This science of adding these ingredients to rubber known as compounding, impregnating chemicals to rubber molecules efficiently, dispersed all over the rubber with the profound knowledge of polymer properties, vulcanizate properties, curing properties, part profile intricacies, method of mixing, method of molding, testing requirements, productivity, application of the part and its atmosphere, surface finish, part service life, cure system, cost of the part are considered while designing the compound. More precisely, a compound refers to a specific blend of chemical ingredients tailored to a set of required characteristics to enable the desired rubber properties. We translate performance specifications drafted in close co-operation with our customers into tailored recipes. For more detailed analyses we co-operate closely with the curriculum related universities and testing laboratories in the South of India.
KPM possesses 400+ formulations based on 125+ polymer grades and which increases by new developments. KPM has for more than two decades its own in-house material development.
The forte of KPM’s process control is based on the requirements defined in the Compound Approval Process and it passes through our process control testing equipment to validate the viscoelastic properties. This specialized process controls the consistent quality in produced parts from lot to lot.
General cure system followed for different applications and polymers are, Sulphur cure, Peroxide cure, Bisphenol cure, Platinum cure, Sulphur-less cure, Metal oxide cure and Di-amine cure. The function of mastication can be accomplished on open roll mills, and dispersion kneaders, most of the burden is placed upon the processing machinery to process this higher degree of dispersion for better performing rubber compounds.
Quality of the adhesion between metal and rubber for rubber-metal bonded parts is one of the key factors affecting the performance of the product. In order to increase the quality of the bond, degreasing, sandblasting, automated application of the adhesive chemicals and oven drying are main stages of the metal surface preparation or any other types of the substrate.
Preparing the surface before the application of the adhesive will result in exemplary performance and life of the bond. The freshness and various parameters of the surface will influence the degree of bonding and strength. KPM follows the best in class system to ensure defect-free bonding process for different polymers with various metal.
Molding / Vulcanizing
The vulcanization of the rubber changes its physical properties and increase its hardness, modulus, tensile strength, abrasion resistance, ageing properties and swell properties the above are proportional to the degree of cross-linking during molding. The molding takes place under high pressure, temperature and specified time. Our unique formulations include best in class compounds that perform in demanding environments where temperatures are extreme, aggressive media, high forms of pressure and stringent standards.
The properly mixed compound is taken according to its weight and added quantity considered for overflow and shrinkage. The rubber is then kept inside the mold profile and heated at high pressure in the mold until it transfers to the rubber and to flow to its geometry of the part.
The types of moldings incorporated in KPM are,
Vacuum compression molding
Compression molding is the simplest and oldest method of in mold vulcanization and is still widely used when a relatively small number of bonded components are required. Compression molds vary considerably in size, shape and complexity and also contain from one to a very high number of cavities.
This process is preferred for open tolerance parts and non-critical parts used for simple applications. This method placing a precut or shaped slug, into a two-piece mold that is closed.
The pressure applied by the press forces the material to fit the shape of the mold, and the slight excess present floes out of the rim of the mold or through special vents. This excess is known as mold flash. The wastages in this process is less compared to other molding types. Can be preferred for most of the polymers to produce parts.
Vacuum Compression Molding
Vacuum Compression Molding is in addition to the compression molding it involves the vacuum chamber. It enables the introduction of vacuum during the first phase of the curing cycle. The advantages of this process is, removes backpressure in the mold while filling the rubber into the part profile. In addition to backpressure, it sucks the flue gases released in the initial phase of curing. The cost of the machine and mold is also higher than compression molding.
This process is preferred for intricate profiles and blow hole free part manufacturing. Most of the o-rings and seals are produced in this machine. Currently, these machines are widely used in technical part manufacturing.
Transfer molding, unlike vacuum compression moulding, can be used in all types of press equipment. The advantage of such moulds lies in its geometry for part flow and fill into extremely complex paths. The process involves the distribution of the uncured stock from transfer pot into the actual mold cavity.
This process permits the molding of complicated shapes or the embedding of inserts in many products and also for highly critical and close tolerance parts; these procedures are difficult and results poor performances with the usual compression molds.
Although the molds are relatively more expensive than compression molds since it requires more number of mold plates, the advantages of this molding are better heat transfer and uniform pressure over the part cavity, resulting in consistent dimensions from part to part.
The wastages are also high because of its sprues and pot flash. We can use the vacuum process for this molding also and is recommended for medium and lower in quantities.
Rubber Injection Molding
Rubber Injection Moulding is the most sophisticated technology for producing high volumes of components having stringent tolerances. In this process, the material is injected via injection points of the point by injection cylinder having material filled and raised to its pre-cure state. The viscosity is then reduced and fed into the mold profile.
Generally, to obtain maximum production efficiency, injection-moulded rubber components are produced using relatively short, high-temperature vulcanization cycles. This method can be completely controlled by programmed-feed, injection, auto-ejection and very less idle time resulting in minimum rejection rates and lower finishing costs. By careful temperature control of the feedstock, items can be vulcanized in shorter cycle time compared to compression and transfer molding process as the material is preheated in the barrel itself.
The latest molds are with cold runner systems to reduce the cost of the part whereas the cost of the machine, mold and cold runner system is high. The initial cost of both the molds and equipment has hindered the adoption of this type of molding.
KPM has broad expertise in bonding elastomers to a wide variety of other materials including metals bakelite and plastics to create custom-engineered composite seals. Composite seals incorporate the seal and another component into one part to increase the performance and reduce assembling costs.
We ensure better bonding performance and is certified by performing the appropriate tests by our team with profound knowledge and skills. KPM has incorporated the Robotic and automation in adhesive application ensures consistency in quality and strength. By introducing automation in application of bonding agent and primer on the part, we can achieve consistency as there is no manual intervention.
KPM has various industry-leading techniques for deflashing and finishing of the vulcanised component.
- Tear trim
- Manual trimming
- Circular part trimming
- Vacuum deflashing
- Cryogenic deflashing
Tear trim deflashing is mainly for rubber parts and metal bonded parts too. The structure of the flash is designed to deflash easily. The weakest section of the molded part with flash having weakest sections, tear easily. The cost for deflashing is low in all types of deflasing systems, but the life of the tear trim will wear-out during its continuous usage.
The bulk quantities can be deflashed by the spin trimming machine by a batch process. Manual deflashing methods are still followed for some areas where tear trimming profiles cannot be formed.
The Circular part deflashing is widely used to form precise sharp sealing edges used in shaft seals and sealing lip forming.
Cryogenic deflashing is used to deflash rubber parts in bulk, used for blunt sealing rubber products.
KPM’s packaging is in bulk to reduce the cost, packages are made according to customer specifications, the packaging materials are eco-friendly and bio-degradable, all packaging materials are free from toxic agents. In the case of international shipping, as per industrial standards and customer requirements, the parts are packed accordingly in order to minimize environmental and safety risks.