1. Reading Precision Sheet Metal Prints

2. Learning Objectives
Describe the methods used to display precision sheet metal fabrication drawings on prints
Read precision sheet metal fabrication prints
Answer questions related to material bending, seams, chassis layout, and other precision sheet metal fabrication practices

3. Learning Objectives Calculate bend allowance
Describe undimensioned drawing practices found on prints
Read prints using undimensioned drawing practices

4. Sheet Metal Definitions
Foil or leaf
Plate
Gauge
Flat pattern
Cut
Bent or bend

5. Common Sheet Metal Materials
Carbon steel
Aluminum
Stainless steel
Copper
Brass

6. Precision Sheet Metal Prints
Tighter tolerances than sheet metal parts used in construction
Formed from a flat pattern
Common industries:
Automotive
Electronic
Product chassis
Aircraft industries

7. Multiview Drawing and Flat Pattern

8. Multiview Drawing with Flat Pattern Reference Using Phantom Lines

9. Flat Pattern, Rectangular Coordinate Dimensioning Without Dimension Lines

10. Flat Pattern Using Tabular Dimensioning

11. Formed Sheet Metal Part Model and Flat Pattern

12. Flat Pattern with Manufacturing Information Extracted to a Table

13. Bend Representation Bend lines: Bend extents:
Often drawn as centerlines
Sometimes drawn as phantom lines
Bend extents:
Sometimes shown, usually as phantom lines

14. Bend Instructions Number of degrees of the bend
Bend direction from the principal plane
Note
Meaning
UP 90°R.120
Bend up 90°with a .120 bend radius
DOWN 90°R.120
Bend down 90°with a .120 bend radius
DN 90°R.120
Bend down (DN) 90°with a .120 bend radius
BUP 90°X R. 250
Bend up (BUP) 90°with a .250 bend radius
BDN 90°X R. 250
Bend down (BDN) 90°with a .250 bend radius

15. Additional Bend Information
Bend tangent line
Center line of bend (CLB)
Inside mold line (IML)
Outside mold line (OML)

16. Bend Allowance Different formulas based on:
Material type and thickness
Bending process
Dies or machine used
Bend angle and radius
Grain of material
Surface condition
Amount of lubrication used

17. Bend Transition Helps ensure manufacturability Common examples: Spline
Radius
Straight

18. Bending a Corner to a Round
May require bend facets when formed using a press break
Smooth when formed in a die

19. Bend Relief

20. Corner Relief

21. Flanges
Contour flange
May require mitered corners

22. Seams Tight joint Specific gap Lapped Single-lap seam Double-lap seam
Welding
Lapped
Mechanical fasteners
Single-lap seam
Double-lap seam

23. Hems

24. Roll Forming Linear or revolved around an axis Rolled surfaces
Contoured rolls
Beads

25. Lancing
Stamping press operation
Does not remove material

26. Metal Grain Structure

27. Blanking
Nesting blanks

28. Undimensioned Drawings
Often full scale
Part and tooling produced by photographic or other processes
Requires stable media
CAD model sent directly to CAM machine tool
ASME Y , Undimensioned Drawings standard

29. Undimensioned Drawings
Dimensional accuracy applications:
Grid lines
Dimensional accuracy points
Registration marks
Artwork alignment in the place of grid lines

30. Grid Lines

31. Dimensional Accuracy Points

32. Registration Marks

33. Sheet Metal Punch Identification
Standard dimensioning practices
Punch identification (ID)