How to Improve your Machine Precision and Performance

EGS Computers India Pvt. Ltd. Chennai mkm@egs.co.in
How improve your
Machine precision and performance
K.Musthafa
Application Engineer

What is GD&T?
 Way of communicating dimensional and tolerance
requirements
 Allowable imperfection
 GD&T practices are governed by standards
manuals

GD&T STANDARDS
Standards
 ASME Y14.5M-1994
 ASME Y14.41-2003

GD&T STANDARDS
ANSI -
Y14.5M-1994: 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 – just
released December 2007

Who Needs GD&T?
GD&T is for designers who:
 Design high precision components
 Design products to be produced in high volume
 Perform tolerance stack-up analyses manually
 Must correctly dimension and tolerance designs
 Anyone who currently suffers from assembly fit
problems.

DimXpert
 Intelligent, automated dimensioning and
tolerancing of 3D models
 Visual feedback on dimensional completeness
 Automatically displays in 2D drawing
 Integrated with TolAnalyst

DimXpert solves a HUGE problem:
 Most time spent in drawing creation is in
dimensioning and tolerancing
 Without DimXpert: Manually dimension and
tolerance, no way to know if the drawing is
complete or correct for manufacturing
 With DimXpert: Dimension and tolerancing is
automated and ensured to be correct for
manufacturing
Benefits of DimXpert

Who needs DimXpert?
 DimXpert is for designers who:
 Detail part drawings
 Annotate parts in 3D
 Want to know designs are completely
dimensioned
 Use +/- and/or geometric tolerances
 Design high precision components
 Currently have assembly fit problems

Parts that are machined: i.e., milled, drilled, and turned parts
- Includes the machined and un-drafted surfaces of castings and forgings
Part Types Not Targeted
Sheetmetal
 Bends not yet supported
 BUT, prismatic type features are supported: planes, holes, slots
Molded/Cast parts
 Draft is not yet supported
 BUT, profile tolerancing is supported
DimXpert: Target Part Types

Manufacturing Feature Types

Examples
Planes
Slot
Notch
Chamfer
Pocket
Countersink Pattern
Slot
Fillet Pattern
Simple Hole
Plane

Intersection Feature Types
Intersect Plane
Plane intersection
between a cylinder
and a cone
Intersect Line
Line intersection between
a two planes
Intersect Point
Point intersection
between a cylinder and
a plane

DimXpert Functionality: Schemes
Supports both geometric and plus-minus dimension and tolerance schemes
Geometric Plus-Minus

Auto Dimension Scheme
 Automation tool for creating dimension and tolerance schemes (patent
pending)
 User can specify Plus-Minus or Geometric
DimXpert Functionality: Automatic Dimensioning
Datum Selection Automatic Dimension and Tolerance Scheme is created

Tolerance Status
1. Informs user when the dimension and
tolerance scheme is complete
2. Each face is colored based on its status:
 Green = Fully constrained
 Yellow = Under constrained
 Red = Over constrained
 Native color = Not Recognized by DimXpert.

Document Properties
Method for tolerancing
dimensions without
tolerance indications
Tolerance values based
on decimal precision
Tolerance value for angle
dimensions without
tolerance indication
Part classification per
ISO 2768

TolAnalyst Overview
 TolAnalyst is a tolerance analysis tool used to study the effects tolerances and assembly
methods have on dimensional stack-up between two features of an assembly.
 The result of each study is a minimum and maximum tolerance stack, a minimum and
maximum root sum squared (RSS) tolerance stack, and a list of contributing features
and tolerances.
 TolAnalyst Works in SolidWorks Professional and SolidWorks Premium Features.

TolAnalyst Study - Steps
Measurement - Establish the measurement, which is a
linear distance between two DimXpert features.
Assembly Sequence - Select the ordered set of parts to
establish a tolerance chain between the two
measurement features. The selected parts form the
“simplified assembly”.
Assembly Constraints - Define how each part is placed
or constrained into the simplified assembly.
Analysis Results - Evaluate and review the minimum
and maximum worst case tolerance stacks.

Tolerance Stack-up Analysis
 Tolerance stack-up analysis is the study of dimension and tolerance schemes to
determine potential form, fit, and function problems in parts and assemblies.

Worst-case analysis
Assumes dimensions vary within the entire range of their tolerance zones and that the
accumulation of tolerances will experience all possible variations
TL (Total Lower Limit) = 26.6 +14.7 + 14.7 +
14.5 = 70.5
TU (Total Upper Limit )= 27.4 + 15.3 + 15.3 +
15.5 = 73.5
(TU – TL) / 2 = (73.5-70.5)/2 = 1.5
Total Nominal = 27 + 15 + 15 + 15 = 72
X = 72 ± 1.5

Root Sum Square (RSS)
 Root Sum Square (RSS) assumes the certainty of tolerance estimate and the
arrangement of tolerances being considered. This statistical method of calculating
tolerance stack-up analysis denotes total tolerance as mentioned below.

Root Sum Square (RSS)
σplate1 = 0.4/3 = 0.133
σplate-2 = 0.3/3 = 0.1
σplate-3 = 0.3/3 = 0.1
σplate-4 = 0.5/3 = 0.167
σ assembly = √ [(σplate-1)^2 + (σplate-2)^2 + (σplate-3)^2 + (σplate-4)^2 ] = 0.256
T = σassembly * 3 = 0.256*3 = 0.768
The thickness dimension (X) with the tolerance zone of assembly would be:
X = 72 ± 0.768

 Worst-case tolerance analysis is dependent on how parts are actually assembled
in real life
 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

TolAnalyst: TolAnalyst Does Not Do…
TolAnalyst Does Not Do
– Statistical Monte-Carlo type analyses
 Allows users to control the distribution types applied to the
features and tolerances
– Runtime access to the analysis engine
 Allows users to apply their own logic and sources of variation
within the tolerance analysis
– Consideration for other (non-tolerance) sources of variation
 Gravity
 Temperature
 Deflection
– Kinematic solutions
 linkages

TolAnalyst - Example

Select the measurement distance from the graphics area.

1. Select the measurement distance from the graphics area > Next.
2. Select the Assembly Sequence > Next.

3. Select the Assembly Constraints > Next.

4. Analysis Results.
From the Analysis symmary in the
property manager, we can see the
values of
 Nominal
 Min
 Max
 RSS Min
 RSS Max

4. Analysis Results > Export Results.

Get Connected with EGS & Reach us for any Support, Comments & Feedbacks!

Chennai | Coimbatore | Trichy
Thank You..!
www.egsindia.com | www.egs.co.in
mkm@egs.co.in 044 2480 3370 +91 6383586117

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