Assembly is not only a simple combination of components, but also three perfect combination aspects divided into optimized combination, control and check. For key process, digital assembly must be used to quantitative control, avoid affecting the following operation, cause the influence of scrap or rework products, whether control of key equipment of process work is done. Via real-time inspection by assembling inspection equipment, make each link of closed loop control, to realize perfect digital assembly.

1. Current Situation of Assembly

The domestic auto parts machining level rapidly increased, but the auto parts and components assembly is still lagging behind at present. Pay attention to the result but not to process control is the difference between the domestic and other countries. Although some domestic enterprises through dismantling of foreign products and designed with reference to its internal structure, the quality can't meet the original design requirements after combination. It is related to manufacturing, but more importantly: assembly quality is unqualified that caused our country automobile industry to stay in a low level, low quality cannot compete with foreign countries.

Assembly quality control for most domestic auto transmission parts manufacturers in one-way circle like assembly - inspection - repair influenced by the concept of traditional assembly. Each vendor pay attention to test after assembly, and all kinds of loading test bench arises at the historic moment. We may solve parts of the problem, but not the whole assembly. Many foreign companies bring drawings to China for commissioned processing, but they control assembly part, foreign companies are often also forbidden outsiders to visit its parts and components parts, Domestic manufacturers provide labor, and the foreign side wins the biggest profit.

Even if the parts are all qualified, but not through strict assembly process, the assembled parts are not necessarily qualified. So there is no qualified component assembly, there is no qualified product quality. In the mass production process, component assembly is particularly important. Most of the domestic auto parts assembly line manufacturers stay at the low level to meet the needs of users now. Without process and critical equipment of assembly lines will only be called conveyor lines. Without good logistics, quality and efficiency will be affected. It is inevitable that such assembled product would suffer from defects.

2、Modern Assembly Technology

It is inevitable that traditional technology is eliminated by advanced technology with the rapid development of science and technology. The  good quality of products in developed countries is due to the application of a large number of advanced technologies, including the use of modern assembly technology. True assembly must have three elements: assembly, control and inspection. Product quality control and inspection must have a unified quantitative standard of assembly quality evaluation. To realize this standard, digital assembly becomes inevitable. It also provides the most important basis for product development, improvement and assembly quality tracking at the same time.

Quantitative control of product quality is carried out by measuring parts and optimizing assembly. Each process is strictly controlled according to process requirements to ensure that nonconforming products do not flow into the following process. In the assembly process, the following process strictly checks the upper process work quality to form a closed loop control. Every factory product has the process parameters of assembling process, so as to ensure that the unqualified products are not shipped. What digital assembly can solve is not only quantitative control of pre-tightening force of cone bearings, but also automatic analysis and processing, drawing various quality charts or providing quality reports through implantation of intelligent software, so as to more accurately determine the assembly quality of cone bearings and the possible causes of problems, which is convenient for timely processing.

The key of the transmission system assembly is to allocate the solution rationally according to the different structure of the transmission system. It is hard to make things perfect if the direction is wrong once the scheme is not reasonable. The incompleteness of the assembly scheme will directly lead to the disqualification of defective products, which will be repeated every day and the unqualified products will flow into the market from the assembly line. This is also the reason why many manufacturers have new assembly lines, but the annual after-sales cost is still rising.

Assembly product percent of pass = Assembly scheme perfect coefficient * Equipment manufacturing quality. Assembly scheme is the early argumentation which needn’t to input. The equipment supplier is not only able to meet the requirements of users from the perspective of equipment manufacturing, but also able to put forward more suggestions on improving product assembly quality and optimizing schemes for users to choose. Equipment suppliers can not only provide equipment, but also provide services. Provide reasonable optimization plan, layout chart, etc. according to the user's product features, process parameters, workshop and capital budget for users to review, achieve interaction, and to the maximum extent to meet user needs.

Make good assembly planning mainly including three aspects: process first, logistics second, and key control equipment (ensure process parameters). These three closely related, and it is necessary to take into account as a whole. The assembly line design company shall arrange the process according to the product drawings, product size and assembly mode, give consideration to logistics, and also, according to the process technical parameters, equip the corresponding process to control key equipment.

The digital assembly is the perfect combination of three elements: optimal combination, control and inspection. Due to the error of parts processing, the assembled parts cannot be simply combined. For example, the spiral bevel gears must be matched by a matching machine and the mounting distance must be marked on the gears before the complete assembly can be carried out. For assembly required by moving parts, it has to be quantified to keep the product consistent. For example, in solving the preload assembly of cone bearings, the preload of cone bearings was controlled by axial clearance in the past, but after assembly, it was checked by rotational torque, and the quality instability was caused by the inconsistent standards between the front and the back. Therefore, control and detection are judged by the moment of rotation, which is the key to ensure the quality of bearing assembly. By selecting the pad to control the pre-tightening force of cone bearings, whether the result after assembly is controlled in place as envisaged, check whether the bearing pre-tightening meets the technical requirements through the main tooth nut tightening machine to forming a perfect closed loop control.

Adopt new assembly method to avoid reverse process. Each process should be controlled by equipment or other equipment to avoid defective products flowing into the next process. Some of the link is a traditional assembly which is difficult to complete, for example, the spiral bevel gear meshing mark control, must wait until the follow-up was gear assembly is completed to grind gear to realize, in order to avoid the reversal process, By selecting pads from key equipment such as cushion machine, ensure that the main tooth is correctly positioned after installation to ensure product assembly quality. There is no need to disassemble the main gear changing pad to ensure smooth assembly process and assembly quality.

What digital assembly brings to us is not only the improvement of work efficiency, but more importantly the stability of the product, especially in mass production, which is the most important standard to establish product quality.

German manufacturing used to be synonymous with shoddy manufacturing in Europe, but today German manufacturing is synonymous with superior products. The secret of its success is to pay attention to details and insist on quantitative control of every link.

In order to improve the quality of products and the core competitiveness of China's automobile industry, we must update the concept of component assembly and attach importance to component assembly.

Let's work together to improve the level of auto parts assembly in China!

--- published in 2008 in China automotive news