Process management is an important condition to ensure the implementation of the formulated painting process, ensure the stability of painting quality and achieve the purpose of painting and the best economic benefit [2]. At present, China's construction machinery enterprises are in the transition period from workshop production to industrialized assembly line production, so it is more important to attach importance to and strengthen painting management. According to the author's investigation of domestic construction machinery enterprises, the painting technology, equipment and technology of many large enterprises are similar, and the main difference lies in the opposite side of management. Many enterprises have passive management attitudes such as carelessness, make do and accommodation, which is one of the main reasons for poor painting quality.
Establishing a perfect process assurance system is the fundamental guarantee for the success of painting engineering. A perfect process assurance system should include enterprise standards, program documents at all levels, management documents, etc. At present, the national standard "JB/T 5946-9 1 General Technical Conditions for Painting of Construction Machinery" can no longer meet the painting requirements of current products. Enterprises should revise according to their own painting process level and quality requirements, and take this as the basis for their own painting process formulation. Process documents are the guiding documents for the correct implementation of painting process and the necessary conditions for obtaining stable and high-quality coatings. Complete process documents should include painting operation card, painting standard operation book, painting inspection standard book, painting workshop cleaning plan and other documents. For automobile manufacturers, these are the most basic process documents, but most construction machinery enterprises only have painting process cards and vehicle inspection cards, which cannot meet the needs of quality management.
In addition, due to the complex product structure, there are many parts in construction machinery, and even large structural parts need external processing. Take the loader as an example, the common parts are bucket, counterweight, cab, hood and fuel tank. The surfaces of these workpieces are basically important painting surfaces (the painting area accounts for 1/3 of the painting area of the whole vehicle, or even more), and the painting of pretreatment, primer and intermediate coating is controlled by the outsourcing manufacturer. There are few full-time painting technicians in outsourcing manufacturers (the survey results of more than 20 outsourcing suppliers by the author). Therefore, it is necessary to strengthen the control of foreign manufacturers, formulate corresponding management systems and sign relevant technical agreements. Taking our company as an example, we have worked out the management operation document "Regulations on the Management of Material Outsourcing Painting", and signed a technical agreement on material painting with the corresponding suppliers, stipulating the pretreatment methods, treatment standards, painting types and corresponding painting technical indicators that must be adopted, and giving technical guidance and supervision.
2.2 Quality management
In the process of automobile manufacturing, painting process is not only a key process, but also a special process. This definition is because the coating quality can not be judged by the final inspection results, and the control of its process (that is, the control of each working procedure and each process parameter) must be strengthened. Therefore, a complete quality control system is essential.
A complete quality control system must include four levels of quality control: customer level, company level, department level and independent level.
2.2. 1 customer level
Customer-level quality control refers to objectively evaluating coating quality on behalf of customers-VES (Vehicle Static Evaluation System-). In other words, VES stands on the position of users and evaluates the whole vehicle with the eyes of experts. VES has to evaluate more than 65,438+0,600 vehicles, which is one of the most stringent quality standards in the world. It is a vehicle evaluation system formulated by Nissan Motor Company of Japan and must be evaluated by appraisers with VES evaluation qualifications. In China, it has replaced the "Blue Book-Inspection and Evaluation Methods for Truck Quality" as a new automobile quality evaluation standard. The complexity of construction machinery manufacturing and assembly and the severity of working environment are much higher than those of automobiles, so it is more necessary to establish a sound and reliable quality evaluation system.
2.2.2 Company level
Company-level quality control is to establish a reliable inspection and inspection system, which is implemented by the quality assurance department. It is generally divided into three parts: incoming inspection, process inspection and final inspection. Detailed regulations must be made for each inspection, such as inspection means, judgment standard, inspection frequency and importance. , the inspection results should be recorded in detail and filed. See table -2 A company loader vehicle inspection reference book (area a) Department-level quality control is an independent control system of painting workshop, and each shift has a special person to make quality records; We should designate a special person to make statistics and analysis, and formulate corresponding countermeasures. The main control items include ① topcoat defect record (DPU- the total number of defects of single vehicle), ② statistical analysis daily report, ② initial and final inspection records of primer and intermediate paint (including film thickness, adhesion, hardness and other indicators), ③ topcoat repair record, ④ statistical analysis daily report, ④ inspection records of sand blasting and shot blasting pretreatment, and statistical analysis daily report.
In addition to the above control items, it is also necessary to implement continuous improvement targets for key items, such as "DPU value" and "amount of paint per vehicle", and monthly control targets can be set according to different colors of paint or different models. Figure 1 is the control target of a certain model product of a company from September 2005 to June 2006 (65438 At present, the coatings for construction machinery are getting closer and closer to the automotive coatings. Taking a heavy industry enterprise in Changsha as an example, the painting of bus products and construction machinery products is mixed production (produced on the same painting line), and the painting quality of construction machinery products and bus products is homogeneous. Taking its pump truck as an example, the spraying scheme of "metallic paint+varnish" is adopted: the paint film is basically free of orange peel, with high brightness (above 90%) and good brightness (people's facial image can be clearly seen on the paint film, as shown in Figure 3; The vertical PGD value (sharpness) is above 0.5) [4]. Therefore, the quality of coating becomes the basic condition for obtaining high-quality coating.
The control of raw materials must establish its own paint and spray painting inspection room. A simple testing room only needs about 50,000 yuan of equipment, which can comprehensively test raw material indicators and construction performance indicators, such as paint solid content, paint dosage, fineness, hiding power, leveling, sag, paint film drying time, paint film thickness, luster, vividness, paint film wear resistance, adhesion, hardness, stone impact resistance, flexibility, neutral salt spray resistance and so on. If you don't do neutral salt spray test, you only need 30 thousand yuan of equipment. For the key items that cannot be tested by themselves, the National Center for Quality Supervision and Inspection of Coatings (Changzhou) or the Center for Quality Supervision and Inspection of Aging of Chemical Synthetic Materials (Guangzhou) can be entrusted for testing, and it is clearly stipulated in the technical agreement of raw materials that: artificial aging is once every two years, salt spray resistance test is once a year, and other water resistance, acid and alkali resistance are once every six months. It should be noted that you must take samples by yourself (from the products normally supplied) and send them, and the cost will be shared by the supplier through negotiation.
Strict control procedures must be adopted when selecting new materials and suppliers. It mainly includes five processes: supplier qualification examination, raw material quality confirmation, prototype test, small batch trial assembly and batch supply, which generally takes 6- 10 months to test.
The inspection of suppliers mainly includes: enterprise scale, technical level, supply capacity and other aspects, as well as relevant qualification certificates of enterprises, such as quality system certification (such as ISO900 1 certification, QS9000 certification, ISO 1400 1 certification), enterprise material testing center qualification (such as national laboratory) and supporting facilities for large enterprises. The work in the above two aspects must be solid and sufficient. For example, we can ask the other party to provide a list of major production equipment, a list of testing equipment and the above qualification certificates for the record, and then conduct targeted field visits.
Protection of metal raw materials
At present, in most construction machinery enterprises, metal raw materials (whether thick plates or thin plates) can be piled up at will, and some even stored in the open air, resulting in serious corrosion of plates. Although pretreatment methods such as shot blasting and sand blasting are effective (generally reaching Sa3 or Sa2.5 level), seriously corroded plates will still bring many adverse effects on painting: ① serious corrosion will affect the production rhythm of pretreatment-prolonging shot blasting time and reducing productivity; (2) Shot blasting and sand blasting are destructive equipment, and the extension of the beat will cause great damage to the equipment and accelerate its aging; (3) The prolongation of the beat will also lead to the waste of energy. The power of shot blasting equipment is generally around 300- 500KW, and the energy consumption is quite amazing. (4) affecting the flatness of the workpiece;
⑤ Increase the complexity of the painting process.
Therefore, it is necessary to protect metal raw materials, organize production reasonably, minimize inventory (try to avoid open storage), protect semi-finished parts (avoid workpiece "landing") and avoid unnecessary metal corrosion.
2.4 Site management
On-site management is an important part of painting quality assurance, which mainly includes the following aspects: on-site production operation and technical management, on-site painting quality management, car body paint film quality tracking, on-site cleaning management and so on. These aspects are interrelated and interrelated. At present, the production mode of construction machinery is basically "multi-variety and small batch", which conforms to the so-called "lean production" mode. The method of "5S" site management is appropriate. Through the "5S" site management activities, the working environment becomes clean and comfortable, and the production is orderly. Equipment failures are effectively prevented and controlled, and product quality is guaranteed. To carry out "5S" activities, we must do the following: full participation and all-round development; Professional organization and guidance; Leaders must personally grasp; We must persevere and persevere.
2.5 Supplier's on-site service
Take a company as an example, the annual output of loaders is 3,000 sets, and the total consumption of paint reaches more than 7 million yuan a year. Enterprises with an annual output of 1 ~ 20000 sets should use more than 30 million paints. With this output value, you can ask the paint supplier to send 1 ~ 2 technicians to the factory. They are at the production site every day, participating in the adjustment of paint parameters, tracking the production situation on the production line, and participating in the analysis and solution of production quality problems. The technical service personnel in the factory should count the relevant quality information, analyze and put forward improvement suggestions while following the shift every day, and feed them back to the relevant departments of the user unit in the form of weekly/monthly reports.
In addition, we should make full use of various resources of suppliers. Use its professional instruments to test the performance of its own equipment and paint film, such as anemometer, furnace temperature tracker, illuminance meter, orange peel tester, etc. You can also send relevant technicians, paint inspectors and front-line operators to their training departments for training and study.