When planning for the processing of rubber or plastic seal products and mechanical components, there are several factors that must be considered to satisfy customer requirements. Although the conventional wisdom is to bring larger volume projects to China for the low prices, American manufacturing innovation and good old fashioned productivity have created many opportunities to produce products domestically – and do it competitively.
The first consideration is the material requirement or specification for the part being considered. The physical requirements for the application will largely determine the material selection, which, in turn, will create the pathways for processing options. As a general rule, thermoset rubber materials have superior physical characteristics over thermoplastics. Theroset rubber materials have traditionally been processed with compression and transfer molding methods, which are quite labor intensive. In the last several years, however, great advances in injection molding technology of thermoset rubber materials have been made domestically. The materials are modified chemically to improve their flow properties, which then allow them to be molded in much the same way that plastics are. They still require secondary finishing to remove flash, but the productive processing rate could make a strong competitive base to work from. If the material is to be thermoplastic, domestic manufacturing is generally more competitive than comparable
The next consideration is the geometry of the part, and the type of tooling necessary to meet geometric, size, and tolerance requirements. There is a limit to the layout of cavities for all processes of molding, so considering spacing and symmetry, the broad rule of thumb is the smaller the geometry, the higher number of cavities. The total volume of the cavities, however, cannot exceed 4 X the projected area of the hydraulic ram tonnage of the press, or the press will not be capable of closing the mold. Generally speaking, thermosetting rubber materials will have a longer cycle time to vulcanization than plastics will to set up, so the productive rate multiplied by the # of cavities will begin to set the stage for the most economical approach to production.
When these parameters begin to be fleshed out, one of the important considerations is what kind of repeatability can be achieved in meeting customer requirements. The more capital intensive the process (generally speaking), the more repeatable the process. Processes that require human interaction will by their very nature vary with the nature of the human element. Advances in controls that include large quantities of sensors create conditions that are optimized by machines, so that any variables are minimized, and so that the process can be stopped at any time if the variables begin to drift away from optimized limits. The result of this approach normally includes a higher yield, better dimensional consistency, and more consistent results overall.
American innovation is on the forefront of advances in capital equipment, primarily in electronic sensors and controls that create higher and higher degrees of control. There is much to be gained by utilizing a more capital intensive approach to production, but the cost of capital can be considerable. While there is still a strong argument for the old fashioned approach in many cases, engineers and designers are wise to keep up with advances in production, and design their rubber and plastic seal products and mechanical components accordingly.
Since it became commercially available in the early 1990’s, TPE (Thermoplastic Elastomer) materials have provided a new dimension to the engineering of elastomeric parts in a multitude of applications. While there are a number of possible advantages in designing TPE’s into applications, there are also quite a few drawbacks. When considering TPE as an option, bear in mind that there are several considerations that should be taken into account.
TPE’s offer process advantages that traditional rubber does not. Since TPE’s are processed in the same manner as traditional plastics, the production process is normally more capital intensive, repeatable, and generally produces a shorter cycle time. TPE’s normally don’t require finishing or post cure, so the TPE process is generally going to be leaner with fewer variables. On the down side, the tooling to produce TPE materials will generally be more expensive, and considerably more expensive if the geometry of the part is challenging.
TPE materials may offer economic advantage, depending on the productive throughput of the process. This normally boils down to the number of cavities that can be fabricated for each process. Comparing TPE materials with thermoset rubber, we can look to the following examples for comparison:
Product “A”:
TPE Process: 4 Cavity mold, 30 second molding cycle, no secondary processing required
4 Cavities X 30 second cycle = 8 parts per minute (480 per hour)
48 Cavities X 20 cycles per hour = 12 parts per minute (960 per hour)
Even with required secondary processing (finish/post cure), the higher productive throughput means the rubber process will offer considerable economic advantage.
Product “B”:
TPE Process: 8 Cavity mold, 30 second molding cycle, no secondary processing required
8 Cavities X 30 second cycle = 16 parts per minute (960 per hour)
15 Cavities X 20 cycles per hour = 3 parts per minute (180 per hour)
Although the rubber process includes almost twice the number of cavities, the TPE process will likely offer substantial economic advantage.
There are dozens of other considerations which could impact processing considerations and resulting economic advantage, and Real Seal engineering and design support has helped hundreds of customers make this determination.
Although TPE materials have improved dramatically in the last 20 years, they are still generally inferior in terms of physical properties. All else being equal, rubber materials will normally have better tensile strength, elongation, and especially compression set. TPE’s offer environmental advantages, as their thermal bonds are reversible, so they can be widely used as “filler” or regrind in a multitude of applications.
As technology continues at a blistering pace, Real Seal technical staff remain on the front of the wave, and are available to help support material and design engineering for elastomeric products.
The traditional model for production has been to get maximum productivity from capital equipment, and to run capacity as close to maximum as possible. The rubber and plastics industry is no exception to this traditional norm, but that norm is changing in favor of a more adaptable model that is more closely aligned with today’s market. Real Seal has adopted such a model, running capacity no higher than 70% before bringing in new capital equipment, and reducing the average amortization cost for tools more than 50% over the last 10 years.
The sales cycle of industrial products has shortened significantly over the last decade, and in some cases has been reduced by more than ½. This is driven largely by international competition, and a generally more innovative market which is empowered by the blistering pace of technology. Industrial products from valve systems to pumps are being reengineered and updated to meet international demands, and products are being “sub categorized” into smaller, more succinct market segments in order to compete globally. The days of American OEM’s offering simple chocolate and vanilla flavored products are long gone – sub markets to satisfy specifically targeted cultures and consumer groups are the driving force for American industry today, and the engineering required to meet these specific needs is more detailed and complex than ever.
Real Seal has adopted a production model to follow this trend. Real Seal utilizes a modular tooling system for injection molding, where most tools are fabricated with inserts which are retrofitted into existing mold bases, which are optimized for the size and tonnage of the machine they are mounted in. These inserts are also standardized, which allows for a more economical baseline for tooling costs. The amount of time and effort required to change out inserts is also a fraction of the time necessary to change out a dedicated mold, saving time and labor. Although the price per individual part is normally slightly higher than the dedicated molds due to cycle time, the dedicated molds are so much more expensive that the difference in price isn’t enough to recoup the initial tooling through the life of the project. Our experience has been that product geometry changes through the life of the project, so the low amortization tooling cost allows for greater flexibility through the life of the project, keeps overall costs to a minimum, and allows for quick and adaptable changes in production scheduling.
The traditional approach to tooling normally means more complex setup time for cycle optimization. This is worth the time and expense if the production run is to be for an extended period (many days into weeks), but in today’s market, these kind of production runs are becoming more the exception than the rule. Manufacturers who can adapt to the more fragmented and dynamic demands of the market have a distinct advantage, even with a higher part cost. Real Seal keeps capacity constraints buffered, amortization costs low, and response/adaptability to customer demand at its maximum level in order to compete in today’s dynamic market.
Design for Manufacture – Yeah, it looks good, but can we make it competitively?
Design engineers wear more hats today than ever before. In the past, organizations had extensive staff that would support design projects, and engineers could specialize – not now. With more material choices than ever, design engineers have to consider not only the cost of the materials designed into a product or component, but they also have to consider the cost of manufacture to produce it. When it comes to rubber and plastic elastomer materials, Real Seal routinely provides design support to engineers to help navigate this path.
The 1st order of business is to narrow down the scope of choices for the Bill of Materials (BOM). Thermoset rubber materials generally still offer superior physical properties for sealing applications, but thermoplastics have improved considerably. For manufacturing consideration, thermoset rubber materials generally require more labor intensive processing for manufacture (which is why the vast majority are all molded in China now), while thermoplastics are more capital intensive, and are generally most competitively sourced in the US. Your best bet is to create a specification for the worst case environmental conditions that the component will see, and get quotes based on molders meeting the spec. Real Seal has a fully equipped rubber laboratory and polymer chemist, and routinely assists customers in developing engineering specifications for application.
Dimensions and tolerances must then be considered. Engineers tend to error on the side of caution, and ask for tighter tolerances than are really necessary, and in many cases, this can add considerable cost to the component. Elastometers in particular are engineered to deflect, so tighter tolerances than industry standard are normally not necessary. If the application absolutely must have the tighter tolerances, it is best to ensure that the part is dimensioned on the control document in a place that is measurable. If you indicate a control dimension, for example, from the center of one radius or diameter to another, how is the producer going to measure this feature? The best rule to follow is, “If you can’t measure it accurately, you can’t control it accurately”.
The next consideration is to review the geometry of the component, and determine if you can make it more “mold friendly”. Symmetry is preferred over asymmetry, and any “undercut” areas (areas of the component that would become trapped in the mold, thus making the part difficult or impossible to get out of the mold during process) should be avoided in order to streamline tooling and processing costs. Blind, sharp corners should be avoided, as they tend to trap air during molding and are expensive to cut in tooling, and the thickness of the part should be as consistent as possible in order to get the best results. For thermoplastic materials, the surface to volume ratio is important to consider, as the higher the StV is, generally the more difficult it is to mold. As a general rule, the more generous you can be with allowing for radii, the better molding results you can achieve. If you can live with a draft angle that will help to remove the part from the mold, this may also offer considerable cost savings.
When the general physical review is complete, actual production methods are determined, the focus should be on development of a control document. This document should achieve (3) primary things:
Identify dimensions and tolerances which are critical to the performance of the unit
Specify raw material(s) which are specific enough to ensure that the unit will perform as designed, but not so specific as to limit sources of raw material supply to the point where it is economically unfavorable
Identify and specify any ancillary features for control, including flash allowance, surface finish, gate location restrictions, or aesthetic standards
Other things to consider may include identifying the cavity number with a small raised number on the surface of the part. This will help to identify issues in the mold which are cavity specific. It may also be to your advantage to identify the part with a specific raised part number, and/or include a distinct color, which would help to control the aftermarket if the component will be changed often over the life of the product it is engineered to perform in.
These considerations reflect a good basis for elastomeric component development, but there are literally hundreds of other possible options to consider. Real Seal has built a strong reputation for design support with our customers, and we bring the collective experience of more than 40 years of product development to the table. Give our website a look and see more specifics of the val
Design for Assembly – looking downstream before pulling the trigger
As engineers are tasked with more responsibility and fewer resources, they are finding themselves challenged to not only meet the performance criterion of the product in application, but also the efficiency of the part as it relates to production assembly. Introducing a new design or material for a component without a plan for assembly is like buying the latest high tech running shoes in the wrong size – one does not work without the other. Design for assembly must include several basic considerations, along with ancillary tenets related to the goals of the finished product.
The first consideration for assembly is whether the unit will be mechanically assembled or hand assembled. Mechanical assembly offers economy and precision, but is expensive to set up… normally there must be volume (000,000’s or more) to offset the set up costs. Depending on the number of components that must be assembled together, this could entail a simple process, or an extended assembly line with both mechanized and manual aspects to assembly. The design of the component must allow for any condition related to the way assembly is set up – for example, does the component need to be symmetrical so it can be assembled in either direction, or must it follow a specific line/pattern to fit into the assembly? The geometry and surface of the component must cater to these realities, and provide as much room for dimensional and assembly variance as possible.
The next consideration is how the component will be located and ultimately affixed in the assembly. Ideally, all components should complement each other so that location can be lead, aligned, and affixed with as little variance as possible. Ancillary consideration must be given to operations such as sonic welding of plastics, fasteners, or adhesives. Does the geometry promote location and alignment with mating parts? Can any fastening mechanism necessary to complete assembly be used without being impeded, and is the fastening material compatible with the component? Does the geometry allow for a repeatable process to be employed when affixing the assembly together? These kinds of “downstream” questions should be asked and validated with process engineers responsible for putting the unit together before finalizing a design. A minor investment in this kind of planning can pay substantial dividends in the long run.
Other ancillary considerations should include surface texture, color identification, part number stamping, and aesthetics. The surface texture must not create undue friction which might impede the flow of the assembly. It should, however, have a texture that will allow for optimum gripping or interface. Component coloration is used in many applications in order to enforce warranty claims or to identify lots or batches of product for traceability. A plan should be coordinated with process engineering to detail the coloration plan, and ensure that production can easily synchronize with assembly to meet plan objectives. Many times specific product identification is necessary with a serial number and/or barcode, so the component must offer a surface area to accommodate this requirement. Throughout this process, aesthetics will have to be considered at every step – virtual 3D CAD models work nicely to get the approval of marketing/sales.
There is an extensive array of material choices to meet engineering objectives, Real Seal has the experience to assist in choosing or developing a material that will meet not only the engineering specifications, but also to meet process and marketing management objectives. The Real Seal Design Support Team has highly qualified and experienced engineering and chemical based personnel who can assist in bringing plastic and rubber products full circle from design to full production and create satisfied end customers.
Design for aftermarket – a complicated captive audience
In many core industries, global competition has created a scenario where many mainstream OEM’s are literally breaking even on their production products, and designing customized designs for components so that they can control a more profitable aftermarket.
Design engineers who could easily design standard nuts, bolts, washers, O-rings, and other standard products are instead being directed to create unique, customized components for their products so that customers are “slaved” to the OEM when maintenance is performed and replacements parts are required. Since the industrial marketplace is becoming more fragmented, there isn’t enough volume of product for manufacturers of component parts to develop tooling to compete with the OEM for the aftermarket. This gives the product OEM the leverage to charge exorbitant prices for their custom aftermarket products with minimal competition. Industries like automotive systems, hydraulics, pneumatics, pumps, heavy equipment, and valve systems are creating unique designs for components as a regular practice, as the majority of margins are realized in aftermarket sales. In many cases, OEM’s are actually selling production product at margins as low as 2% in order to command the aftermarket business!
In most cases, the OEM customer does not understand why the prices are so high, and why they cannot simply purchase their spare parts needs from local, trusted sources. We have all experienced the “sticker shock” of purchasing replacement ink or toner cartridges for our printers, and the industrial marketplace is quickly following suit.
Since most OEM’s are cumbersome to deal with, aftermarket “kit packagers” have taken over much of the aftermarket business. The OEM’s have pushed the “custom” design components in order to thwart the kit packagers’ ability to cut into their aftermarket share. Kit packagers normally have to purchase a complete OEM machine in order to reverse engineer the individual components, so when they find they cannot source the components with standard product and available tooling, it raises the threshold for their costs, and makes it more difficult to compete. To complicate matters further, OEM’s are specifying unique colors, material specifications, and even specific part number identification on the surface of the aftermarket part. Although these tactics may make it more difficult for aftermarket copycats to produce conforming parts, it also complicates the sourcing for the OEM.
Twenty-first century, high tech approaches are also being tested. Much like software and other high tech products, some OEM’s are experimenting with hologram imbedded images and/or tiny identification chips to authenticate their aftermarket products. As the cost associated with this sort of identification continues to go down, and as production techniques allow for more complex means of modifying finished products, the battle will continue.
When it comes to rubber and plastics seal products and mechanical components, Real Seal has a long history of providing conformance to customer specification. Real Seal is adaptable to customer requirements, and pragmatic enough to make these adaptations without undue cost. Our engineering support services may offer alternative tooling and production methods that will meet your objectives competitively. Please contact us for more information.
From the beginning when man took his first tentative steps into outerspace, space propulsion has remained largely the same. Even with the incremental advances in the efficiency of chemical fuels and O rings, the basic nature of rocketry is still defined by the basic Delta V Rocket Equation with all its limitations; be it the powerful boosters used to obtain orbital velocity or the low impulse Ion Thrusters used to power deep space missions. This backward approach to propulsion limits both the potential flight parameters of deep space missions and the life span of earth orbiting satellites in a wide range of applications.
The electronics and gasket seals of the satellite may last indefinitely in earth orbiting satellites; the useable lifespan of that satellite is limited by the availability of on-board propellants used for orbital maintenance. Under normal operating environments, a space vehicle’s components, such as its rubber o-rings and silicone seals can go on and on. It is only once the chemical propellant is exhausted, when the satellite no longer has the capability of maintaining a station properly. This is where electro-magnetic propulsion and electro-dynamic braking comes in.
Chemical propellants allow the International Space Station to offset orbital decay. The need and use of these chemical propellants increases the potential for catastrophic accident, increases the cost of operational maintenance, and requires the commitment of launch capacity for that purpose. Interplanetary and deep space missions face similar limitations inherent to dependence on chemical propellants for propulsion.
Obtainable velocities, launch windows, and other flight parameters remain severely limited by dependence upon the same Newtonian Propulsion methods used by the ancient Chinese to power their rudimentary rockets, despite the fact that gravitational assist has been a regular tool used in both navigation and imparting changes in specific orbital energy. Even Ion Propulsion, which uses electro-magnetic acceleration of the ion fuel to achieve impulse, is still a type of Newtonian Propulsion where the total energy imparted is limited by exhaust velocity and total available fuel mass as defined by the basic rocket equation. Newtonian Propulsion may have gotten us to earth orbit and beyond; but it will be Electro-magnetic propulsion that will carry us to the stars. In the mean time, its development will allow us to achieve flight parameters previously unattainable with only chemical propellants as the means of space propulsion.
Both Electro-magnetic Propulsion and it’s inverse, Electro-dynamic Braking, when combined with the now and near term future technologies related to super conductivity, dielectric capacitance, and other related technologies; will introduce a new paradigm in space propulsion and the space program as a whole. For additional information, visit www.real-seal.com/ at 1971 Don Lee Place, Escondido, CA 92029 to learn more.
