1. Mechanical Fastening Processes Brazing
Brazing – joining process where just the filler material’s heat is raised to its melting temperature to join materials
First used as far back as 3000 to 2000 B.C.
Filler material has a lower melting temperature than components that you are joining.

2. Mechanical Fastening Processes Brazing
Brazing uses a flux in order to prevent oxidation during the joining process
Factors that affect braze strength
Joint clearance
Joint area
The bond formed between the filler material and the base metal
Proper use of flux

4. Brazing Various Methods
Torch – uses oxyfuel thru a torch
Furnace – parts preloaded with consumable inserts then placed in furnace for uniform heating
Induction – Heats thru use of High freq AC
Dipping – dips entire base material into molten filler metal bath (used for very small parts)

6. Mechanical Fastening Processes Soldering
Main difference between soldering and Brazing lies in Temperature.
Uses primarily tin-lead as filler material
Main use is for electronics which can’t withstand extreme heat of brazing.
Uses same techniques as brazing as well as that of Wave soldering – very useful for circuit boards.

8. Adhesive Bonding Types of Adhesives
Natural adhesives-starch, dextrin, soya flour, and animal products
Inorganic Adhesives-sodium silicate and magnesium oxychloride
Synthetic organic adhesives-thermoplastics, thermosetting polymers (most important in manufacturing)

9. Adhesive Bonding
Electronically Conducing Adhesives
Developed to replace lead-based solder, added metal particles (40% to 70%)
Used in electronics such as calculators, TVs, and LCDs

10. Adhesive Bonding

11. Adhesive Bonding Surface Prep, Process Capabilities, and Applications
Surface Preparation
Surface must be free of dirt, dust, oil and any other contaminants
Porous or rough surface is desirable, improve adhesion
Process Capabilities
Used to bond metallic and non-metallic material
Do not subject to peeling

12. Adhesive Bonding Surface Prep, Process Capabilities, and Applications
Used in most industries
Allows bond between dissimilar metals and reduces vibration and noise
Distributes the load eliminating local stresses that usually result from mechanical fasteners
External appearance is unaffected
Thin and fragile components can be bonded without weight increase

13. Adhesive Bonding Design for Adhesive Bonding
Ensure that joints are subjected only to compressive, tensile, and shear forces, not to peeling or cleavage

14. Mechanical Fasteners Ease of manufacturing
Preferred over other methods because of the following:
Ease of manufacturing
Ease of assembly and transportation
Ease of disassembly, maintenance, part replacement, or repair
Ease in creating designs that have movable joints
Lowers cost

15. Mechanical Fasteners Hole Prep Threaded Fasteners Rivets
Using different methods to create the hole produces different characteristics
Hole with some residual stress is desirable, improves fatigue life
Threaded Fasteners
Common bolts and screws
Rivets
Most common method of permanent and semipermanent mechanical joining
Works by placing rivet through hole and deforming end

16. Mechanical Fasteners Other Fastening Methods Design
Metal Stitching and stapling
Similar to ordinary stapling
Seaming
Folding two pieces of material together
Crimping
Physically forcing on piece onto another
Design
Use fewer, but larger, rather than many small
Fit between joined parts
Use standard sizes and keep holes away from edges or corners

17. Mechanical Fasteners

18. Joining Plastics, Ceramics, and Glasses
Joining Thermoplastics
Thermal Methods
Using heat to soften or melt two pieces at the interface to ensure good bond
Many way to apply the heat
Adhesive Bonding
Uses adhesives previously discussed to attach the plastics
Joining Thermosets
Joined using threads, mechanical fasteners, solvent bonding, co-curing and adhesive bonding

19. Joining Plastics, Ceramics, and Glasses
Joining Ceramics and Glasses
Ceramics
Treat surface with coating that is easily bonded
Braze tungsten carbide and titanium carbide
Join during their primary shaping process
Glasses
Are bonded easily
Done by softening and pressing two pieces together and cooling
Can be bonded to metals due to diffusion of metal ions into the glass sturcture.

20. 32.7 Economics of Joining Ops
Cost from highest to lowest of various Joining Operations
Highest: Brazing, bolts, nuts, and other fasteners.
Intermediate: Riveting and adhesive
Low: Seaming and crimping

21. Closer look at Brazing Costs
Manual Brazing:
Basic equipment costs $300
$50,000+ for automated systems
Furnace Brazing:
Wide range from $2,000 for batch furnaces to $300,000 for continuous vacuum furnaces.
Induction Brazing:
$10,000 for small units

22. Closer look at Brazing Costs
Resistance Brazing:
$1,000 for simple units
$10,000+ for larger units
Dip Brazing
$2,000 to $200,000+, depends on equipment which may be computer controlled
Infrared Brazing:
$500 to $30,000
Diffusion Brazing:
$50,000-$300,000

23. Closer look at Brazing Costs
High End Convection CAB Brazing Furnace
High End Vacuum Furnace

24. Surface Technology How do we react to surfaces? Touch Roughness
Texture
Scratches
Sight
Waviness
Color
Reflectivity

25. Surface Technology
Jargon: “Surface Integrity” Describes the physical, chemical and mechanical characteristics of surfaces
Influences on surfaces
Friction and wear of tools, molds, dies and of the products themselves.
Effectiveness of lubricants during manufacturing and throughout the products life.
Thermal and electrical conductivity of contacting bodies.

26. Surface Technology Influences on surfaces (cont.)
Appearance and geometric features of the part and their role in subsequent operations, such as welding, soldering, adhesive bonding, painting, coating and corrosion.
Crack initiation as a result of surface defects like roughness, scratches, seams, and heat–affected zones. These can lead to weakening and premature failure of a part.

27. 33.2 Surface Structure and Integrity
Chapter 33 Surface Roughness and Measurements of Friction, Wear and Lubircation
33.2 Surface Structure and Integrity
Metal surfaces generally contain several layers
1ST Layer: Bulk Metal (substrate) has a structure that depends on the composition and processing history.
2ND Layer: Above the bulk metal is “Surface Structure” that is plastically deformed and work hardened more so than the Bulk Metal. The depth & properties of this layer depend on processing method and friction.

28. 33.2 Surface Structure and Integrity
3RD layer: Is the “Oxide Layer.” The only way to avoid this is to keep the metal in an oxygen free environment or work with a noble metal (gold, platinum).
4TH layer: is the “Absorbed Layer.” This layer absorbs gas and moisture.
5TH layer: Is the outermost layer that may be covered with contaminants such as dirt, dust, grease, various residues and other environmental pollutants.

29. 33.2 Surface Structure and Integrity

30. Surface Integrity
Surface integrity describes topological, physical, and chemical as well as their mechanical, metallurgical properties and characteristics. Various surface defects can weaken the Sruface Integrity
Cracks: internal, external and microscopic
Craters: shallow depressions
Heat-affected zones

31. Surface Integrity Surface Defects (continued)
Inclusions: small nonmetallic elements
Intergranular attack: the weakening of grain boundaries
Laps, Folds and Seams: overlapping of material during processes
Metallurgical transformations: microstructural changes caused by temperature cycling of the material
Pits: shallow surface depressions from chemical or physical attack

32. Surface Integrity Surface Defects (continued)
Residual stresses: Either by tension or compression and causes nonuniform deformation and temperature distribution.
Splatter: Small resolidified molten metal particles on the surface.
Surface Plastic deformation: Severe surface deformation caused by high stress from friction, tool and die geometry, worn tools, and processing methods.

33. 33.3 Surface Texture and Roughness
Surface Texture are characteristics that define a surface. These can be separated into four categories which are:
Flaws or defects: random irregularities, such as scratches, cracks, holes, depressions, seams, tears, or inclusions
Lay (directionality): direction of the predominant surface pattern
Roughness: closely spaced, irregular deviations on a small scale
Waviness: recurrent deviation from a flat surface
Surface roughness is usually described in two ways:
Arithmetic mean value (R a) – the schematic illustration of a rough surface
Root-mean roughness height – was known as RMS
Maximum roughness height (R t) – the height from the deepest trough to the highest peak; indicates how much material has to be removed to obtain a smooth surface

34. R q = sq rt [(a2 + b2 + c2 + d2 + ….)/n]
Coordinates used for surface-roughness measurements
R a = ( a + b + c + d + ….)/ n
R q = sq rt [(a2 + b2 + c2 + d2 + ….)/n]

35. Standard terminology and symbols used to describe surface finish
Some symbols used to represent surface finish

36. Measuring Surface Roughness
When measuring surface roughness, instruments called surface profilometers are used. Profilometers are tipped with a diamond stylus which usually has a 10 micon diameter. The way profilometers are used is they travel over the surface in a straight line recording about 10 to 15 roughness irregularities. The distance travel maybe anywhere from .08 to 25 mm. The most common distance used is .8 mm.

37. 3d surface measurement
There are other ways of measuring surface measurement. This is done by using either an Optical-interference microscope or an atomic-force microscope.
Optical-interference microscopes: shine a light against a reflective surface and record the interference fringes that result from the incident and its reflective waves
Atomic-force microscopes (AMFs): it’s a very fine surface profilometer with a laser.

38. 33.4 Friction
There are several theories that explain friction. Two of the more commonly accepted theories are the adhesion theory and the abrasion theory.
Adhesion theory: theory that states that the contact of two items is actually only a fraction of their apparent contact area.
Abrasion Theory: theory that states that the asperities of a harder surface penetrates and plows through a softer surface.
Another thing to take in to account is that all friction dissipates energy. This energy is converted into heat. Sometimes the heat may soften or even melt the material in use

39. Plastics and Ceramics
Plastics generally possess low frictional characteristics. This is better for creating items such as bearings, gears, seals, prosthetic joints. But, an important consideration is that plastics have a low melting point. So, any heat caused by friction must be taken into account. Ceramics on the other hand have generally the same frictional characteristics as metals.

40. Reducing friction Some ways of reducing friction are :
Selection of materials used
Lubricants or solid films (such as graphite)
Ultrasonic vibrations

41. Frictional measurement
The coefficient of friction is found during the manufacturing process or in laboratory tests using smaller versions of various sizes of the material. One of the common tests used is called the ring-compression test. This is where a flat ring is upset plastically between two flat platens. If the both the diameters of the ring expand outward then the friction is zero. If the inner diameter becomes smaller, then there’s an increase of friction.

42. 33.5 Wear
Wear changes the shapes of tools and dies, affects the tool life, tool size, and the quality of the parts produced.
Importance of wear is evident in the number of parts and components that continually have to be replaced or repaired.
i.e. dull drill bits, worn cutting tools and dies

43. 33.5 Wear Running In period removes the peaks from asperities.
Under controlled conditions, wear may be regarded as a type of smoothing or polishing process.

44. Adhesive Wear
A tangential force is applied and shearing takes place either at
a) the original interface
b) along a path below or above the interface
*adhesive bonds often are stronger than the base metals.
Schematic illustration of (a) two contacting asperities, (b) adhesion between two asperities, and (c) the formation of a wear particle.

45. Abrasive Wear
Caused by a hard rough surface sliding across another surface. Microchips and slivers are produced, leaving grooves or scratches on the softer surface.
*processes: filing, grinding, ultrasonic machining and abrasive jet machining act in this manner

46. Other types of Wear Corrosive.
Fatigue-when the surface of a material is subjected to cyclic loading
Erosion-caused by loose abrasive particles on a surface
Fretting
Impact

47. 33.6 Lubrication 4-Regimes of Lubrication in Manufacturing Ops.
1)Thick-film: surfaces separated completely by a film of lubricant. Results in dull, grainy surface appearance after forming operations
2) Thin-film: Load between the die and work piece increases, or the speed and viscosity of fluid decrease, the lubricant becomes thinner raising friction and results in slight wear

48. 33.6 Lubricants
3)Mixed: a significant portion of the load is carried by the physical contact of the two surfaces. The rest is carried by the fluid film trapped in the valleys (asperities).
4) Boundary: load supported by contacting surfaces covered with boundary film of lubricant. The lubricant is attracted physically to the metal surfaces, thus preventing direct metal-to-metal contact and reducing wear.

49. 33.7 Metalworking Fluids Reduce friction Reduce wear
Improve material flow
Act as a thermal barrier between the workpiece and its tool and die surfaces
Act as a release or parting agent

50. Oils and Emulsions
Oils are very effective in reduction of friction and wear and have low thermal conductivity but they do not conduct away the heat generated by friction effectively.
*It is difficult and costly to remove oils from component surfaces that are to be painted or welded, and is
difficult to dispose of.
Emulsion: mixture of oil and water in various proportions along with additives. aka water-soluble oils or coolants
1)direct: mineral oil dispersed in water in very small droplets
Important in metalworking b/c the presence of water gives them high cooling capacity.

51. Synthetic solutions Soaps, greases, waxes
Synthetic Solutions: chemical fluids that contain inorganic and other chemicals dissolved in water (contain NO mineral oils) Oil Pepboys
Soaps: reaction products of sodium or potassium salts with fatty acids. Effective boundary lubricants. Alkali soaps are soluble in water but metal soaps are generally insoluble
Greases: solid or semisolid lubricant that consists of soaps, mineral oil, and additives. Highly viscous and adhere well to metal surfaces.
Waxes: Less greasy and more brittle. Limited to metalworking operations

52. Additives Metalworking fluids usually blend with various additives:
Oxidation inhibitors
Rust-preventing agents
Foam inhibitors
Wetting agents
Odor-Controlling agents
Antiseptics

53. Solid Lubricants
Graphite: effective at elevated temps, however friction is low only in the presence of air
or moisture.
Molybdenum disulfide: lamellar solid lube, similar appearance to graphite however has a high friction coefficient in an ambient environment. Oils commonly used with MoS2.
Metallic & polymeric Films: Thin layers of soft metals and polymer coatings. Suitable metals include lead, indium, tin, silver, PTFE(Teflon).

54. Selection of Metalworking Fluids
Considerations of several factors:
Particular manufacturing process
Work piece material
Tool or die material
Processing parameters
Compatibility of the fluid with the tool and die materials and the work piece.
Required surface preparation
Method of fluid application
Removal of fluid and cleaning after processing
Contamination of the fluid by other lubricants
Storage and maintenance of fluids
Treatment of waste lubricant
Biological and Environmental considerations
Costs involved in all of the aspects listed

55. Biological and Economical Considerations
Potential hazards may be involved by contacting or inhaling some fluid. Improper disposal of fluids may cause adverse effects on the environment.
Much progress has been made in developing environmentally safe fluids, technology, and equipment for their proper treatment, recycling, and disposal.

56. Bibliography http://www.muggyweld.com/1clip7.html
rough
wood
mirror
wavy metal
surface structure of metals
Convection CAB Brazing Furnace
vacuum furnace