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GD&T
DimXpert
TolAnalyst
GD&T
DimXpert
TolAnalyst
• Geometric Dimensioning & Tolerancing
• Communicating dimensional and tolerance requirements
• Allowable imperfection
• GD&T practices are governed by standards manuals
• ANSI, ASME • Y14.5M-1994 & Y14.5-2009*
• Application of GD&T • Y14.41-2003
• Display of GD&T in 3D
• ISO • ISO 1101
• Application of GD&T • ISO 16792
• Display of GD&T in 3D
*Not all specifications of Y14.5-2009 have been implemented. If you run into a limitation, contact Quest Integration to submit the request to the Product Definition team. Ref. SPR 482875
Geometric Tolerancing Plus/Minus Tolerancing
X
Surface Plate
Inspection Method 1
Surface Plate
X
Inspection Method 2
More than one way to measure this hole location…
Proper GD&T provides critical information necessary for manufacturing and inspection
• Plus-minus tolerancing typically locates holes using square tolerance zones. Geometric tolerancing utilizes cylindrical tolerance zones
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s S
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Zo
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Po
sitio
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ylin
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GD&T yields 57% more tolerance than Plus/Minus!
Bonus Tolerance:
Both MMC (Maximum Material Condition) and LMC (Least Material Condition) allow a Bonus Tolerance
Only GD&T emphasizes the relationship between diameter tolerance and center positional tolerance
• Maximum Material Condition (MMC) = largest shaft in smallest hole
• Least Material Condition (LMC) = smallest shaft in largest hole
Blue Area = Bonus Tolerance!
• Imaginary, geometrically perfect references for comparison
• Flat plane, point, line, circle, cylinder, cone, sphere
• Primary, Secondary and Tertiary – order for fixturing
Primary, Secondary, Tertiary Datums
Geometric Characteristic
• Form Tolerances:
Flatness applied to a plane:
Tolerance zone: two parallel planes separated by the specified tolerance
Conformance: all surface points lie within a flatness zone no greater than 0.25
• Orientation Tolerances:
Parallelism applied to a plane
Tolerance zone: two parallel
planes separated by the
specified tolerance that are
parallel to datum plane A
Conformance: the smallest parallelism zone to which the feature conforms
• Location Tolerances:
Position applied to a hole pattern:
Tolerance zone: 2 cylindrical boundaries with a diameter equal to the specified tolerance that are perpendicular to datum plane A, and basically located to datum planes B and C
Conformance: the smallest position zone to which the features conform
• Runout:
Circular runout applied to a boss:
Tolerance zone: two circles concentric with datum axis A whose radial separation is the specified tolerance
Conformance: the smallest circular runout zone to which the feature conforms
• Profile:
Surface profile applied to a part boundary:
Tolerance zone: two uniform boundaries equally disposed about the nominal surface separated by the specified tolerance
Conformance: the smallest surface profile zone to which the feature conforms
GD&T
DimXpert
TolAnalyst
• 3 DimXperts
• 2D Drawings – Introduced with version 2007
• 3D Parts – Introduced with version 2008
• 3D Assemblies – Introduced with version 2016*
*Comes with SOLIDWORKS MBD license
•Machined Parts • Milled • Drilled • Turned • Undrafted surfaces
• Drafted surfaces can be toleranced (surface profile)
•Geometric and Plus-Minus Tolerance
• Sheetmetal • Bends not supported
• Prismatic type features are supported (planes, holes, slots)
• Molded/Casted Parts • Draft not supported
• Profile tolerancing is supported
• Special Geometries • Including gears, threads and cams
Countersink Cone Hole Counterbore
Slot Notch Boss Cylinder
Pocket Surface Chamfer Fillet
Plane
Width
Intersect Line Intersect Point Intersect Plane
Plane intersection between a cylinder
and a cone
Line intersection between a two
planes
Point intersection between a cylinder
and a plane
• Model faces colored based on status • Green = Fully Constrained
• Yellow = Under Constrained
• Red = Over Constrained
• Native Color = Not Recognized by DimXpert
• Sketch Dimensions • Facilitate part creation, configurations, design tables
• Linked to construction geometry not present in finished part
• Aren’t always consistent with methods used for manufacturing
• Don’t always meet requirements necessary to support geometric tolerancing
• DimXpert Dimensions • Communicate part’s functional requirements
for assembly, manufacturing and inspection
• Always associated with manufacturing features
• Always associated with a tolerance
• Dimensions (basic) associated with geometric tolerances originate from and are oriented to the datum reference frame
Tolerance type and values created by Size Dimension and Auto Dimension Scheme
Chain Baseline
• Example 1 – ADS (Automatic Dimensioning Scheme) and Geometric Tolerancing
• Example 2 – ADS and Plus-Minus Tolerancing
• Example 3 – ADS and Selected Features
• Example 4 – ADS and the Wedge
• Example 5 – ADS and Concentric Features
• Example 6 – Feature Selector
Plus and Minus
Geometric
Location Dimension Size Dimension
GD&T
DimXpert
TolAnalyst
• Tolerance stack-up analysis is the study of dimension and tolerance schemes to determine potential form, fit, and function problems in parts and assemblies
What the permissible gap (G) between Part1 and Part4 ?
• Assumes dimensions vary within the entire range of their tolerance zones and that the accumulation of tolerances will experience all possible variations
Gmin = L1 + L2 + L3 + L4… + Ln
= L1 + L2 + L3 + L4
= 152.75 + (-60.75) + (-42) + (-50.5)
= -0.5 Interference
• Assumes dimensions vary randomly within a normal distribution (±3σ) centered about midpoint of the tolerance zone.
G = Gnominal ± √ T12 + T2
2 + T32… TN
2
= 2 ± √ 0.252 + 0.752 + 12 + 0.52
= 2 ± 1.369
Gmin = 0.631, Gmax = 3.369
Gnominal = 153 - 60 - 41 - 50
= 2
• It is incorrect to think max worst case is when the parts are at their largest and min worst case is when they are at their smallest
Part Nominal Assembly Worst-case
Maximum Worst-case
Minimum
Functional Requirement: D >= 39
Top Plate Angle Bracket Bushing
Before After
To reduce the tolerance stack by 0.8
(39 – 38.2) the tolerance of each
dimension would have to be changed
to ± 0.1
Before After
By increasing the width between the faces
locating the two angle brackets by 1 mm the
results for the minimum worst-case gap would
be 39.2 (38.2 + 1)
By adding a dimension between the planes which locate
the axel supports and removing the 40 dimension on the
right side of the part the tolerance stack between the
planes is reduced from ± 1.1 to ± 0.3. As a result the
new worst-case minimum dimension would be 39.
Before
After Before
GD&T
DimXpert
TolAnalyst