Commonly used welding processes in the wire harness industry include: diffusion welding (too expensive), high-frequency welding (high welding temperature), cold pressure welding (high pressure required) and ultrasonic welding. However, due to their own limitations, the first three welding methods have not been widely used. Only ultrasonic welding has become the mainstream welding method for wire harnesses and cables with its unique simplicity and economy.
Ultrasonic welding uses high-frequency vibration waves to transmit to the surfaces of two wire harness workpieces to be welded. Under pressure, the two wire harness workpiece surfaces rub against each other to form a fusion between the molecular layers.
Its advantages are fast, energy-saving, high fusion strength, good conductivity, no sparks, and close to cold processing; its disadvantages are that the welded metal parts cannot be too thick (generally less than or equal to 5mm), the welding point cannot be too large, and pressure is required. The following are two forms of ultrasonic welding, double-sided welding and single-sided welding.
In the wiring harness industry, ultrasonic welding is divided into the following three welding processes according to the location of the ultrasonic wave: pre-installation welding, wire-side welding, and online welding. Next, we will introduce the advantages and disadvantages of these three welding processes respectively:
1.pre-assembly welding. As the name implies, it is a process of welding wires in the pre-assembly area. Its characteristic is that the original wire is directly sent to the pre-assembly area for ultrasonic crimping after being opened. The advantage is that the original wire is transported in a short distance. At the same time, since it is in the pre-assembly area, it corresponds to all projects in the final assembly area, so it can achieve centralized production and mass production. When materials are sufficient and inventory is allowed, uninterrupted production can greatly improve the utilization rate of equipment; but there are also great disadvantages. The disadvantage is that in the pre-assembly area, the demand information for final assembly is seriously lagging, which leads to the need for plan-led production. In this way, there will be a large number of WIP materials in the material temporary storage area. Once there is a fluctuation in orders or errors in process parameters, a large number of crimping kanbans will be scrapped.
2.wire-side crimping welding, which means crimping on the assembly line. The difference between it and pre-installed crimping is that the crimping equipment is moved from the pre-installed area to the assembly area. The production method changes from the planned production method (push-type) to the pull-type production method. The change in production method leads to a large reduction in WIP between stations. However, due to the reduction of WIP kanban, it is necessary to reserve a certain lead time for ultrasonic stations to prepare materials when designing the production line, otherwise there will be a risk of untimely material supply and stagnation and line stoppage.
3.online welding. Online welding is divided into online welding at KIT stations and online welding at assembly stations. No matter which station is welded, its production method is pulled by the demand on the production line to achieve zero inventory. However, the biggest disadvantage of this production method is that the equipment utilization rate is relatively low (as shown in the figure below, ultrasonic station human-machine analysis), and the equipment utilization rate cannot reach 100%.
The ultrasonic welding process of automotive wiring harnesses occupies an important position in the automotive manufacturing industry with its unique advantages. With the continuous advancement of technology and the continuous expansion of application fields, ultrasonic welding technology will bring more innovations and breakthroughs to automotive wiring harness manufacturing.
