase the utilization rate of the equipment.
The standard operating procedure (SOP) shall determine each execution step of the commissioning work. Determine what to do at each step and how to do it in chronological order. For example, the type of CNC machine tool can be changed according to the sequence of changing the jaws-calling the program-according to the tool number used in the program-checking-tool setting-positioning the workpiece-setting the zero point-executing the program step by step. Scattered work is carried out in a certain order to avoid omissions.
At the same time, for each step, how to operate and how to check are also stipulated. For example, how to detect whether the jaws are eccentric after changing the jaws. It can be seen that the debugging standard operating procedure is the optimization of the control point operation of the debugging work, so that every employee can do things in accordance with the relevant regulations of the procedure, and there will be no big mistakes. Even if there is a mistake, it can be quickly checked through the SOP to find the problem and improve it.
2. Really implement the principle of “prevention first”
It is necessary to transform the theoretical “prevention first, combining prevention and gatekeeping” into “real” prevention. This does not mean that gatekeepers are no longer gated, but the function of gatekeepers is to be further improved, that is, the content of gatekeepers. It includes two aspects: one is the check of product quality, and the next step is the check of process quality. To achieve 100% qualified products, the first important thing is not the inspection of product quality, but the strict control of the production process in advance.
06>>How to prepare multi-variety, small-batch production plan
1. Comprehensive balance method
The comprehensive balance method is based on the requirements of objective laws, in order to achieve the plan objectives, to ensure that the relevant aspects or indicators in the planning period are properly proportioned, connected to each other, and coordinated with each other, using the form of a balance sheet to determine through repeated balance analysis and calculations. Plan indicators. From the perspective of system theory, that is to keep the internal structure of the system orderly and reasonable. The characteristic of the comprehensive balance method is to carry out a comprehensive and repeated comprehensive balance through indicators and production conditions, maintaining a balance between tasks, resources and needs, between part and the whole, and between goals and long-term. Pay attention to the management of hundreds of companies, and receive massive data for free. It is suitable for preparing long-term production plan. It is conducive to tap the potential of the enterprise’s people, finances and materials.
2. Proportion method
The proportional method is also called the indirect method. It uses the long-term stable ratio between the past two relevant economic indicators to calculate and determine the relevant indicators in the planning period. It is based on the ratio between the relevant quantities, so it is greatly affected by the accuracy of the ratio. Generally suitable for mature companies that accumulate long-term data.
3. Quota method
The quota method is to calculate and determine the relevant indicators of the planning period according to the relevant technical and economic quota. It is characterized by simple calculation and high accuracy. The disadvantage is that it is greatly affected by product technology and technological progress.
4. Cyber Law
The network method is based on the basic principles of network analysis technology to calculate and determine the relevant indicators. Its characteristics are simple and easy to implement, arranged according to the order of operations, can quickly determine the focus of the plan, the scope of application is very wide, suitable for all walks of life.
5. Rolling plan method
The rolling plan method is a dynamic method of preparing a plan. It adjusts the plan in a timely manner according to the implementation of the plan in a certain period of time, considering the changes in the internal and external environmental conditions of the organization, and accordingly extends the plan for a period, combining the short-term plan with the long-term plan It is a method of preparing a plan.
The rolling plan method has the following characteristics:
1. The plan is divided into several execution periods, among which the short-term plan must be detailed and specific, while the long-term plan is relatively rough;
2. After the plan is executed for a certain period of time, the content of the plan and related indicators will be revised, adjusted and supplemented according to the implementation situation and environmental changes;
3. The rolling plan method avoids the solidification of the plan, improves the adaptability of the plan and the guidance to the actual work, and is a flexible and flexible production plan method;
4. The preparation principle of the rolling plan is “nearly fine and far rough”, and the operation mode is “implementation, adjustment, and rolling”.
These characteristics show that the rolling plan method is constantly adjusted and revised with the changes in market demand, which coincides with the multi-variety, small-batch production method that adapts to the changes in market demand. Using the rolling plan method to guide the production of multiple varieties and small batches can not only improve the ability of enterprises to adapt to changes in market demand, but also maintain the stability and balance of their own production, which is an optimal method.