Manufacturing Engineering MECH 314

1
Manufacturing Engineering - MECH 314

• Lecture 5

2
Working Drawings - Assembly
Surface Roughness

• January 16, 2007

3
Working Drawings

• Consist of
• Detail Drawings
• include all needed dimensions
• include all other information required to
  manufacture the part
• Assembly Drawings
• show how parts fit together

4
Revolving Clamp Example
Custom Component
Pictorial
Standard Component
Parts List
Title Block
Notes
5
Elements of Working Drawing 1/3

• Pictorial
• an image of the device assembled
• Legend/Title Block
• identifies designer, company, date
• Notes
• general tolerances
• fillets and rounds
• gtgtgt

6
Elements of Working Drawing 2/3

• Bill of Materials/Parts List (BOM)
• part , name
• quantity needed
• material specifications
• Standard Components
• full spec. listed but not drawn (Parts 4 and 9)

7
Elements of Working Drawing 3/3

• Custom Components (Detail Drawings)
• orthographic views with
• internal details
• detail dimensions
• tolerances
• finishing treatment
• Assembly Drawing missing on Revolving Clamp dwg
• orthographic sectioned assembly

8
Interpreting the Drawing

• Must understand function of each part
• Parts must FIT together in order to function
  properly
• Fits can be resolved from
• limit dimensions (tolerances)
• specific manufacturing process (e.g. copper braze
  Part 5 into Part 6)

9
Revolving Clamp Main Function

• Most important feature
• main body (1) can be rotated to any position
  around bushing (2)
• held in position by a cap screw (4)
• flat washer (3) assists in holding main body in
  place
• gtgtgt

10
Main Function Body Bushing
Finish Mark
Limit Dimension
Limit Dims
Limit Dimension

• Bushing will go at least (1.874 - 1.870) 0.004
  past top of body
• Flat Washer (3) sits on top of bushing
• Cap screw goes through bushing and fastens it to
  work table
• Body free to rotate about bushing
• held in place when clamped
• gtgtgt

11
Working End of Clamp
Thread Note

• Threaded stem (7)
• 5/8" diameter thread
• 5/8" thread in small hole in body
• establishes position
• can be raised or lowered by turning knob (8)

Thread Note
12
Thread Note

• 5/8-11 UNC-2A on Part 7 (Stem)
• 5/8 inch diameter
• 11 threads/inch (Thread Pitch)
• Unified Coarse thread (Shape of profile)
• class 2 external thread (A)
• 5/8-11 UNC-2B on Part 1 (Body)
• internal thread (B)

13
Toggle Pad Assembly

• Contacts workpiece
• Thread note indicates that assembly threads onto
  stem (7)
• gtgtgt

6
14
Toggle Pad Assembly

• As pad tilts, spherical surfaces can slide along
  one another

Toggle pad is threaded onto the stem
Spherical Contact
15
Cap Screw

• Socket-headed cap screw
• standard part
• not included in detail drawings
• would be shown on assembly drawing
• shown in Giesecke, Appendix 19
• gtgtgt

16
Bolts, Screws Studs
Hex Head Cap Screw
Socket Head Cap Screw

• Length of the cap screw (L) is 5
• distance from the underside of the head to the
  end of the thread
• Head is 7/8" dia (G) and 5/8" long (H)
• Threaded portion (l) is about 2/3 of length

17
Pin

• Pin (9) should be shown on your drawing
• dimensions given on the drawing
• holds knob (8) on stem (7)
• use broken section through stem to show

18
Assembly Drawing Example
Use Broken Section
Exterior
Use Broken Section
Half Section
Exterior
Full Section
Exterior
19
SURFACE TEXTURE (Roughness, Waviness, and Lay)

• Significance
• Formation
• Characterization
• Specification

20
Significance

• Surface - boundary between a workpiece and its
  environment.
• Nominal Surface - theoretically perfect surface
  as specified on drawing.
• Functional Surface - surface that interacts or
  functions with another surface (bearing surface).
• Non-functional Surface - surface that does not
  interact or function with any surface (outside
  surface of an engine block).
• Dilemma Smooth surface is NOT always the best!
• Why?

21
Consider the following aspects

• Smooth surfaces stick to each other and do not
  slide well (e.g. glass and gauge block surfaces)!
• Wrong surface for bearing application which need
  an engineered textured surface so that the
  roughness can trap oil for much needed
  lubrication.
• Surface quality reflects state of production
  process, so it can be used to monitor process
  through surface monitoring.

22
Surface Formation Type

• Material Removal
• turn (lathe), grind, mill, etc.
• Material Addition
• plate, paint, plasma spray, etc.
• Material Forming
• roll, drop forge, shot peen, etc.
• Random Type of Surface
• isotropic, no pattern (shot peen)
• Periodic Type of Surface
• anisotropic, regular pattern (lathe)

23
Surface Characterization

• Visual or Tactile
• compare with standard reference surfaces or with
  reference parts
• fingernail test - subjective and inaccurate
• Instruments
• objective, repeatable (quantifiable)
• Stylus-based pickup - like a record player
• Optical (laser) pickup - works by focusing on the
  surface
• Optical (multiple wavelength) pickup - works by
  phase shifting interferometry
• Skid Pickup - skid follows large-scale surface
  irregularities
• Skidless Pickup - measure complete profile

24
Classification of Surface Irregularities

• Roughness - small scale irregularity
• Waviness large scale irregularity
• Scale is relative and depends on the application.
• Different causes for each type of irregularity.
• Must be separated by filtering to identify each
  characteristic.
• Use Cut-off Length (lc) to separate roughness
  from waviness, recommended value for lc is 0.030
  or 0.8mm unless otherwise specified.

25
Parameters

• Numerical value (Ra) derived from surface
  profile.
• Used for concise description of a surface.
• Cut-off Length (lc) gt 2.5 x Peak Spacing.
• Traverse Length (lm) _at_ 5 x Cut-off Length.

26
Ra Arithmetic Mean Roughness Value

• The arithmetic average value of filtered
  roughness profile determined from deviation about
  the centre line within the evaluation length lm

Most common in µinch or µm Average deviation
of surface profile from mean line Not good for
distinguishing surface types Need other
parameters to describe
27
Approximation of the average roughness

• An approximation of the average roughness may be
  obtained by adding the y increments shown in
  figure below without regard to sign and dividing
  the sum by the number of increments taken

• Older instruments calibrated for root-mean-square
  average are approximately 11 per cent higher on a
  given surface than those calibrated for
  arithmetical average.
• Instruments originally calibrated to read
  root-mean-square average can, in many cases, be
  adjusted to read arithmetical average.

28
Surface Specification (CSA Standard B95)

• Applied to surface viewed in profile (edge view)
• Standard values to be used for Ra specification
• Lay - specify direction of surface texture
  pattern using lay symbols ( ? X M C R)
• Surface Roughness or texture must be less than
  Geometric Tolerance range to be meaningful, Ra
  lt 1/20 to 1/8 of Geometric Tolerance

29
Roughness Characteristics

• CSA B95-1962 (re.1996)

30
Lay Symbols
31
Lay Symbols - continued
32
Surface Specification (CSA Standard B95)
Preferred Roughness Height ratings are
established values for Texture Comparison
Specimens

33
Surface Texture Interpretation

• This on a drawing
• Means this on a part

The above specs are interpreted (and measured) on
the part like this