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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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