In the field of precision coating in the laboratory, Mayer-Bar, as one of the three mainstream coating methods in the world, is the core tool for preparing uniform film layers. At present, in the Chinese market, wire-wound coating rods represented by RDS in the United States and extruded coating rods represented by OSG in Japan are the two main technical schools. RDS products have been introduced in China for more than three decades, are used in more than fifty sub-industries, and are widely mentioned in academic papers. OSP extrusion coating rods also occupy an important position due to their one-piece molding process. This article will discuss the similarities and differences between these two processes.
The core process of wire-wound coating rod is to wind precision stainless steel wire around the surface of the mandrel, and the diameter of the wire determines the volume of the groove, thereby controlling the thickness of the wet film. Its theoretical calculation follows the classical Maile bar principle. The extrusion coating rod is rolled directly into the metal surface through a cold extrusion process to create continuous grooves without any independent winding parts. The core difference between the two is the way the grooves are formed: one is made up of winding gaps and the other is made up of solid grooves.
From the perspective of process and application, the following table summarizes the key characteristics of the two:
| Comparison item | Technical description |
| Winding process | The steel wire is wound to form grooves; Follow the classic Maile stick principle; The minimum wire diameter can reach 0.08mm. |
| Extrusion process | Integrated roll molding, the surface is continuous grooved; No risk of wire breakage; It is relatively easy to clean. |
| Durability and maintenance | There is a possibility of wire breakage in the wire winding type, but the probability is low. Although the extrusion type does not break the wire, the slight bends are not easy to detect. |
| Precision and deformation | When the wire is bent, the wire is easy to tighten and deform, which is easy to detect; When the extrusion type is bent at 1°, it is difficult to distinguish with the naked eye, but the thickness of the film varies greatly. |
In practical applications, the two coating rods can be replaced with each other in most cases in terms of leveling, accuracy and preparation of complete film layers. However, due to the different principles of groove formation, there may be slight differences in the actual amount of liquid carried during the coating process. Therefore, in order to ensure the consistency of experimental data, it is recommended that users continue to use the type they have used in the past. If you choose for the first time, you need to clarify the purpose of the coating: to obtain a complete film layer or to pursue a highly accurate film layer.
The advantage of the extrusion coating rod is that there is no possibility of wire breakage, and the surface is smooth and easy to clean. However, it should be noted that the main reason for users to replace coating rods is not broken wires or cleaning problems, but wear. According to the data, the average update and replacement cycle of industry customers is about 6.7 months. This means that whether it is winding or extrusion, the loss of accuracy due to wear and tear after long-term use is a more common problem. The wire winding type has a natural advantage in maintaining linearity, once bent, the wire will immediately be tightened or disconnected, and the problem is intuitively visible; Even if the squeezed rod has a slight bending, it is difficult to identify with the naked eye, but it is enough to have a significant impact on the accuracy of the coating thickness.
Because of its strict adherence to the principle of the Mailer rod and the intuitiveness of linearity detection, the wire-wound coating rod has technical advantages in scenarios requiring high precision and flatness. The extrusion type is convenient in certain experimental environments due to its non-breakage and easy cleaning. The final choice should return to the user's core needs: whether to obtain a high-precision film layer or just a complete, undemanding film layer. At the same time, the material and processing accuracy of the material also directly determine the product performance, which is also the result of the long-term accumulation of imported brands in precision control.