Discussion on Various Challenges Automotive Subassembly Engineers Tackle

Once the material choices are manageable, economics become a large part of the equation. Depending on the geometry of the part, there are several manufacturing methods which may be considered. If the part is simple and symmetrical, it favors almost any manufacturing method, and is most desirable. If the engineered plastics part is more complex, it may limit the manufacturing and tooling methods that would otherwise be available for consideration. The raw material cost, the number of available cavities to mold the part, the part tolerances, aesthetics, and control methods will also have to be considered, as well as the tooling cost, which can vary widely, depending on many variables. Perhaps the most impactful factor is the required volume of product, as considerable economies may come into play with larger volumes, but tooling may become an issue for smaller volumes.

The next step is to consider the “down-stream” elements of the project. These elements are generally more abstract and intuitive, and require considerable thought. For example, does the model you have developed lend itself to assembly? If you have the most economical model available with a dynamite material such as engineered rubber, but it is difficult to assemble in the application, it may not be worth going down this path. Is it possible that proximity to other components may cause issues? For example, ozone has a detrimental effect on many rubber materials, so everything else may be right on target, but the part will craze and crack due to ozone exposure.

How about aesthetics and/or marking? If the part is to be assembled in any area which is visual for the customer, the engineered rubber and plastics must not leave a mark or create any crazing or cracking with mating parts. Some automotive OEM’s are demanding environmental compliance with ISO 14000, which calls for recyclable materials, and could create major constraints. If the part is to be “pre-assembled” with the intent of the automotive OEM taking the part out of the box and assembling it, are the rubber and plastic components affixed to the unit in a way that will withstand the rigors of shipment? Most automotive OEM’s will not accept a component if one if the parts has become dislodged, even if it is a simple refit process to put it back on. Slight modifications to the geometry of the part may be required to ensure that all downstream considerations are covered, but everything must be analyzed abstractly in order to head off potential problem. Once the tooling is produced, it is very expensive to make changes.

When these considerations have been qualified, it’s time to review tooling. The complexity of the part will largely determine the tooling cost, and anything that can be done to avoid sharp corners and blind pockets will promote flow and avoid air trap between polyurethane o-rings, for example. A smart engineer will go as far as to visualize parting lines in the mold, and work them into the solid model to create the splits and review the resulting tool. If there is any way to avoid undercuts (areas that prevent normal opening and closing of conventional tooling), it will pay large dividends. If undercuts cannot be avoided, making them perpendicular to the parting line will soften the costs associated with tool construction, as core pulls and slides are easier to design and integrate. For additional information, please visit: http://www.real-seal.com/ to learn more.

Maximizing Equipment Life By Identifying Failure Modes

The RCM (Reliability-Centered Maintenance) methodology can be used effectively if we just learn about our equipment and its individual components, ie. rubber o-rings. Take a simple component such as a mechanical pump seal as an example. This mechanical seal is made up of some individual components such as O-rings, springs, gasket seals, seal faces, set screws, etc. Understanding all of the ways these components can fail can help us understand how to make the seal last longer.

What is a failure mode? A failure mode by RCM definition is any way that a component can fail in your process that will affect operation, rate, quality, or create an environmental, health and safety issue. Below is a list of failure modes for various mechanical seal systems. If we understand and determine the reason for failure in lost cases, the reason can be prevented or eliminated.

Mechanical seal failure modes:
• Improper storage and handling
• Improper installation
• Failure of shaft O-Ring
• Inability to adjust for wear
• Seal cover O-Ring Failure
• Failure of spring tension component
• Fails due to coupling misalignment
• Fails due to impeller imbalance
• Fails due to bearing wear
• Fails due to shaft deflection
• Fails due to operating with no fluid film
• Fails due to foreign material
• Fails due to broken drive pin
• Fails due to over-pressure

These are common failure modes for mechanical seals. If we can determine which of these failures have occurred, we can take steps to predict, prevent or eliminate the failure. An example may be the shaft O-ring, which is a common failure component. By looking at the O-ring, we may determine it has overheated. Our options may be to cool the liquid around the seal, change the high performance o-rings to another material or install a double seal with cooling media. We can now have longer life and extended run times, which means more products and more profit and less parts cost.

We can look at any piece of plant equipment or any plant process and break it down into components. We want to break the system or piece of equipment down to levels where we think the components may be failing. But the intent of understanding detailed component failures is that the learning curve can be improved to a much higher level. For additional information on identifying and rectifying failures, visit http://www.real-seal.com/ to learn more.

Not Your Run-Of-The-Mill Seal Application: Seals For High-End Electronics

High-end electronics with specialized o-rings pose a number of challenges that conventional seal applications do not. While most conventional seal applications focus on media compatibility, physical properties, and longevity, high-end electronics are generally require more emphasis on cleanliness, repeatable processing, dielectric properties, and ease of assembly.

Many electronic components rely on a high purity media to conduct energy. These media can take several different forms, but the purity of the media can be paramount in the performance of the component. Liquid media, for example, depends on the purity of media to maintain performance. Media such as acenitrile depends on the purity to store and transmit charges in application. If the material of rubber o-rings, for instance, has any ingredients (waxes, plasticizers, process aids) or ancillary residual material (mold releases, residual cleaning media) which could leech out of the rubber and into the fluid, it could compromise the effectiveness of the electrical component.

Studies have shown that performance of specialty seals can be altered as much as 12% from fugitive chemicals that are released from rubber and/or plastic parts that are exposed to the media. The raw material choices and processing characteristics for materials which will be exposed to medial in applications of this nature should go through extraction testing, which is the process of testing the actual fluid before and after exposure to the intended application media. Real Seal can help in determining acceptable levels of fugitive extractable material, which is normally measured in ppm.

Due to the exacting nature of electronics, most manufacturers expect and demand the highest degree of repeatability in processing. This can create issues with thermosetting rubber materials, as the process is highly labor intensive, and the mixing of material is performed in lots which are a fraction of the size of thermoplastics. Ironically, the very things that create the best physical properties in the vulcanized rubber material of specialty o-rings are the same things that make processing more of a challenge. For example, the less plasticizer and process aids that are included in a rubber recipe, the better the properties of the finished, molded product, and the lesser the chance of extraction into the media meant to be sealed.

There is a delicate balance to be struck between process economy and efficiency, and the properties of the finished molded part. The geometry of the seal plays an important part in the decision making process as well. The more challenging the geometry of the part, the more difficult it is to engineer a process that nets the most consistent result. Processing techniques such as rubber injection molding, LIM systems, and vacuum press systems should be considered in the choice of material and processing, including the tooling for each method, as the cost can vary widely.

Other electrical applications such as hydrogen fuel cell technology may require many of these features, and depending on the engineering requirements, dielectric properties may also need to be considered. The rubber material chosen for a seal application may be required to insulate or regulate electrical energy, while providing a positive seal at the same time. The science of measuring dielectric properties, or the amount of electrical energy transmitted through the rubber material, can therefore be very important in creating a balanced and efficient system of energy distribution. Using the seal for both purposes can create a very nice engineering result, as the elastomer can help to make up for dimensional variance in the other components with its flexible properties. A precision molded part can achieve many desired engineering objectives, providing greater economies for the other components.

Rubber and plastics can be molded with a number of different techniques, and the latest technologies can provide for consistent and repeatable results. The design of these parts should include a generous radius in place of sharp edges, draft angles to enhance both molding and location/assembly of the part, and a general geometry that will pay dividends in both processing and tool cost. A generous radius will allow the part to be tooled for more easily, as conventional cutters can be used to cut the cavity and core in the mold. Sharp edges are a natural air trap mechanism during the molding process, so the radius will normally increase the molding yield by avoiding air trap issues. If the part design is symmetrical, it will pay dividends in yield and assembly, and any design should avoid undercut geometry for ease of molding. The closer to the middle of the part you can plan the parting line for molding, the more it will tend to favor a positive result in processing, particularly in thermoplastic molding. All of these features should be considered, and taken advantage of in order to maximize the repeatability of processing, and consequently reduce the bell curve results as much as possible.

Although many do not consider rubber and plastics to be as critical as metal, chemical, or electrical engineering of a product, rubber and plastics can find their way into being one of the most critical and economically impactful components in the design. Real Seal regularly engages in design support services, and can offer insight of this nature in a wide variety of applications. For more information, visit http://www.real-seal.com/ for a consultation.

gasket seals | Polyurethane Compounds And Applications

Having become the industry standard for physical toughness in various components including o-rings, polyurethane sees active service in applications requiring resistance to abrasion, tear, and high tensile strength. Urethanes possess a unique molecular structure of tight bonds between soft polyol segments and hard isocyanate segments, creating a strong but flexible elastomeric backbone. Polyurethanes are also unique in that they have a number of serviceable forms, from low strength liquids to highly cross-linked thermoplastics. Premiere urethane product supplier Real Seal commonly handles the two most often used in the sealing industry; Thermosetting and Thermoplastic.

Thermosetting polyurethanes possess bonds that are similar to standard elastomeric materials in that they are non thermally-reversible; that is to say that once they are formed, the bonds cannot be broken down and then reformed with the addition and subsequent subtraction of heat. Thermosetting polyurethanes are typically processed in the same manner as other thermosets, being mixed in standard rubber equipment such as rubber o-rings. Typically molded through compression, transfer, or hot platen injection molding methods, this class of urethanes also covers those formed through liquid casting, rotational molding, RIM, and autoclave.

Thermoplastic polyurethanes possess thermally reversible bonds that allow gasket seals, for instance, to liquefy with the addition of sufficient heat and resolidify upon cooling. Thermoplastic urethanes are typically formed using injection molding equipment, however, extrusion, thermoforming, vacuum molding, and hot-knife welding are also possible.

The chemical type of the polyol backbone used when compounding polyurethane material is one of the two major contributors to its physical properties and relative chemical resistances. There are three types normally utilized in the production of o-rings and specialty seals:

Polyester Based: The most commonly used, providing excellent mechanical properties with resistance to hydrocarbon oils and hydraulic oils. Most urethane seals are based on polyesters.

Polyether Based: Compounded for better hydrolytic stability and good low temperature properties while maintaining the other excellent properties that urethane possesses.

Polycaprilactone Based: A subgroup of polyesters, polycaprilactones impart some of the hydrolysis resistance and low temp properties of the polyethers to the outstanding oil resistance and mechanical properties of polyesters. For additional information on polyurethane o-rings and seals, please visit http://www.real-seal.com/ to learn more.

Automotive Subassembly Engineers Face A Multitude Of Challenges

It used to be that automotive companies took ownership for all aspects of the finished vehicles. Scores of engineers worked on the improvements and innovation that put American automotive companies at the top of the industry for decades. In today’s market, however, automotive companies have evolved into professional assemblers. Automotive companies have passed the burden of design, performance, longevity, aesthetics, warranty, and most importantly, cost reductions, to their suppliers, and the suppliers in turn have passed much of this burden to their suppliers. The resulting shakeout has created some interesting dynamics for engineers, as they are weighed down with having to engineer sub-assembled products (such as specialty o-rings) which may or may not be in their specialty. Rubber and plastics often come into play in these circumstances, as both rubber and plastics are somewhat unique in the broad field of industrial engineering.

The first consideration for engineers in this predicament is to qualify the physical demands of the application, for instance of automobile or aircraft o rings in a given program.

Automotive engineering is generally more complex than most industrial engineering, as there are so many physical, environmental, and longevity considerations, as well as numerous constraints. If the sub-assembled unit goes under the hood, for example, vibration, heat, cold, exposure to hydrocarbon oils or fuel must be considered. Since auto o rings as well as other rubber and plastics are normally used to control the flow of fluids or gasses, they must be engineered to seal out any foreign media. ASTM standards for tensile strength, elongation, heat aging, compression set, and media exposure have to be kept in line with performance requirements. There are several established specifications for rubber and plastic materials, depending on the OEM, and most will establish the specification and provide a drawing only. The required dimensions and associated tolerances of specialty rubber o-rings, for example, will also have an impact on material choice, as the processing method and tooling considerations can vary widely based on the material. It is then up to the project engineer for the sub- assembler to choose and qualify a material to meet this criterion.

The next step is to narrow down the material choices based on the physical demands of the application. Qualifying the physical requirements of the application will normally limit the field of materials. If the application demands high temperature resistance as well as resistance to hydrocarbon oils, for example, the only realistic choices are FKM or FS rubber. If the application demands high temperature resistance without hydrocarbon resistance, then silicone rubber will normally be suitable. If the temperature does not exceed 240°F or so, then NBR or HNBR may be used, and thermoplastic materials may come into play. Once material choices have been filtered down and qualified against required specifications, the picture becomes much more finite. For additional information on automotive and mechanical engineering topics, please visit http://www.real-seal.com/ to learn more.

Important Things Come In Small Packages: Engineered Thermoplastic Components

Polyurethane is generally the material of choice to create longevity in products due to its resistance to abrasion and performance in harsh environments. Components used in specialty seals and other sealing systems that were traditionally metallic in nature have largely been replaced with thermoplastic materials that offer greater resilience, improved frictional properties, improved resistance to wear, weathering and oxidation, and overall improved aesthetics.

Rubber has its own unique array of available materials and associated properties, and can be produced in almost any conceivable configuration, including bonding to metal components and various application-specific seal systems. Rubber materials possess some physical properties that are superior to many plastics, and can provide several advantages, including compression set resistance, thermal conductivity, and resistance to fluid swell.

High performance o-rings are arguably one of the simplest yet most engineered, precise, and useful seal designs ever developed. Though tiny compared to other machine components, o-rings are one of the most common and important elements of machine design. They are available in various metric and inch standard sizes. Sizes are specified by the inside diameter and the cross section diameter (thickness).

In the United States the most common standard inch sizes are per SAE AS568B specification (i.e. AS568-214). ISO 3601-1:2008 contains the most commonly used standard sizes, both inch and metric, worldwide. The UK also has standards sizes known as BS sizes, typically ranging from BS001 to BS932. Several other size specifications also exist.

Successful o-ring joint design depends on rigid mechanical mounting that applies a predictable deformation to the o-ring. This introduces a calculated mechanical stress at the o-ring contacting surfaces. As long as the pressure of the fluid being contained does not exceed the contact stress of the rubber o-rings San Diego experts explain, leaking cannot occur. Fortunately, the pressure of the contained fluid transfers through the essentially incompressible o-ring material, and the contact stress rises with increasing pressure. For this reason, an o-ring can easily seal high pressure as long as it does not fail mechanically. The most common failure is extrusion through the mating parts.

Seals are designed to have a point contact between the o-ring and sealing faces. This allows a high local stress, able to contain high pressure, without exceeding the yield stress of the o-ring body. The flexible nature of o-ring materials accommodates imperfections in the mounting parts. But it is still important to maintain good surface finish of those mating parts, especially at low temperatures where the seal rubber reaches its glass transition temperature and becomes increasingly crystalline. Surface finish is also especially important in dynamic applications. A surface finish that is too rough will abrade the surface of the o-ring, and a surface that is too smooth will not allow the seal to be adequately lubricated by a fluid film. For additional information about sealing systems and machine components, please visit http://www.real-seal.com/ to learn more.

Prolonging Equipment Life By Identifying Failure Modes

Equipment and smaller equipment components, such as rubber o-rings San Diego manufacturing industry experts tell us, fail in all of these operations, and many times the failures are defined at every level. The motor failed because it burned out. The bearing failed because it wore out. The pump seal failed because the gasket seals started leaking. The real reasons these components failed is because of many other more detailed reasons that are usually not determined. There are a number of reasons we don’t take the time to look at the real reason the component failed. When the functionality of an entire piece of equipment sometimes depends on its seal systems Escondido-based distributor and manufacturer of seals and related products stresses the importance of proper preventive maintenance.

According to related sources that say the manufacturing and process industry in America spends more than $700 billion a year in repairs and maintenance. In general, this money is spent to keep plants operating and making products to sustain their profit margins. This article examines how this money is spent and whether or not it is being moved into the business profit margin. Here are a few of the reasons why don’t we ask more questions when we have equipment failures.

One reason is industry culture. We have created cultures in many plants that if the equipment components fail, make sure we have spares and get them changed as quickly as possible. Another reason is that we are reactive. We do most of our repairs in a reactive state, so we must have parts and we must do the repairs quickly and without much precision in the work process. Lastly, there is a general lack of training to teach people how components fail and, more importantly, how to keep them from failing. Programs such as root cause analysis (RCA) and Reliability-Centered Maintenance (RCM) can be educational processes for critical plant equipment and lead to longer life cycles of the components like high performance seals.

Through a team effort, the RCM process examines processes and determines how the components in a plant can fail, have failed and will fail. Then, the process determines ways to predict the failure, prevent the failure and eliminate the failure. This process scares many companies away since it requires people and time resources, and the objective is to run hard and make money. But in most cases, the running hard step is leading to more downtime, short equipment life cycles and money losses to the bottom line. For more information on components such as O-rings, sealing systems, engineered rubber and plastics components, please contact http://real-seal.com/.