The book describes good joint design and implementation, the geometry and nature of the component parts, the types of load involved, and other basic information necessary in order to work successfully in this field. Throughout, the treatment is practice-oriented and focused on everyday problems and situations. The 7th edition introduces a completely new chapter on overmolding and in-mold assembly, as well as a new chapter on bonding, including accompanying examples.
Laser molding and ultrasonics coverage are also brought up to date, with illustrative case histories. The detailed yet simplified discussion of material selection, manufacturing techniques, and assembly procedures enables the reader to evaluate plastic materials and design plastic parts with confidence. Good joint design and implementation, the geometry and nature of the component parts, the types of load involved, and other fundamental information necessary for a successful outcome are all included.
The 8th edition introduces a completely new chapter on fasteners, including discussion and evaluation of thread forming and thread cutting screws, with accompanying examples. New case histories in the fields of elasticity and annular snap fits that illustrate the hazardous consequences of inadequate part design are also included. Since injection molding is the most widely used manufacturing process for the production of plastic parts, a full understanding of the integrated design process presented is essential to achieving economic and functional design goals.
Features over drawings and photographs. Contents: Introduction to Materials. Manufacturing Considerations for Injection Molded Parts. The Design Process and Material Selection. Structural Design Considerations. Prototyping and Experimental Stress Analysis. Methods Citations. Figures and Tables from this paper. Citation Type. Has PDF. Publication Type. More Filters. Highly Influenced. View 23 excerpts, cites background and methods.
The subject of the bachelor thesis is the specification of the description assembly operations of bonding of manufactured parts, their process analysis and detection of parameters of a collaborative … Expand. View 3 excerpts. The book serves as a practical guide for making sustainability decisions about how plastics are made and used, including current developments in the newest bio-based plastics.
Designers, marketers, academics, and. Get Injection Molds Books now! This book provides a structured methodology and scientific basis for engineering injection molds. The topics are presented in a top-down manner, beginning with introductory definitions and the big picture before proceeding to layout and detailed design of molds.
The book provides very pragmatic analysis with worked examples that can be. The book has been completely updated and a new chapter on laser welding of. Design for Manufacturing assists anyone not familiar with various manufacturing processes in better visualizing and understanding the relationship between part design and the ease or difficulty of producing the part. Many electrical-shielding applications skip the corners. Figure 6. These racks both secure and orient the parts for total immersion and complete draining at each step.
Your part must be stiff enough to resist flexure and distortion when clamped onto the rack. Otherwise, the thinplated layer could crack as the parts are removed and handled. Consider edge-stiffening and surface-crowning to reduce flexure and cracking see figures 6. The points where the rack clamps contact the part will not plate. Plan for these contact points and work with your plater to find suitable clamp locations. An inert gas plasma Because vacuum metallization film typically 1.
The process phase transition. Sputter deposition offers thicker line-of-sight pattern, deep recesses usually begins with the application of a metallic layers, and more metal choices than and undercuts will not coat. Typically, specially formulated base coat to traditional vacuum metallization. Common the part must rotate for full coverage smooth out surface irregularities and metals and alloys include chromium, copper, gold, of surfaces and standing features.
After curing, tungsten, stainless steel, and brass. Complete to provide the uniform coverage during front-and-back coverage may require the line-of-sight deposition process.
Vacuum then condensing it onto the part metallization works best on parts with surface. Tungsten filaments or relatively simple shapes that require electron beams typically provide the coating on just one side. The process energy to vaporize the source metal is often limited to sizes that will fit in through direct sublimation from a standard vacuum chambers.
After metallization, Vacuum metallizing is much less decorative parts usually receive a sensitive to processing and part design clear topcoat to protect the thin than electroplating. Adherence to metal film from abrasion. Metallized standard plastic part design guidelines surfaces in protected environments, and good molding practices is usually such as reflectors in sealed lighting sufficient to obtain satisfactory results.
Any openings in the enclosure assembly, and Radio Frequency Interference RFI become increasingly whether they be intentional — holes and cooling vents — Important design considerations. EMI and RFI problems occur or unintentional — gaps along mating edges, can allow electromagnetic when electromagnetic energy escapes an electrical device radiation to escape. The length of the opening determines the frequency and reaches an unintended device, causing a malfunction or of radiation that can escape.
Long gaps, such as between mating halves, could interference. Untreated plastic parts generally appear release a wide range of frequencies. One design employs contact fingers with a slight interference fit to create A variety of shielding methods exist, including coatings, sheet- a low-impedance connection and reduced gap size. The finger spacing metal shrouds, adhesive foils, and special conductive determines the slot length and the minimum frequency that can escape.
More often, manufacturers use metallic Consult your shielding experts for help in calculating the correct spacing coating. Each of the metallic-coating processes covered in this for your application. A number of factors determine design process to assure a good combination of performance and the best process for your application, such as part geometry and manufacturability. In one process, the patterned plastic parts see figure 6.
In commonly made of silk, polyester, or another process, a smooth pad picks up stainless steel, which has been stretched a pattern of ink from an etched plate in a frame. Stencils, often made using that was flooded with ink and then a photoetching process, are then placed wiped with a blade, leaving ink in the on the screen where ink transfer is etched recesses of the pattern.
In both not desired. A rubber squeegee forces processes, the loaded ink pad then ink through the screen and onto the stamps the pattern onto the plastic part. The screening process The soft pad can accommodate textures requires careful control of the ink and many irregular shapes. Irregular viscosity and ambient conditions to shapes cause distortions in the printed avoid fluctuations in temperature and pattern that must be compensated by humidity that could cause the screen to adjustments in the ink pad pattern.
Screens also require periodic cleaning to remove dried ink that could clog screen. In this process, a 6. The force and heat Laser printing produces designs and simultaneously melt a recess and transfer ink symbols in plastic parts either by direct from the foil see figure 6.
Dome printing, a marking of the plastic or by selective variation of the hotstamping process, prints on top evaporation of a coating applied to of raised features or patterns in the molded part the plastic. In direct laser printing, the see figure 6. The reinforced silicone laser usually burns dark symbols into rubber pad used in this process compensates for FIG. Some dark-colored plastics have been developed that produce light-colored symbols during laser printing.
This FIG. White, back-lit symbols can be produced on a dark background by first coating white plastic with an opaque dark paint. The laser then vaporizes the paint in the shape of the symbol, and exposes the white plastic substrate.
The pigmented, white plastic reflects the laser beam without marking. Available in transparent, opaque, metallic, or embossed materials, they offer an unlimited choice of shapes and colors. Opaque labels are particularly helpful for hiding trimmed sprue gates.
Instead of relying upon a self-adhering backing, heat-transfer labeling uses a heated platen to release the print from a carrier and attach it to the plastic part. Labels and decals occasionally have problems with adhesion. Carefully pretest and evaluate any proposed adhesive system on actual production parts. Also, avoid placing decals and labels on irregular surfaces, as they will lift more easily. Closely scrutinize your total design for opportunities to combine function and reduce final assembly count.
By way of example, figure 7. A variety of factors — including required strength, wear properties, and moldability — determine which of these design options is most feasible. They also add to the cost of dismantling products for repair or recycling. To reduce costs, consider replacing mechanical fasteners with snap-fit joints, molded-in hinges, latches, and other similar design features. When you must use fasteners, choose from the multitude of inexpensive, off-the-shelf varieties to lower costs.
Avoid expensive, custom, or low-production fasteners, unless the performance advantage justifies the additional costs. Whenever possible, standardize fasteners to simplify inventory control and automation processes, as well as reduce unit cost.
See Fig. For example, use hex holes to captivate nuts during assembly see figure 7. Although they vary in appearance, all snap-fit joints rely upon the brief deflection of a flexible member to interlock a depression or undercut with a protrusion on a mating part.
Varieties include cantilever FIG. The shape of the undercut determines if the joint can be separated later. Snap-fit designs with an angled undercut contact can be disassembled without first deflecting the snap feature to disengage the connection. They also as solenoids and switches, replacing facilitate quick and easy detachment more expensive screws see figure 7. Some rules of thumb as latches for access doors and panels.
Rounded lids — such as on film during snapping does not exceed canisters or food-storage containers—use the allowable strain limit of the annular snap-fit designs for continuous material; attachment and a good seal.
To lower mold-construction and maintenance costs, design simple, FIG. In some designs, the proximity of the snap-fit joint to other part or mold features does not leave enough room for a slide mechanism. Annular designs can be particularly difficult to mold. Some need collapsible cores or ejector sleeves, which can be problematic and difficult to maintain. Consult an experienced mold engineer before specifying any design that uses slides or other mechanisms to clear or eject undercuts.
The molding process offers the versatility to customize snap-fit designs for each application. For example, snap arms on frequently used doors or access panels could have finger tabs added for easier opening see figure 7. Limited-access doors could have hidden snap-fit joints or require special tools. Some applications may require modifications in the snap arm to prevent excessive material strain during deflection. The wall from which the snap protrudes is assumed to be rigid in the conventional formulas.
This is a valid assumption for long cantilevers, but not short cantilevers. The intersecting wall actually deforms under load for short beams. The results of this study were compiled and are shown in Figure 7. An example illustrates the procedure for designing a snap-fit. Formulas for calculating maximum strain, deflection and amount of force required to assemble the parts are also given.
A special snap-fit manual with more detail is available. Although 2. Formula is only valid when the shaft and 3. Formula assumes zero metals, a good design is more critical for hub are the same material. Since plastics creep or 4. Creep must be fully analyzed. Determine the maximum due to plastic creep relaxation. Two similar or dissimilar materials can be assembled together in a strong leak-tight bond.
Various joint designs are shown in Figure 7. The choice of the adhesive depends on the application and its end-use environment. Polyurethanes— High strength, good impact resistance, good low temperature flexibility, two parts usually , limited moisture resistance, long cure times, and usually needs to be fixtured.
Epoxies— High strength, high temperature resistance, two parts usually , poor impact resistance, long cure times, and usually needs to be fixtured. Silicones— Low strength, very high heat resistance, two parts usually , good low temperature flexibility, good impact resistance, good sealing capability, very long cure times, usually needs to be fixtured, and very high material cost.
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