Assembly Techniques and Concerns Rey Jordan Tim Goldmann Phillip Pinsonneault Caleb Hanson

Soldering and Brazing Soldering and brazing are used when you want to join materials that cannot withstand high temperatures, such as electric components.

Soldering Soldering was first used as far back as B.C. A soldering iron heats the solder to a molten state.

Soldering Soldering comes from the Latin word solidare meaning to make solid. Solder is a type of metal with a low melting point.

Soldering Part a: Not enough solder Part b: Right amount of solder Part c: Too much solder.

Brazing Brazing and soldering are distinguished arbitrarily by temperature. Low temperature is for soldering, higher temperature is used brazing.

Brazing Brazing was first used as far back as B.C.

Brazing Surfaces that are to be brazed must be cleaned free of rust, oil and other contaminants in order to obtain proper wetting and spreading of the molten filler metal in the joint and develop max bond strength.

Flux Flux is essential in brazing to prevent oxidation and to remove oxide films from workpieces. Generally made of Borax, boric acid, borates, florides and chlorides.

Flux Because most fluxes are corrosive, they must be removed after brazing, usually by washing with hot distilled water.

Fillers Metals to be bondedFiller metals Degrees C  Aluminum AlloysAlum-silicon Magnesium alloys Magnesium- aluminum Copper AlloysCopper-phosphorous Ferrous and non- ferrous Silver, copper-alloy Iron-nickel and cobalt Gold Stainless steelNickel-silver

Mechanical Fasteners Ease of manufacturing Ease of assembly Ease of disassembly, maintenance, parts replacement, or repair Lower overall cost of manufacturing the product

Threaded Fasteners Bolts and screws Most commonly used threaded fasteners Can be secured with a nut and lock washer Can be self-tapping

Rivets and Staples The most common method of semi- permanent joining is by riveting Stapling is fast, and best suited for joining thin metallic and non- metallic materials

Seaming and Crimping Seaming is similar to joining two pieces of paper by folding the corner Crimping can be done on both tubular and flat parts A good example of crimping use is attaching electrical connectors to wiring

Snap-in Fasteners Several different types Fast and economical Used widely in automotive bodies and household appliances

Shrink and Press Fits Shrink fitting is based on the thermal contractions of two components In press fitting, one component is forced over another A good example of shrink/press fit is a timing gear onto a crankshaft

Design for Mechanical Fastening Less costly to use fewer (but larger) fasteners Fit between parts should be loose to reduce cost and facilitate assembly Standard size fasteners should be used when possible Holes should not be too close to edges or corners

Joining Thermoplastics Ultrasonic welding is the most common used process to join thermoplastics Adhesive bonding as seen in household plumbing Mechanical fastening with self tapping screws

Joining Thermosets Threaded or molded-in inserts Self-tapping screws and integrated snap fasteners Solvent or adhesive bonding

Joining Ceramics and Glasses Ceramics can be joined during their primary shaping prior to firing Ceramics can be brazed after they have been coated with a metallic layer Glasses are joined by heating the surface to be joined and pressing the two pieces together

Surface Structure Bulk metal or substrate Work hardened layer Oxide layer (rust) Adsorbed layer Surface layer

Surface Integrity Heat-affected zone is the portion of a metal that is heated without melting Inclusions are small, nonmetallic, elements in the material Residual stresses are caused by non-uniform deformations and temperature distributions

Surface Texture and Roughness Regardless of the method of production, all surfaces have their own characteristics which are known as surface texture. Geometrical properties of surface texture are complex, however there have been simple guidelines defined to identify surface texture in measurable quantities.

Surface Texture and Roughness Lay- is the direction of the predominant surface pattern and usually visible to the naked eye. Roughness- closely spaced, irregular deviations expressed in terms of height, width and distance along the surface. Waviness- reoccurring deviation from the flat surface. Measured between crests

Measuring Surface Roughness Instruments called surface profilometers are used to measure and record surface roughness A diamond stylus travels in a straight line over the surface The path of the stylus in surface roughness measurements is used instead of the actual surface roughness profile.

Friction Friction- is the non conservative resistance force that occurs when two surfaces travel along each other when forced together. It causes physical deformation and heat buildup. Two bodies in contact showing the real area of contact

Reducing Friction Friction can be reduced by the careful selection of materials with low adhesion Lubricants interpose an adherent film which greatly minimizes friction between one surface and another

Friction Measurement Ring Compression Test –a flat ring is pressed between two flat plates. –As its height is reduced the ring expands radially outward. –If the friction at the interfaces were zero, both the ID and OD would expand as if it were a solid disk. –Increasing friction shrinks the ID

Wear Wear is significant because it changes the shape of tools and dies also affecting tool life, size and the quantity of parts produced. The effects of wear are evident in the number of parts and components that have to continually be replaced. (a)- wire brush (b)- ground surface

Adhesive and Abrasive Wear Adhesive wear occurs when two surfaces sliding across each other and there is a constant breaking of the micro welds. Abrasive wear occurs when a hard rough surface slides across a softer surface causing chips and slivers

Other Types of Wear 1. Erosion-loose particles abrading a surface 2. Pitting (lubricated dies only) 3. Thermal Fatigue 4. Mechanical Fatigue 5. Plastic Deformation

Lubrication Lubricants are used widely for many rotary and linear moving components in metal work and machining (a)Thick film- prevent accuracy (b)Thin film- less friction with slight wear (c)Mixed- load carried by metal contact (d)Boundary- no metal to metal contact

Metal Working Fluids Functions of metal working fluids include: –Reduce friction –Reduce wear –Improve material flow –Thermal barrier between tool and work piece –Act as a release or parting agent in dies and molds

Metal Working Fluids Oils- effective in reducing friction and wear but do not prevent heat generation or plastic deformation Emulsions- water soluble oils which offer the cooling attributes of water with the lubrication properties of oils

Metal Working Fluids Soaps- good boundary lubricants Greases- adhere well to metal surfaces Waxes Additives- oxidation and foam inhibitors, rust preventing, wetting and odor controlling agents

References Wright, Thomas, Processes of Manufacturing, Goodheart-Wilcox Company, Inc., 1990 Lindbeck, John R., Product Design and Manufacture, Prentice-Hall, 1995 Kalpakjian & Schmid, Manufacturing Engineering and Technology, Prentice-Hall, Fifth Ed.