Rubber Metal Shock-Absorbing
Rubber-metal shock-absorbing components play a crucial role in the automotive industry, serving not only as integral parts of the vehicle suspension system but also as key factors ensuring driving safety and comfort. However, much like many engineering fields, these components face various challenges related to defects that can impact vehicle performance, durability, and overall safety. This article delves into the common defects of rubber-metal shock-absorbing parts, their root causes, and effective countermeasures, aiming to provide valuable insights for automotive engineers and manufacturers.
| Question | Cause Analysis | Solution |
| Degumming | Description: Mainly manifested by the separation of the rubber and metal bonding surfaces | |
| 1. Wrong selection of glue | 1. Refer to the specific user manual to select the appropriate adhesive | |
| 2. The metal surface treatment failed so the physical adsorption of the primer could not be achieved well. | 1. Roughen the metal surface to ensure a certain roughness on the metal bonding surface. (Commonly used treatment methods, the surface roughness observed under a microscope from large to small are sandblasting, shot blasting > phosphating > galvanizing) 2. There should be no rust on the metal surface, and no oil, dust, impurities, etc. should stick to it. | |
| 3. The glue coating process has poor stability, the glue is too thin, missed coating, insufficient coating, residual solvent, etc. | 1. Pay attention to the operation to prevent glue leakage and apply less glue. 2. The metal parts coated with glue should be fully dried to allow the solvent to fully evaporate to prevent residual solvent from evaporating during vulcanization, causing bonding failure. 3. It is necessary to ensure a certain glue thickness, especially the surface coating glue. (In this way, on the one hand, there can be enough material to fully carry out mutual diffusion and co-crosslinking; on the other hand, a certain modulus gradient layer can be achieved) | |
| 4. The formula is unreasonable and the rubber vulcanization speed is inconsistent with the glue vulcanization speed. | 1. Improve the recipe to ensure sufficient scorching time 2. Improvements in molds and formulas ensure that the rubber reaches the bonding part as quickly as possible 3. Try to use ordinary and semi-effective vulcanization systems and increase the amount of sulfur to achieve polysulfide cross-linking 4. Improve vulcanization conditions (temperature, time, pressure) 5. Reduce the use of bloom-prone plasticizers to prevent them from migrating to the rubber surface, thereby affecting the bonding 6. The rubber has been parked for too long. Use fresh rubber instead. | |
| 5. Not enough pressure | 1. Increase vulcanization pressure 2. Pay attention to the location and size of the overflow port and vacuum tank to prevent excessive communication with the atmosphere. 3. Ensure the mold is tightly closed to prevent insufficient local pressure | |
| 6. The active ingredients of the glue volatilize or solidify | 1. For metal parts that need to be pre-baked before vulcanization, attention should be paid to the time and temperature control of pre-baking. Excessive pre-baking will cause the volatilization of reactive substances and the maturation of the glue. 2. During operation, be careful that the metal parts stay in the mold for too long. | |
| 7． Foreign matter such as vulcanized rubber and glue is mixed into the mixed rubber and vulcanized together with the rubber, causing degumming in a small area and causing large-area peeling of the product. | 1. Strengthen material management | |
| Big bubbles | Description: The main manifestation is the presence of large bubbles on the surface of the rubber body of the shock absorber. | |
| 1. The product is not fully vulcanized, resulting in large bubbles on the surface of the rubber product (the interior is like a honeycomb sponge when cut open) | 1. Extend the vulcanization time and increase the vulcanization temperature 2. Ensure sufficient pressure for vulcanization 3. Adjust the formula to increase the vulcanization speed | |
| 2. Degumming will cause a large amount of gas to remain in the bonded part. (When the pressure is applied, the gas is compressed. Once the pressure is removed, the gas diffuses, and bubbles will appear between the rubber and the metal where the rubber layer is thin and the area is large.) | 1. Extend the vulcanization time and increase the vulcanization temperature 2. Ensure sufficient pressure for vulcanization 3. Adjust the formula to increase the vulcanization speed | |
| 3. If there is gas entering the rubber material, the gas is not easy to be eliminated and will be vulcanized together with the rubber material, thus causing bubbles to appear on the surface of the product. | 1. Increase the number of loosening times after the mold is closed 2. Vacuum the mold 3. Improve mix hardness 4. Use rubber with higher Mooney viscosity 5. Break the air bubbles on the rubber material before feeding 6. Improve the mixing process of the open mill and try to avoid gas mixing into the rubber material 7. Improve injection conditions so that the rubber can enter the mold cavity more slowly 8. Improve the exhaust groove, overflow groove, etc. of the mold | |
| 4. There are volatile substances in the rubber formula | 1. Pay attention to adjusting the appropriate vulcanization conditions, and the temperature should not be too high. 2. The various raw materials used should be protected from moisture before use and can be dried if necessary. 3. Reduce the use of raw materials that produce gases and other small molecular substances during vulcanization 4. Reduce the use of low-boiling plasticizers, extenders, and softeners | |
| Thin-skinned bubbles | Description: The main manifestation is that there are a certain number of small bubbles in the shallow layer of the rubber body of the shock-absorbing parts. | |
| 1. Vulcanization conditions and improper combination of vulcanizing agents | 1. Pay attention to adjusting the appropriate vulcanization conditions, and the temperature should not be too high. 2. Adjust the appropriate accelerator ratio and avoid excessive amounts. | |
| 2. There are volatile substances in the rubber formula | 1. Pay attention to adjusting the appropriate vulcanization conditions, and the temperature should not be too high. 2. Adjust the appropriate accelerator ratio and avoid excessive amounts. | |
| 3. The plastic bags partially filled with rubber raw materials during mixing are not completely melted and evenly dispersed in the mixed rubber. | 1. Increase mixing temperature 2. Try to remove plastic bags, etc. | |
| Fillet | Description: It is mainly manifested by the presence of spongy or obvious sticky protrusions on the surface of the rubber body of the shock absorber. | |
| 1. Gas is trapped locally in the mold cavity, thus affecting heat transfer and thermal vulcanization of the rubber material. | 1. Vacuum the mold to ensure that the cavity is in a vacuum state when the rubber material enters the cavity. Ensure that the vacuum is intact to extract the gas in the mold. 2. Increase the number of loosening times after the mold is closed 3. Set up an exhaust slot or overflow slot on the mold | |
| 2. The mold cavity is asymmetrical, and has dead corners, and uneven heat transfer leads to uneven vulcanization. | 1. Adjust the compound formula and use a compound with a long flat vulcanization curve. 2. Adjust vulcanization conditions, extend vulcanization time, or increase vulcanization temperature | |
| 3. Gas is trapped when the rubber material is extruded or calendered | 1. Improve the calendering and extrusion condition buckling process | |
| Lack of material | Description: The main symptom is that the rubber of the shock absorber does not fill the entire cavity. | |
| 1. Too little glue used | 1. Increase the amount of glue used 2. Adjust the extrusion system to ensure sufficient extrusion | |
| 2. The overflow opening is too large so that the rubber material cannot fill the mold cavity and overflows from the overflow opening. | 1. Change the size of the overflow port or reduce the number of overflow ports | |
| 3. Too much release agent is used, causing the rubber materials to not close together at the junction in the cavity. | 1. Reduce the amount of release agent used 2. Note that the glue should not be contaminated with oil before use. | |
| 4． The vulcanization speed of the rubber is too fast so the rubber is vulcanized before it crowds into the mold cavity and cannot flow. | 1. Adjust the rubber compound formula to extend the scorch time 2. Increase the size of the feed opening or increase the number of feed openings | |
| 5. The mold inlet design is inappropriate and the rubber cannot flow into the mold cavity. | 1. Improve mold | |
| 6. The rubber material is too hard or the flow state is not good. If it does not fill the mold cavity, it has been vulcanized and cannot flow. | 1. Improve the flow state of rubber materials | |
| Shrinkage jacket | Description: Mainly manifested by larger holes and grooves appearing on the rubber surface of shock-absorbing parts, such as the material inlet, overflow port, parting surface, or the bonding between rubber and metal. (Although shrinkage cavities and interlayers are different phenomena, many of their causes are the same) | |
| 1. Insufficient scorching time of the rubber material can easily form vulcanized rubber particles and rubber chips. | 1. Extend the scorch time of the rubber compound 2. Adjust vulcanization time (lower temperature to extend vulcanization time) 3. Avoid using compounds that have been parked for too long | |
| 2. The process is unreasonable and there is too much rubber that cannot overflow. During vulcanization, it is vulcanized before the surface of the product so that it is sandwiched between the parting surface and other parts. | 1. Use extrusion systems wherever possible 2. The rubber material should be accurately weighed and fed | |
| 3. Mold contamination, the rubber material is not clean | 1. Clean molds and rubber compounds | |
| 4． The mold parting surface is not tightly matched, the design is unreasonable, and the overflow hole is too large | 1. Improve the mold and try to avoid the parting surface appearing in sensitive locations such as the bonding parts of the product. | |
| 5. The heat transfer rate of the rubber is slow. During vulcanization, the temperature of the outer layer of the rubber body is inconsistent. The outer layer of rubber has been vulcanized, but the inner layer of rubber has expanded due to heat, forcing overflow and causing shrinkage of the skin. | 1. Improve rubber compound formula | |
| Spray frost | Description: Mainly manifested by the formation of a layer of white substance similar to frost on the surface of the rubber body after the shock absorber is placed. | |
| 1. When raw materials such as vulcanizing agents, accelerators, and active agents are used in excessive amounts, the dissolution in the rubber has reached saturation and then slowly migrates to the rubber surface. | 1. Control the dosage of various raw materials by testing the total amount | |
| 2. The product is not fully vulcanized and lacks sulfur. | 1. Fully vulcanized | |
| Layered | Description: The main symptom is that the rubber body of the shock absorber cannot continuously form a whole, and appears layer by layer. | |
| 1. Surface contamination of the rubber material, especially oil contamination | 1. Clean the rubber surface or replace it with clean rubber | |
| 2. Spray frost | 1. Control the dosage of various raw materials by testing the total amount 2. Fully vulcanized | |
| 3. Different rubbers with poor compatibility are mixed unevenly | 1. Pay attention to choosing rubber with good compatibility | |
| Tear, plucking | Description: The main manifestation is that the rubber body of the shock absorber is torn or the surface of the rubber body is not smooth and flat. | |
| 1. The demoulding method is unreasonable and hard to demould, causing the product to be torn or roughened. | 1. Improve the demoulding method and improve the mold structure 2. Spray release agent | |
| 2. The product is over-vulcanized, causing the physical properties such as rubber strength to decrease and the product to be torn or broken. | 1. Adjust vulcanization conditions to normal vulcanization | |
| 3. Vulcanization temperature is too high | 1. Adjust the rubber compound formula and lower the vulcanization temperature | |
In the pursuit of automotive excellence today, understanding and addressing the common defects of rubber-metal shock-absorbing components is paramount. By adopting a scientific approach, conducting in-depth analyses of the origins of defects, and formulating practical countermeasures, we can continually enhance vehicle performance, reliability, and safety. It is crucial not only to strengthen quality control during the design and production phases but also to perform regular maintenance and inspections during usage to ensure that rubber-metal shock-absorbing components consistently deliver optimal performance. Through collaborative efforts, we can continuously improve these critical components, providing drivers with a safer and more comfortable driving experience and driving the ongoing development of the automotive industry.
